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Document:	Programming in VAX FORTRAN (Ver 4.0)
Order Number:	AA-DO034D-TE
Revision:	000
Pages:	621
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OCR Text

Programming in

VAX FORTRAN
AA-00340-TE

Programming in

VAX FORTRAN
AA-00340-TE

September 1984
This manual is designed to provide all of the basic information
needed to use a VAX/VMS V4 system in developing VAX FORTRAN
programs. It also provides a complete description of the VAX
FORTRAN language.

Software Version: V 4.0

digital equipment corporation . maynard, massachusetts

First Printing, September 1984

The information in this document is subject to change without notice and should not be construed as
a commitment by Digital Equipment Corporation. Digital Equipment Corporation assumes no responsibility for any errors that may appear in this document.
The software described in this document is furnished under a license and may be used or copied only
in accordance with the terms of such license.
No responsibility is assumed for the use or reliability of software on equipment that is not supplied by
Digital Equipment Corporation or its affiliated companies.
Copyright © 1984 by Digital Equipment Corporation
All Rights Reserved.
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Contents

Preface
..................... .
Chapter 1 Using the VAX/VMS Operating System .

Page

1.1 VAXNMS Commands for Program Development-Overview

. 1-1

xix

. 1-2
. . 1-3

1.1.1 Commands. . . . .
1.1.2 Command Qualifiers

. 1-3

1.2 Accessing the System .

Logging In . . . . . .
Logging Out . . . . . .
Changing Your Password
Declaring Your Terminal Type
Logging In to Other Network Nodes.

. 1-4
. 1-4
. . 1-5
. 1-5
. 1-6

1.3 Using DCL . . . . . . . . . . . . . . . .

. 1-7

1.2.1
1.2.2
1.2.3
1.2.4
1.2.5

1.3.1 Rules for Entering and Editing DCL Commands .
1.3.2 Rules for Defining DCL Symbols

. 1-7
. 1-8

1.4 Getting HELP From VAXNMS . . . . .
1.5 Working with Files . . . . . . . . . .

. 1-9
1-10

1.5.1 File Specifications . . . . . . .

1-10

1.5.1.1
1.5 .1.2
1.5.1.3
1.5.1.4

File Specification Defaults
Wild card Characters . . .
Directories and Subdirectories.
Logical Names ..

1-21

1.5.2 File-Handling Commands .
1.5.2.1
1.5 .2 .2
1.5 .2 .3
1.5 .2 .4
1.5 .2 .5
1.5.2.6
1.5.2.7

1-13
1-14
1-14
1-17

Moving Files . . .
Deleting Files . . .
Listing File Na mes .
Renaming Files . . . . . .
Handling File Protections .
Searching File Contents. .
Printing and Typing Files. .

iii

1-22
1-23
1-24
1-25
1-25
1-26
1-26

1.6 Using Command Procedures. . . . . . . . .
1.6.1 Using Symbols . . . . . . . . . . . .
1.6.2 Assigning Character Values to Symbols
1.6.3 Assigning Numeric Values to Symbols.
1.6.4 Symbol Substitution . . . . . . . . .
1.6.5 Passing Param~ters to Command Procedures.
1.6.6 Passing .Fixed Data to Programs . . . . . . . .
1.6.7 Controlling Command Procedure Input/Output.
1.6.8 Controlling Command Procedure Execution Flow.
1.6.9 Handling Command Procedure Errors . . . . . .
1.6.10 Submitting Command Procedures in Batch Mode.
1.6.11 Login Command File . . . . . . . . .

Chapter 2 Creating and Modifying Programs
2.1 Introduction to EDT . . . . . . . . .

1-27
1-28
1-29
1-29
1-31
1-32
1-33
1-34
1-35
1-36
1-37
1-38

. Page
. 2-1

2.1.1 The Help Facilities. . . . . . . . . .
2.1.2 Invoking and Terminating EDT . . .
2.1.2.1 Invoking EDT . . . . . . .
2.1.2.2 Terminating an EDT Session

. 2-2
. 2-3
. 2-3
. 2-4

2.1.3 Entering and Exiting Editing Modes.
2.1.4 Protecting and Recovering Text .
2.1.5 Creating a New File . .

. 2-5
. 2-5
. . 2-6
. . 2-6

2.2 Character Mode Editing. . . .
2.2.1
2.2.2
2.2.3
2.2.4

. . 2-7
2-10
2-10
2-11

Maneuvering the Cursor
Inserting New Text . . .
Deleting and Undeleting Text . .
Moving Text . . . . . . . . .

2-12

2.3 Line Mode Editing . . . . . . . . .
2.3.1 Line Editing Command Summary.
2.3.2 Specifying Line Ranges . .
2.3.3 Displaying Lines of Text . .
2.3.4 Maneuvering in a File . . .
2.3.5 Inserting New Text . . . . .
2.3.6 Deleting and Replacing Text
2.3.7 Moving Text . . . . . . : .
2.3.8 Substituting Text. . . . . . . .
2.3.9 Input From and Output To Files
2.3.10 Editing a File From Another Directory .

2-12
2-14
2,.-17
2-18
2-18
2-19
2,.-20
2-20
2-21
2-22

2.4 EDT Aids for the Programmer. . . . .

2-23

2.4.1 Structured Tabs . . . . . . . .
2.4.2 Special-Purpose Key Definitions.
2.4.3 Startup Command Files . . . .

2-23'
2-24
2-25

Chapter 3 Compiling FORTRAN Programs

. Page
. . 3-1

3.1 Functions of the Compiler.
3.2 The FORTRAN Command . . . . . . . .

. 3-2

. 3-2
. 3-3
. . 3-4

3.2.1 Specifying Input Files . . . . . . . .
3.2.2 Specifying Output Files. . . . . . . .
3.2.3 Qualifiers to the FORTRAN Command

. . 3-6
. 3-7
. . 3-7
. . 3-8
. . 3-9
. 3-9
. 3-9
3-10
3-10
3-11
3-11
3-11
3-12
3-12
3-12
3-13
3-14
3-15

3.2.3.1 /CHECK Qualifier . . . . . . .
3.2.3.2 /CONTINUATIONS Qualifier. . .
3.2.3.3 /CROSS_REFERENCE Qualifier.
3.2.3.4 /DEBUG Qualifier . . . . . . .
3.2.3.5 /D-1..INES Qualifier . . . . . .
3.2.3.6 /DML Qualifier. . . . . . . . .
3.2.3.7 /EXTEND-80URCE Qualifier.
3.2.3.8 /F77 Qualifier . . . . . .
3.2.3.9 /G_FLOATING Qualifier . . . .
3.2.3.10 /14 Qualifier. . . . . . . . . .
3.2.3.11 /LIBRARY Qualifier . . . . . .
3.2.3.12 /LIST Qualifier . . . . . . . .
3.2.3.13 /MACHINE_CODE Qualifier .
3.2.3.14 /OBJECT Qualifier . .
3.2.3.15 /OPTIMIZE Qualifier .
3.2.3.16 /SHOW Qualifier . . .
3.2.3.17 /STANDARD Qualifier
3.2.3.18 /WARNINGS Qualifier

3-15

3.3 Using Text Libraries . . . . . . . . .
3.3.1
3.3.2
3.3.3
3.3.4

Using the LIBRARY Commands.
Naming Text Modules . . . . . . . . . .
.
Specifying Library Files on the FORTRAN Command Line.
Search Order of Libraries . . . . . : ..
3.3.4.1 User-Supplied Default Libraries . .
.
3.3.4.2 System-Supplied Default Library . . .

3-17
3-17
3-18
3-18
3-18
3-19

3.4 Using the VAX Common Data Dictionary . . . . . .

3-19

3.4.1 Accessing the CDD from FORTRAN Programs.
3.4.2 Creating CDD Structure Declarations ..
3.4.3 FORTRAN and CDDL Data Types

3-21
3-22
3-22

3.5 Compilation Control Statements.

3-24

3.5.1 INCLUDE Statement. . .
3.5.2 OPTIONS Statement. . .
3.5.3 DICTIONARY Statement.

3-24
3-26
3-27

3.6 Compiler Diagnostic Messages and Error Conditions
3.7 Compiler Output Listing Format

3-28
3-28

Source Code Section . . . . .
Machine Code Section . . . .
Storage Map Section . . . . .
Compilation Summary Section

3-28
3-29
3-32
3-35

3.7.1
3.7.2
3.7.3
3. 7.4

Chapter 4 Linking and Running FORTRAN Programs .

. . Page
. 4-1

4.1 Linking FORTRAN Programs.
4.1.1 Functions of the Linker.
4.1.2 The LINK Command . .

.·

. 4-1
. 4-2

4.1.2.1 Linker Output File Qualifiers . . . . . . .
4.1.2.2 /DEBUG and /TRACEBACK Qualifiers .
4.1.2.3 Linker Input File Qualifiers.

. . . . 4-3
. 4-5
. 4-5

4.1.3 Linker Messages . . . .

. 4-6

4.2 Running FORTRAN Programs.

. . . . 4-6

4.2.1
4.2.2
4.2.3
4.2.4

The RUN Command . .
.
System Processing at Image Exit
Interrupting a Program . . . . . . . . . . . .
Returning Status Values to the Command Interpreter

. . 4-6
. . 4-7
. 4-7

4.3 Finding and Correcting Run-Time Errors . . . . . .

.. 4-8
.. 4-8

4.3.1 Effects of Error-Related Command Qualifiers

. . . . 4-9

Chapter 5 Introduction to VAX FnRTRAN . . . . . .

Page

5.1 VAX FORTRAN Language Definition . . . . . . .
5.2 ELEMENTS OF FORTRAN SOURCE PROGRAMS.

. 5-1
. 5-2

5.2.1 Program Units . . . . . . . . . . . . . . . .
5.2.2 Statements. . . . . . . . . . . . . . . . . .

. . 5-2
. . . . 5-2

5.2.2.1 Order of Statements in a Program Unit .

. 5-2

5.2.3 Symbolic Names . .
5.2.4 Comments . . . . . . . . . . . . . . . .

. 5-4
. 5-5

5.3 FORTRAN Character Set . . . . . . . . . . . .
5.4 Format Requirements of FORTRAN Source Code

. . . 5-6
. 5-7

5.4.1 Fixed-Format Lines. . . . .
5.4.2 Tab-Format Lines . . . . .
5.4.3 Statement Label Field . . .

. . . . 5-7
. . . 5-9
5-10

5.4.3.1 Comment Indicator.
5.4.3.2 Debugging Statement Indicator .
5.4.4 Continuation Indicator Field
5.4.5 Statement Field . . . .
5.4.6 Sequence Number Field . . .

5-10
5-10
5-11
5-11
5-11

Chapter 6 Data Types, Data Items, and Expressions
6.1 Data Types . . . . . . . . . . . . . . .
6.1.1 Storage Requirements. . . . . . .
6.1.2 VAX Implementations of REAL*8 . .

Page
. . 6-1
. . . . . . . . . 6-2
. 6-3

6.2 Data Items . . . . . . . . . . .

. 6-4

6.2.1 Constants . . . . . . . .

. 6-4

6.2.1.1
6.2.1.2
6.2.1.3
6.2.1.4
6.2.1.5
6.2.1.6
6.2.1.7

Integer Constants.
Real Constants . .
Complex Constants .
Octal and Hexadecimal Constants.
Logical Constants. .
Character Constants . . . . . . .
Hollerith Constants. . . . . . . . .

. 6-5
. 6-5
. 6-9
6-11
6-13
6-13
6-14

6.2.2 Variables. . . . . . . . . . . . . .

6-15

6.2.2.1 Data Type by Specification .
6.2.2.2 Data Type by Implication . .

6-16
6-17
6-17

6.2.3 Arrays . . . . . . . . . . .
6.2.3.1
6.2.3.2
6.2.3.3
6.2.3.4
6.2.3.5
6.2.3.6
6.2.3.7

6-18
6-19
6-19
6-21
6-21
6-21
6-21

Array Declarators. . . . . .
Array Subscripts . . . . . .
Arrangement of Array Elements in Storage.
Data Type of an Array . . . . . . . .
Array References Without Subscripts
Adjustable Arrays . . .
Assumed-Size Arrays . .

6-22
6-23

6.2.4 Character Substrings . . . . .. .
6.2.5 Records . . . . . . . . . . .
I

6.2.5.1 Overview of Records and Structures .
6.2.5.2 Arrangement of Records in Storage
6.2.5.3 Record and Field References . .
6.2.6 Terminology Used to Refer to Data Items

. ....

6-23
6-24
6-30
6-31
6-33

6.3 Expressions. . . . . . . . . . . .
6.3.1 Arithmetic Expressions . . .
6.3.1.1 Use of Parentheses .
6.3.1.2 Data Type of an Arithmetic Expression

6-33
6-34
6-35

6.3.2 Character Expressions . . .
6.3.3 Relational Expressions . . .
6.3.4 Logical Expressions. . . . .

6-37
6-38
6-39

Chapter 7 Assignment Statements .

Page
. . 7-1
. 7-3
. 7-4
. 7-5
. . 7-6

7.1
7.2
7.3
7.4
7.5

Arithmetic Assignment Statement.
Logical Assignment Statement. . .
Character Assignment Statement
Aggregate Assignment Statement .
ASSIGN Statement. . . . . . . .

Chapter 8 Specification Statements
8.1
8.2
8.3
8.4

BLOCK DATA Statement . . . .
COMMON Statement . . . . . .
DATA Statement . . . . . . . . .
Data Type Declaration Statements

Page
. 8-2
. . 8-3
. 8-4
. . 8-7

8.4.1 Numeric Type Declaration Statements.
8.4.2 Character Type Declaration Statements .

. . 8-7
. 8-8
. 8-9
8-10

8.5 DIMENSION Statement . . . . . .
8.6 EQUIVALEN CE Statement. . . . .
8.6.1 Making Arrays Equivalent . .
8.6.2 Making Substrings Equivalent . . .
. . .
8.6.3 EQUIVALENCE and COMMON Interaction. .

vii

8-11
8-13
8-16

8. 7 EXTERNAL Statement.
8.8 IMPLICIT Statement . .
8.9 INTRINSIC Statement .
8.10 NAMELIST Statement .
8.11 PARAMETER Statement
8.12 PROGRAM Statement. .
8.13 RECORD Statement. . .
8.14 SAVE Statement . . . . .
8.15 Structure Declaration Block

8-16
8-17
8-18
8-20
8-21
8-23
8-23
8-24
8-25

8.15.1 Structure Declaration.
.
8.15.2 Substructure Declarations.
8.15.3 Union Declarations.

8-26
8-31
8-31

8.16 VOLATILE Statement. . . . .

8-34

Chapter 9 CONTROL Statements .

Page

9.1 CALL Statement . . . . . . .
9.2 CONTINUE Statement. .
9.3 DO Statement . . . . . .

. 9-2
. 9-3
. 9-3

9.3.1 Indexed DO Statement .

. 9-3

9.3.1.1
9.3.1.2
9.3.1.3
9.3.1.4

DO Iteration Control .
Nested DO Loops. . .
.
Control Transfers in DO Loops
Extended Range

. 9-4
. 9-6
. 9-7
. 9-7

9.3.2 DO WHILE Statement .

. 9-9

9.4 END DO Statement . . . . .
9.5 END Statement . . . . . . .
9.6 GO TO Statements . . . . . .

. 9-9
9-10
9-10

9.6.1 Unconditional GO TO Statement . .
9.6.2 Computed GO TO Statement .
9.6.3 Assigned GO TO Statement.

9-10
9-11
9-12

9.7 IF Statements . . . . . . . . .

9-12

9.7.1 Arithmetic IF Statement
9.7.2 Logical IF Statement . .
9.7.3 Block IF Statements . .

9-13
9-13
9-14

9.7.3.1 Statement Blocks.
9.7 .3.2 Block IF Examples .
9.7.3.3 Nested Block IF Constructs .

9-17
9-17
9-19

9.8 PAUSE Statement .

.
9.9 RETURN Statement . . . . . . . . . . .
9.10 STOP Statement . . . . . . . . . . . .

9-20
9-21
9-23

Chapter 1O Subroutines and Functions - Subprograms

Page

10.1 Subprogram Arguments . . . . . . . . . . . . . . . .

10-2

10.1.1 Actual Argument and Dummy Argument Association.

10-2

10.1.1.1 Adjustable Arrays. . .
10.1.1.2 Assumed-Size Arrays .

10-3
10-4

viii

10.1.1.3 Passed-Length Character Arguments. . . . . . . . . .
10.1.1.4 Character and Hollerith Constants as Actual Arguments
10.1.1.5 Alternate Return Arguments. . . . .

10-5
10-6
10-6

10.1.2 Built-In Functions . . . . . . . . .

10-7

10.1.2.1 Argument List Built-In Functions .
10.1.2.2 %LOC Built-In Function

10-7
10-8

10.2 User-Written Subprograms .

10-9

10.2.1 Statement Functions . . .
10.2.2 Function Subprograms . .

10-9
. 10-11

10.2.2.1 Logical and Numeric Functions .
10 .2 .2 .2 Character Functions . . . . .
10.2.2.3 Function Reference . . . . . . .

. 10-12
. 10-12
. 10-13

10.2.3 Subroutine Subprograms - SUBROUTINE Statement . .
10.2.4 ENTRY Statement . . . . . . . . . . . . .

. 10-14
. 10-16

10.2.4.1 ENTRY in Function Subprograms .
10.2.4.2 ENTRY in Subroutine Subprograms .

. 10-17
. 10-18
. 10-19

10.3 FORTRAN Intrinsic Functions . . . .

Intrinsic Function References .
Generic Function .References .
Intrinsic and Generic Function Usage
Character and Lexical Comparison Library Functions

. 10-19
. 10-20
. 10-22
. 10-24

10.3.4.1 Character Functions. . . . . .
10.3.4.2 Lexical Comparison Functions .

. 10~24
. 10-26

Chapter 11 VAX FORTRAN Input/Output . . . . .
11.1 Overview of VAX FORTRAN I/0 . . . . . . .

Page
11-1

Identifying Logical Input/Output Units
Types of I/0 Statements . . .
Interprocess Communication
Forms of I/0 Statements .

11-2
11-2
11-3
11-3

10.3.1
10.3.2
10.3.3
10.3.4

11.1.1
11.1.2
11.1.3
11.1.4

11-4

11.2 Elements of I/0 Processing. . . . . .
11.2.1 File Specifications . . . . . . . . .
11.2.2 Logical Names and Logical Unit Numbers.
11.2.2.1
11.2.2.2
11.2.2.3
11.2.2.4

FORTRAN Logical Names. . . .
Implied FORTRAN Logical Unit Numbers .
File Specification in the OPEN Statement .
Assigning Files to Logical Units-Summary.

11.2.3 File Organizations, I/O Record Formats, and Access Modes.
11.2.3.1
11.2.3.2
11.2.3.3
11.2 .3 .4

11-4
11-5
11-6
11-7
11-8
11-9
. 11-10
. 11-10
. 11-11
. 11-12
. 11-14

File Organizations . .
Internal Files . . ..
I/0 Record Formats .
Record Access Modes

. 11-16

11.3 Components of 1/0 Statements .

. 11-16

11.3.1 Control List
11.3.1.1 Logical Unit Specifier .
11.3.1.2 Internal File Specifier .
11.3.1.3 Format Specifiers .
11.3.1.4 Namelist Specifier.
11.3.1.5 Record Specifier .
11.3.1.6 Key-Field-Value Specifier
11.3.1.7 Key-of-Reference Specifier .
11.3.1.8 1/0 Status Specifier .
11.3.1.9 Transfer-of-Control Specifiers
11.3.1.10 Rules for Specifying Control List Parameters-Summary .

. 11-23

11.3.2 1/0 List
11.3.2.1 Simple List Elements .
11.3.2.2 Implied-DO Lists in 1/0 Statements

. 11-26

11.4.1 Sequential READ Statements .

Formatted Sequential READ Statement
List-Directed Sequential READ Statement .
Namelist-Directed Sequential READ Statement.
Unformatted Sequential READ Statement

. 11-27
. 11-28
. 11-30
. 11-34
. 11-35

11.4.2 Direct Access READ Statements
11.4.2.1 Formatted Direct Access READ Statement .
11.4.2.2 Unformatted Direct Access READ Statement .
11.4.3 Indexed READ Statements .

. 11-23
. 11-24
. 11-26

11.4 READ Statements .
11.4.1.1
11.4.1.2
11.4.1.3
11.4.1.4

. 11-17
. 11-17
. 11-17
. 11-18
. 11-19
. 11-19
. 11-20
. 11-21
. 11-21
. 11-22

. 11-36
. 11-36
. 11-37

11.4.3.1 Formatted Indexed READ Statement.
11.4.3.2 Unformatted Indexed READ Statement.

. 11-38
. 11-38
. 11-39

11.4.4 Internal READ Statement
11.4.4.1 Formatted Internal READ Statement.
11.4.4.2 List-Directed Internal READ Statement

. 11-40
. 11-40

. 11-41

11.5.1 Sequential WRITE Statements . .

. 11-41

11.5 WRITE Statements
11.5.1.1
11.5.1.2
11.5.1.3
11.5.1.4

Formatted Sequential WRITE Statement .
List-Directed Sequential WRITE Statement
Namelist-Directed Sequential WRITE Statement .
Unformatted Sequential WRITE Statement.

. 11-46

11.5.2 Direct Access WRITE Statements .
11.5.2.1 Formatted Direct Access WRITE Statement
11.5.2.2 Unformatted Direct Access WRITE Statement
11.5.3 Indexed WRITE Statements

. 11-42
. 11-43
. 11-44
. 11-45

. 11-47
. 11-47
. 11-47

11.5.3.1 Formatted Indexed WRITE Statement .
11.5.3.2 Unformatted Indexed WRITE Statement .

. 11-48
. 11-49

11.5.4 Internal WRITE Statement . . . . . . . . . . . .
11.5.4.1 Formatted Internal WRITE Statement . . .
11.5.4.2 List-Directed Internal WRITE Statement . .

. 11-49
. 11-50
. 11-50

11.6 REWRITE Statement . . . . . . . . . . . .

. 11-50

11.6.1 Formatted REWRITE Statement . . .
11.6.2 Unformatted REWRITE Statement . .

. 11-51
. 11-51

11.7 ACCEPT Statement . . . . . .
11.8 TYPE and PRINT Statements.

. 11-52
. 11-53

Chapter 12 Format Statements. .

Page
. . . 12-1
. 12-3

12.1 Syntax of Format Statement .
12.2 Field and Edit Descriptors . . .
12.2.1 Repeat Counts and Group Repeat Counts
12.2.2 Variable Format Expressions
12.2.3 Blank Control Editing . . .

. 12-3
. 12-4
. 12-5

12.2.3.1 BN Edit Descriptor
12.2.3.2 BZ Edit Descriptor

. 12-5
. 12-5

12.2.4 Sign Control Editing . . . .

. 12-6

12.2.4.1 SP Edit Descriptor
12.2.4.2 SS Edit Descriptor
12.2.4.3 S Edit Descriptor .

. 12-6
. 12-6
. 12-6

12.2.5 Integer Editing. . . . . . .

. . . 12-6

12.2.5.1 I Field Descriptor .
12.2.5.2 0 Field Descriptor. .
12.2.5.3 Z Field Descriptor.

. 12-6
. 12-8
. 12-9

12.2.6 Real Editing . . . . . . . .
12.2.6.1
12.2.6.2
12.2.6.3
12.2.6.4
12.2.6.5

. 12-10

F Field Descriptor . .
E Field Descriptor.
D Field Descriptor.
G Field Descriptor.
Complex Data Editing . .

12.2.7 Scale Factor Editing - P Edit Descriptor .
12.2.8 Logical Editing - L Edit Descriptor
12.2.9 Character Editing . . . . .

. 12-10
. 12-11
. 12-13
. 12-13
. 12-15
. 12-16
. 12-18
. 12-18

12.2.9.1 A Field Descriptor. .
12.2.9.2 H Field Descriptor. .
12.2.9.3 Character Constants.

. 12-18
. 12-20
. 12-20

12.2.10 Default Field Descriptors ..
12.2.11 Positional Editing . . . . ..

. . 12-21
•" 12-22

X Edit Descriptor .
T Edit Descriptor .
TL Edit Descriptor
TR Edit Descriptor

. 12-22
. 12-22
. 12-23
. 12-23

12.2.11.1
12.2.11.2
12.2.11.3
12.2.11.4

12.3
12.4
12.5
12.6
12.7
12.8

12.2.12 Miscellaneous Editing Operations

. 12-24

12.2.12.1 Q Edit Descriptor .
12.2.12.2 Dollar Sign Descriptor.
12.2.12.3 Colon Descriptor

. 12-24
. 12-24
. 12-25

Carriage Control.
. ...
Format Specification Separators
External Field Separators
Run-Time Format .
Format Control Interaction With I/0 Lists
Summary of Rules for Format Statements

. 12-25
. 12-26
. 12-27
. 12-27
. 12-28
. 12-29

12.8.1 General Rules
12.8.2 Input Rules
12.8.3 Output Rules.

. 12-31
. 12-32
. 12~32

. .

Chapter 13 Auxiliary lnpuVOutput Statements
13.1 OPEN Statement .
13.1.1 ACCESS Keyword .
. .
13.1.2 ASSOCIATEVARIABLE Keyword.
13.1.3 BLANK Keyword
13.1.4 BLOCKSIZE Keyword .
13.1.5 BUFFERCOUNT Keyword .
13.1.6 CARRIAGECONTROL Keyword
13.1.7 DEFAULTFILE Keyword.
13.1.8 DISPOSE Keyword. . .
13.1.9 ERR Keyword .
13.1.10 EXTENDSIZE Keyword.
13.1.11 FILE Keyword
13.1.12 FORM Keyword.
13.1.13 INITIALSIZE Keyword
13.1.14 IOSTAT Keyword.
13.1.15 KEY Keyword . . .
13.1.16 MAXREC Keyword.
13.1.17 NAME Keyword
13.1.18 NOSPANBLOCKS Keyword.
13.1.19 ORGANIZATION Keyword ..
13.1.20 READONLY Keyword.
13.1.21 RECL Keyword .
13.1.22 RECORDSIZE Keyword.
13.1.23 RECORDTYPE Keyword
13.1.24 SHARED Keyword
13.1.25 STATUS Keyword
13.1.26 TYPE Keyword .
. .
13.1.27 UNIT Keyword .. .. .
p.1.28 USEROPEN Keyword.
13.2 CLOSE Statement. ~ . .
13.3 INQUffiE Statement., .
13.3.1
13.3.2
13.3.3
13".3'.4

Page
13-1
13-6
13-6
13-6
13-7
13-7
13-8
13-8
13-9
13-9
. 13-10
. 13-10
. 13-10
. 13-11
. 13-11
. 13-12
. 13-13
. 13-13
. 13-13
. 13-13
. 13-14
. 13-14
. 13-15
. 13-15
. 13-16
. 13~16
. 13-17
. 13-17
. 13-17
. 13-18
. 13-19

ACCESS Specifier .
BLANK Specifier.
CARRIAGECONTROL Specifier
DIRECT Specifier
. . .

. 13-20
. 13-20
. 13-20
. 13-21

xii

13.4
13.5
13.6
13.7
13.8

13.3.5 ERR Specifier . . . . . .
13.3.6 EXIST Specifier . . . .
13.3.7 FORM Specifier . . . .
13.3.8 FORMATTED Specifier
13.3.9 IOSTAT Specifier . .
13.3.10 KEYED Specifier . .
13.3.11 NAME Specifier. . .
13.3.12 NAMED Specifier. .
13.3.13 NEXTREC Specifier
13.3.14 NUMBER Specifier .
13.3.15 OPENED Specifier .
13.3.16 ORGANIZATION Specifier
13.3.17 RECL Specifier . . . . . .
13.3.18 RECORDTYPE Specifier .
13.3.19 SEQUENTIAL Specifier . .
13.3.20 UNFORMATTED Specifier

. 13-21
. 13-21
. 13-22
. 13-22
. 13-22
. 13-22
. 13-23
. 13-23
. 13-24
. 13-24
. 13-24
. 13-24
. 13-25
. 13-25
. 13-25
. 13-26

REWIND Statement. . .
BACKSPACE Statement.
ENDFILE Statement
DELETE Statement . . .
UNLOCK Statement . .

. 13-26
. 13-27
. 13-27
. 13-28
. 13-30

Chapter 14 Using Structures and Records
14.1 Structures. . .
14.2 Records . . . .
14.3 Uses of Records

Page
14-2
14-3
14-3

Chapter 15 Using Indexed Files
15 .1 Creating an Indexed File . . .
15.2 Writing Indexed Files . . . .

15.3
15.4
15.5
15.6
15.7

15-2
15-3

15.2.1 Duplicate Values in Key Fields .
15.2.2 Preventing the Indexing of Alternate Key Fields .

15-3
15-4

Reading Indexed Files . . . . . . . . . .
Updating Records . . . . . . . . . . . .
Deleting Records. . . . . . . . . . . . .
Current Record and Next Record Pointers.
Exception Conditions . . . . .

15-5
15-6
15-7
15-7
15-7

Chapter 16 Using Character Data
16.1
16.2
16.3
16.4
16.5
16.6
16.7

Page
16-1
16-2
16-2
16-3
16-4
16-4
16-5

Character Substrings. . . . .
Building Character Strings . . .
Character Constants . . . . . .
Declaring Character Data . . .
Initializing Character Variables.
Passed-Length Character Arguments
Character Library Functions .
16.7.1
16.7.2
16.7.3
16.7.4
16.7.5

CHAR Function .
.
!CHAR Function . . .
INDEX Function . . .
LEN Function . . . . . . . . . .
LGE, LGT, LLE, LLT Functions .
xiii

16-5
16-6
16-6
16-6
16-7

16.8 Character Data Examples . . . . . . . . . . .
16.9 Character I/0 . . . . . . . . . . . . . . . . .

16-7
16-7

Chapter 17 Debugging VAX FORTRAN Programs.

. Page
17-2
17-2
17-3

17.1 Debugging Overview. . . . . . . . . . . . . .
. ...
17.2 Preparing a Program for Debugging-Compiling and Linking.
17.3 Invoking and Terminating the Debugger . . . . . . . . . .
17.3.1
17 .3.2
17.3.3
17 .3.4
17 .3.5

Invoking the Debugger with the RUN Command . .
Invoking the Debugger During Program Execution .
Suspending the Debugger to Issue DCL Commands
Interrupting the Debugger . . .
Terminating a Debugger Session

17-3
17-4
17-4
17-5
17-5

17.4 The Debugger Environment . .

17-5

17.4.1 Using Debugger HELP .
17.4.2 Entering Commands . .

17-5
17-6

17.4.2.1 Normal Keyboard Entry.
17.4.2.2 Keypad Entry. . . . . .
17.4.3
17.4.4
17.4.5
17.4.6
17.4.7

User-Defined Keypad Command Keys.
Using Debugger Command Procedures.
Initializing a Debugging Session. . . .
Recording Debug Sessions in Log Files.
Debugger Command Syntax and Summary

17-6
17-6
17-7
17-8
17-9
17-9
. 17-10

17 .5 Controlling Program Execution . . .

. 17-17

17.5.1 Starting Program Execution.

. 17-17

17.5.1.1
17.5.1.2
17.5.1.3
17.5.1.4

GO Command . .
STEP Command .
CALL Command . .
SHOW CALLS Command .

17 .5.2 Suspending or Tracing Program Execution. .

. 17-17
. 17-18
. 17-19
. 17-19
. 17-20

17.5.2.1 Breakpoints and Tracepoints.
17.5.2.2 Watchpoints . . . . . . . . . .

. 17-20
. 17-23

17 .5.3 Displaying Source Lines . . . . . . . . .
17 .5.4 Using the Debugger's Logical Control Commands

. 17-23
. 17-25

17 .6 Using Symbolic Names and Accessing Program Locations

. 17-25

17 .6.1 Making Symbolic Names Accessible - SET MODULE
17 .6.2 Referencing Locations in a Program . . . . . . .

. 17-26
. 17-28

17 .6.2.1 Specifying Data Addresses . . . . . . .
17.6.2.2 Current, Previous, and Next Locations .
17 .6.2.3 Specifying Program Addresses . . . . .

. 17-28
. 17-28
. 17-29

17 .6.3 Making Symbolic References Unique - Prefixes and Scope.

. 17-29

17.6.3.1 Pathname Prefix . . . .
17 .6.3.2 SET SCOPE Command . . . . . . . . . .

. 17-30
. 17-31

17 .6.4 Defining Addresses Symbolically . . . . . . . . . .
17 .6.5 Displaying Symbol Information - SHOW SYMBOL.

. 17-31
. 17-31

xiv

17.7 Examining and Manipulating Data . . . .
17.7.1
i7.7.2
17.7.3
17.7.4
17.7 .5
17.7.6
17.7.7

. 17-32

Hints about the Use of Expressions
Displaying Values - EXAMINE .
Calculating Values - EVALUATE
Assigning Values - DEPOSIT ..
Specifying Data Type. . . . . . .
Specifying Radix . . . . . . . . . . . . .
Using Numeric Data Types in Expressions.

. 17-33
. 17-34
. 17-35
. 17-35
. 17-35
. 17-36
. 17-37

17.8 Using Screen Displays . . . . . . . . . . . . . .

. 17-38

17 .8.1 Invoking and Terminating Screen Mode .
17 .8.2 Defining Windows . . . . . . . .
17 .8.3 Manipulating Displays . . . . . .
17.8.3.1
17 .8.3.2
17.8.3.3
17 .8.3.4

Scrolling Screen Displays
Creating Screen Displays
Accessing Displays . . . . . .
Removing Screen Displays .

17 .9 Sample Debugging Sessions . . . . . . . .
17.9.1 Debugging a FORTRAN Program Unit . . . . . . .
17.9.2 Debugging a FORTRAN Program with Subprograms.

Chapter 18 Error Processing. . . . . . . . .
18.1 Run-Time Library Default Error Processing . .
18.2 Using the ERR and END Specifiers. . . .
18.3 Using the IOSTAT Specifier . . . . . . .

Appendix A Additional Language Elements
A.1
A.2
A.3
A.4
A.5
A.6

The ENCODE and DECODE Statements .
DEFINE FILE Statement . . . . .
FIND Statement . . . . . . . . . . . . .
PARAMETER Statement. . . . . . . . . . .
Octal Notation for Integer Constants . . . . '\ . . .
/NOF77 Interpretation of the EXTERNAL Statement

Appendix B Character Sets

Appendix C FORTRAN Data Representation
LOGICAL*l (Byte) Representation
INTEGER*2 Representation .
INTEGER*4 Representation ..
Floating-Point Representations
C.4.1
C.4.2
C.4.3
C.4.4
C.4.5

. 17-41
. 17-41
. 17-43
. 17-43
. 17-43
. 17-43
. 17-46
Page
18-1
18-6
18-6
Page
.A-1
.A-3
.A-4
.A-5
.A-6
.A-6
. Page
.B-1
.B-2
.B-3

B.1 FORTRAN Character Set.
B.2 ASCII Character Set . . .
B.3 Radix-50 Constants and Character Set

C.1
C.2
C.3
C.4

. 17-39
. 17-40
. 17-41

Page
. C-1
. C-1
. . C-2
. C-2
. C-2
. C-3
.C-4
. C-4
. C-6

REAL*4 (F_floating) .
REAL*8 (D_floating) . .
REAL*8 (G_floating) .
REAL*l6 (H_floating) .
COMPLEX*8 (F_floating)

C.4.6 COMPLEX*16 (D_floating) .
C.4.7 COMPLEX*l6 (G_floating) .

. C-6
. C-7

C .5 Logical Representation . .
C.6 Character Representation . . . . . . .
C.7 Hollerith Representation . . . . . .

.C-8
C-10
C-10

Appendix D FORTRAN Language Summary . .

Page
.D-1
.D-2
D-30
D-38

D.1
D .2
D .3
D .4

Expression Operators . . . . .
Statements . . . . . . . . .
LIBRARY Functions . . . . ..
System Subroutine Summary .
D.4.1
D.4.2
D.4.3
D.4.4
D.4.5
D.4.6
D.4.7
D.4.8

DATE Subroutine. .
IDATE Subroutine .
ERRSNS Subroutine
EXIT Subroutine . .
SECNDS Subroutine
TIME Subroutine . .
RAN Subroutine . .
MVBITS Subroutine

D-39
D-39
D-40
D-40
D-41
. D-41
D-42
D-42

D .5 Bit Functions . . . . . . .

D-43

D.5.1 Bit Position. . . . .
D.5.2 Bit Function Arguments.

D-43
D-43

Appendix E Diagnostic Messages

Page
.E-1

E.1 Diagnostic Messages From the Compiler.
E.1.1 Source Program Diagnostic Messages.
E.1.2 Compiler-Fatal Diagnostic Messages
E.1.3 Compiler Limits . . . . . . . . . . .

. E-1
E-26
E-27

E.2 Run-Time Diagnostic Messages . . . . . . .

E-28

E.2.1 Run-Time Library Diagnostic Message Presentation.
E.2.2 Run-Time Library Diagnostic Messages.

E-28
E-29

E.3 Dictionary Error Messages

E-41

Figures . . . . . . . . . . . . .

Page
. 1-2
1-16
. 2-8
. 2-8
. 2-9
3-16
3-29
3-30
3-34
3-35
4-10
. 5-3
. 5-8
. 5-9

1-1
1-2
2-1
2-2
2-3
3-1
3-2
3-3
3-4
3-5
4-1
5-1
5-2
5-3

Program Development Process
A Directory Hierarchy
VT52 Keypad . . . . . . . .
VTlOO Keypad . . . . . . . .
VT200 Keypad . . . . . . . .
Creating and Using a Text Library
Sample Listing of Source Code .
Sample Listing of Machine Code .
Sample Storage Map Section . . .
Sample Compilation Summary . .
Sample FORTRAN Program and Traceback.
Required Order of Statements and Lines.
FORTRAN Coding Form .
Line Formatting Example . . . . . . . .

xvi

6-1 Array Storage . . . . . . . . . . . . . . . . . . .
8-1 Equivalence of Array Storage . . . . . . . . . . . .
8-2 Equivalence of Arrays with Nonunity Lower Bounds .
8-3 Equivalence of Substrings. . . . . . ..
8-4 Equivalence of Character Arrays . . .
9-1 Nested DO Loops . . . . . . . . . .
9-2 Control Transfers and Extended Range
9-3 Examples of Block IF Constructs . . .
.
10-1 Multiple Functions in a Function Subprogram
10-2 Multiple Function Name Usage . . . .
12-1 Variable Format Expression Example .
16-1 Character Data Program Example . . .
16-2 Output Generated by Example Program
17-1 Default Keypad Definitions-VTlOO . .
17-2 Sample FORTRAN Program . . . . . .
17-3 Sample Debugging Session. . . . . . .
17-4 Sample FORTRAN Program with Subprograms.
17-5 Sample Multiunit Debugging Session . . . . .
E-1 Sample Diagnostic Messages (Listing Format).

Tables
1-1 Common File Types . . .
1-2 File Specification Defaults
1-3 Predefined System Logical Names.
1-4 Summary of Operators in Expressions .
1-5 Severity Codes . . . . . . . . . . . .
2-1 Summary of Line Editing Commands .
2-2 Single-Line Range Specifications . .
2-3 Multiple-Line Range Specifications .
3-1 FORTRAN Command Qualifiers . .
3-2 Commands to Control Library Files .
4-1 LINK Command Qualifiers . . . . . . .
4-2 /DEBUG and !TRACEBACK Qualifiers .
5-1 Entities Identified by Symbolic Names .
6-1 Data Type Storage Requirements . . . .
7-1 Conversion Rules for Assignment Statements
10-1 Argument List Built-In Functions and Defaults .
10-2 Types of User-Written Subprogram.
10-3 Generic Function Name Summary .
11-1 Available I/0 Statements . . . . .
11-2 Predefined System Logical Names .
11-3 Implicit FORTRAN Logical Units .
. .
11-4 Valid Combinations of Record Access Mode and File Organization .
11-5 List-Directed Output Formats . . . . . . . . . . .
12-1 Effect of Data Magnitude on G Format Conversions.
12-2 Default Field Descriptor Values . .
12-3 Carriage Control Characters . . . .
12-4 Summary of FORMAT Codes . . .
13-1 OPEN Statement Keyword Values.
13-2 Record Size (RECL) Limits . .
17-1 Summary of Debug Commands
17-2 Debugger Command Qualifiers.
17-3 Debugger Operators . . . . . .

xvii

6-20
8-12.
8-13
8-14
8-15
. 9-6
. 9-8
9-16
. 10-18
. 10-22
. 12-5
. 16-9
. 16-10
. 17-7
. 17-43
. 17-44
. 17-46
. 17-47
. E-3
Page
1-12

1-13
1-19
1-30
1-36
2-13
2-15
2-16
. 3-5
3-17
. 4-2
. 4-9
. 5-5
. 6-2
. 7-3
10-8
10-9
. 10-21
11-4
. 11-6
. 11-8
. 11-14
. 11-43
. 12-14
. 12-21
. 12-25
. 12-30
. 13-3
. 13-14
. 17-11
. 17-33
. 17-34

18-1 Summary of FORTRAN Run-Time Errors
B-1 ASCII Character Set. . . . .
D-1 Expression Operators. . . . . . . . .
D-2 VAX FORTRAN Statements . . . . .
D-3 Intrinsic Functions. . . . . . . . . .
E-1 Source Program Diagnostic Messages .
E-2 Compiler-Fatal Diagnostic Messages
E-3 Compiler Limits . . . . . . . .
E-4 Run-Time Diagnostic Messages . .
E-5 CRX Error Messages . . . . . . .

xviii

18-3
.B-2
. . D-1
.D-2
D-31
.E-4
. E-27
E-28
E-29
. E-41

Preface
Manual Objectives
The primary objective of this document is to present a complete description of the elements
of DIGITAL's VAX FORTRAN language and to explain how to create, compile, link,
execute, and debug FORTRAN programs on the VAXNMS operating system.
This manual is designed to serve as a reference document, not as a tutorial document.
Detailed information about how to optimize VAX FORTRAN programs and how to access
VAXNMS system services is provided, for advanced programmers, in the VAX FORTRAN
User's Guide.

Intended Audience
This manual is intended for programmers and students who have a basic understanding of
the FORTRAN language. It is not necessary for the reader to have a detailed understanding
of the VAXNMS operating system, but some familiarity with VAXNMS is helpful. For
detailed information concerning VAXNMS, refer to the documents listed under the heading "Associated Documents."

Structure of This Document
To promote ease of reference, this manual is divided into four major segments:
• Section I - Chapters 1 through 4
Provides general information about how to use the VAXNMS system; how to create a
source file; and how to compile, link, and run a program in a source file.
• Section II -

Chapters 5 through 13

Provides a complete specification of the VAX FORTRAN language.

xix

• Section III - Chapters 14 through 18
Provides application-oriented information about several important VAX FORTRAN
extensions to standard FORTRAN (that is, structures and records, indexed files, and
character data) and provides information on the VAXNMS Symbolic Debugger and
on error handling.
• Section IV - Appendixes A through E
Contains information on some additional statements and language features that provide compatible support for programs written in older versions of FORTRAN; summarizes the character sets supported by VAX FORTRAN; describes how VAX
FORTRAN data is represented in memory; summarizes the language elements and
intrinsic functions supported by VAX FORTRAN; and lists compilation and run-time
messages.

Associated Documents
The following documents may be of interest:
• Introduction to VAX/VMS
• VAX FORTRAN User's Guide
• Guide to Using DCL and Command Procedures on VAX/VMS
• VAX/VMS Run-Time Library' Routines Reference Manual
• VAX/VMS Symbolic Debugger Reference Manual
• VAX/VMS Linker Reference Manual
For a complete list of all VAX documents, including brief descriptions of each, see the
VAX/VMS Master Index.

Conventions Used in This Document
The following syntactic conventions are used in this manual:
• Uppercase words and letters used in examples indicate that you should type the word
or letter as shown.
• Lowercase words and letters used in syntax specifications indicate that you are to
substitute a word or value of your choice.
• Brackets ([ ]) indicate optional elements.
• Braces ({ }) are used to enclose lists from which one element is to be chosen.
• Ellipses ( ... ) indicate that the preceding item(s) can be repeated one or more times.

• "Real" (lowercase) is used to refer to the REAL*4 (REAL), REAL*8, and REAL*16
data types as a group; likewise, "complex" (lowercase) is used to refer to the
COMPLEX*8 (COMPLEX) and COMPLEX*l6 (DOUBLE COMPLEX) data types
as a group; "logical" (lowercase) is used to refer to the LOGICAL*2 and LOGICAL*4
data types as a group; and "integer" (lowercase) is used to refer to the INTEGER*2
and INTEGER*4 data types as a group.
• VAX FORTRAN extensions to the FORTRAN-77 standard are printed in blue.
In addition, the following notations are used to denote special nonprinting characters:
Tab character

<TAB>

Space character

xxi

Chapter 1

Using the VAX/VMS Operating System
The VAXNMS operating system and the Digital Command Language (DCL) provide
numerous tools and utilities for program development. This chapter summarizes what you
need to know to use a VAXNMS system. The following topics are discussed in this chapter:
• How to create and execute a FORTRAN program-an overview
• How to access a VAXNMS system
• How to enter DCL commands
• How to get help from VAXNMS
• How to handle files
• How to use command procedures
Whenever possible, the system information presented in this chapter is oriented toward
FORTRAN. A tutorial presentation of the system-specific information is provided in the
Introduction to VAX/VMS. The Guide to Using DCL and Command Procedures on
VAX/VMS gives detailed definitions of commands and file specifications.

1.1 VAX/VMS Commands for Program
Development-OVERVIEW
Figure 1-1 illustrates the development of a FORTRAN program from its inception to its
execution.

1-1

COMMANDS

INPUT/OUTPUT FILES

$EDIT AVERAGE.FOR
Use the file type of FOR to
indicate the file contains a

VAX FORTRAN
program.

----C-re-a-te_a_ __.
_ soU<ce pmgrnm

---~._ LJ
~

AVERAGE.FOR

$FORTRAN AVERAGE
The FORTRAN command
assumes the file type of an
input file is FOR.
(If you use the /LIST
qualifier, the compiler
creates a listing file.)

Comp;le the

'--s-ou-rce-pro-gra-m~ - - - - ~

AVERAGE.OBJ
(AVERAGE.LIS)
libraries

$LINK AVERAGE
The LINK command assumes
the file type of an input file
is OBJ.

Link the
object module

AVERAGE.EXE
(AVERAGE.MAP)

(If you use the IMAP qualifier,
the Iinker creates a map file.)

$RUN AVERAGE
The RUN command assumes
the file type of an image is
EXE.

Run the
executable
image
ZK-791-82

~igure 1-1:

Program Development Process

1.1.1 Commands
The steps shown in Figure 1-1 are performed when you enterthe following commands to the
VAX system:
$
$
$

EDIT file-spec
FORTRAN file-spec
LINK file-spec
RUN file-spec

(Note: File-spec is the file specification of the file to be processed.)
The EDIT command and the .EDT editor are described in detail in Chapter 2, the
FORTRAN command is described in Section 3.2, and the LINK and RUN commands are
described in Sections 4.1 and 4.2, respectively.
1~2

Using the VAXNMS Operating System

Qualifiers can be included with each command to define further system actions or to
modify the processing performed by the system.

1.1.2 Command Qualifiers
Qualifiers specify special actions to be performed. They can be used on the OPTIONS
statement and on FORTRAN, LINK, and RUN commands. Qualifiers have the following
form:
/qualifier

Many qualifiers have a corresponding negative form, /NOqualifier, which negates the specified action. For example, the /LIST qualifier specifies that the compiler is to produce a
listing file. The /NOLIST qualifier specifies that the compiler is not to produce a listing
file.
Some qualifiers accept values, allowing you to activate or deactivate a particular form of
processing. To specify a qualifier value, type the qualifier name followed by an equal sign
( =) and the value. For example:
/CHECK=BOUNOS

To specify a list of qualifier values, enclose the values in parentheses. For example:
/CHECK=CBOUNDS10VERFLOW>

Defaults have been established for each qualifier, based on the actions that are appropriate
in most cases. Sections 3.2.3 and 4.1.2, which describe the qualifiers for each command,
contain tables indicating the defaults.
You can specify qualifiers so that all files included in the command are affected, or only
certain files are affected. When the qualifier follows the command name immediately, it
applies to all files. For example, if you specify the following command, you receive listing
files for ABC, XYZ, and RST.
$FORTRAN/LIST ABC1XYZ1RST

If you include a qualifier as part of a file specification, in most cases it affects only the file
with which it is associated. For example, use of the /NOLIST qualifier in the following
command provides you with listing files for ABC and RST, but not for XYZ.
$FORTRAN/LIST ABC1XYZ/NOLIST1RST

Qualifiers included with file specifications that are part of a concatenated list of input files
are exceptions to this rule. See Example 5 in Section 3.2.2.

1.2 Accessing the System
In order to develop VAX FORTRAN programs, you must be able to log in and out of the
VAXNMS system. During the login process, the system determines whether your account
is valid and your password is correct. The logout process releases the system resources
assigned to you and protects your account.
Using the VAXNMS Operating System

1-3

Sections 1.2.1 through 1.2.5 describe the procedures you use to do the following:
• Log in and out
• Change your password
• Give the system information about the kind of terminal you have and its data transmission rate
• Connect your terminal to another network node, that is, another computer in a network that includes your computer

1.2.1 Logging In
Accessing a VAXNMS system from a terminal is very simple. Once you have turned on the
terminal, you alert the system to your presence by typing RETURN, <CTRL/C>, or
<CTRL/Y>. Then, VAXNMS issues the following prompt:
Userna111e:

You respond by typing in your account name and a RETURN. (Note: Some VAXNMS
systems include an optional feature that requires you to enter a system password before it
issues the "Username:" prompt.)
Next, VAXNMS prompts you with the following:
You respond by typing in your password and a RETURN. Note that VAXNMS does not
display your password when you type it on the terminal. This helps to protect your password from accidental discovery.
The following example shows the login procedure:
<RET>
Userna111e: JONES
Pass1,.1ord:
Welcome to VAX/VMS Version

a.o on node BACKUS

1.2.2 Logging Out
To end your terminal session, you type the LOGOUT command. VAXNMS responds with
the brief form of the logout message, as shown in the following example:
$

LOGOUT
JONES

lossed out at 30-MAR-198a 12:30:00,00

If you add the /FULL qualifier to the LOGOUT command (or if VAXNMS executes the

LOGOUT command in a batch file), the long form of the logout message is printed. For
example:
$

LOGOUT/FULL
JONES

1-4

lossed out at 30-MAR-198a 12:30:00.00

Using the VAXNMS Operating System

Accountins inforMation:
Buffered I/O count:
22
Direct I/O count:
10
Pase faults:
GB
Elapsed CPU tiMe: 0 00:01:30,50

PeaK worKinS set size:
80
PeaK virtual size:
68
Mounted voluMes:
0
Elapsed tiMe:
0 04:58:02.63

1.2.3 Changing Your Password
If your system manager allows it, you can change your password with the SET
PASSWORD command. (Note that you must use this command interactively from your
terminal; it cannot be executed in a batch file.) The steps for changing your password are
as follows:

1. You type SET PASSWORD, followed by a RETURN. VAXNMS then prompts you
to enter your current password.
2. Enter your current password, followed by a RETURN. Note that VAXNMS does
not display the current password. VAXNMS then prompts you for your new password, which can have a maximum of 31 characters chosen from the set A through Z,
a through z, 0 through 9, dollar sign($), and underscore(_), Note that VAXNMS
does not display the new password.
3. To verify that you have typed your new password correctly, VAXNMS prompts you
to enter your new password again. If the two new passwords do not match, the
original password remains in effect.
A sample dialog follows:
SET PASSWORD
Old Pass1A1ord:
Ne1A1 Pass1A1ord:
t.Jerification:
$

1.2.4 Declaring Your Terminal Type
When you log in, VAXNMS may or may not know what type of terminal you have. To set
the terminal type, you use the SET TERMINAL command. The simplest form is:
SET TERMINAL/INQUIRE

When you enter this form of the command, VAXNMS determines what type of terminal
you have and sets several parameters to appropriate values. For example, if you have a
VTlOO terminal, VAXNMS sets parameters so that your terminal has lowercase characters
and tabs, so that the screen is 80 columns wide by 24 lines high, so that the terminal can
buffer characters for the type-ahead feature, and so forth. Since you nearly always need to
set the terminal type, you may want to put the SET TERMINAL/INQUIRE command into
your LOGIN.COM file; then, the command will be executed every time you log in. (See
Section 1.6.11 for information on LOGIN .COM files.)

Using the VAXNMS Operating System

1-5

If you want to determine the current parameter settings for your terminal, use the SHOW
TERMINAL command. VAX/VMS responds with a list of all of the parameters that can be
set for a terminal, and the current settings for your terminal.

At times you may need to inform the system of the speed at which your terminal operates.
When doing this, you must tell VAX/VMS the speed to which you will set your terminal
before you actually set it; if you set the terminal speed first, VAX/VMS will not be able to
understand the characters you type. To set the terminal's speed, use the SET TERMINAL
command with the /SPEED qualifier. For example, if you want to change your terminal to
run at 4800 bits per second, use the following command:
SET TERMINAL/SPEED=a800

After you enter this command, VAX/VMS will not recognize any characters that you type
until you change your terminal's setting-by means of a manual setting or the SET-UP
procedure (depending on your terminal type)-to 4800 bits per second.
The SET TERMINAL command has many other qualifiers available for more specific
purposes. For a complete list of these qualifiers, see the description of the SET
TERMINAL command in the Guide to Using DCL and Command Procedures on
VAX/VMS.

1.2.5 Logging In to Other Network Nodes
If you work on a VAX/VMS system with DECnet-VAX software and your system is on a
computer network, you can connect your terminal to other computers on the network by
entering DCL commands. You must know the name of the computer, or node, that you
want to reach,and you must have access to an account there.

You can find out which network nodes are accessible with the SHOW NETWORK command. For example:
SHOW NETWORK
VAX/VMS Network status for local node

2.18 KLEE on

The next hop to the nearest area router is node
Node
2. 18 KLEE
2. 1
BOSS
2.2
ECHO
2.a
MARC

Lin f( s
0
0
0
0

Cost
0

NEST

2+25

Hops
0

3
3
3
2

a-JUN-188a 13:51:a3.81

2.a MARC.

Next HoP to Node
<Local)
-> 2. 18
UNA-0
-> 2. 1
UNA-0
-> 2.2
UNA-0
-> 2.a
UNA-0

2. 18

KLEE
BOSS
ECHO
MARC
FLOSS

Total of 12 nodes.

For more information on the SHOW NETWORK command, see the Guide to Using DCL
and Command Procedures on VAX/VMS.

1-6

Using the VAXNMS Operating System

To connect your terminal to other network nodes, use the SET HOST command, as in the
following example:
$ SET HOST MARC
Usernar11e: AUGUST
Pass1"1ord:

This command connects a terminal to the network node named MARC. After you have
successfully connected your terminal to another node, follow the login procedure outlined
in Section 1.2 .1.

1.3 Using DCL
Once you have logged in to a VAXNMS system, you can use DCL commands for tasks
such as executing programs or printing files. The next two sections present rules and
conventions for entering these commands and for defining symbolic names for them.

1.3.1 Rules for Entering and Editing DCL Commands
When entering DCL command lines, you should pay particular attention to the rules in the
following list. Other rules for entering DCL command lines are described in the Guide to
Using DCL and Command Procedures on VAX/VMS.
• You can truncate any command name or qualifier name to four characters. Fewer than
four characters are acceptable if the truncated name is unique to the command that
you want.
• You must precede each qualifier name with a single slash character (/).
• If you omit a required parameter (for example, a file specification), the VAXNMS

DCL command interpreter will prompt you for it.
• You can enter a command on as many lines as you wish, as long as you end each line
(except the last) with a hyphen ( - ).
• After you have entered a complete command, you must type a RETURN to pass the
command to the system for processing.
• You can cancel an entire command, before the final RETURN, by typing <CTRL/Y>.
• You can cancel the current line of a multiline command by typing <CTRL/U>.
• You can interrupt command execution (and user programs) by typing <CTRL/Y>. To
resume the interrupted command, enter the CONTINUE command. To stop processing completely after typing <CTRL/Y>, simply do not enter the CONTINUE command. At that point, you can enter other DCL commands or run other programs.
If you enter a command incorrectly (for example, if you misspell a command or qualifier

name), the command interpreter issues an error message and you must either retype the
entire command or edit the command and then reenter it.

Using the VAXNMS Operating System

1-7

CTRL/B

Recalls successive command lines so that they can be edited.

CTRL/H

Moves the cursor to the beginning of the command line being displayed.
(BACKSPACE key generates <CTRL/H> .)

CTRL/E

Moves the cursor to the end of the command line being displayed.

{CT~LID}

Moves the cursor one character to the left.

{ CT~L/F}

Moves the cursor one character to the right.

CTRL/J

Deletes the characters or word to the left of the cursor; that is, characters
up to the next blank are deleted. (LINEFEED key generates <CTRL/J>.)

CTRL/A

Alternates between insert and overstrike mode. Depending on the
<CTRL/A> setting the characters that you enter either replace existing
characters or are added to the command line. For example, after typing
<CTRL/B>, you are in overstrike mode by default; to get into insert mode,
you type <CTRL/A>; to return to overstrike mode, you type <CTRL/A>;
and so on.

CTRL/U

Deletes all characters between the current cursor position and the beginning of the command line.

CTRL/C

Cancels the entire operation.

Command line editing enables you to correct typographical errors and other errors in
lengthy command lines and saves you the trouble of reentering the entire line.

1.3.2 Rules for Defining DCL Symbols
One of the most useful features of VAXNMS is its ability to recognize symbols that
represent commands and partial command strings. You define a symbol by placing one of
the assignment operators := or :== between the symbol and the string it represents. If you
use the :== operator, VAXNMS inserts the symbol in the global symbol table; if you use
the := operator, VAXNMS inserts the symbol in a local symbol table.
The Guide to Using DCL and Command Procedures on VAX/VMS describes symbol tables
in detail. Briefly, VAXNMS creates a global symbol table for you when you log in. Then,
each time you execute a command procedure, VAXNMS creates a new command level and
a local symbol table for that level. If one command procedure executes another procedure,
VAXNMS creates another new-lower-command level and another local symbol. table,
and so forth. Every command level can access the symbols in the global symbol table, as
well as symbols in local symbol tables at higher command levels. In other words, you can
define local symbols in a command procedure that are available to lower-level procedures.
Note that VAXNMS discards local symbols and their values when a procedure exits. That
is, a program or command procedure can create local symbols, but the symbols disappear

1-8

Using the VAXNMS Operating System

when the program or procedure ends. However, you can define local symbols at DCL
command level, and these symbols remain until you explicitly remove them or until you log
out.
For example, the following command defines the local symbol FORTRAN as a command to
invoke the FORTRAN compiler, with two added qualifiers:
$

FORTRAN := FORTRAN/G_FLOATING/NDLIST

You can pass information to a higher-level command procedure by defining a global symbol
to contain the information. Because there is only one global symbol table, and it is accessible at all command levels, the higher-level command procedure can simply test the value of
the symbol.
You can tell VAXNMS that you want to allow abbreviations of a symbol by using the
asterisk ( *) character to end the acceptable abbreviation. For example, if you wanted to
abbreviate the command FORTRAN to FOR, you could use the following command:
$

FDR*TRAN :== FORTRAN/G_FLOATING/LIST

Once you have defined this symbol, you can type FOR, FORT, FORTR, FORTRA, or
FORTRAN to invoke the FORTRAN compiler with the /G_FLOATING and /LIST qualifiers. Note that the double equal sign in this symbol definition denotes the creation of a
global symbol.
You can determine the definition of a symbol by typing SHOW SYMBOL followed by the
symbol name. For example:
$

SHOW SYMBOL FDR
FDR*TRAN = FDRTRAN/G_FLDATING/LIST

To delete a symbol, type DELETE/SYMBOL, followed by the symbol name. If you do not
specify a symbol table qualifier, LOCAL is assumed. If the symbol is in the global table,
type DELETE/SYMBOL/GLOBAL followed by the symbol name. For example, you could
delete the symbol FORTRAN, which you had defined previously, by typing:
$

DELETE/SYMBOL/GLOBAL FORTRAN

Many VAXNMS users keep a file of symbols for the system to define every time they log
in, thus creating a set of personal commands for special purposes. For information on
having the system read such a file each time you log in, see Section 1.6.11 on the
LOGIN.COM file. Sections 1.6.1 to 1.6.4 contain information on using symbols in command procedures.

1.4 Getting Help from VAX/VMS
You can get help from VAXNMS on commands, qualifiers, and other keywords by using
the HELP command:
HELP [topic [subtopic ... ]]

Using the VAXNMS Operating System

1-9

For instance, to find out about the FORTRAN command, type HELP FORTRAN. If you
type only HELP, you get a list of all of the topics for which help is available, and if you type
HELP FORTRAN, you get a list of FORTRAN qualifiers, parameters, and other topics for
which help is available. You can also have the help text written to a file by specifying the
/OUTPUT qualifier and a file specification, after the HELP command. For example, to
create a file named CROSS.TXT, containing the HELP information on the /CROSS qualifier to the FORTRAN command, enter:
$

HELP/OUTPUT=CROSS.TXT FORTRAN /CROSS

See Section 1.5.1 for more information on file specifications.

1.5 Working with Files
In order to name, access, and use your files effectively, you need information about:
• File specifications, which you use to refer to a particular file
• File-handling commands, which you use to perform any of the following operations on
files: move, delete, list directory, rename, set protection, search contents, and display
or print contents
• Command procedures (including the LOGIN.COM command procedure), which allow
you to execute multiple DCL commands both from a terminal and from a batch job

1.5.1 File Specifications
A file specification provides the system with all of the information it needs to uniquely
identify a file. The maximum length of a file specification, including all delimiters, is 255
characters. Note that you do not have to enter each field in every file specification; often
you can use the system-supplied default values. The fields of a file specification are:
node"access-control-string"::device:[directory]filename.type;version

For example:
VIOLET'ROTHKO MARK'::USERO:[ROTHKOJPAINTINGS,TXT;3

The fields are explained below:
node"access-control-string"

When copying files to or from another network node, you must include the node name,
followed by two colons.
Depending on your privileges and the operation that you are going to perform, you
· may have to provide an access control string. An access control string specifies the
user name and password to be used on the remote node. If you include the access
control string, you must enclose it in quotation marks, and it must precede the two
colons. The access control string cannot be longer than 42 characters, and the password cannot be longer than 31 characters.
1-10

Using the VAXNMS Operating System

If the file specification for the remote node does not conform to VAX/VMS syntax,

you must enclose everything after the two colons in quotation marks.
device

Your system manager sets up logical names for the storage devices attached to your
system. You should use these logical names, rather than physical device names, when
referring to files on these devices. For example, the sample file specification shown
previously indicates that the logical name USERD has been defined as the name of
the device containing the directory [ROTHKO].
directory

A named catalog of files. You specify a directory as a character string of up to 39
alphanumeric characters (dollar sign and underscore are also allowed after the first
character) or as a sequence of character strings separated by periods. In each case you
must enclose the directory name in square brackets ( []) or angle brackets ( <>).
The following examples show how you can refer to directories:
[360,015]
[KANDINSKY]
[KANDINSKY.FORT]
See Section 1.5.1.3 for a description of directories and directory hierarchies.
filename

A string of up to 39 alphanumeric characters (in addition, optionally, to dollar sign
and underscore-with the first character an alphanumeric) that you assign to a file.
The following examples show legal file names:
FORT_TEST
BUDGETER$
APR23RECS
a
avery longfilename
Note that the case of the letters in the file name does not matter-the system recognizes both lowercase and uppercase and does not distinguish between them.
type

A character string that, by convention, describes the contents of the file. For example,
the file type .FOR is used to denote FORTRAN source programs. Any alphanumeric
characters (in addition to dollar sign and underscore; with first character an alphanumeric), can be used in file types, and the string can be up to 39 characters long. The
file type must be preceded in the file specification by a period.
Some of the most common file type conventions are listed in Table 1-1.
version

A decimal integer between 1 and 32767, preceded by a semicolon or a period. When
you update or modify a file without specifying the version number of the output file,

Using the VAXNMS Operating System

1-11

the system increments the current version number by 1 when creating the output file.
You must specify a version number when you delete a file. You can use a version
number of 0, or omit the integer and include only the semicolon or period, to refer to
the most recently created version of the file. For example:
FORPROG.LIS;5
FORPROG .LIS .5
FORPROG .LIS ;O
FORPROG.LIS;
Given that FORPROG.LIS;5 is the latest version of the file and thus has the highest
version number, all of these file specifications refer to the same file.
Table 1-1 shows the most common file types used by FORTRAN programmers.
Table 1-1: Common File Types
Type

Expected File Contents

FOR

FORTRAN source program; default input type for FORTRAN command

COM

Command procedure file to be executed interactively or as a batch job

DAT

Input or output data file

DIR

Directory file

EXE

Executable image file; default output type for LINK command; default input type
for RUN command

HLB

Help text library file

HLP

Input text for help libraries

JOU

Journal file for the EDT editor

LIS

Listing file; default listing output type for FORTRAN command; default input
type for the PRINT and TYPE commands

LOG

Batch job output file

MAI

Mail message file

MAP

MAP image map; default listing output type for LINK command

OBJ

Object file; default output type for FORTRAN command; default input type for
LINK command

OLB

Object module library

TMP

Temporary file

TXT

Input file for text libraries, mail utility

1-12

Using the VAXNMS Operating System

1.5.1.1 File Specification Defaults
Not all elements of a file specification need to be written each time you use a file. The
default values that the system supplies for unspecified elements are summarized in Table
1-2.
For example, if you specify only a file name when compiling a FORTRAN program, the
compiler can process the source program if the file meets the following three requirements:
• The file is stored on the default device on the local node.

• It is cataloged under the default directory name.
• It has a file type of FOR.
If more than one file meets these conditions, the compiler processes the file with the highest
version number.

For example, assume that your default device is USERD, your default directory is SMITH,
and you supply the following file specification CIRCLE to the compiler.
The compiler searches device USERD in directory SMITH, seeking the highest version of
CIRCLE.FOR. If you do not specify an output file, the compiler generates the file
CIRCLE.OBJ, stores it on device DBAO in directory SMITH, and assigns it a version
number that is 1 higher than any other version of CIRCLE.OBJ currently cataloged in
directory SMITH on USERD.

Table 1-2: F,ile Specification Defaults
Element

Default Value

Node
Device
Directory
File type

Local network node
User's current default device
User's current default directory
Depends on usage:
Input to compiler
Text library input to compiler
Output from compiler
Input to linker
Output from linker
Input to RUN command
Compiler source listing
Linker map listing
Input to executing program
Output from executing program
Input: highest existing version
Output: 1, if no existing version,
otherwise, highest
existing version plus 1

Version

FOR
TLB
OBJ
OBJ

EXE
EXE
LIS
MAP
DAT
DAT

Using the VAXNMS Operating System

1-13

1.5.1.2 Wildcard Characters
You can often substitute characters called wildcards for directories, file names, file types,
and version numbers in file specifications. There are two types of wildcards: (1) generalpurpose wildcard characters used in input file specifications and (2) special wildcard characters used only in alphanumeric directory specification fields. Both types of wildcards can
be combined in numerous ways in directory specifications.
The special wildcard characters are ellipsis ( ... ) and minus sign ( - ) . Their use is explained
in Section 1.5.1.3.1.
The general-purpose wildcard characters are the asterisk ( *) and the percent sign ( % ) .
• An asterisk represents a string of characters of any length from zero to the maximum
allowed. For example, *.FOR refers to all files whose file types are FOR. A*.FOR refers
to all files with names starting with A or with the name A and with a file type of FOR,
such as AXA.FOR.

• A percent sign represents exactly one character. For example, Z%.FOR refers to all
files whose types are FOR and whose names have two characters: Z followed by any
other valid character.
The following example shows how to use general-purpose wildcard.s with file specification
fields to keep track of groups of files. If you have a number of FORTRAN programs, and
you use default file types, you can refer to all of the FORTRAN source files on your current
directory with the specification:
*•FOR

You can refer to the most recent executable versions of programs that exist in subdirectory
[FORTRAN.EXECUTE] by specifying a semicolon version number delimiter, but omitting
the version number itself:
CFORTRAN.EXECUTEJ*.EXE;

You can refer to help files on the network node HUNTER with the specification:
HUNTER::SYSSHELP:*•*

Not all commands allow the use of wildcard characters in file specifications. For instance,
wildcards cannot be used in the FORTRAN command. Each file that you wish to compile
must be explicitly named.

1.5.1.3 Directories and Subdirectories
Directories are "file catalogs," each of which is owned by a particular user. The system
identifies each directory by an alphabetic name, and you use these names in referring to
the directory. A directory name consists of up to thirty-nine alphanumeric characters and
can contain any characters that are allowed in file names. Directories are just special files
that always have a file type of .DIR and a version of 1. Often, the directory that you own
has the same name as the account under which you log in.
VAXNMS allows you to create subdirectories within a directory. Like directories, subdirectories have names. Subdirectory names are written as lists of directory names, separated by periods; the entire list is enclosed in square brackets. The first directory name in
1-14

Using the VAXNMS Operating System

the list represents the highest-level directory; the last name in the list represents the
subdirectory to which you are referring, with any intermediate directories listed in between
them. For example:
$ DIRECTORY CFAULKNER.PROGRAMS.FORTJ

The top-level directory in this example is FAULKNER, the intermediate subdirectory is
PROGRAMS, and the subdirectory is FORT. The DIRECTORY command lists all files in
the specified (or default) directory.
VAXNMS keeps track of your current default device and directory. When you log in, your
default device and directory are set to your home disk area. To determine the current
default values, use the SHOW DEFAULT command. For example:
$ SHOW DEFAULT
WORKD:CBRONSTEIN.FORTJ

You can change these default values with the SET DEFAULT command. For example, if
your default directory when you log in is [FAULKNER] and you wish to work on files in the
directory [FAULKNER.PROGRAMS], you can avoid typing the directory name with each
file name by using the following command:
$SET DEFAULT [,PROGRAMSJ

The files in each directory and subdirectory occupy a certain amount of disk space. If disk
quotas are enabled on the disk you work on, you cannot exceed the quota assigned to you.
You can use the SHOW QUOTA command to determine how much disk space is occupied
by files in a directory or subdirectory. In response to SHOW QUOTA, the system tells you
how much disk space you are using, what your quota is, and how much free space is
available to you. For example:
$ SHOW QUOTA
User CBRONSTEINJ has 278 blocks used1 722 available' of 1000
authorized and Perwitted overdraft of 50 blocks on WORKD

If no disk quotas are in effect for your disk, the SHOW QUOTA command informs you that

the disk quota accounting file is not active.

Creating a Subdirectory
To create a subdirectory, use the CREATE/DIRECTORY command. For example, if you
wish to create the subdirectory [FAULKNER.PROGRAMS.FORT], enter the following
command:
$ CREATE/DIRECTORY EFAULKNER.PRDGRAMS.FDRTJ

If you have already executed the command SET DEFAULT [FAULKNER.PROGRAMS],

your current default directory is [FAULKNER.PROGRAMS]. This would enable you to use
the following, shorter, form of the command:
$CREATE/DIRECTORY [,FORTJ

After you execute this command, the directory [FAULKNER.PROGRAMS] will contain
the file FORT.DIR, which is the catalog of the files in [FAULKNER.PROGRAMS.FORT].

Using the VAXNMS Operating System

1-15

You can use the VAXNMS facility for creating directories and subdirectories to construct
trees-hierarchies-of logically related files. The number of directories you can create is
limited only by your available disk space; however, no hierarchy can contain more than
eight levels. Figure 1-2 illustrates the concept of directory hierarchies.
$DIRECTORY (000000)
MALCOLM.DIR
301300.DIR
HIGGINS.DIR
301301.DIR
MFD

LEVEL

$DIRECTORY [HIGGINS)
PAYROLL.DIR
USER.DOC
MEMO.LIS
LOGIN.COM

$DIRECTORY [HIGGINS.PAYROLL)
A subdirectory can catalog files
and/or additional subdirectories.
The subdirectory file named
[HIGGINS) PAYROLL.DIR

The subdirectory file named [HIGGINS.PAYROLL) DATA.DIR
lists additional subdirectory files.
$DIRECTORY [HIGGINS.PAYROLL.DATA)-'---------$DIRECTORY [HIGGINS.PAYROLL.LISTINGS)
$DIRECTORY [HIGGINS.PAYROLL.SOURCE)
FICA.LIS
TAXES.LIS
FICA.FOR
TAXES.MAR
PAYROLL.FOR

$DIRECTORY [HIGGINS.PAYROLL.DATA.MARCH)

FICA.DAT
STATETAX.DAT
FEDTAX.DAT
EMPTTL.DAT

Figure 1-2: A Directory Hierarchy

1-16

Using the VAXNMS Operating System

FICA.DAT
STATETAX.DAT
FEDTAX.DAT
EMPTTL.DAT

nextlevel.DIR

•
•
•

You may often refer to files that are somewhere in your directory hierarchy but not in your
current default directory. Two special symbols exist to make references easier: the ellipsis
( ... ) and the hyphen or minus sign (-). The ellipsis is used to search down a directory
hierarchy, and the hyphen is used to search up the hierarchy.
For example, [BRONSTEIN ... ] refers to the directory [BRONSTEIN] and all of the subdirectories in the hierarchy below [BRONSTEIN]. The directory specification [.... FORT]
refers to all subdirectories named FORT below the current default directory. Since you can
specify the current default directory with [ ], you can refer to the entire hierarchy under
your current default directory with [... ].
Hyphens allow you to search up the hierarchy one directory at a time; each hyphen stands
for one hierarchical level. If, for example, your current default directory is
[BRONSTEIN.FORT.TEST], you can refer to [BRONSTEIN] by[--]. The directory specification [-] refers to [BRONSTEIN .FORT], and [-.SOURCES] refers to
[BRONSTEIN.FORT.SOURCES].

Deleting a Subdirectory
To delete a subdirectory properly, you must first remove any files in it. Then, you can
delete the DIR file. Note that directory and subdirectory files are protected to prevent
accidental deletion; you cannot delete them without first resetting the file protection. (For
more information on file protection, see Section 1.5.2.5.)
1.5.1.4 Logical Names
Logical names are a shorthand way of specifying device, directory, or file names to which
you refer frequently.
Logical names are alphanumeric character strings, up to 255 characters long.
Every logical name is paired with one or more equivalence name. An equivalence name can
be a file specification, part of a file specification (a device or a device and a directory), or
another logical name. When programs and command procedures refer to physical files by
logical name, VAXNMS translates the logical name into its equivalence name.
Logical names that translate to more than one equivalence name are called search lists.
Search lists are useful in referring to groups of files that are not collected together in a
single directory.
The remainder of this section contains information about the following topics:
1. Defining logical names
2. Logical name tables
3. Predefined logical names
4. Deleting and showing logical names
5. Assigning a logical name with the MOUNT command
6. Search lists
The topics are addressed, in the order shown here, under the headings that follow.
Using the VAXNMS Operating System

1-17

Defining Logical Names
Two VAXNMS commands, ASSIGN and DEFINE, equate a logical name and an equivalence name. The commands differ in two respects: (1) the order in which they require the
logical name and the equivalence name and (2) if you supply a terminating colon with the
logical name, ASSIGN removes it, whereas DEFINE does not.
The following example shows how to equate a logical name, TEST, and a file specification,
using the ASSIGN and DEFINE commands:
$ASSIGN USERD:EJUNG.FORTJFORTEST.FOR TEST
$ DEFINE TEST USERD:EJUNG.FORTJFORTEST.FDR

The preceding commands equate the logical name TEST to the file specification
USERD:[JUNG.FORTJFORTEST.FOR. After you have issued one of these commands,
you can then refer to the file by the name TEST. For example:
$ TYPE TEST

You can also run programs and execute command procedures that refer to the logical name
TEST. For example, suppose that you have written a FORTRAN program that opens a file
using the following code:
OPEN CUNIT=1 t FILE='TEST', DRGANIZATIDN='SEQUENTIAL', STATUS='OLD')

When you run your program and this line is executed, FORTRAN passes the string TEST
to VAXNMS as the file specification. In searching for the corresponding file, VAXNMS
first tries to translate the string TEST. If TEST is a logical name, the translation yields an
equivalence name, which is translated in turn. When no further translations are possible,
VAXNMS assumes that it has a file specification, and your program opens the file
USERD: [JUNG .FORTJFORTEST .FOR. You can specify a different file when you run the
program again by issuing another ASSIGN (or DEFINE) command to create a new equivalence name for the logical riame TEST. For example:
$ASSIGN WDRKD:EJUNGJREAL.DAT;7 TEST

If you enter the preceding ASSIGN command and then rerun your program, the program
opens the file WORKD:[JUNGJREAL.DAT;7.

Logical Name Tables
Logical names are kept in logical name tables. Five specific logical name tables-USER,
PROCESS, JOB, GROUP, and SYSTEM-are of special interest.
• User logical name tables contain logical names that are local to the program that is
currently executing. They automatically go away when the execution of the program
ends. Use the ASSIGN/USER command to put a logical name into the user table.
• Process logical name tables contain logical names that are local to your process; the
ASSIGN and DEFINE commands place logical names in the process logical name
table by default.

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Using the VAXNMS Operating System

• Job logical name tables contain logical names that are local to your current process
and any descendent processes created using the SPAWN command. You must use the
/JOB qualifier to refer to the job logical name table.
• Group logical name tables can be used by anyone in a user group (as defined by the
group field in the user identification code); you must use the /GROUP qualifier to refer
to the group logical name table.
• The system logical name table contains entries that can be accessed by any process in
the system; you must use the /SYSTEM qualifier to refer to the system logical name
table.
To place logical names in the group table, you need the GRPNAM privilege; to place
logical names in the system table, you need the SYSNAM privilege.
See the VAX/VMS DCL Dictionary for detailed information on the use of logical name
tables.

Predefined Logical Names
The operating system supplies a number of predefined logical names that are already
associated with particular file specifications. Table 1-3 lists the logical names of special
interest to FORTRAN users.
Table 1-3: Predefined System Logical Names
Name

Meaning

Default

SYS$COMMAND

Default
stream

SYS$DISK

Default device

As specified by the user

SYS$ERROR

Default error message output
file

User's terminal (interactive); batch
log file (batch)

SYS$INPUT

Default input stream

User's terminal (interactive); batch
command file (batch)

SYS$NODE

Current local node

Network node name for the local
system if DECnet-VAX is active on
the system

SYS$0UTPUT

Default output stream

User's terminal (interactive); batch
log file (batch)

SYS$LOGIN

User's output file for system

Established by system manager

SYS$SCRATCH

Default device and directory
for scratch files created by
the compiler

Established by the system manager

command

input

User's terminal (interactive); batch
command file (batch)

Using the VAXNMS Operating System

1-19

Deleting and Showing Logical Names
To delete a logical name from a logical name table, use the DEASSIGN command. For
example:
$ DEASSIGN TEST

The preceding command deletes the logical name TEST from the process logical name
table. To remove logical names from the job, group, and system logical name tables, you
must use the /JOB, /GROUP, and /SYSTEM qualifiers. You need the GRPNAM privilege
to remove a logical name from the group table and the SYSNAM privilege to remove a
logical name from the system table. (Note: All logical names are deleted from the user
logical name table each time a program completes. See Section 1.5.1.3.)

Y~u can ask VAXNMS to show you the equivalence name for a logical name with the
SHOW LOGICAL command. This command accepts the logical name as a parameter. If
repeated translation is necessary (that is, if the logical name stands for another logical
name, and so on), up to 10 translations are performed.
The SHOW TRANSLATION command, on the other hand, does not do repeated translation; translation is repeated until an equivalence name is found that is not, itself, a logical
name. The response to SHOW TRANSLATION is the equivalence name that corresponds
to the first occurrence of that logical name in the logical name tables. The tables are
searched in the following order: process, job, group, and system. For example, suppose you
define TEST with the following ASSIGN command:
$

ASSIGN

TEST_FILE TEST

If TEST_FILE is a logical name pointing to USERD:[JUNG.FORTJFORTEST.FOR, the

responses to the SHOW LOGICAL and SHOW TRANSLATION commands are as follows:
$
$

SHOW TRANSLATION TEST
TEST = II TEST _FI LE II ( LNM$ PROCESS_ TABLE)
SHOW LOGICAL TEST
TEST = II TEST _FI LE II ( LNM$PROCESS_ TABLE)
TEST _FILE = 11 USERD: [JUNG, FORT] FORTEST, FOR 11

(

LNM$PRDCESS_ TABLE)

Assigning a Logical Name with the MOUNT Command
You can specify a logical name as a parameter of the MOUNT command when mounting a
volume on a device. The MOUNT command has the form:
$ MOUNT device-name, ... [volume-label, ... ] [logical-name[:]]

If your program refers to devices by means oflogical names, you can change the association

between the device name and the logical name when you mount the device. For example:
$

MOUNT MTAO:

TAPE2 MYTAPE

The preceding command associates the logical name MYTAPE with device name MTAO
and volume label TAPE2. Whenever your program refers to logical name MYTAPE, access
is to the volume labeled TAPE2 mounted on a system-assigned magnetic tape unit. If you

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Using the VAXNMS Operating System

subsequently mount a different tape to be referenced by the logical name MYTAPE, you
can change the logical name association when you issue the MOUNT command. For
example:
$ MOUNT MTAO: TAPE7 MYTAPE

The preceding command associates the logical name MYTAPE with device name MTAO
and volume label TAPE7.

Search Lists
Search lists are logical names that translate to an ordered list of equivalence names, rather
than to a single name. You create search lists by specifying a list of equivalence names,
separated by commas, in place of the single equivalence name in the ASSIGN and DEFINE commands. The translation behavior of search lists depends on whether they are
being used for input files or output files. The typical user of search lists is to collect, under
one logical name, groups of files that are in different places. For example, suppose you are
working on two projects, called A and B. Suppose that the important files for project A are
kept in directory [A.LIB] and those for project B, in directory [B.LIBJ. If you wish the
system to search for files first in [ROTHKOJ and then in [A.LIB] and then in [B.LIBJ, you
can define a search list with the following command:
$DEFINE SRC ERDTHKOJ 1CA+LIBJ tCB+LIBJ

The preceding command establishes the logical name SRC as a search list with the equivalence names of [ROTHKOJ, [A.LIB], and [B.LIBJ, in that order. You can then use the name
SRC whenever you want the system to search these directories for a specified file. For
example, the command
$ FORTRAN SRC:FDURIER

searches for the file FOURIER.FOR in [ROTHKOJ first; then, if no file by that name is
found there, searches [A.LIB]; and finally, if no such file is found there, searches [B.LIBJ.
The search terminates in the first place that FOURIER.FOR is found, and that file is used
for the input to the FORTRAN command.
If a search list is used for an output file specification, the new file is created in the directory

specified by the first name in the list. For example, if FOURIER.FOR existed only in
[A.LIB], the following command would compile [A.LIBJFOURIER.FOR and create the
object file [ROTHKOJFOURIER.OBJ:
$ FORTRAN/OBJECT=SRC: SRC:FOURIER

1.5.2 File-Handling Commands
The most common file-handling operations are:
• Moving files
• Deleting files
• Listing and changing file names

Using the VAXNMS Operating System

1-21

• Handling file protections
• Displaying the contents of files on your terminal or printing them on a line printer
The following sections describe the commands used to perform these operations. Note that
these commands affect entire files; they do not act on the contents of the files. (See the
Guide to Using DCL and Command Procedures on VAX/VMS for complete descriptions of
all DCL commands.)

1.5.2.1 Moving Files
Two DCL commands, COPY and APPEND, move files:
• COPY makes a new copy of the file in a directory you specify, thus allowing you to
move the file to a new device if you wish.
• APPEND copies the contents of the files that you specify into a single file.
In both cases, the original files are retained; they must be explicitly deleted if you do not
want to keep them.
(Note: The RENAME command does not move files; it simply changes the directory entry
for the file. For a description of RENAME, see Section 1.5.2.4.)

COPY Command
To copy a file from one directory to another or from one device to another, use the COPY
command, listing the input file specification(s) first and the output specification second.
Only one output specification is allowed. However, you can use wildcards in the output
specification to copy a group of files to another device or directory. For example:
$COPY WORKD:CBACKLJS,FORTlA*+*tB*•* CMINEl*•*

The preceding command copies every file in WORKD:[BACKUS.FORT] that has a name
starting with A or B to the directory WORKD:[MINE]. The files retain their names.
If you are on a DECnet network, you can also use the COPY command to copy files from
one network node to another. For example:
$COPY RIDER::USERD:FILE+TXT *•*

The preceding command copies FILE.TXT from device USERD on node RIDER to the
current default directory.

APPEND Command
To copy two or more files into a single file, use the APPEND command. APPEND concatenates the files you specify as input, in the order in which you have listed them. You can
add the input files to an existing file or to a new file. For example:
$APPEND PARSER+FOR1HELPER+FOR1MYPROG.FOR TEST.FOR/NEW

The preceding command creates a new file called TEST .FOR consisting of the three FORTRAN source files in the order shown. The /NEW qualifier is required if you want to create
a new file.

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Using the VAXNMS Operating System

You can also use wildcard characters to concatenate files with the APPEND command. For
example:
$ APPEND *•TXT WHOLE.TXT

When you execute the preceding command, all files of type TXT are appended to the
existing file WHOLE.TXT. If WHOLE.TXT did not exist, you would get an error message,
unless you used the /NEW qualifier.

1.5.2.2 Deleting Files
Two DCL commands, DELETE and PURGE, delete files.
DELETE Command
The DELETE command eliminates the specified files from the disk and makes the space
they occupied available for other files. You cannot retrieve files once you have deleted
them; therefore, you should be as explicit as possible when specifying files to be deleted. In
order to minimize the number of deletions performed by mistake, VAXNMS requires
information about the version numbers of the files to be deleted.
You can delete the latest version in the specified directory by using a version number of 0 or
by supplying only the semicolon. For example, the following command deletes the most
recent version of TEST.FOR, leaving earlier versions intact.
$ DELETE TEST.FOR;

To delete all versions of TEST .FOR, use the following command:
$

DELETE TEST.FORi*

PURGE Command
The PURGE command deletes old versions of a file. It allows you to specify how many of
the most recent, or highest numbered, versions you want to keep. By default, it deletes all
versions except the most recent.
PURGE does not require you to enter version numbers. For example, the following PURGE
command deletes all but the latest version of TEST.FOR:
$

PURGE TEST.FOR

The following PURGE command is more general. It purges all but the latest version of
every file in every directory and subdirectory in the hierarchy under the directory [JONES].
$PURGE [JONES,,,]

To keep more than the latest version of files in directories you purge, you must use the
/KEEP qualifier to indicate the number of versions that you wish to retain. For example,
the following command retains the three latest versions of every file in the directory
[JONES], and all subdirectories below it as well (if that many versions exist).
$ PURGE/KEEP=3 [JONES,,,]

Using the VAXNMS Operating System

1-23

If there are fewer than three versions of a file, none of the existing versions are deleted.

To allow extra checking when deleting files, use the /CONFIRM qualifier. To verify what
files are being moved or deleted, use the /LOG qualifier.
1.5.2.3 Listing File Names
The DIRECTORY command lists the files in the specified directory in alphabetical order.
If you omit a directory specification, typing the DIRECTORY command lists the files in
the current default directory. To get additional information, or to format the output, you
can add qualifiers to the DIRECTORY command. For example:
$

DIRECTDRY/COLUMNS=1/DATE=CREATED/PRDTECTIDN

The preceding command tells VAXNMS to list the files in your directory in a single
column instead of in the default four columns, and to include the date of creation and the
protection in effect for each file.
You can obtain all of the information available on a file or group of files with the /FULL
qualifier of the DIRECTORY command. This qualifier causes the following attributes to be
listed for each file:
File name
File type
Version number
Number of blocks used
Number of blocks allocated
Date of creation
Date of last backup
Date last modified
Date of expiration
File owner's UIC
File protection
File identification number (FID)
File organization
Other file attributes
Record attributes
Record format
Access control list (ACL)
These items are described in the VAX Record Management Services Reference Manual.
You can use the /TOTAL qualifier to find out how many files exist in a directory. You can
use the /SIZE qualifier to find out how many blocks of disk space each file takes up. If you
combine these qualifiers, you can find the total number of files and the total space used,
without getting a list of the file names. For example:
$

DIR/SIZE/TOTAL

Directory USERD:[THDMPSON.DDCTORJ
Total of 191 files, 5169/5£109 blocf\s,

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Using the VAXNMS Operating System

The Guide to Using DCL and Command Procedures on VAX/VMS contains a complete list
of the qualifiers you can use with DIRECTORY. You can also type HELP DIRECTORY to
get a list of qualifiers.

1.5.2.4 Renaming Files
You can use the RENAME command to change the directory specification, file name, file
type, and file version of an existing file. For example, the following command changes the
directory and file name of the file AVERAGE.OBJ:
$ RENAME AVERAGE.OBJ [FAULKNERJOLDAVERAGE.OBJ

The following RENAME command changes the directory specification of the latest version
of the file SAVE.DAT from [FORTRAN.SOURCES.TEST] to [FORTRAN.SOURCES],
one level higher in the directory hierarchy:
$ RENAME [FORTRAN.SOURCES.TESTJSAVE.DAT [-J

1.5.2.5 Handling File Protections
File protections allow you to regulate access to your files. Access is granted according to the
class of the user who requests it. Users can be in one of four classes: SYSTEM, OWNER,
GROUP, and WORLD. SYSTEM users have low group numbers (the exact range is established by the system manager), and are usually system programmers, system managers,
and operators. OWNER is the user with the same user identification code (UIC) as the
creator of the file. GROUP users are those who have the same group number (the first
number in the UIC) as the file's creator. WORLD users are those who do not belong to any
of the other categories.
You can use the SET PROTECTION command to establish protection levels for each class
of users. Class names can be spelled out or abbreviated to a single letter. Protection codes
are R (read), W (write), E (execute), and D (delete). For example, you might want to give
system users and your project members (who are in your UIC group) complete access to
your file A.FOR, and give others only read access. The following command accomplishes
this:
$SET PROTECTION=CS:RWED10:RWED1G:RWED1W:R) A.FOR

You can prevent files from being deleted by setting their protections so that deletion is not
allowed. For example:
$ SET PROTECTION A.FOR/PROTECTION=CS:RWE10:RWE1G:RE1W) ,_
$_ B.FOR/PROTECTION=CO:RWE1G:RE1W:R)

The preceding command sets protection on two files, A.FOR and B.FOR. A.FOR is protected so that system users and the owner have read, write, and execute access to the file;
group members can read and execute the file, but world users have no access to it. B.FOR
is protected so that the owner has read, write, and execute access, group members have
read and execute access, and world users have read access to it. Because the class
SYSTEM was omitted from this command, system users have the same access that they
had before the command was entered. Note that this command was continued on a second
line with the use of the hyphen continuation character.

Using the VAXNMS Operating System

1-25

If you have access to a file, you can determine its current protection by using the

DIRECTORY command with the /PROTECTION qualifier. See Sections 1.5.1.3 and
1.5.2.3 for information about the DIRECTORY command.
The SET PROTECTION/DEFAULT command allows you to choose the protection codes
to be assigned to files you create in the current terminal session or batch job. For example,
$SET PROTECTIDN=(GtW) /DEFAULT

The preceding command tells VAXNMS to give no access to group or world users for any
files you create during the current session.

1.5.2.6 Searching File Contents
The SEARCH command allows you to search the contents of a file or a collection of files for
a specified text string or strings. You can control how SEARCH finds matching strings and
what it tells you about them, and you can look at the lines surrounding the line where the
match occurred. For example, you can find all occurrences of a certain variable name in
any file whose type is FOR, or you can look at a particular line from a compilation listing
file. Type HELP SEARCH or see the Guide to Using DCL and Command Procedures on
VAX/VMS for descriptions of all of the qualifiers you can use with SEARCH.
Suppose you need to know which routines in all FORTRAN source files in your current
default directory contain references to the variable Too_Many_Files. The following example shows how you can search the specified files:
$ SEARCH *•FDR Too_ManY_Files
* ***** ***** *** *** *** **** **** **
USERD:EHST.FDRTJINITVARS,FOR;2
Too_Many_Files = True
*** ****** **** **** ***** ********
USERD:EHST.FDRTJDPENFILE,FOR;1
IF (Too_Main_Files ,EQ, True) THEN

If you wanted to see the two lines following the reference to Too_Many_Files in OPEN-

FILE.FOR, you could use the /WINDOW qualifier as follows:
$ SEARCH/WINDDW=(O 12) DPENFILE.FDR "Too_Man}'_Files"
IF (Too_Man}'_Files .EQ, True) THEN
PRINT *1'Too Many files,'
END IF

1.5.2.7 Printing and Typing Files
The PRINT and TYPE commands allow you to look at the contents of a file. If you want to
look at the file contents on a line-printer listing, use the PRINT command. If you want to
look at the contents on your terminal screen, use TYPE. For example:
$ PRINT *+LIS/COPIES=10

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Using the VAXNMS Operating System

The preceding command causes VAX/VMS to group all files whose file type is LIS into a
single print job, and then queue the job to be printed. When the printer is on line and free,
10 copies of each file will be printed.
The /AFTER qualifier of the PRINT command allows you to queue files for printing at a
later time. To specify when you want the files printed, follow the /AFTER qualifier with
the time (in 24-hour format) when you want the file printing to begin. For example:
$

PRINT TEST.LIS/AFTER=20:10

The preceding command queues the file TEST.LIS for printing at 8:10 p.m. At the time
specified, the job is released from the queue for printing. For more information on how to
spec)fy times, see the Guide to Using DCL and Command Procedures on VAX/VMS or
type HELP SPECIFY DATE_TIME.
The TYPE command causes VAX/VMS to display the file on your terminal. You can
control the output with the commands <CTRL/S>, <CTRL/Q>, and <CTRL/0>. When
you type <CTRL/S>, VAX/VMS stops sending characters to your terminal; when you type
<CTRL/Q>, VAX/VMS starts sending characters again. Thus, you can scan a file quickly
until you reach something of interest, type <CTRL/S> and examine the current screen
carefully, and then type <CTRL/Q> to begin scanning again. (If your terminal has a NO
SCROLL or HOLD SCREEN key and the key is enabled, you can use it like <CTRL/S>
and <CTRL/Q> to stop and start the display of your file.)
To suppress the display of output without halting execution of the command, type
<CTRL/0>. <CTRL/0> causes the output from the executing command to be discarded
instead of being displayed. If you type <CTRL/0> again before the command finishes
executing, the display of output is resumed.
When you use TYPE with a group of files, you can use <CTRL/0> to examine only the
beginning of each file. For example, suppose you enter the following command:
$

TYPE [-]*+FDR

The preceding command searches for files with the file type FOR in the directory that is
one hierarchy level up from the current default directory. Any files found are displayed on
the terminal. If you type <CTRL/0> while the first one is being displayed, the rest of the
file is suppressed and the display of the second is begun. Thus, you can look at the
beginning of the next file by typing <CTRL/0> after the first few lines of the current file.

1.6 Using Command Procedures
VAX/VMS enables you to group DCL commands into files and execute them as a unit.
These files are called command procedures and they have the default file type COM. You
can create a command procedure with a text editor, a program, or another command
procedure. Once a command procedure exists, you can execute it by appending its file
name to the@ (Execute) or SUBMIT commands or the STATUS= 'SUBMIT' qualifier on
the FORTRAN OPEN or CLOSE statement.

Using the VAXNMS Operating System

1-27

You should use a command procedure whenever you want to execute a group of commands
repeatedly. In its simplest form, a command procedure is just a file containing a DCL
command on each line, preceded by a"$" character. Comments can be interspersed with
the commands by preceding them with exclamation point ( ! ) characters. If you wish to
execute a command procedure interactively, use the @ command, for instance:
$

@COMFILE

The preceding command begins execution of the command procedure contained in the file
COMFILE.COM. If you wish to execute a command procedure as a separate, batch process, use the SUBMIT command or specify the command file as the STATUS qualifier of a
FORTRAN OPEN or CLOSE statement. For example:
$

SUBMIT COMFILE.COM

The preceding command submits the file COMFILE.COM as a batch job. See the Guide to
Using DCL and Command Procedures on VAX/VMS or type HELP SUBMIT for more
information about the SUBMIT command.
When you use the @ command, the system by default does not display the commands as
they are executed. To have the system display the commands as they are executed, enter
the SET VERIFY command before executing the command file. Enter a SET NOVERIFY
command to return the system to its default, or silent, behavior.

1.6.1 Using Symbols
Symbols in command procedures are alphanumeric character strings that represent numeric, character-string, or logical values. For example, you can define a symbol to represent a DCL command with some particular set of options you use frequently:
$

MD := DIRECTORY/COLUMNS=l/SIZE/PROTECTION

Once you have created the symbol MD with this command, typing MD in response to the
VAXNMS prompt is the same as typing:
$

DIRECTORY/COLUMNS=l/SIZE/PROTECTION

You can create a symbol and assign a value to it in a command p~ocedure by:
• Equating a symbol name to a constant value or another symbol name using an assignment operator (:= or :==) (See Sections 1.6.2 and 1.6.3.)
• Passing parameters and fixed data to a command procedure or a batch job (See
Sections 1.6.5 and 1.6.6.)
• Using the INQUIRE and READ commands to prompt for a value for the symbol (See
Section 1.6.7 .)
A symbol name can be up to 255 characters long, and can contain letters, underscores (_),
and dollar signs ( $). Lowercase letters are translated to uppercase by the command interpreter.

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Using the VAXNMS Operating System

1.6.2 Assigning Character Values to Symbols
To assign a character-string value to a symbol, use one of the following forms of the
assignment command:
symbol-name := character-string-value symbol-name :== character-string-value

Note that one equal sign defines a local symbol; two equal signs define a global symbol.
Section 1.3.2 contains more information on defining both kinds of symbols.
The character-string value can contain any alphanumeric or special characters, but if it
contains leading spaces or tabs, multiple spaces or tabs, lowercase letters, or any other
characters not legal in a symbol name, you must enclose it in double quotation marks. If
you need to specify a string that contains quotation marks, you must enclose the entire
string in quotation marks and include a double set at the point where you want literal
quotation marks to appear. For example:
HELLO

"JOHN SAYS "HI""

This command assigns the value JOHN SAYS 11 HI 11 to the symbol HELLO.
You can indicate a null string by using a double set of quotation marks with nothing
between them, or by specifying no string at all. Both of the following examples specify the
null string:
NULLSTRING
NULLSTRING

:=
:=

1.6.3 Assigning Numeric Values to Symbols
To equate a symbol name to a numeric value, use one of the following forms of the
assignment command:
symbol-name = expression
symbol-name == expression

An expression can be any literal numeric value or an arithmetic or logical expression. As
with character values, one equal sign defines a local symbol; two equal signs define a global
symbol.
Table 1-4 lists the operators you can use in forming expressions with symbols.

Using the VAXNMS Operating System

1-29

Table 1-4: Summary of Operators in Expressions
Operator

Precedence

Logical
Operators

Arithmetic
Comparison
Operators

String
Comparison
Operators

Operation

.OR.
.AND.
.NOT.

2
3

Logical OR
Logical AND
Logical complement

.EQ.
.GE.
.GT.
.LE.
.LT.
.NE ..

4
4
4
4
4
4

Arithmetic equal to
Arithmetic greater than or equal to
Arithmetic greater than
Arithmetic less than or equal to
Arithmetic less than
Arithmetic not equal to

.EQS.
..GES.
.GTS.
.LES.
.LTS.
.NES.

4
4
4
4
4
4

String equal to
String greater than or equal to
String greater than
String less than or equal to
String less than
String not equal to

5
5

7
7

*
I

6
6

Arithmetic sum
Arithmetic difference
Arithmetic unary plus
Arithmetic unary negate
Arithmetic product
Arithmetic quotient

5
5

String concatenation
String reduction

Arithmetic
Operators

String
Operators

The following examples demonstrate how to form expressions with the operators listed in
Table 1-4.
1.

3 • OR.

This expression has the numeric value 7, which is the result of a logical OR operation
on the values 3 and 5.
2.

A.• EQS.

This expression compares the values of string symbols A and B. It has the logical value
FALSE. Such logical values, whether TRUE or FALSE, can be assigned to another
symbol or used as the condition for an IF ... THEN statement. See Section 1.6.4 for
information on the IF ... THEN statement.

1-30

Using the VAXNMS Operating System

1 +GT+

This expression compares the numeric values 1 and 2, and has the value FALSE.
4.

"MAYBE"

.LTS+

r11a}·be 11

This expression compares two strings. String comparisons start with the leftmost character and compare the ASCII hexadecimal values. Since uppercase letters have lower
ASCII values than lowercase letters, "MAYBE" is less than "maybe", and the expression has the value TRUE.

1.6.4 Symbol Substitution
The command interpreter substitutes the current values of symbols for the symbol names
in a command string. In some contexts, you need to tell the command interpreter to
perform symbol substitution; in other contexts, substitution is automatic. For a full description of the command interpreter's symbol substitution algorithm and examples of the
results, see the Guide to Using DCL and Command Procedures on VAX/VMS. The basic
substitution rules are as follows:
• Automatic substitution occurs in IF ... THEN and WRITE statements and on the right
side of arithmetic assignment statements. In these contexts, the command interpreter
assumes that strings starting with an alphabetic character are symbols, and strings
starting with a number are numeric literals.
For example, in the following IF ... THEN statement, A and B are assumed to be
symbols, and the command interpreter substitutes their values when evaluating the
expression:
IF A ,EQ, B THEN GOTO NEXT

The arithmetic assignment statement that follows increments the value of the numeric
symbol COUNT. The command interpreter substitutes the value of COUNT on the
right side only.
COUNT = COUNT + 1

• Automatic substitution occurs for command synonyms. If the first word on a command
line is recognized as a symbol, its value is automatically substituted in the command
line.
For example, suppose you have entered the following definition for the symbol ME:
$

ME :== SET DEFAULT SYSSLOGIN

Once the symbol ME is defined, you can treat ME as ifit were a DCL command. Since
the command interpreter automatically substitutes SET DEFAULT SYS$LOGIN for
ME, the effect of typing ME is to set your default directory to your login directory
Suppose you have entered the following definition:
$

PDEL :== DELETE SYSSPRINT/ENTRY=

Using the VAXNMS Operating System

1-31

Then you could use PDEL to delete entry number lSl from the SYS$PRINT queue:
$

PDEL 181

Note that the space following PDEL delimits the symbol; the command interpreter
would not recognize PDELlSl. Delimiters can be any of the characters that are not
legal symbol-name characters, for example, parentheses: $ PDEL < 181 , 182'183 l
Since the left parenthesis is not a legal symbol-name character, it is interpreted as a
delimiter. Therefore, this command causes entries lSl, 1S2, and 1S3 to be deleted from
SYS$PRINT.
• Symbols on the right side of nonarithmetic assignment statements and symbols used
in place of command parameters or qualifiers must be enclosed by apostrophes ( ') to
force the command interpreter to substitute current values for the symbol.
In the following example, the apostrophes force the command interpreter to substitute
the value of the symbol FILENAME for the symbol itself before performing the assignment. If the apostrophes were omitted, OLDSTRING would be assigned the value
FILENAME instead.
OLDSTRING

'FILENAME'

• Symbols inside quoted strings must be preceded by two apostrophes and followed with
a single apostrophe to force the command interpreter to substitute the symbol values
for the symbols.
For example, the following assignment statement gives PRINT_STRING a value
based on the current value of the symbol FILENAME:
PRINT_STRING

"Creatins file

''FILENAME',TST"

1.6.5 Passing Parameters to Command Procedures
You can pass up to eight parameters to a command procedure by including them on the
command line following the @ (Execute) command and the command procedure name.
When the command interpreter executes the command line, it assigns the parameter values supplied to symbols Pl through PS. If you specify only one parameter, it is assigned to
Pl; P2 through PS receive null values. If you specify two values, they are associated with Pl
and P2, and so on. You can use a pair of double quote characters to specify a null value for
a particular parameter.
The following example shows how to pass a value for the parameter Pl to a command
procedure. Suppose you want to use a command procedure named FORTEST in your
default disk area to compile, link, and run a program that you call NEWTEST.FOR. You
would enter the following DCL command:
$

@FORTEST NEWTEST

Upon receiving this string, the command interpreter assigns the value NEWTEST to the
symbol Pl. FORTEST can then request the value of Pl when it needs the file name.

1-32

Using the VAXNMS Operating System

The following example shows how FORTEST might refer to the file name that you entered.
This DCL command appends the string FOR to the file name and compiles the file named
by the resulting string.
$FORTRAN/WARNING/LIST 'P1',FOR

The single quotes around Pl tell the command interpreter to perform symbol substitution.
Without the single quotation marks, the command procedure would attempt to compile the
file Pl .FOR.
When you pass a number of parameters, you must separate them with one or more spaces,
as in the following example:
$ @RUNPROGS PROGA PROGB PROGC PROGD

When it receives this command line, the command interpreter assigns the value PROGA to
Pl, PROGB to P2, PROGC to P3, and PROGD to P4.
You can pass parameters to a batch job with the PARAMETERS qualifier of the SUBMIT
command. If you have more than one parameter to pass, enclose the list in parentheses and
separate the parameters with commas. For example:
$SUBMIT RUNPROGS /PARAMETERS=(PROGA1PROGB1PROGC1PROGD>

1.6.6 Passing Fixed Data to Programs
You can pass fixed data to a program by including the data in a command procedure that
runs the program. (See Section 1.6.7 for a description of how to pass data that is not fixed.)
The following command procedure illustrates how to include fixed data in a command
procedure. Note that the data begins on the first line after the RUN command, and that
the lines do not begin with a dollar sign. The first line that begins with a dollar sign signals
the end of the data.
$ FORTRAN AVERAGE
$ LINK At.IERAGE
$ RUN Al,IERAGE
33
GG
99
9999

$ DELETE AVERAGE.OBJ;

If a line of data to be passed to a program must begin with a dollar sign, you must use the
DCL commands DECK and EOD to begin and end the data. For example:
$ FORTRAN MESSAGE
$ LINK MESSAGE
$ RUN MESSAGE
$ DECK
This is a line of data that doesn't
30.02

be~in

with a$,

$
$

EDD

$ DELETE MESSAGE.OBJ;

In the preceding example, both lines between the DECK and EOD commands are passed to
the program as data.
Using the VAX/VMS Operating System

1-33

1.6.7 Controlling Command Procedure Input/Output
You control command procedure input and output (1/0) operations by assigning appropriate values to the system logical names SYS$COMMAND, SYS$INPUT, and
SYS$0UTPUT. The following list describes the rules VAXNMS uses to assign these
logical names, and explains how you can reassign them to perform special tasks:
• SYS$COMMAND is the logical name for the source of input to the command interpreter. SYS$COMMAND does not change: if you execute a procedure interactively,
SYS$COMMAND is assigned to your terminal; if a batch job executes the command
procedure, SYS$COMMAND is assigned to the batch file.
• SYS$INPUT is the logical name for the default input file. When you execute a command procedure, SYS$INPUT is assigned to the command procedure file. When programs request data from the input device, the command interpreter reads from
SYS$INPUT to find the data. Thus, you can change the source of your input data by
reassigning SYS$INPUT.
• SYS$0UTPUT is the logical name for the default output file. When you execute a
command procedure, SYS$0UTPUT is assigned to your terminal, unless you use the
/OUTPUT qualifier with the @ (Execute) command. If you submit the procedure as a
batch job, SYS$0UTPUT is assigned to the LOG file associated with the batch job.
The LOG file is written on your login disk area, and when the batch job is completed,
the system queues the LOG file to SYS$PRINT. You can tell VAXNMS not to print
the LOG file by including the /NOPRINT qualifier with the SUBMIT command.
You can direct interactive command procedures to accept input from your terminal by
temporarily reassigning SYS$INPUT. For example, you could create a command procedure
that runs a text editor for you, lets you edit as much as necessary, and resumes control
when you exit from the editor. The command ASSIGN/USER_MODE places a logical
name in the process logical name table and removes it after the next image (for example, a
DCL command or a program) executing in the process exits.
The following example shows how a command procedure temporarily reassigns
SYS$INPUT to the terminal:
S ASSIGN/USER-MODE SYSSCOMMAND SYSSINPUT
S EDIT/EDT 'Pl' ,FOR
S FORTRAN/DEBUG 'Pl'
$ LINK/DEBUG 'Pl
S ASSIGN/USER_MODE SYSSCOMMAND SYSSINPUT
$ RUN Ip 1
I

By reassigning SYS$INPUT to SYS$COMMAND, this command procedure allows you to
edit a file at your terminal. When you exit from the editor, SYS$INPUT reverts to the
command procedure. The command procedure then compiles and links your program,
including debugging information. Finally, the command procedure runs your program and,
by reassigning SYS$INPUT once again, allows you to interact with the debugger.

1-34

Using the VAXNMS Operating System

You can generalize your command procedures by using the INQUIRE, READ, and WRITE
commands. INQUIRE writes a prompt string and accepts a value for a symbol. READ
accepts data from a specified file. WRITE writes a character string to a specified file.
The following example reworks the preceding one so that the command procedure uses the
INQUIRE and WRITE commands to request a file name and write it to the user's terminal
before performing each operation.
$ INQUIRE FILENAME "File na111e"
$ ASSIGN/USER_MODE SYS$COMMAND SYS$INPUT
$EDIT/EDT ~FILENAME',FOR
$ !
$ WRITE SYS$0UTPUT "Co111Pilina' "FILENAME"'
$ FORTRAN/DEBUG 'FILENAME'! $
$WRITE SYS$0UTPUT "Linf\ina' ''FILENAME'"
$ LINK I DEBUG IF I LENAME I
$ !
$WRITE SYS$0UTPUT "Runnina' debua'a'er 1,.1ith "FILENAME'"
$ ASSIGN/USER_MODE SYS$COMMAND SYS$INPUT
$ RUN 'FILENAME'
$ E)<IT

1.6.8 Controlling Command Procedure Execution Flow
Some DCL commands are intended to control the flow of execution in command procedures. The most commonly used flow-control commands are EXIT, GOTO, and
IF ... THEN.
• EXIT directs the command interpreter to stop processingthe current command procedure and resume e~ecuting commands interactively (or from the next outermost level
of command procedure).
• GOTO tells the command interpreter to change the .order in which it processes commands (usually sequential) and to begin processing at a specified label.
• IF ... THEN requests evaluation of a condition and performance of an action ·if the
condition holds.
For example:
$ INQUIRE CHECK "Y to pura'e files·t E to
$IF CHECK ,EQS, "E" THEN EXIT
$IF CHECK .NES, "Y" THEN GOTO BYE
$ PURGE!LOG [KLEE,, ,J
$ BYE:
$ LOGOUT

exit"

When you execute this command procedure, it prints the following characters on your
terminal:
Y to :p u r 8' e f i ·l e.s , E to ex.it :

If you respond with E, you exit from the procedure immediately. ff you respond with Y, the
next statement executed is PURGE [KLEE ... ]. If you respond with anything but E or Y,
Using the VAXNMS Operating System

1-35

including a response of just a RETURN, control is transferred to the first command following the label BYE:. This command procedure is a convenient one to use when you log out,
because it reminds you to purge your disk area.

1.6.9 Handling Command Procedure Errors
Two types of errors occur in command procedures: those that result from the command
procedure containing errors, and those that result from an attempt by the procedure to
perform an operation that fails. VAXNMS provides the SET VERIFY, ON ... THEN, and
SET NOON commands and the reserved symbols $STATUS and $SEVERITY to help you
deal with these errors.
The SET VERIFY command can help you discover and correct command procedure execution errors. When you enter SET VERIFY before executing a command procedure, the
system displays the procedure lines as they are executed. Thus, you can see which commands are executed and in what order, and detect errors as they happen.
You have two options in dealing with command procedure operations that fail. You can
choose to have a certain command executed whenever an error of a specified severity
occurs, using the ON ... THEN command. Or you can disable system error checking with
SET NOON, and use the VAXNMS error status information to decide what action to take.
VAXNMS provides error status information in the reserved global symbols $STATUS and
$SEVERITY. $STATUS contains a condition code, while $SEVERITY contains only the
severity code, which is the three low-order bits of $STATUS. By VAXNMS convention, an
odd condition value signals success and an even value signals failure. The codes and their
values are shown in Table 1-5.
Table 1-5: Severity Codes
Value

Severity

Warning

Success

Error

Information

Severe, or fatal, error

You can use an ON ... THEN command to specify execution of a DCL command (such as
GOTO) in case of an error. The ON clause names the least severe class of errors for which
the DCL command should be executed. The command interpreter executes the THEN
clause when errors of the named class or errors in more severe classes occur. The severity
levels, in order of increasing severity, are WARNING, ERROR, and SEVERE_ERROR.

1-36

Using the VAXNMS Operating System

For example, if you want your procedure to stop when an error of any severity level occurs,
use the following command:
$ ON WARNING THEN EXIT

If you were to specify ERROR instead of WARNING, the procedure would exit on errors

and severe errors, but execution would continue if a warning occurred.
You can use the SET NOON command (which is the negation of SET ON) to request the
system not to check $STATUS. The command interpreter continues to load the severity
code into $STATUS, but takes no actions based on its value. Thus, you can act on error
conditions as you prefer.
When you use SET NOON, you usually test $STATUS with the IF ... THEN command.
Because an odd integer is evaluated as TRUE and an even integer, as FALSE, you can use
the following command to exit when an error of any severity level occurs:
$ IF .NOT, $STATUS THEN EXIT

For more information on using $STATUS and related symbols, and for a full description of
error checking in command procedures, see the Guide to Using DCL and Command Procedures on VAX/VMS.

1.6.1 O Submitting Command Procedures in Batch Mode
The SUBMIT command causes the command interpreter to execute your command procedures in batch mode, freeing your terminal for other work. Section 1.6.5 discusses the
method of·passing parameters to batch jobs. This section demonstrates how you can get
VAXNMS to perform the following operations:
• Run your batch job at a specific time
• Tell you when the batch job has completed
• Print or save the LOG file
The I AFTER qualifier of the SUBMIT command tells VAXNMS to wait until the time
specified before beginning to execute the batch job. For example, the command
$ SUBMIT/AFTER=17:00 COMPILES

tells VAXNMS to submit the file COMPILES.COM to the default batch queue at
5:00 P.M.
The /NOTIFY qualifier requests VAXNMS to ring the bell on your terminal and print a
message informing you that your batch job has been completed. The message also informs
you of the severity level of any error that causes the batch job to be aborted. For example:
$ SUBMIT/NOTIFY COMPILES

The /NOPRINT qualifier tells VAXNMS not to queue the LOG file for printing. If you do
not specify /NOPRINT, the LOG file is automatically queued to the printer when the batch
job exits, and the LOG file is deleted when it has been printed. If you wish to print the LOG
file but do not want it deleted, specify the /KEEP qualifier.
Using the VAXNMS Operating System

1-37

The /LOG qualifier allows you to control the creation and location of the LOG file. If you
specify /NOLOG, VAXNMS does not create a LOG file. If you use /LOG=file-spec,
VAXNMS creates the LOG file with the name that you specify. For example, the command
$ SUBMITJNOPRINT/LDG=[J COMPILES

causes VAXNMS to create a file. called COMPILES .LOG on the current default directory.

1.6.1.1 Login Command File
VAXNMS recognizes a special command procedure, called alogin command file (or sim~
ply a login file), that the system tries to locate and execute every time you log in. When you
log in,. VAXNMS looks on your default device and directory for a file called LOGIN .COM.
If the file exists, it is executed as an interactive command procedure before. the login
procedure is completed.
The LOGIN .COM file therefore gives you a way to set up an environment that will be the
same for every terminal sessfon. For example, you can define logical names that you use in
every session, you can set job and terminal parameters, and so forth. A sample
LOGIN .COM file is shown in the following example:
$DEFINE TOOLS USERD:CKLEE+TOOLSJ
$ SET TERMINAL /INOUlRE
$ RUN TOOLS:.CALENDAR

This LOGIN file defines· the logical name TOOLS as· the subdirectory [KLEE.TOOLS],
which contains some commonly used programs· such as· CALENDAR.EXE.
For more information on DCL command procedures, see the Guide to Using DCL and
Command Procedures on VAX/VMS.

l-38

Using the VAXNMS· Operating System

Chapter 2

Creating and Modifying Programs
The first step in developing a VAX FORTRAN program consists of creating the program's
source file. The VAX/VMS EDT text editor can be used to perform this operation. This
chapter provides an introduction to the use of EDT.
There are three other sources of information on EDT available to you. The first is the VAX
EDT Reference Manual. The second is the computer-assisted course titled "Introduction to
the EDT Editor" supplied with the VAX/VMS operating system. The third is EDT's help
facility, described in Section 2.1.1.

2.1 Introduction to EDT
EDT, the DEC Standard Editor, is an interactive general-purpose text editor. It offers two
modes of operation: line mode editing, in which operations are performed on single lines of
text; and character mode editing (also known as change mode editing), in which operations
are performed on characters and words as well as on lines. Line editing is possible on either
hardcopy or video terminals. Character editing, while usable on hardcopy terminals, is
most effective on video terminals.
Line editing, with its English-like commands, is easy for the inexperienced user to learn.
Character editing, while requiring practice, is also very simple. This makes EDT especially
suitable for an inexperienced user who wants to quickly learn how to perform some basic
text-handling operations.
EDT also offers many advanced features for experienced users who use it heavily:
• Multiple text buffers. By default, editing operations take place within a single text
buffer called MAIN. However, you can maintain an unlimited number of alternate
text buffers as "holding areas" for text that you do not necessarily wish to incorporate
in the output file.
• Flexible input and output commands. You can copy files into an EDT text buffer after
beginning the editing session, and you can output text buffers (or portions of text
buffers) to files before ending the session.

2-1

• Macro capability. You can create sequences of line editing commands that you invoke
with a single command.
• The ability to define keys for custom character editing applications. For example, a
keypad key can be defined so that it inserts a specified line of text each time it is
pressed. This function is especially useful in programming applications where certain
statements may be repeated frequently.
Finally, EDT protects your text. Should your editing session end in an unexpected manner,
you can recover all your editing operations by reentering the EDT command line with the
/RECOVER qualifier. EDT then "replays" your editing session up to the point of interruption, using the contents of the journal file that it maintained during the lost session.
The following subsections introduce EDT's help facilities and explain how to invoke and
terminate EDT, how to enter and exit editing modes (line mode and character mode), how
to protect and recover text, and how to create a new file.

2.1.1 The Help Facilities
EDT offers on-line help in both line mode and character mode.
In line mode, you invoke the help facility by entering the HELP command. Issued without
parameters, this command displays information on how to get further help, plus a list of
subjects for which help is available. If you enter one of the subjects as a parameter to the
HELP command, EDT displays information on that subject, and possibly another list. For
example:
*HELP DELETE
DELETE
The DELETE (abbreviation: D> command deletes the line specified

Additional information available:
/QUERY
*HELP DELETE /QUERY
DELETE
/QUERY

CJ
A

CJuitt do not delete any of the remainind
lines
All t delete all of the remaining lines

*
2-2

Creating and Modifying Programs

In character mode, you obtain help by pressing the HELP key on your keypad; EDT will
display a diagram of the keypad that identifies all of the key functions. You can then
obtain help on an individual function by pressing the key that invokes that function.
(Figure 2-2 shows the location of the HELP key.)

2.1.2 Invoking and Terminating EDT
An editing session begins when you invoke EDT with the EDIT/EDT command and ends
when you terminate EDT with the EXIT or QUIT command.
When you start an editing session, you can specify the name of a new file or the name of an
existing file. In the former case, you can use your editing session to create a new file with
the name that you specified. In the latter case, EDT loads the existing file into its MAIN
text buffer, and you can then add to or modify the text in the file. EDT does not destroy the
contents of the existing file that you are editing; it simply produces a new version, leaving
the old version intact.

2.1.2.1 Invoking EDT
To invoke EDT, issue an EDIT/EDT command in the format
EDIT/EDT[/qualifier ... ]

file-spec

Qualifiers

Defaults

[NOJCOMMAND[=file-specl
[NOJJOURNAL[=file-specl
[NOJOUTPUT[=file-specl
[NOJREAD
[NOJRECOVER

/COMMAND=EDITINI.EDT
/JOURNAL=infile-name.JOU
/OUTPUT=infile-spec
/NOREAD_ONLY
/NORECOVER

where:
file-spec

specifies the file to be created or edited. If the file does not exist, EDT creates it.
EDT does not provide a default file type. If you do not specify one, the, file type is
null.
/OUTPUT[ =file-spec]

supplies an alternate file specification for the output file. By default, EDT creates an
output file upon exit that has the same name and type as the input file and a version
number of 1 (if the input file does not exist) or 1 higher than the highest existing
version (if the input file does exist).

If you specify /NOOUTPUT, EDT does not automatically create an output file when
you issue the EXIT command.

Creating and Modifying Programs

2-3

The remaining qualifiers, which describe specialized editor functions, are described elsewhere: the /COMMAND qualifier, in Section 2.4.3; the /JOURNAL, /READ_ONLY, and
/RECOVER qualifiers, in Section 2.1.4.
For convenience, you can issue the following command to equate a short command symbol
(EDT, in this example) to EDIT/EDT:
$

EDT

:==

"EDIT/EDT"

After you issue this command, the command interpreter will recognize the symbol EDT (or
any other symbol you specify) as equivalent to EDIT/EDT.
When you invoke EDT, the response varies depending on whether the file that you specify
exists. (Other factors, such as commands contained in a startup command file named
EDTINl.EDT (see Section 2.5.3), may further alter the response.) If the file does not exist,
EDT so informs you, and prompts you to issue editing commands:
$

EDIT/EDT METRIC.FOR

InPut file does not exist

[EOBJ

*
The asterisk ( *) is EDT's line editing prompt. When EDT is displaying the asterisk
prompt, you can enter any of the commands listed in Table 2-1.
If the file exists, its first line is displayed instead of [EOBJ:
$

EDIT/EDT METRIC.FOR
PROGRAM METRIC

*
NOTE
If you invoke EDT and it does not display an asterisk prompt, you cannot enter
line editing commands. This condition can result when the current default directory contains a startup command file named EDTINl.EDT that causes EDT to
enter character mode directly. If this happens, you can enter line mode by
typing a <CTRL/Z>. You can override any unwanted effects of a startup command file by including the /NOCOMMAND qualifier on the command line.

2.1.2.2 Terminating an EDT Session
Use the EXIT command to terminate EDT and create an output file from the contents of
the MAIN text buffer. To override the default output file, you can specify an output file
with the EXIT command, as shown in the following example:
*EXIT ALTNAME.FOR
_DBl:[PRDJECTJALTNAME.FORil

55 lines

The QUIT command terminates EDT without creating an output file. You can use QUIT if
you are simply reading a file without modifying it or if you do not want to save your edits.
The EXIT and QUIT commands are used in both editing modes, and the effects are the
same in both modes. In line mode, you simply type the command name after the prompt
2-4

Creating and Modifying Programs

(*)and then press <RET>. In character mode, you press the GOLD key; then you press the
COMMAND key; then you type the command in response to the prompt; and then you
press the ENTER key.

2.1.3 Entering and Exiting Editing Modes
To change from line mode to character mode, use the CHANGE command (abbreviation
C). When you issue the CHANGE command, the screen first goes blank and then fills with
text. You will find the cursor somewhere on the screen, positioned at the current line or the
line you specified with the CHANGE command. (If the buffer is empty, the cursor and
[EOB] appear at the top of the screen.)
EDT does not display line numbers while in character mode, although it does continue to
assign them as you insert text.
To change from character editing mode to line mode, enter a <CTRL/Z>. This terminates
character editing and causes EDT to display the asterisk prompt. You can then perform
line editing operations or end the editing session, as appropriate.

2.1.4 Protecting and Recovering Text
Three qualifiers to the EDIT/EDT command allow you to protect files against inadvertent
modification and to recover editing operations that have been lost.
The /READ_ONLY qualifier controls whether journaling and the creation of an output file
are enabled. (Specifying /READ_ONLY is equivalent to specifying /NOOUTPUT and
/NOJOURNAL.) /NOREAD_ONLY, the default, allows EDT to create an output file and
a journal file. Use /READ_ONLY in situations where you want to be sure you do not
create a modified file, or for reading a file in a directory where you do not have write
privileges.
The /JOURNAL qualifier allows you to disable (using /NOJOURNAL) or to specify the
name of the journal file that EDT creates to record your editing activity. By default, EDT
creates a journal file with the file name of the input file and a file type of JOU. If the
editing session ends abnormally, EDT can use the contents of the journal file to re-create
the session. If the editing session ends normally (that is, as the result of an EXIT or QUIT
command without a /SAVE qualifier), EDT deletes the journal file.
The /RECOVER qualifier causes EDT to use the contents of a journal file to re-create a
previous editing session, perhaps one that was lost as the result of an accidental
<CTRL/Y> or system problem. If you specify /RECOVER, EDT locates a file with the
same name as the input file and a file type of JOU; then it applies all of the editing
operations recorded in the journal file to the input file. These operations appear on your
terminal as EDT performs them. When EDT has exhausted the contents of the journal file,
the activity on the terminal ceases. You can then continue to edit.
Two notes of caution are necessary. First, it is important for the EDIT/EDT command that
starts a recovery operation to match exactly the command that started the lost session,

Creating and Modifying Programs

2-5

including any special startup command files. The only difference between the two commands should be the /RECOVER qualifier. In particular, the input file must be the same
version that you started with at the beginning of the lost session. Second, note that EDT
does not necessarily recover your session to the exact point where it was lost. A few
keystrokes may be missing, possibly including a partial command sequence. To clear any
partial command sequences, press <CTRLIX> before continuing the editing session.

2.1.5 Creating a New File
To create a new file, you issue an EDIT/EDT command that specifies a file that does not
currently exist in your directory. In character mode, the designation [EOB] appears on the
screen. This indicates that you are currently at end-of-buffer and that any text you insert
will be the only text in the buffer. You can then enter as many line of text as you wish.
When you have finished entering text, terminate your EDT session as described in Section
2.1.2.2.
In line mode, after EDT responds with the asterisk prompt, issue the INSERT command
(abbreviation I) followed by <RET>. The cursor or print head then moves to the right 16
spaces; this space is left by EDT to accommodate line numbers, although none appear at
this stage. You can now enter as many lines of text as you wish. When you are finished
entering text, terminate the insert with <CTRL/Z>.
In line mode, if you do not want EDT to leave space in front of each line for line numbers,
you can issue the SET NONUMBERS command; EDT will then begin each line at the left
margin of the terminal. EDT continues to number lines, but does not display the numbers.
You can restore the line number display later by issuing a SET NUMBERS command.

2.2 Character Mode Editing
EDT's character mode allows you to perform editing operations at any position in your text
instead of line by line. For most applications, especially those requiring extensive modification of existing text, character editing is faster and more straightforward than line editing.
When you use character mode on a video terminal, your screen always contains an accurate
picture of the area of the file in which you are working. The terminal's cursor shows exactly
where you are at all times.
There are two types of character editing: nokeypad and keypad. Nokeypad character editing works on all terminals, including hardcopy terminals. It requires you to enter short
commands through the keyboard and terminate each command with a <RET>. Keypad
character editing works on the VT50-, VTlOO-, and VT200-series video terminals and on
terminals that are compatible with them. In keypad editing, you request editor functions
by pressing keys on the auxiliary keypad; no <RET> is required to terminate the command. Anything you type on the keyboard, including carriage returns, is inserted into the
file as text.

2-6

Creating and Modifying Programs

This section describes.only keypad character editing. To learn about nokeypad character
editing, read the VAX EDT Reference Manual.
The keypads for the VT52, VTlOO, and VT200 (and compatible) terminals are different.
Therefore, the following description refers to functions rather than to specific keys. It is a
good idea to keep a copy of the appropriate keypad diagram handy while you are learning
character editing. Figures 2-1, 2-2, and 2-3 contain the keypad diagrams for the VT52,
VTlOO, and VT200, respectively. The numbers or characters shown in the upper right of
each key correspond to what you see on the key.
Note that most keys perform two functions. To use the upper of the two functions shown on
a key, press the key. To use the lower function, press and release the GOLD key before
pressing the function key.

2.2.1 Maneuvering the Cursor
Before performing most character editing operations, you must move the cursor to the
location in the file where you wish the operation to take place. There are many ways to
move the cursor; experience eventually teaches which is best in a given situation.
The LEFT and RIGHT functions move the cursor one character to the left or right. If the
cursor is at the end of a line, the RIGHT function moves it to the beginning of the next line.
Conversely, if the cursor is at the beginning of a line, the LEFT function moves it to the
end of the previous line.
The UP and DOWN functions move the cursor one line up or down. The column position of
the cursor does not change, unless there is no text in the corresponding column above or
below (that is, the line that you are moving to is shorter than the line that you are moving
from). In the latter case, the cursor moves to the end of the line that is above or below.
·The beginning-of-line function, obtained by pressing the BACKSPACE key, moves the
cursor to the beginning of the line in which it is positioned. If the cursor is already at the
beginning of a line, the function moves it to the beginning of the previous line.

Creating and Modifying Programs

2-7

r----..,...I -----,------r----,
I
.
tI

I
I

GOLD

HELP

1
I
UP
I REPLACE I

DEL L
UND L

L-----t------t------1-----l
I
1 1
aI
9 I
iI
I
I

·1

PAGE

I COMMAND I

I
I

FNDNXT
'FIND

I
I

DEL w
UND w

I
I

DOWN
SECT

r----r----~----r---~

I
ADVANCE I
BOTTOM

BACKUP
TOP

I
I

- I

DEL
UND c

RIGHT
SPECINS

CUT
PASTE

LEFT
APPEND

r----;-+---~+----3-t----=-1

WORD

I CHNGCASE I

EOL
DEL EOL

L____ L----~----i----1

0 I

•I

ENTER

I
I
I
LINE
I SELECT I ENTER I
OPEN LINE
I RESET I SUBS I
L _________ .l ____ _L _ _ _ _ J

I
I
I

ZK-020-81

Figure 2-1: VT52 Keypad
r---~r----,---.=r---=-..1

I
I

I
'I

DOWN

L---~-----L

I
I

LEFT

I
RIGHT

I
I

____ L ____ ~

j---pF-;-r---p;21---p;3;---PF~

GOLD

I
I

HELP

SECT
FILL

FNDNXT
FIND

APPEND

I
I

DEL L
UND L

DEL w
UND w

~---~~----;r---9+----~

PAGE

I COMMAND I

I REPLACE I

I
I

~---~+----~----~----~

I
I ADVANCE I
I BOTTOM I
I

I
I

BACKUP
TOP

I
I

CUT
PASTE

DEL c
UND c

I
I

11 ____ L----~----L---~
1 I
I
I
WORD
I
I CHNGCASE I

EOL
DEL EOL

I
I

CHAR
SPECINS

I
I
I

ENTER I

I
I

~----L---;~---~: ~~

I
I
I

LINE
OPEN LINE

I
I

SELECT
RESET

I
I

L _________ L ____ L ___

ZK-021-81

Figure 2-2: VTlOO Keypad

2-8

Crea ting and Modifying Programs

VT200

~F.==103
t___::::_J~.

DDD
[]

cg
FIELD
7
,ADVFIELD

4
ADVANCE
BOTTOM

PF3
FNDNXT
FIND

PF2
HELP
HELP FMT

009 ~
0.
5
BACKUP
TOP

DEL W
, UNO W

a·
D
B
BBB
D

PF4
DEL ACE
UNO ACE

•

DEL C
UNO C

EOL
DEL EOL

·O

ENTER

OVER ACE
INSERT

ZK-1758-84

Figure 2-3: VT200 Keypad

The TOP and BOTTOM functions move the cursor to the beginning and end of the buffer,
respectively.
All the remaining cursor movement functions depend in part. on the ADVANCE and,
BACKUP functions. The ADVANCE function causes subsequent cursor movement to occur in the forward direction, that is, toward the, end of the. buffer .. The BACKUP function
causes subsequent cursor movement to occur in the backward direction, toward the. beginning of the buffer. When character editing, begins, cursor movement is forward,, until
reversed' by the BACKUP function.
The following functions depend on the current. direction established by ADVANCE and
BACKUP:
• The. CHAR function moves the. cursor one character.
• The WORD function moves the cursor to the beginning of the next. or previous word
(the end~of~line character is considered a word)..
• The LiNE functfon moves the. cursor to the beginning of the next line, if the current
direction is forward. If backward, the LINE function moves the cursor to the beginning
of the line in which the cursor is positioned, or, if the cursor is at the beginning of a
line, to the beginning of the previous. line.
• The EOL (for end~of-line) function moves the cursor to the next or previous end~of~Iine
character.

Creating and Modifying. Programs

2-9

• The SECT (for section) function moves the cursor one 16-line section.
• The PAGE function moves the cursor to the next or previous page mark (by default, a
form feed).
All of these cursor movement functions can be combined with a repeat count, causing the
function to be repeated a specified number of times. To enter a repeat count, press the
GOLD key, then type in the count on the keyboard (not keypad) number keys, then type in
the function to be repeated. As you enter the repeat count, the numbers appear on the
screen below the area reserved for text. The numbers disappear as soon as you enter the
function.
You can also use FIND and FNDNXT (for find next) to move the cursor to a certain string.
To find a string, enter the FIND function. EDT prompts you for a search string. Type the
search string without delimiters, and terminate it with either the ADVANCE or BACKUP
function to determine the direction of search. EDT moves the cursor to the beginning of the
search string. If the search string is not found, EDT issues a message and does not move the
cursor.
The FNDNXT function finds the next occurrence of the current search string in the current
direction. The current search string is the last string you entered with the FIND function.
Note that you can locate strings that include carriage returns with the FIND function.
Simply enter the carriage return as part of the search string. The carriage return does not
terminate the search string; you do that with the ADVANCE or BACKUP function. EDT
echoes a carriage return in a search string as AM.

2.2.2 Inserting New Text
Once the cursor is positioned, you can insert text in front of it simply by typing the text on
the keyboard. No command is required and whatever you type becomes part of the file.
Your insertion appears on the screen as you type it, and the surrounding text moves as
necessary to accommodate it.
When you insert text at the beginning or in the middle of a line, the end of the line may
disappear off the edge of the screen. The text is not lost, however: if you enter a carriage
return in the text you are typing, the text appears on the next line. To avoid this problem,
you can use the OPEN LINE function. When the cursor is at the beginning of a line, OPEN
LINE provides a blank line above that line, and positions the cursor at the beginning of the
blank line.
As you type new text, you may notice errors in surrounding text. You can move the cursor
to these errors and correct them at any time, and then move the cursor back and continue
to insert text.

2.2.3 Deleting and Undeleting Text
EDT character editing provides several methods of deleting text in units of varying sizes.
EDT also maintains three buffers to contain text that has been deleted. The character

2-10

Creating and Modifying Programs

buffer contains the last character deleted; the word buffer contains the last word deleted;
and the line buffer contains the last line deleted. You can insert the contents of each of
these three buffers at the cursor position by using the UND C, UND W, and UND L
functions, respectively. There is no limit to the time or number of operations between a
delete operation and the undelete operation that reinserts the deleted text. Furthermore,
you can undelete one unit of text as many times as you wish, and at any locations you wish.
The DEL C (for character) function deletes the character at which the cursor is positioned,
and moves the cursor to the next character. The DELETE key on the keyboard deletes the
character before the cursor position (the last character typed, if you are inserting text) and
does not change the cursor position. Both of these ftinctions move the deleted character
into the character buffer, from which it can be retrieved by using the UND C function.
The DEL W (for word) function deletes from the current cursor position to (but not
including) the first character of the next word. The LINE FEED key on the keyboard
deletes from (but not including) the cursor position back to the first character of the
current word. Both of these functions move the deleted text into the word buffer, from
which it can be retrieved by using the UND W function.
The DELL (for line) function deletes from the cursor position through the next end-of-line
character. The DEL EOL (for end-of-line) function is similar, except that it does not delete
the end-of-line character. Typing <CTRL/U> deletes from (but not including) the cursor
position to the beginning of the current line. All of these functions move the deleted text
into the line buffer, from which it can be retrieved by using the UND L function.

2.2.4 Moving Text
Character editing provides two basic methods of movihg text. The first is available through
the three undelete functions. You can delete a unit of text from one location, move the
cursor to another location, and undelete the text there. However, this method is only
effective for units that can be deleted by the various functions described in Section 2.2.3.
To move larger or more precise blocks of text, use CUT and PASTE. These two functions
allow you to "cut" any amount of contiguous text from one location and "paste" it elsewhere.
The first step is defining the text to be moved. To do this, move the cursor to either the
beginning or end of the text and enter the SELECT function. Then move the cursor to the
other extremity of the text. In so doing, you create a select range, that is, all of the text
between the cursor position and the position at which you entered the SELECT function.
On VTlOO and VT200 terminals, EDT highlights the select range with reverse video. If you
make a mistake while you are defining the select range, enter the RESET function to
cancel the select range currently in effect.
Once you have defined the select range, enter the CUT function. The text within the select
range disappears. (EDT moves it into a text buffer named PASTE.) Move the cursor to the
position at which the text is desired, and enter the PASTE function. The text appears at
the cursor position.

Creating and Modifying Programs

2-11

You can paste the cut text in as many locations as required. Specifically, you can paste the
text as soon as you cut it, then move the cursor and paste the text again. This is in effect a
copy operation.
Each CUT operation destroys the previous contents of the PASTE buffer and replaces
them with the select range. To add the select range to the contents of the PASTE buffer,
use the APPEND function.
The PASTE buffer is an ordinary EDT text buffer. You can edit within it, load it from a file
with the INCLUDE command, or create a file from its contents with the WRITE command.

2.3 Line Mode Editing
To edit an existing file in your directory, issue an EDIT/EDT command that specifies its
name. (To edit a file from a directory other than your own, see Section 2.3.10). EDT
displays the first line in the file, as shown in the following example:
$

EDIT /EDT DrnMPLE, TXT
1
This is the first

line of EXAMPLE+TXT

*
The number 1 to the left of the line is the line number. It is not part .of the file. The file
starts with the word "This."
The line displayed is the current line. EDT uses the current line as the default in many of
:its operations. For example, an INSERT command that does not specify a range causes
EDT to insert text in front of the current line.
The concept of "range" is central to all EDT line editing operations. The next section
describes ways of specifying range. The sections that follow describe the most common and
useful line editing operations.

2.3.1 line Editing Command Summary
When you invoke EDT, and throughout your editing session, EDT prompts you to enter
line editing commands by displaying an asterisk. For example:
$

ED'! TI EDT METRI'C, FOR
1
PROGRAM .METRIC

*
Table 2-1 describes briefly (in alphabetical order) the most .useful commands that you can
enter in respons~ to the line editing prompt (*). Each command has a .smallest acceptable
abbreviation, shown .in bold type in the table.
All line editing commands are terminated with a <RET>. Most of the commands allow or
require you to specify a ·range or ranges; the range spec'ification tells EDTwhere the action
of the command should take place. Section ·2:3.2 summarizes range specifications, and the
command examples show various ways of specifying a range.
2-12

Creating and Modifying Programs

Table 2-1: Summary of Line Editing Commands
Command

Function

CHANGE [range]

Invokes character mode editing for specified buffer

CLEAR

Deletes the contents of a text buffer

COPY [rangel]
[/QUERYJ

[range2]

Copies lines specified by rangel to a location in an EDT
buffer specified by range2; does not delete lines from original location

DEFINE I KEY I MACRO }

Defines a new or revised key function for character mode
editing, or defines a macro name

DELETE [range] [/QUERYJ

Deletes a specified line or lines

EXIT [file-spec]

Terminates EDT, saving the contents of the text buffer
MAIN as the output file

FILL [range]

Reformats a block of text, filling lines with the maximum
number of full words without exceeding the right margin

FIND range

Establishes the first line in range as the current line

HELP [topic ... J

Displays information on the specified EDT command or
function

INCLUDE file-spec [range]

Copies an external file to a location in a text buffer specified by range

INSERT [range]

Opens a text buffer for the insertion of text at the location
specified by range

MOVE [rangel]
[/QUERYJ

[range2]

Moves lines specified by rangel to the location specified by
range2, deleting the lines from the source location

PRINT file-spec [range]

Creates a listing file with the specified file name

QUIT [/SA VEJ

Terminates EDT without creating an output file, optionally
saving the journal file

REPLACE [range]

Deletes specified lines from a text buffer and leaves the
buffer open for insertion of text

RESEQUENCE [range]

Assigns new line numbers to a range of lines

SET [parameter]

Sets a variety of editor operating parameters

SET[[NOJNUMBERJ

Enables/disables the display of line numbers

SHOW [parameter]

Displays specified editor operating parameters

SUBSTITUTE
/stringl/string2/[range]
[/QUERY]

Replaces string! with string 2, either in the current line or
in the specified range

Creating and Modifying Programs

2-13

Table 2-1 (Cont.): Summary of Line Editing Commands
Command

Function

[SUBSTITUTE] NEXT
[/string1/string2J

Replaces stringl with string2, based either on the strings
specified or on the previous SUBSTITUTE command

TAB ADJUST [-Jn [range]

Shifts each line in a range of lines by a specified number of
logical tab stops

[TYPE] [range]

Displays specified lines and makes the first line in range
the current line; the default command

WRITE file-spec [range]

Moves a copy of specified text from a buffer to a file

2.3.2 Specifying Line Ranges
A range is the line or lines on which EDT performs an operation. A range specification is a
description of a range in terms that EDT can understand. All the line editing commands
(except SUBSTITUTE NEXT) described in the sections that follow accept one or more
range specifications, although many do not require one.
The simplest range specification ideptifies a single line of text. A line can be located by its
position in the file relative to the current line, by a text string that it must contain, or by its
line number.
When you insert lines of text in a new file, or when EDT loads an existing file into its
MAIN buffer, each line of the file receives a number. The numbering starts with 1 and is
incremented by ls. If you insert lines of text between existing lines, EDT numbers the new
li~ies using appropriate decimal increments. This technique ensures enough unique line
numbers to cover any reasonable editing operation. EDT displays the line numbers whenever it displays text, unless you have issued the SET NONUMBERS command. In that
case, EDT does not display line numbers, but it does continue to assign them.
Single-line range specifications are listed in Table 2-2; examples appear below the table.

2-14

Creating and Modifying Programs

Table 2-2: Single-Line Range Specifications
Specification

Meaning
The current line

number

The line specified by the number

'string' or "string"

The next line containing the string you specify

- 'string' or -"string"

The preceding line containing the string you specify

[range] { + I - I [number]

The line that is the specified number of lines after (or before, if
minus) the single line specified by range (range defaults to the
current line; number defaults to 1)

BEGIN

The first line in the text buffer

END

An empty line (designated by [EOBJ) following the last line of
text in the text buffer

Examples:
Specification
20.6
"EQUIVALENCE"
11
-D_FLOATING COMPLEX"

-6
11
SUBROUTINE 11 +4

Meaning
The line numbered 20.6
The next line that contains the string EQUIVALENCE
The first preceding line that contains the string
D_FLOATING COMPLEX
The line six lines before the current line
The line four lines after the line that contains the string
SUBROUTINE

When EDT searches for a string, the case of the search string need not match the case of
the target. For example, record is a match for RECORD or Record. This condition is the
default; you can change it with the SET SEARCH command.
There are several methods available for specifying a range of more than one line. They are
listed in Table 2-3; examples appear below the table.

Creating and Modifying Programs

2-15

Table 2-3: Multiple-Line Range Specifications
Specification

Meaning

[rangel] { : I THRU l [range2]

The set of lines from rangel through range2, which are single line range specifications (the default for both rangel
and range2 is the current line)

[range] { # I FOR l number

The specified number of lines beginning with the single line
specified by range (the default for range is the current line)

BEFORE

All lines in the buffer that precede the current line

REST

The current line and all lines in the buffer that follow it

WHOLE

The entire buffer

range, range ...
or
range AND range AND ...

All lines specified by each single line range

[range] ALL' string'

All lines in the range containing the specified string (the
default for range is the entire buffer)

Examples:
Specification
2:6.5
'STRUCTURE' #5
.-10:.
10:50 ALL 'READ '

Meaning
Lines 2 through 6.5, inclusive
The line containing the string STRUCTURE and the
four lines following it, for a total of five lines
The line 10 lines before the current line through the
current line, inclusive
All lines from line 10 through line 50 that contain the
string READ

Most range specifications can be combined with a text buffer specification. During your
editing session, you may wish to hold and edit text in buffers other than MAIN. To create
and gain access to alternate buffers, include the name of the buffer in a range specification,
using the following syntax:
=buffer [range]
or
BUFFER buffer [range]

In this syntax, "buffer" stands for the name of the buffer. It can be from 1 to 30 alphanumeric characters, but it must start with an alphabetic character. If you include a range of
lines following the buffer name, you specify the range within the named buffer. If you omit
the range specification, you specify either the entire named buffer or its first line, depending on context.

2-16

Creating and Modifying Programs

The following examples show buffer specifications in use.
Specification

Meaning

=PROGl

The entire contents of the text buffer named
PROGl, or (for commands requiring a single-line
range specification) its first line

=INC 'STRUCTURE': 'END
STRUCTURE'

The lines that contain the strings STRUCTURE
and END STRUCTURE in the text buffer named
INC, and all lines between

=COM ALL 'LOGICAL'

All lines that contain the string LOGICAL in the
buffer named COM

2.3.3 Displaying Lines of Text
The TYPE command and a RETURN in response to the asterisk prompt are the two
methods of displaying text.

TYPE Command
The TYPE command, followed by a range, causes EDT to display the line or lines in the
range and resets the current line to the first (or only) line displayed. The word TYPE
(abbreviation T) is optional; it does not need to be entered. For example:
*T 1: 3
2
3

This is the first line of E}-(AMPLE, rnT
This is the second line of E>:AM PLE. nn
This is the third line of E}-(AMPLE. nn

*t'.1#2

a
5

This is the fourth line of E}<AMPLE. nn
This is the fifth 1 in e of E>:AMPLE, rnT

If you do not include the word TYPE and the range specification begins with an alphabetic
character (such as WHOLE or REST), you must precede it with a percent sign (%).
Otherwise, EDT tries to interpret the range specification as a command. For example:
*REST
Unrecosnized command
*!..REST
a
This
5
This
G
This
7
This

is
is
is
is

the
the
the
the

fourth line of E>:AM PLE, rnT
fifth line of E}-:AMPLE, rnT
sixth line of E}-:AMPLE, rnT
seventh line of E}<AMPLE, rnT

*
To cancel any form of type command while text is being displayed, enter a <CTRL/C>.
This operation does not cause repositioning; the first line displayed remains as the current
line.
Creating and Modifying Programs

2-17

RETURN
A RETURN in response to the asterisk prompt displays the line following the current line
and sets the current line to the displayed line. A series of returns, therefore, displays
successive lines and sets the current line to the displayed line each time. This is an easy
way to work through a file line by line. For example:
*<RET>
This is the fifth 1 in e of E)<AMPLE rnT

*<RET>
This is the sixth line of E)<AM PLE rnT

2.3.4 Maneuvering in a File
The FIND command (abbreviation F) locates a specified line without displaying it. It is
useful for setting the current line to the top of a large block of text that would be cumbersome to display on the terminal. For example, each of the following commands resets the
current line to the top of the MAIN text buffer:
*=MAIN
*F =MAIN

However, the first command (an implied TYPE command) displays the entire contents of
the MAIN text buffer. The second command just sets the current line and displays an
asterisk prompt.
If you specify a range that EDT cannot locate, EDT issues a message and does not change
the current line setting.

2.3.5 Inserting New Text
The procedure for inserting new text in a buffer already containing text is exactly the same
as that for inserting text in an empty buffer (see Section 2.1.5), except that you can control
where the text goes by including a range specification with the INSERT command. The
lines you insert are placed in front of the line you specify. If you specify multiple lines, the
insert goes in front of the first line in the range. If you omit the range specification, the
insert goes in front of the current line.

In the following example, the INSERT command causes EDT to insert text in front of line
5 in the current buffer. Then, the range specification (an implied TYPE command) causes
EDT to display lines 4 through 6, showing the result of the insertion.

2-18

Creating and Modifying Programs

First insert line
Second insert line
Third insert line
<CTRLIZ> ''Z

* l'.I: G

a
a. 1
a. 2
l'.1.3
5

This is the fourth line of EXAMPLE.TXT
First insert line
Second insert line
Third insert line
This is the fifth line of EXAMPLE.TXT
This is the sixth line of EXAMPLE.TXT

*
NOTE
EDT, which inserts text in front of the current line, is different from many other
text editors that insert text following the current line.

2.3.& Deleting and Replacing Text
Use the DELETE command (abbreviation D) to delete a specified range. If you omit the
range, the DELETE command deletes the current line. After a delete operation, EDT
displays the line following the last line deleted; this is the new current line. For example:
*D l'.I, 1 #2

2 lines deleted
l'.1.3
Third insert line
*D

1 line deleted
5

This is the fifth

line of EXAMPLE.TXT

*
The /QUERY qualifier to the DELETE command causes EDT to prompt you before deleting each line of the range. The prompt is a question mark (?). You can respond to the
prompt in one of four ways:
Y (yes)
N (no)
A (all)
Q (quit)

Delete this line
Do not delete this line
Delete all remaining lines in the specified range
Quit the delete operation

The REPLACE command (abbreviation R) deletes a specified range and allows you to
insert lines to replace those deleted. You terminate the insertion with a <CTRL/Z>, just as
with the INSERT command.

Creating and Modifying Programs

2-19

2.3.7 Moving Text
The COPY and MOVE commands (abbreviations CO and M, respectively) allow you to
move one or more lines of text from one place in the buffer to another, or from one buffer to
another. The effect of these commands is similar; the only difference is that the COPY
command does not delete the text from its original location, whereas the MOVE command
does.
The following example illustrates both commands, as well as alternative ways of specifying
a range:
*'X.WHDLE
1
2
3

This
This
This
This
This
This
This

5
G
7
*COPY 1: 3 TO 'S!){TH'
3 lines COPied
*5:6
5
This
5. 1
This
5.2
This
5.3
This
G
This
*M 5. 1 #3 TO BEGIN
3 lines 1T101.1 e d
*'X.WH
0. 1
This
0.2
This
0.3
This

2
3

a
5
G
7

This
This
This
This
This
This
This

is
is
is
is
is
is
is

the
the
the
the
the
the
the

first line of D(AMPLE. nn
second line of E){AMPLE, rnT
third line of E){AMPLE, T){T
fourth line of D(AMPLE, T){T
fifth line of E>(AM PLE, T){T
sixth line of E){AMPLE. nn
se1.1enth line of E){AM PLE, T){T

is
is
is
is
is

the
the
the
the
the

fifth line of E>(AMPLE, T){T
first line of D(AMPLE, T){T
second line of D(AMPLE. T){T
third line of D(AM PLE. T){T
sixth line of E)<AMPLE. T){T

is
is
is
is
is
is
is
is
is
is

the
the
the
the
the
the
the
the
the
the

first line of D(AM PLE. TKT
second line of E>:AMPLE. rnT
third line of E){AMPLE. T)<T
first line of E){AM PL[. nn
second line of E){AMPLE. nn
third line of D(AMPLE, T){T
fourth line of E>:AMPLE. T){T
fifth line of E){AMPLE. nn
sixth line of E>(AM PLE. nn
se1.1enth 1 in e. of D(AMPLE. T){T

The /QUERY qualifier to either COPY or MOVE causes EDT to prompt you before copying
or moving each line of the range. It operates the same way as the /QUERY qualifier to
DELETE (see Section 2.3.6).

2.3.8 Substituting Text
Two commands, SUBSTITUTE and SUBSTITUTE NEXT, substitute one string for another within a line or lines. These are the only line editing commands that can alter text
within a line, as opposed to changing the entire line. The SUBSTITUTE command (abbre-

2-20

Creating and Modifying Programs

viation S) operates on the current line or on a specified range; the SUBSTITUTE NEXT
command (abbreviation N) makes a substitution at the next opportunity within the buffer.
The format of the SUBSTITUTE command is:
SUBSTITUTE /string1 /string2/[range] [/QUERY]

The command finds stringl and substitutes string2 for it. If you do not specify a range, the
substitution takes place in the current line. If you do, the command makes every substitution within the range. The following example illustrates the command first without and
then with a range specified:
This is the first

line of D(AMPLE, rnT

*S /first/1st/
1

1 substitution
*S /of/in/ll:G
ll

5
G

This is the 1st line of E){AMPLE. nn

.
\

This is the fourth line in E){AMPLE, rnT
This is the fifth line in D(AMPLE, T:<T
This is the sixth line in D(AMPLE, rnT

3 substitutions

*
Slashes (/) are not the only characters you can use to delimit stringl and string2. Any
nonalphanumeric character will work, as long as the delimiters are matched and do not
occur in either string. For example, the following command substitutes the string A/3 for
A/2 in the current line, using dollar signs ($) as delimiters:
*S $A/2$A/3$
25
1 substitution

SIZE

= A/3

*
The /QUERY qualifier to SUBSTITUTE causes EDT to prompt you before making each
substitution. It operates the same way as the /QUERY qualifier to DELETE (see Section
2.3.6).
The SUBSTITUTE NEXT command (abbreviation N) substitutes for the next occurrence
of stringl that it finds in the buffer. If you specify neither stringl nor string2, the command
takes the values of both strings from the last SUBSTITUTE command you issued. For
example:
*N I in/ of/
ll

This is the fourth

line of E>(AMPLE. nn

This is the fifth

line of E>(AMPLE, rnT

*N
*

2.3.9 Input From and Output To Files
Two EDT commands, INCLUDE and WRITE, allow you to incorporate text from files and
output text to files during your editing session.

Creating and Modifying Programs

2-21

INCLUDE Command
The INCLUDE command (abbreviation INC) incorporates the contents of a file at a
specified location in a text buffer. If you do not want the entire file incorporated in the
MAIN text buffer, you can specify an alternate buffer as the range and then copy the
desired portions of the file to their proper places in MAIN. For example:
*INC SBRTNES,FOR =SUBS

*
This command creates a buffer called SUBS and fills it with the contents of the file
SBRTNES.FOR from the EDT default directory (that is, the directory of the input file
given with the EDIT/EDT command).

WRITE Command
The WRITE command (abbreviation WR) creates a file by copying the contents of a
specified range in a text buffer. The text is not deleted from the text buffer and EDT does
not terminate following the operation. If you do not specify a range with the command,
EDT outputs the entire contents of the current text buffer. The following example shows
the command used with a range:
*WR ROUTINE1.FOR =SUBS 'SUBROUTINE': 'END'
_DB1:EPROJECTJROUTINE1,FOR;1 Q5 lines

*
This command creates the file ROUTINEl.FOR from the lines that contain the strings
SUBROUTINE and END in the buffer named SUBS, and all lines in between.
Unless you include a directory in the file specification, WRITE always creates the file in
your current default directory. This is true even if the input and output files are in another
directory.

2.3.1 O Editing a File From Another Directory
You can edit a file that exists in another directory and use the /OUTPUT qualifier to
EDIT/EDT to direct the output file to your directory. However, EDT uses the directory of
the input file that you specify in the EDIT/EDT command line as its default directory.
This default has the following effects:
• EDT attempts to create its journal file in its default directory, that is, in the other
directory. If you do not have the privilege to do this, EDT issues an error message and
terminates. You should instead use the /JOURNAL qualifier to place the journal file in
your directory. (See Section 2.1.4 for a description of the journal file and /JOURNAL.)
• If you issue an INCLUDE command and do not specify a directory, EDT attempts to
locate the file in its default directory, that is, in the other directory. To specify a file in
your own directory, use a directory specification with INCLUDE.

2-22

Creating and Modifying Programs

In the following example, a user with the directory [WYLBURJ edits a file from the directory [PROJECT]:
$
_$

EDIT/EDT CPROJECTJDATADEF.FDR /OUTPUT=CWYLBURJ /JOURNAL=CWYLBURJ

*INCLUDE CWYLBURJENTRIES.FOR

The input file for this editing session is [PROJECTJDATADEF.FOR; the output file is
[WYLBURJDATADEF.FOR. The INCLUDE command incorporates a file from directory
[WYLBURJ. If the INCLUDE command had not specified a directory, EDT would have
looked for the file [PROJECTJENTRIES.FOR.

2.4 EDT Aids for the Programmer
In addition to the general-purpose editing operations discussed in Section 2.1, EDT provides some advanced functions that are especially useful for programming. The following
sections introduce some of these.

2.4.1 Structured Tabs
Although FORTRAN is a free-form language, in which excess spaces and tabs have no
significance, it is common practice to indent lines to indicate the relationship of statements. It is laborious to enter repeatedly the correct combination of tabs and spaces to
achieve the desired indention. EDT solves this problem by providing a system of structured
tabs in character mode editing. While you are inserting text, a depression of the tab key
inserts the correct combination of tabs and spaces to bring the cursor to the desired
column. When ·you need to begin lines at a different column, you can increase or decrease
the indention level to move the starting column to the right or left, respectively, by a preset
increment.
To use the structured tab feature, follow these steps:
1. While in line mode, set the increment between tabs by issuing the SET TAB command with a suitable value. For example:
*SET TAB

*
At this point, the first <TAB> on a line (while in character mode) positions the
cursor at column 5. Subsequent tab stops are at the normal locations.
2. When you want to change the indention level, use <CTRL/E> or <CTRL/D>. Each
depression of <CTRL/E> increases the indention by one increment; the first tab stop
is n spaces further to the right, where n is the number you gave with the SET TAB
command. Pressing <CTRLID> decreases the indention level.

Creating and Modifying Programs

2-23

3. If you want to set the indention level to correspond to a given column, position the
cursor at that column and press <CTRL/A>. The column must be at an even multiple of n spaces from the left edge of the screen.
4. If you want to change the indention of a block of lines, first define a select range that
includes the lines to be shifted. (To define a select range, position the cursor at one
end of the block of lines, enter the SELECT function, and then position the cursor at
the other end.) Then enter a repeat count (the GOLD key followed by a number
typed on the keyboard) to indicate how many units of n spaces the lines should be
shifted. A positive repeat count shifts the lines to the right; a negative repeat count
shifts the lines to the left. Finally, press <CTRLtr>.
Before you enter <CTRL!r> at the EDT command level, note that you must disable
the DCL <CTRL!r> if you want the EDT <CTRL!r> to take effect. You establish
the DCL <CTRLtr> mode with the SET [NOJCONTROL=T command.

2.4.2 Special-Purpose Key Definitions
EDT allows you to redefine the functions invoked by all the keys on the auxiliary keypad
and many control characters as well. There are two ways to redefine a key's function:
• While in character mode, press <CTRL/K>. EDT prompts you to press the key you
wish to define. Once you have pressed the key, EDT prompts you to enter the new
function. You can do this either by typing the nokeypad commands that make up the
function, or by pressing the keypad keys that correspond to the functions you require.
You must follow the function specification with a period. The ENTER function terminates a definition of this type.
• While in line mode, issue the DEFINE KEY command. You define the new function to
perform as a string of nokeypad character editing commands, followed by a period.
The string and period must be enclosed in quotes.
Key redefinition requires a good grasp of nokeypad character editing syntax, as well as a
good deal of practice. The EDT help facility (particularly HELP DEFINE KEY and HELP
CHANGE SUBCOMMANDS) and the VAX EDT Reference Manual are good sources of
information. However, this section describes one common application: the redefinition of a
key to insert a string of text.
While writing a program, you may find that you are typing the same group of words over
and over. For example, you might get tired of typing CHARACTER*. In character mode,
follow this procedure to define a key to insert the string CHARACTER*:
1. Press <CTRL/K>. EDT prompts you as follows:
Press the Key you wish to define

2. Select a function that you do not use often, for example, SPECINS. You might also
select a control character. Enter the function or control character. EDT then
prompts you as follows:
Now enter the definition terMinated bY ENTER

2-24

Creating and Modifying Programs

3. Type the following:
iCHARACTER*<CTRLIZ>.

(The period is required syntax.)
4. Press ENTER to terminate the definition procedure.
For the remainder of the editing session, the key that used to invoke the SPECINS function
will instead insert the string CHARACTER* at the cursor position.
In line mode, you can redefine a key by using the DEFINE KEY command. To identify a
keypad key in the command, you use a number. You can find out which numbers are
assigned to which keys by issuing the command HELP DEFINE KEY VT52 or HELP
DEFINE KEY VTlOO. These commands display the numbers assigned to keypad keys on
the respective terminals.
Next, you issue a DEFINE KEY command, specifying the key and the function you wish
the key to perform. The following example redefines the SPECINS function (GOLD/3 on a
VTlOO) to insert the string CHARACTER*:
*DEF I NE KEY GOLD 3 AS

i CHARACTER*,, z. II

*
The quotes and period are required syntax. The "Z is not a <CTRL/Z>, but a circumflex
followed by a Z; it indicates the end of an inserted string. or the remainder of the editing
session, GOLD/3 will insert the string CHARACTER* at the cursor position.
The preceding examples represent only a small fraction of the capabilities of key redefinition. With practice, you can create powerful custom functions that can save you a great
deal of time. You may want to store these functions in a startup command file so that you
will not have to define them each time you begin an editing session. The next section
describes startup command files.

2.4.3 Startup Command Files
When you invoke EDT, it searches your current default directory for a file named
EDTINI.EDT. If EDT finds such a file, it executes the line editing commands contained in
the file before turning control over to you. This function allows you to customize EDT to
suit your needs. Some of the commands that a startup command file might contain are:
• DEFINE KEY. These commands redefine the function invoked by a keypad key or
control character while in character mode. (See Section 2.4.2.)
• DEFINE MACRO. These commands associate a name with a sequence of line-editing
commands stored in a text buffer. You can then invoke the sequence by entering the
macro name in response to the line-editing asterisk prompt.
0

INCLUDE. These commands bring text from a file into a text buffer. You might use
them to load macros into a buffer, or to fill a buffer with text that you often use. (See
Section 2.3.9.)

Creatin'g and Modifying Programs

2-25

• SET. These commands establish EDT operating parameters. Particularly useful are
SET TAB, which establishes the increment for structured tabs, and SET MODE
CHANGE, which causes EDT to enter directly into character mode. (Section 2.4.1
describes the use of structured tabs.)
You can use the /COMMAND qualifier to the EDIT/EDT command to cause EDT to
search for a file other than EDTINl.EDT. This means that you can have several startup
command files, each designed for a particular application. You may want to include a
command in your login command procedure file (see Section 1.6.11) to equate a short
mnemonic to an EDIT/EDT command that invokes a special startup command file. For
example, if you have the following line in your login command file:
EDP

:==

"EDIT/EDT/COMMAND=FDRT.EDT"

then the comand
EDP METRIC.FOR

invokes EDT with the startup command file FORT.EDT to edit the file METRIC.FOR.

2-26

Creating and Modifying Programs

Chapter 3

Compiling FORTRAN Programs
This chapter describes how to use the FORTRAN command to compile your source programs into object modules. The following topics are discussed:
• The functions of the compiler (Section 3.1)
• The syntax of the FORTRAN command and its qualifiers (Section 3.2)
• The use of text libraries (Section 3.3)
• The Common Data Dictionary (CDD) (Section 3.4)
• Compilation control statements (Section 3.5)
• Compiler diagnostic messages and error conditions (Section 3.6)

3.1 Functions of the Compiler
The primary functions of the VAX FORTRAN compiler are as follows:
• To verify the FORTRAN source statements and to issue messages if there are any
errors
• To generate machine language instructions from the source statements of the FORTRAN program
• To group these instructions into an object module for the linker
When the compiler creates an object file, it provides the linker with the following information:
• The program unit name. This is taken from the name specified in the PROGRAM,
SUBROUTINE, FUNCTION, or BLOCK DATA statement in the source program. If a
program unit does not have any of these statements, the source file name, with
"$MAIN" (or "$DATA", for block data subprograms) appended, is used.
• A list of all entry points and common block names that are declared in the program
unit. The linker uses this information when it binds two or more program units together and must resolve references to the same names in the program units.
3-1

• Traceback information. This is used by the system default condition handler when an
error occurs that is not handled by the program itself. The traceback information
permits the default handler to display a list of the active program units in the order of
activation, which aids program debugging.
• If specifically requested (with the /DEBUG qualifier), a symbol table. A symbol table
lists the names of all external and internal variables within a module, with definitions
of their locations. The table is of primary use in program debugging.

The linker is described in Chapter 4.

3.2 The FORTRAN Command
The FORTRAN command initiates compilation of a source program.
The command has the form:
$ FORTRAN[/qualifiers] file-spec-list[/qualifiers]

where:
/qualifiers

Indicates either special actions to be performed by the compiler or special properties
of input or output files.
file-spec-list

Specifies the source file(s) containing the program unit(s) to be compiled. You can
specify more than one source file. If source file specifications are separated by commas, the programs are compiled separately. If source file specifications are separated
by plus signs, the files are concatenated and compiled as one program.
In interactive mode, you can also enter the file specification on a separate line by typing
the command FORTRAN, followed by a carriage return. The system responds with the
prompt:
_File:

Type the file specification immediately after the prompt and then type RETURN.

3.2.1 Specifying Input Files
In specifying a list of input files on a FORTRAN command, you can use abbreviated file
specifications for those files that share common device names, directory names, or file
names. The system applies temporary file specification defaults to those files with incomplete specifications. The defaults applied to an incomplete file specification are based on
the previous device name, directory name, or file name encountered in the list.

3-2

Compiling FORTRAN Programs

For example, assume that the current default device and directory name are
USR2:[MONROEJ. The following FORTRAN command shows how temporary defaults are
applied to a list of file specifications:
$FORTRAN USR1:CADAMSJTEST11TEST21CJACKSONJSUMMARY1USR3:CFINALJ

The preceding FORTRAN command compiles the following files:
USR1:CADAMSJTEST1.FOR
USR1:CADAMSJTEST2.FOR
USRl:CJACKSONJSUMMARY.FOR
USR3:[FINALJSUMMARY.FOR

To override a temporary default with your current default directory, specify the directory
as a null value. For example:
$ FORTRAN CAL PHA JTEST 1 , [ JTEST2

In this case, the empty brackets indicate that the compiler is to use your current default
directory to locate TEST2.
You must use /LIBRARY qualifiers in your FORTRAN command if text libraries are
accessed by programs in the source files that you specify. The LIBRARY qualifier is
discussed at length in Section 3.3.3.

3.2.2 Specifying Output Files
The output produced by the compiler includes the object and listing files. You can control
the production of these files by using the appropriate qualifiers in the FORTRAN command.
The compiler generates an object file by default. In interactive mode, the compiler does not
generate listing files; you must use the /LIST qualifier to generate the listing file. In batch
mode, however, the compiler generates a listing file by default. To suppress it, use the
/NOLIST qualifier.
During the early stages of program development, you may find it helpful to use the
/NOOBJECT qualifier to suppress the production of object files until your source program
compiles without errors. If you do not specify /NO OBJECT, the compiler generates object
files as follows:
• If you specify one source file, one object file is generated.
• If you specify multiple source files, separated by commas, each source file is compiled
separately and an object file is generated for each source file.
• If you specify multiple source files, separated by plus signs, the source files are concatenated and compiled, and one object file is generated.

You can use both commas and plus signs in the same command line to produce different
combinations of concatenated and separate object files (see Example 4).

Compiling FORTRAN Programs

3-3

To produce an object file with an explicit file specification, you must use the /OBJECT
qualifier, in the form /OBJECT=file-spec (see Section 3.2.3.14). Otherwise, the object file
has the name of its corresponding source file and a file type of OBJ. By default, the object
file produced from concatenated source files has the name of the first source file. All other
file specification fields (node, device, directory, and version) assume the default values.
The following examples show a variety of FORTRAN commands. Each command is followed by a description of the output file(s) it produces.
1.

FORTRAN I LI ST

AAA , BBB , CCC

Source files AAA.FOR, BBB.FOR, and CCC.FOR are compiled as separate files, producing object files named AAA.OBJ, BBB.OBJ, and CCC.OBJ; and listing files named
AAA.LIS, BBB.LIS, and CCC.LIS.
2.

FORTRAN )-0()-{+YYY+ZZZ

Source files XXX.FOR, YYY.FOR, and ZZZ.FOR are concatenated and compiled as
one file, producing an object file named XXX.OBJ, but no listing file. (A listing file
named XXX.LIS would be produced in batch mode.)
3.

FORTRAN /OBJECT= SQUARE I NOLI ST
_File:
CIRCLE

00)

The source file CIRCLE.FOR is compiled, producing an object file named
SQUARE.OBJ, but no listing file.
4.

FORTRAN

AAA+BBB tCCC/ LI ST

Two object files are produced: AAA.OBJ (comprising AAA.FOR and BBB.FOR) and
CCC.OBJ (comprising C.CC.FOR). One listing file is produced: CCC.LIS (comprising
CCC.FOR).
5.

FORTRAN

ABC+CIRC/NOOBJECT+}{YZ

When you include a qualifier in a list of files that are to be concatenated, the qualifier
affects all files in the list. The command illustrated above completely suppresses the
object file. That is, source files ABC.FOR, CIRC.FOR, and XYZ.FOR are concatenated
and compiled, but no object file is produced.

3.2.3 Qualifiers to the FORTRAN Command
FORTRAN command qualifiers influence the way in which the compiler processes a file. In
many cases, the simplest form of the FORTRAN command is sufficient. However, you can
select appropriate optional qualifiers if special processing is required.
Table 3-1 lists the FORTRAN command qualifiers. Sections 3.2.3.1 through 3.2.3.18 describe each qualifier in detail.
You can override some qualifiers specified on the command line by using the OPTIONS
statement. The qualifiers specified by the OPTIONS statement affect only the program
unit where the statement occurs. Refer to Section 3.5.2 for more information.

3-4

Compiling FORTRAN Programs

Table 3-1: FORTRAN Command Qualifiers
Qualifier

Negative Form

Qualifier

/NOC HECK

/CHECK=(NOBOUNDS,
OVERFLOW)

/CONTINUATIONS=n

None

/CONTINUATIONS=19

/CROSS-REFERENCE

/NOCROSS--REFERENCE

/NO CROSS-REFERENCE

/NODEBUG

/DEBUG=(NOSYMBOLS,
TRACEBACK)

ID-LINES

/NOD-LINES

/DML

None

/EXTEND-80URCE

/NOEXTEND-80URCE

/F77

/NOF77

/F77

/G_FLOATING

/NOG_FLOATING

/NOGJLOATING

/14

/N014

/14

/LIBRARY

None

Not applicable

/LIST[=file-spec]
/LIST (batch)

/NO LIST

/NOLIST (interactive)

/MACHINE_CODE

/NOMACHINE_CODE

/OBJECT[=file-specl

/NO OBJECT

/OBJECT

/OPTIMIZE

/NO OPTIMIZE

/OPTIMIZE

/NOSHOW

/SHOW=(NODICTIONARY,
NOINCLUDE,MAP,
NOPREPROCESSOR,
SINGLE)

/NOSTANDARD

/NOWARNINGS

IWARNINGS=(NODECLARA-

/CHECK=

i~g:g:~~~Wi
ALL
NONE

[NOJSYMBOLS )
/DEBUG= [NOJTRACEBACK(
{
{ ALL
NONE
}

/SHOW=

[NOJDICTIONARY
[NOJINCLUDE
[NOJMAP
[NOJPREPROCESSOR
[NOJSINGLE

ALL
NONE

/STANDARD=lE~~:::-l
NONE

[NOJDECLARATIONS}
/WARNINGS= ~~GENERAL
{
NONE

TIONS,
GENERAL)

Compiling FORTRAN Programs

3-5

3.2.3.1 /CHECK Qualifier
The /CHECK qualifier produces run-time checks for the conditions indicated.
The qualifier has the form:
ALL
[NO] BOUNDS
/CHECK =

[NO]OVERFLOW
{ [NO] UNDERFLOW
NONE

where:
BOUNDS

Specifies that array and substring references are checked by the system to ensure that
they are within the address boundaries specified in the array or character variable
declaration.
For array bounds, only the address reference is checked; that is, the system only
checks to determine whether you are in· the same array; it does not check each
individual dimension. Also, array bounds checking is not performed for arrays that
are dummy. arguments in which the last dimension bound is specified as * or both
upper and lower dimensions are 1. For example:
DIMENSION 6(0:1010:*)

or
DIMENSION Al 1)
OVERFLOW

Specifies that BYTE, INTEGER*2, and INTEGER*4 calculations are checked for
arithmetic overflow. Real and complex calculations are always checked for overflow ·
and are not affected by /NOCHECK. Integer exponentiation is performed by a routine in the mathematical library. The routine in the mathematical library always
checks for overflow, even if /CHECK=NOOVERFLOW is specified.
UNDERFLOW

Specifies that real and complex calculations are checked for floating underflow. Refer
to the VAX FORTRAN User's Guide for information about floating underflow.
ALL

Specifies that OVERFLOW, BOUNDS, and UNDERFLOW checks are performed.
NONE

Specifies that no checks are performed.
The default is /CHECK=OVERFLOW. Note that /CHECK is the equivalent of
/CHECK=ALL, and /NOCHECK is the equivalent of /CHECK=NONE.

3-6

Compiling FORTRAN Programs

3.2.3.2 /CONTINUATIONS Qualifier
The /CONTINUATIONS qualifier specifies the number of continuation lines allowed in a
source program statement.
The qualifier has the form:
/CONTINUATIONS=n

where:
n

is an integer from 0 to 99.
If you omit the /CONTINUATIONS qualifier, the default value is 19.

Because the compiler has to assume maximum-length continuation lines (66 or 126 characters) when allowing space for continuation line sequences, the actual number of continuation lines allowed in any given statement usually exceeds the limit specified by the
/CONTINUATIONS qualifier.
NOTE
A common problem is an attempt to use the character zero (0) as a continuation
character. This is not allowed. A line with a "continuation" character of 0 is
treated as an initial line; it does not indicate that the /CONTINUATIONS value
needs to be increased.

3.2.3.3 /CROSS_HEFERENCE Qualifier
The /CROSS__REFERENCE qualifier specifies that the storage map section of the listing
file is to include information about the use of symbolic names. The cross-reference contains
the numbers of the lines in which the symbols are defined and referenced.
The qualifier has the form:
/CROSS_REFERENCE

The /CROSS__REFERENCE qualifier is ignored ifthe listing file is not being generated.
The default is /NOCROSS__REFERENCE.
See Section 3.7.3 for a description of the listing format used when /CROSS__REFERENCE
is specified.

Compiling FORTRAN Programs

3-7

3.2.3.4 /DEBUG Qualifier
The /DEBUG qualifier specifies that the compiler is to provide information for use by the
VAX Symbolic Debugger and the run-time error traceback mechanism.
The qualifier has the form:
/DEBUG =

ALL
}
[NO]SYMBOLS
{ [NO]TRACEBACK
NONE

where:

SYMBOLS
Specifies that the compiler is to provide the debugger with local symbol definitions for
user-defined variables, arrays (including dimension information), structures, and labels of executable statements.
TRACEBACK
Specifies that the compiler is to provide an address correlation table so that the
debugger and the run-time error traceback mechanism can translate virtual addresses
into source program routine names and compiler-generated line numbers.
ALL
Specifies that the compiler is to provide both local symbol definitions and an address
correlation table.

NONE
Specifies that the compiler is to provide no debugging information.
If you do not specify the /DEBUG qualifier, the ,default is /DEBUG=TRACEBACK. Note

that /DEBUG is the equivalent of /DEBUG=ALL, and /NODEBUG is the equivalent of
/DEBUG=NONE.

NOTE
The use of /NOOPTIMIZE is strongly recommended when the /DEBUG qualifier is used. Optimizations performed by the compiler can cause several different
kinds of unexpected behavior when using VAX DEBUG. See Chapter 1 of the
VAX FORTRAN User's Guide for more information on this subject.
For more information on debugging and traceback, see Section 4.3 and Chapter 17.

3-8

Compiling FORTRAN Programs

3.2.3.5 /DUNES Qualifier
The /D_LINES qualifier specifies that lines with a D in column 1 are to be compiled and
are not to be treated as comment lines.
The qualifier has the form:
/D_LINES

The default is /NOD_LINES, which means that lines with a Din column 1 are treated as
comments.

3.2.3.6 /DML Qualifier
The /DML qualifier specifies that the FORTRAN Data Manipulation Language (DML)
preprocessor is to be invoked before the compiler. The preprocessor produces an intermediate file of FORTRAN source code in which FORTRAN DML commands are expanded into
FORTRAN statements. The compiler is then automatically invoked to compile this intermediate file.
The qualifier has the form:
/DML

You use the /SHOW=PREPROCESSOR qualifier in conjunction with the /DML qualifier
to cause the preprocessor-generated source code to be included in the listing file. For more
information on the DML preprocessor, refer to the VAX DBMS FDML Reference Manual.

NOTE
Because the intermediate file is deleted by the FORTRAN DML preprocessor
immediately after compilation is complete, the debugger cannot access the
source program when the /DML qualifier is used.

3.2.3. 7 /EXTEND_SOURCE Qualifier
The /EXTEND_SOURCE qualifier specifies that the compiler is to extend the range of
FORTRAN source text from columns 1 through 72 to columns 1 through 132.
The qualifier has the form:
/EXTEND_SQURCE

This qualifier can also be specified on the OPTIONS statement. The default in either case
is /NOEXTEND_SOURCE.
If a source line is longer than 132 characters, a fatal read error is signaled and the compila-

tion is immediately terminated.

Compiling FORTRAN Programs

3-9

3.2.3.8 /F77 Qualifier

The /F'77 qualifier specifies that FORTRAN-77 interpretation rules are used for those
statements that have a meaning incompatible with FORTRAN-66. See Appendix A in the
VAX FORTRAN User's Guide for a discussion of these incompatibilities.
The qualifier has the form:
/F77

The default is /F'77. If you specify /NOF77, the compiler selects FORTRAN-66 interpretations in cases of incompatibility.
3.2.3.9 /G_FLOATING Qualifier

The /G_FLOATING qualifier controls how the compiler implements REAL*8, COMPLEX*l6, DOUBLE PRECISION, and DOUBLE COMPLEX quantities.
The qualifier has the form:
/G_FLOATING

/NOG_FLOATING, the default, causes the compiler to implement double-precision quantities using the VAX D_floating data type. /G_FLOATING causes the compiler to implement such quantities using the VAX G_floating data type.
If your program requires the G_floating form of double precision for its correct operation
(that is, it uses a range larger than 10**38), you should use the /G_FLOATING qualifier in
an OPTIONS statement in your source program. The implementation of REAL*8 in VAX
FORTRAN is further discussed in Section 6.1.2.

Note that routines between which double-precision quantities are passed should not mix
the D_floating and G_floating data types.
CAUTION
VAXNMS systems support both D_floating and G_floating implementations
of REAL*8. On different systems, however, the performance of a program can
vary widely depending on whether your program is compiled with G_floating or
D_floating. The disparity exists when a particular system supports one floating
type in hardware and the other in software. Thus, if you wish to optimize
performance and if range and accuracy constraints do not prescribe one of the
two options, you must ensure that the most efficient option is in effect during
the compilation process.
You can select G_floating or D_floating by means of an OPTIONS statement
in your source program or by means of qualifiers on the FORTRAN command.
For more information on floating-point data types, see Sections 6.1.2, C.4.2, and C.4.3.

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Compiling FORTRAN Programs

3.2.3.10 /14 Qualifier
The /14 qualifier controls how the compiler interprets INTEGER and LOGICAL declarations that do not have a specified length.
The qualifier has the form:
/14

The default is /14, which causes the compiler to interpret INTEGER and LOGICAL declarations as INTEGER*4 and LOGICAL*4. If you specify /NOl4, the compiler interprets
them as INTEGER*2 and LOGICAL*2.

3.2.3.11 /LIBRARY Qualifier
The /LIBRARY qualifier specifies that a file is a text library file.
The qualifier has the form:
text-library-file/LIBRARY

The /LIBRARY qualifier can be specified on one or more text library files in a list of files
concatenated by plus signs. At least one of the files in the list must be a nonlibrary file. The
default file type is TLB.
The use of text libraries is discussed at length in Section 3.3.

3.2.3.12 /LIST Qualifier
The /LIST qualifier specifies that a source listing file is to be produced.
The qualifier has the form:
/LIST[=file-spec]

You can include a file specification for the listing file. If you do not, it defaults to the name
of the first source file and to a file type of LIS.
In interactive mode, the compiler does not produce a listing file unless you include the
/LIST qualifier. In batch mode, the compiler produces a listing file by default. In either
case, the listing file is not automatically printed; you must use the PRINT command to
obtain a line printer copy of the listing file.
See Section 3.7.1 for a discussion on the format of listing files.

Compiling FORTRAN Programs

3-11

3.2.3.13 /MACHINLCODE Qualifier
The /MACHINE_CODE qualifier specifies that the listing file is to include a symbolic
.representation of the object code generated by the compiler. Generated code and data is
represented in a form similar to a VAX MACRO assembly listing. Do not attempt to
assemble this listing file; several items included in the listing file are not supported by
VAX MACRO assembler.
The qualifier has the form:
/MACHINE_CODE

This qualifier is ignored if no listing file is being generated. The default is
/NOMACHINE_CODE.
See Section 3.7.2 for a description of the format of a machine code listing.

3.2.3.14 /OBJECT Qualifier
The /OBJECT qualifier specifies the name of the object file.
The qualifier has the form:
/OBJECT[=file-spec]

The default is /OBJECT. The negative form, /NO OBJECT, can be used to suppress object
code (for example, when you want to test only for compilation errors in the source program).
If you omit the file specification, the object file defaults to the name of the first source file
and to a file type of OBJ.

3.2.3.15 /OPTIMIZE Qualifier
The /OPTIMIZE qualifier specifies that the compiler is to produce optimized code.
The qualifier has the form:
/OPTIMIZE

The default is /OPTIMIZE. The negative form /NOOPTIMIZE should be used during a
debugging session to ensure that the debugger has sufficient information to locate errors in
the source program. (See the VAX FORTRAN User's Guide for information on optimizations performed by the VAX FORTRAN compiler.)

3-12

Compiling FORTRAN Programs

3.2.3.16 /SHOW Qualifier
The /SHOW qualifier controls whether optionally listed source lines (that is, text module
source lines and preprocessor generated source lines) and a symbol map are to appear in the
source listing.

The /LIST qualifier must be specified in order for the /SHOW qualifier to take effect.
The qualifier has the form:

/SHOW=

ALL
[NO] DICTIONARY
[NO] INCLUDE
[NO]MAP
[NO] PREPROCESSOR
[NO]SINGLE
NONE

where:
ALL

specifies that all optionally listed source lines are to be included in the listing file.
INCLUDE

specifies that the source lines from any file specified by INCLUDE statements are to
be included in the source listing.
DICTIONARY

specifies that FORTRAN source .representations of any CDD records referenced by
DICTIONARY statements are to be included in the listing file.
MAP

specifies that the symbol map is to be included in the listing file. If the /CROSS_
REFERENCE qualifier is specified, MAP is ignored.
PREPROCESSOR

specifies that preprocessor-generated source lines are to be included in the listing file.
The negative form, NOPREPROCESSOR, specifies that the source lines are to be
excluded from the source listing.
NONE

specifies that no optionally listed source lines are to be included in the listing file.
SINGLE

specifies that names only referenced once (that is, those names that appear only in
declarations) are to be included with multiply-referenced names in cross-reference
listings. NOSINGLE specifies that names only referenced once are to be suppressed.
This is useful for cross-reference listings of small programs that specify INCLUDE
declarations but use only a small number of the names declared.

Compiling FORTRAN Programs

3-13

The /SHOW qualifier defaults are NOPREPROCESSOR, NOINCLUDE, NODICTIONARY, MAP, SINGLE.
Specifying the qualifier /SHOW without any arguments is equivalent to specifying
/SHOW=ALL; specifying /NOSHOW without any arguments is equivalent to specifying
/SHOW=NONE.

3.2.3.17 /STANDARD Qualifier
The /STANDARD qualifier specifies that the compiler is to generate informational diagnostics for non-semantic VAX extensions to FORTRAN-77.
The qualifier has the form:

/STANDARD =

{

tNL~]SYNTAX

}

[NO]SOURCE_FORM

NONE

where:
SYNTAX

specifies that an informational message is to be issued for syntax extensions to the
current ANSI standard.
SOURCE_FORM

specifies that an informational message is to be issued for statements that use tab
formatting or contain lowercase characters.
ALL
specifies that informational messages are to be issued for both syntax and source form
extensions to the current ANSI standard.
NONE

specifies that no informational messages are to be issued for extensions to the current
ANSI standard.
The default is /NOSTANDARD, which is equivalent to /STANDARD=NONE.
If you have specified the /NOWARNINGS qualifier, the /STANDARD qualifier is ignored.
Specifying /STANDARD with no arguments is equivalent to specifying
/STANDARD=(SYNTAX, NOSOURCE_FORM).

The compiler does not diagnose semantic extensions if /STANDARD=ALL is specified.
Semantic extensions are standard conforming statements that become nonstandard because of the way in which they are used.

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Compiling FORTRAN Programs

3.2.3.18 /WARNINGS Qualifier
The /WARNINGS qualifier specifies that the compiler is to generate informational (I) and
warning (W) diagnostic messages in response to informational and warning-level errors.
The qualifier has the form:

/WARNINGS =

where:

t~~]

DECLARATIONS)
[NO]GENERAL

NONE

GENERAL
causes the compiler to generate informational and warning diagnostic messages. An
informational message indicates that a correct VAX FORTRAN statement may have
unexpected results or contains nonstandard syntax or source form. A warning message
indicates that the compiler has detected acceptable, but nonstandard, syntax or has
performed some corrective action; in either case, unexpected results may occur. To
suppress I and W diagnostic messages, specify the negative form of this qualifier
(NOGENERAL). The default is GENERAL.
DECLARATIONS
causes the compiler to print warnings for any undeclared data item used in the
program. DECLARATIONS acts as an external IMPLICIT NONE declaration. The
default is NODECLARATIONS.
ALL
causes the compiler to print all informational and warning messages, including warning messages for any undeclared data items.

NONE
suppresses all informational and warning messages.
Appendix B discusses compiler diagnostic messages.

3.3 Using Text Libraries
A text library contains modules of source text that you can incorporate in a program by
using the INCLUDE statement. Modules within a text library are like ordinary text files,
but they differ in the following ways: they contain a unique name, called the module name,
that is used to access them, and several can be contained within the same library file.
Modules in text libraries can contain any kind of text; this section only discusses their use
when FORTRAN language source is used.
To create and modify modules in text libraries, you use the VAXNMS LIBRARY command. Text libraries have a default file type of TLB.

Compiling FORTRAN Programs

3-15

To access a source module in a text library, you do one of the following:
• Specify only the name of the module in an INCLUDE statement in your FORTRAN
source program.
• Specify the name of both the library and module in an INCLUDE statement in your
FORTRAN source program.
• Specify the name of the library using the /LIBRARY qualifier in the FORTRAN
command that you use to compile the source program; or define a default library.
For information on how to use INCLUDE statements and the /LIBRARY qualifier, see
Sections 3.5.2 and 3.3.3, respectively.
Figure 3-1 illustrates the creation of a text library and its use in compiling FORTRAN
programs.
INPUT/OUTPUT FILES

COMMAND

Create a library
containing the
modules APPLIC
and DECLARE

$LIBRARY/TEXT/CREATE FORFILES
$_FILE: APPLIC.SYM,DECLARE.FOR

'---------J

Process the input file
METRIC.FOR, and
$ FORTRAN METRIC+FORFILES/LIBRARY

--t3

D
D

-lo-ca-te_t_h_e
files in -IN_C_L_U-DE__.J----library
FORFILES.TLB

;:;

APPLIC.SYM
DECLARE.FOR

FORFILES.TLB

METRIC.FOR

L..

ZK-792-82

Figure 3-1: Crea ting and Using a Text Library

3-16

Compiling FORTRAN Programs

3.3.1 Using the LIBRARY Commands
Table 3-2 summarizes the commands that create libraries and provide maintenance functions. For a complete list of the qualifiers for the LIBRARY command and a description of
other DIGITAL Command Language (DCL) commands listed in Table 3-2, see the Guide
to Using DCL and Command Procedures on VAX/VMS.
Table 3-2: Commands to Control Library Files
Function

Command Syntax 1

Create a library

$ LIBRARY!I'EXT/CREATE library-name file-spec, ...

Add one or more modules to a library

$ LIBRARY!I'EXT/INSERT library-name file-spec, ...

Replace one or more modules in a library

$ LIBRARY!I'EXT/REPLACE library-name ____$ file-spec, ...

Specify the names of modules to be
added to a library

____$ file-spec/MODULE=module-name

Delete one or more modules from a library

_$ library-name

Copy a module from a library into another file

_$ /OUTPUT=file-spec library-name

List the modules in a library

$ LIBRARY!I'EXT/LIST=file-spec library-name

$ LIBRARY!I'EXT/INSERT library-name $ LIBRARY!I'EXT/DELETE=(module-name, ... )$ LIBRARY!I'EXT/EXTRACT=module-name-

The LIBRARY command qualifier/I'EXT indicates a text module library. By default, the LIBRARY command assumes an object module library.
2

REPLACE is the default function of the LIBRARY command if no other action qualifiers are
specified. If no module exists with the given name, /REPLACE is effectively /INSERT.

3.3.2 Naming Text Modules
When the LIBRARY command adds a module to a library, it uses by default the file name
of the input file as the name of the module. In the example in Figure 3-1, the LIBRARY
command adds the contents of the files APPLIC.SYM and DECLARE.FOR to the library
and names the modules APPLIC and DECLARE.
Alternatively, you can name a module in a library with the /MODULE qualifier. For
example:
$

LIBRARY/TEXT/INSERT FORFILES

DECLARE,FDR/MODULE=EXTERNAL_DECLARATIONS

The preceding command inserts the contents of the file DECLARE.FOR into the library
FORFILES under the name EXTERNAL_DECLARATIONS. This module can be included in a FORTRAN source file during compilation with the statement:
INCLUDE 'FORFILES(EXTERNAL_DECLARATIDNS>

Compiling FORTRAN Programs

3-17

3.3.3 Specifying library Files on the FORTRAN Command Line
The /LIBRARY qualifier is used on the FORTRAN command line to identify text libraries.
If a source file that you are compiling includes a module from a text library, you concatenate the name of the text library to the name of the source file and append the /LIBRARY
qualifier to the text library name. Concatenation is specified with a plus sign. For example:
$ FORTRAN APPLIC+DATAB/LIBRARY

Whenever an INCLUDE statement occurs in APPLIC.FOR, the compiler searches the
library DATAB.TLB for the source text module identified in the INCLUDE statement and
incorporates it into the compilation. See Section 3.5.1 for a description of the INCLUDE
statement.

3.3.4 Search Order of Libraries
When more than one library is specified on a FORTRAN command, the FORTRAN compiler searches the libraries in the order specified, on the command line, each time it
processes an INCLUDE statement that specifies a text module name. For example:
$ FORTRAN APPLIC+DATAB/LIBRARY+NAMES/LIBRARY+GLOBALSYMS/LIBRARY

When FORTRAN processes an INCLUDE statement in the source file APPLIC.FOR, it
searches the libraries DATAB.TLB, NAMES.TLB, and GLOBALSYMS.TLB, in that order, for source text modules identified in the INCLUDE statement.
On a command that requests multiple compilations, a library must be specified for each
compilation in which it is needed. For example:
$FORTRAN METRIC+DATAB/LIBRARYt APPLIC+DATAB/LIBRARY

In this example, FORTRAN compiles METRIC.FOR and APPLIC.FOR separately and
uses the library DATAB.TLB for each compilation.
After the compiler has searched all libraries specified in the command, it searches the usersupplied default library, if any, specified by the logical name FORT$LIBRARY, and then
the system-supplied default library SYS$LIBRARY:FORSYSDEF.TLB.

3.3.4.1 User-Supplied Default Libraries
You can define one of your private text libraries as a default library for the FORTRAN
compiler to search. The FORTRAN compiler searches the default library after it searches
libraries specified in the FORTRAN command.
To define a default library, assign an equivalence for the logical name FORT$LIBRARY, as
in the following example of the VAXNMS ASSIGN command:
$ASSIGN DBAO:[LIBJDATAB FORTSLIBRARY

While this assignment is in effect, the compiler automatically searches the library
DBAO:[LIBJDATAB.TLB for any include modules that it cannot locate in libraries explicitly specified on the FORTRAN command, if any.

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Compiling FORTRAN Programs

You can define the logical name FORT$LIBRARY in any logical name table. If the name is
defined in more than one table, the FORTRAN compiler uses the equivalence for the first
match it finds in the normal order of search (that is, the process, then group, then system
table). Thus, if FORT$LIBRARY is defined in both the process and group logical name
tables, the process logical name table assignment overrides the group logical name table
assignment.
If FORT$LIBRARY is defined as a search list, the compiler opens the first text library
specified in the list. If the include module is not found there, the search is terminated and
an error message is issued.

3.3.4.2 System-Supplied Default Library
When the FORTRAN compiler cannot find the include modules in libraries specified on
the FORTRAN command or in the default library defined by FORT$LIBRARY,
FORTRAN searches the system-supplied library SYS$LIBRARY:FORSYSDEF.TLB.
SYS$LIBRARY identifies the device and directory containing system libraries and is normally defined by the system manager. FORSYSDEF .TLB is a library of include modules
supplied by VAX FORTRAN. It contains local symbol definitions required for use with
system services, and return status values from system services.
Refer to Appendix C in the VAX FORTRAN User's Guide for more information on the
contents of FORSYSDEF.

3.4 Using the VAX Common Data Dictionary
The Common Data Dictionary (CDD) is an optional VAX software product available under
a separate license. The CDD allows you to maintain a set of shareable data definitions
(language-independent structure declarations) that are defined by a system manager or
data administrator. See the VAX Common Data Dictionary Utilities Reference Manual
and the VAX CDD Data Definition Language Reference Manual for detailed information
about the CDD.
CDD data definitions are organized hierarchically in much the same way that files are
organized in directories and subdirectories. For example, a dictionary for defining personnel data might have separate directories for each employee type. A directory for salesmen
might have subdirectories that would include data definitions for records such as salary
and commission history or personnel history.
Descriptions of data definitions are entered into the dictionary in a special-purpose language called CDDL (Common Data Dictionary Language). Then, the CDDL compiler
converts the data descriptions to an internal form and inserts them into the CDD, thus
making them independent of the language used to access them.

Compiling FORTRAN Programs

3-19

During the compilation of a FORTRAN program, CDD data definitions can be accessed by
means of DICTIONARY statements. If the data attributes of the data definitions are
consistent with FORTRAN requirements, the data definitions are included in the
FORTRAN program. CDD data definitions, in the form of FORTRAN source code, appear
in source program listings if you specify the /SHOW=DICTIONARY qualifier on the FORTRAN command or /LIST in the DICTIONARY statement.
The advantage in using the CDD, instead of FORTRAN source, for structure declarations
is that CDD record declarations are language independent and can be used with several
supported VAX languages.
The following examples illustrate how data definitions are written for the CDD. The first
example is a structure declaration written in CDDL. The second example shows the same
structure as it would appear in a FORTRAN listing.
• CDDL Representation:
PAYROLL_RECORD STRUCTURE,
SALESMAN STRUCTURE.
DATATYPE IS TEXT 30,
NAME
ADDRESS
DATATYPE IS TEXT ao.
SALESMAN_ ID
DATATYPE IS UNSIGNED NUMERIC 5,
END SALESMAN STRUCTURE,
END PAYROLL-RECORD STRUCTURE,

• FORTRAN Source Code Representation:
STRUCTURE /PAYROLL_RECORD/
STRUCTURE SALESMAN
CHARACTER*30 NAME
CHARACTER*aO ADDRESS
STRUCTURE SALESMAN_ID
CHARACTER*3 %FILL
END STRUCTURE
END STRUCTURE
END STRUCTURE

The CDD provides two utilities for creating and maintaining a dictionary:
• The Dictionary Management Utility (DMU)
• The Dictionary Verify/Fix Utility (CDDV)
The Dictionary Management Utility (DMU) is for creating and maintaining the CDD's
directory hierarchy, history lists, and access control lists. The Dictionary Verify/Fix Utility
(CDDV) is for repairing damaged dictionary files. See the VAX Common Data Dictionary
Utilities Reference Manual for details.

3-20

Compiling FORTRAN Programs

3.4.1 Accessing the COD from FORTRAN Programs
DMU commands create directories and define record paths. Once these paths are established, records can be extracted from the CDD by means of DICTIONARY statements in
VAX FORTRAN programs.
At compile time, the CDD record and its attributes are extracted from the designated CDD
record node. Then, the compiler converts the extracted record into a FORTRAN structure
declaration and includes it in the object module.
The DICTIONARY statement incorporates VAX Common Data Dictionary data definitions into the current FORTRAN source file during compilation. It can occur anywhere in a
FORTRAN source file that a specification statement (such as a STRUCTURE/END
· STRUCTURE block) is allowed. The format of the DICTIONARY statement is described
in Section 3.5.3.
A DICTIONARY statement must appear as a statement by itself; it cannot be used within
a FORTRAN structure declaration. For example, the following DICTIONARY statement
INTEGER*Ll PRICE
DICTIONARY 'ACCOUNTS'

would result in a declaration of the form
INTEGER*Ll PRICE
STRUCTURE /ACCOUNTS/
STRUCTURE NUMBER
CHARACTER*3 LEDGER
CHARACTER*5 SUBACCOUNT
END STRUCTURE
CHARACTER*12 DATE

END STRUCTURE

When you extract a record definition from the CDD, you can choose to include this translated record in the program's listing by using the /LIST in the DICTIONARY statement or
the /SHOW=DICTIONARY qualifier in the FORTRAN command line.
CDD data definitions can contain explanatory text in the CDDL DESCRIPTION IS
clause. If you specify /SHOW=DICTIONARY on the FORTRAN command (or /LIST in
the DICTIONARY statement), this text is included in the FORTRAN listing as comments.
The programmer may use these comments to indicate the data type of each structure and
member. The punctuation for CDDL comments is the same as for other FORTRAN programs.
Because the DICTIONARY statement generally contains only structure declaration blocks
(see Section 8.15), you will usually also need to include one or more RECORD statements
(see Section 8.13) in your program to make use of these structures.

Compiling FORTRAN Programs

3-21

3.4.2 Creating COD Structure Declarations
CDD source files must be written in the Common Data Dictionary Language (CDDL). You
enter them using the EDT editor, just as you would any other file. After you have created a
CDD source file, you can then invoke the CDD compiler to insert your record definitions
into the CDD. See the VAX CDD Data Definition Language Reference Manual for detailed
information about the CDDL language and compiler.

3.4.3 FORTRAN and COOL Data Types
The CDD. supports some data types that are not native to FORTRAN. If a data definition
contains an unsupported data type, FORTRAN makes the unsupported data type accessible by declaring it as an inner STRUCTURE containing a single CHARACTER %FILL
field of an appropriate length. FORTRAN does not attempt to approximate a data type
that is not supported by FORTRAN. For example, an UNSIGNED LONG number is
declared:
STRUCTURE

/whatever/

STRUCTURE

na111e

CHARACTER*a
END STRUCTURE
END STRUCTURE

%FILL

and not INTEGER*4, which would result in signed operations if the field was used in an
arithmetic expression.
The following table summarizes the CDDL data types and corresponding FORTRAN data
types. For further information on CDDL data types see the Common Data Dictionary Data
Definition Language Reference Manual.
CDDL Data Type
DATE
DATE AND TIME
VIRTUAL
BIT m ALIGNED
BIT m
UNSPECIFIED
TEXT
VARYING TEXT
VARYING STRING
D_FLOATING
D_FLOATING COMPLEX
F_FLOATING
F_FLOATING COMPLEX

3-22

Compiling FORTRAN Programs

FORTRAN Data Type
STRUCTURE (length 8)
STRUCTURE (length n)
ignored
STRUCTURE (length n+7/8)
STRUCTURE (length n+7/8)
STRUCTURE (length n)
CHARACTER*n
STRUCTURE (length n)
STRUCTURE (length n)
REAL*8 (/NOG_FLOAT only)
COMPLEX*16 (/NOG_FLOAT only)
REAL*4
COMPLEX*8

CDDL Data Type

FORTRAN Data Type

G___FLOATING
G___FLOATING COMPLEX
H___FLOATING
H___FLOATING COMPLEX
SIGNED BYTE
UNSIGNED BYTE
SIGNED WORD
UNSIGNED WORD
SIGNED LONGWORD
UNSIGNED LONGWORD
SIGNED QUADWORD
UNSIGNED QUADWORD
SIGNED OCTAWORD
UNSIGNED OCTAWORD
PACKED NUMERIC
SIGNED NUMERIC
UNSIGNED NUMERIC
LEFT OVERPUNCHED
LEFT SEPARATE
RIGHT OVERPUNCHED
RIGHT SEPARATE

REAL*8 (/G___FLOAT only)
COMPLEX*l6 (/G___FLOAT only)
REAL*16
STRUCTURE (length 32)
LOGICAL*!
STRUCTURE (length 1)
INTEGER*2
STRUCTURE (length 2)
INTEGER*4
STRUCTURE (length 4)
STRUCTURE (length 8)
STRUCTURE (length 8)
STRUCTURE (length 16)
STRUCTURE (length 16)
STRUCTURE (length n)
STRUCTURE (length n)
STRUCTURE (length n)
STRUCTURE (length n)
STRUCTURE (length n)
STRUCTURE (length n)
STRUCTURE (length n)

NOTE
D_floating and G_floating data types cannot be mixed in one subroutine; both
types cannot be handled simultaneously. You can use both types, each in a
separate subroutine, depending on the OPTIONS statement qualifier in effect
for the individual subroutine. For a discussion of the handling of REAL*8 data
types in VAX FORTRAN, see Section 6.2.1.2.
FORTRAN ignores CDD features that are not supported by FORTRAN, but issues error
messages when the features conflict with FORTRAN.

Compiling FORTRAN Programs

3-23

3.5 Compilation Control Statements
In addition to qualifiers on the FORTRAN command, several statements used in the body
of a FORTRAN program also influence the compilation process.
• The INCLUDE statement incorporates external source code into your programs during
the compilation process.
• The OPTIONS statement establishes compiler qualifiers that would otherwise be
specified on the FORTRAN command. If the same qualifier is specified on both the
OPTIONS statement and the FORTRAN command, the OPTIONS statement version
overrides if a conflict occurs.
• The DICTIONARY statement extracts records from the CDD (Common Data Dictionary) and converts them into VAX FORTRAN records for use in the program.

3.5.1 INCLUDE Statement
The INCLUDE statement specifies that the contents of a file or a text library module are to
be incorporated in the FORTRAN compilation directly following the INCLUDE statement.
The INCLUDE statement has no effect on program execution. It simply directs the compiler to read FORTRAN statements from a different file or a text library.
The INCLUDE statement has the form:
INCLUDE

,[file-spec] (module-name)[/[NO]LIST]'}
{ 'file-spec[/[NO]LIST]'

where:
file-spec

A character string that specifies either (1) a file to be included in the compilation or
(2) a text library containing a module to be included in the compilation. This file
specification must be acceptable to the operating system. (See Section 1.5.1 for the
form of a file specification.)
module-name

The name of a text module, located in a text library, that is to be included in the
source file. The name of the module must be enclosed in parentheses. It can be up to
31 characters long and can contain any alphanumeric character and the special characters dollar sign ($) and underscore (_),
/[NO]LIST

The /LIST qualifier indicates that the statements in the specified file or module are to
be listed in the compilation source listing. A number indicating the depth of nesting
of include files precedes each statement listed. The /NOLIST qualifier indicates that
the included statements are not to be listed in the compilation source listing. The
default is /NOLIST.

3-24

Compiling FORTRAN Programs

When the compiler encounters an INCLUDE statement, it stops reading statements from
the current file and reads the statements in the included file or module. When it reaches
the end of the included file or module, the compiler resumes compilation with the next
statement after the INCLUDE statement.
An INCLUDE statement can be contained in an included file or module.
An included file or module cannot begin with a continuation line. Each FORTRAN statement must be completely contained within a single file or module.
The INCLUDE statement can appear anywhere within a program unit, as shown in Figure
5-1. Any FORTRAN statement can appear in an included file or module. However, the
included statements, when combined with the other statements in the compilation, must
satisfy the statement-ordering restrictions described in Section 5.2.2.1.
In the following example, the file COMMON .FOR defines the size of the blank common
block and the size of the arrays X, Y, and Z.
Main Program File

INCLUDE 'COMMON.FDR'
DIMENSION ZCM)
CALL CUBE
DD 51 I=11M
Z(I) = XCI)+SORTCYCI))

File COMMON.FOR
PARAMETER CM=100)
COMMON )-((M) 1YCM)

END

SUBROUTINE CUBE
INCLUDE 'COMMON.FDR'
DD 101 I=11M
XCI) = YCI)*3
RETURN
END

Compiling FORTRAN Programs

3-25

3.5.2 OPTIONS Statement
The OPTIONS statement can be used to override or confirm the FORTRAN command
qualifiers in effect in a program unit. It has the form:
OPTIONS qualifier[,qualifier ... ]

where:
qualifier

is one of the following:
/[NO]G_FLOATING
/[NO]l4
/[NO]F77

/CHECK=

ALL
~
[NO] OVERFLOW
[NO] BOUNDS
[NO] UNDERFLOW (
NONE
)

/NOCHECK
/[NO]EXTEND_SOURCE

The qualifiers have the same syntax and abbreviations as the FORTRAN command line
qualifiers. Refer to 3.2.3 for a detailed explanation of the specific qualifiers.
The OPTIONS statement must be the first statement in a program unit, preceding the
PROGRAM, SUBROUTINE, FUNCTION, and BLOCK DATA statements.
The OPTIONS qualifiers take precedence over qualifiers defined on the FORTRAN command line. However, the qualifiers remain in effect only until the end of the program unit
in which they are defined. Thus, an OPTIONS statement must appear in each program
unit in which you wish to override the command line qualifiers. For example:
OPTIONS /CHECK/EXTEND_SOURCE
END
OPTIONS /G_FLDATING

The first OPTIONS statement in the preceding example specifies that the program unit
immediately following is to be compiled with full checking and extend-source options,
regardless of the /CHECK and /EXTEND_SOURCE specifications on the FORTRAN
command line. The next OPTIONS statement specifies that the program unit following it
is to be compiled with the G_floating option. The check and extend-source options do not
remain in effect across program unit boundaries.

3-26

Compiling FORTRAN Programs

3.5.3 DICTIONARY Statement
The DICTIONARY statement incorporates VAX Common Data Dictionary data definitions into the current FORTRAN source file during compilation. It can occur anywhere in a
FORTRAN source file that a specification statement (such as a STRUCTURE/END
STRUCTURE block) is allowed.
The format of the DICTIONARY statement is:
DICTIONARY 'cdd-path [/[NO]LIST]'

where:
cdd-path

The cdd-path is interpreted as the full or relative pathname of a CDD object. The
resulting pathname must conform to the rules for forming VAX CDD pathnames.
/[NO]LIST

The /LIST qualifier controls whether the source code representation of the resulting
structure declaration is to be listed in the compilation source listing. The default is
/NO LIST.
There are two types of CDD pathname: full and relative. A full pathname begins with
CDD$TOP and specifies the given names of all its descendants; it is a complete path to the
record definition. Descendant names are separated from each other by a period.
A relative pathname begins with any generation name other than CDD$TOP and specifies
the given names of the descendants after that point. A relative path may be accomplished
by establishing a default directory with a logical name. For example:
$ DEFINE CDD$DEFAULT CDD$TOP,FOR

This logical name definition specifies the beginning of the CDD pathname; thus, a relative
pathname specifies the remainder of the path to the record definition. Note also that a
CDD pathname beginning with CDD$TOP overrides the default CDD pathname. Refer to
the VAX Common Data Dictionary Utilities Manual for further details.
For example, if you have a record with the following pathname:
CDD$TOP,SALES,JONES.SALARY

and you have defined CDD$DEFAULT to be CDD$TOP.SALES.JONES, then you may
specify a relative pathname as
DI CT I DNA RY

SALARY

or an absolute pathname as
DICTIONARY 'CDD$TOP+SALES,JONES.SALARY'

Compiling FORTRAN Programs

3-27

3.6 Compiler Diagnostic Messages and Error Conditions
One of the functions of the FORTRAN compiler is to identify syntax errors and violations
of language rules in the source program. If the compiler locates any errors, it writes messages to your default output device; thus, if you enter the FORTRAN command interactively, the messages are displayed on your terminal. If the FORTRAN command is executed in a batch job, the messages appear in the batch job log file.
When it appears on the terminal, a message from the compiler has the following format:
%FORT-s-ident, message-text
[text-in-error] in module module-name at line n

Diagnostic messages usually provide enough information for you to determine the cause of
an error and correct it.
Each compilation with diagnostic messages terminates with a summary that indicates the
combined number of error, warning, and informational messages generated by the compiler. The diagnostic summary has the following form:
%FORT-s-ident, source-file-spec completed with n diagnostics

If the compiler creates a listing file, it also writes the messages to the listing. Messages
typically follow the statement that caused the error.

Additional information about diagnostic messages, including descriptions of the individual
messages, is contained in Appendix E.

3. 7 Compiler Output Listing Format
A compiler output listing produced by a FORTRAN command with the /LIST qualifier
consists of the following sections:
• A source code section
• A machine code section (optional)
• A storage map section (cross-reference, optional)
• A compilation summary
Sections 3.7 .1 through 3.7.4 describe the compiler listing sections in detail.

3. 7.1 Source Code Section
The source code section of a compiler output listing displays the source program as it
appears in the input file, with the addition of sequential line numbers generated by the
compiler. Figure 3-2 shows a sample of a source code section of a compiler output listing.

3-28

Compiling FORTRAN Programs

0001
0002

SUBROUTINE RELAX21EPS)

0003
OOOLI
0005
0006
0007
0008
0009
001C>
0011
0012
0013
001 LI
0015
0016
0017
0018
0019
0020

PARAMETER IM=LIO, N=60)
DIMENSION XIO:M,O:Nl
COMMON )-(
LOGICAL DONE
DONE = .TRUE,

DO 10 J=11N-1
D010I=1,M-1
)-(NEW = ()-(( I-11J)+)-(( I+11J)+)-(( I 1J-1)+X(I1J+1)) /LI
IF CABSll<NEW-)-(( I 1J)) .GT, EPS) DONE = .FALSE.
)-((I,Jl = l<NEW
IF ( , NOT, DONE) GO TO 1
RETURN
END

Figure 3-2: Sample Listing of Source Code

Compiler-generated line numbers appear in the left margin and are used with the %LINE
prefix in debugger commands. If you create the source file with an editor that generates line
numbers, those numbers also appear in the source listing. In this case, the editor-generated
line numbers appear in the left margin, and the compiler-generated line numbers are
shifted to the right. The %LINE specification still applies to the compiler-generated line
numbers, not the editor-generated line numbers.
Compile-time error messages that contain line numbers refer to the editor-generated line
numbers present in the source code listing; otherwise, they refer to compiler-generated line
numbers. Run-time error messages that contain line numbers refer to the compiler-generated line numbers in the source code listing section. (See Appendix E for a summary of
error messages.)

3. 7.2 Machine Code Section
The machine code section of a compiler output listing provides a symbolic representation of
the compiler-generated object code. The representation of the generated code and data is
similar to that of a VAX MACRO assembly listing.
The machine code section is optional. To receive a listing file with a machine code section,
you must specify:
$

FORTRAN/LIST/MACHINE-CODE

Compiling FORTRAN Programs

3-29

Figure 3-3 shows a sample of a machine code section of a compiler output listing.

3-30

Compiling FORTRAN Programs

The following notes give a detailed explanation of how generated code and data are represented in machine code listings.
1. Machine instructions are represented by VAX MACRO mnemonics and syntax.
Compiler-generated line numbers corresponding to generated code lines are listed at
the right margin, preceding the machine code generated for the line.

2. The first line contains a .TITLE assembler directive, indicating the program unit to
which the machine code corresponds.
• For a main program, the title is as declared in a PROGRAM statement. If you did
not specify a PROGRAM statement, the main program is titled filename$MAIN,
where filename is the name of the source file.
• For a subprogram, the title is the name of the subroutine or function.
• For a BLOCK DATA subprogram, the title is either the name declared in the
BLOCK DATA statement, or filename$DATA by default.
3. The lines following .TITLE provide information such as the contents of storage
initialized for FORMAT statements, DATA statements, constants, and subprogram
argument call lists.
4. The VAX general registers (0 through 12) are represented by RO through R12. When
register 12 is used as the argument pointer, it is represented by AP; the frame pointer
(register 13) is FP; the stack pointer (register 14) is SP; and the program counter
(register 15) is PC. Note that the relative PC for each instruction or data item is
listed at the left margin, in hexadecimal.
5. Variables and arrays defined in the source program are shown as they were defined in
the program. Offsets from variables and arrays are shown in decimal.
6. FORTRAN source labels referenced in the source program are shown with a period
prefix (.). For example, if the source program refers to label 300, the label appears in
the machine code listing as .300. Labels that appear in the source program, but are
not referenced or are deleted during compiler optimization, are ignored. They do not
appear in the machine code listing unless you specified /NOOPTIMIZE.
7. The compiler may generate labels for its own use. These labels appear as L$n, where
the value of n is unique for each such label in a program unit.
8. Integer constants are shown as signed integer values; real and complex constants are
shown as unsigned hexadecimal values preceded by "X.
9. Addresses are represented by the program section name plus the hexadecimal offset
within that program section. Changes from one program section to another are indicated by PSECT lines.

Compiling FORTRAN Programs

3-31

3. 7.3 Storage Map Section
The storage map section of the compiler output listing is printed after each program unit,
or module. It summarizes information in the following categories:
• Program sections: The program section summary describes each program section
(PSECT) generated by the compiler. The descriptions include:

PSECT number (used by most of the other summaries)
Name
Size in bytes
Attributes
PSECT usage and attributes are described in the VAX FORTRAN User's Guide.
• Total memory allocated: Following the program sections, the compiler prints the total
memory allocated for all program sections compiled in the following form:
Total Space Allocated nnn

• Entry points: The entry point summary lists all entry points and their addresses. If the
program unit is a function, the declared data type of the entry point is also included.
• Statement functions: The statement function summary lists the entry point address
and data type of each statement function. If all of the references to a statement
function generate inline code, the body of the statement function is not compiled, and
a double asterisk (**) appears instead of an address.
• Variables: The variable summary lists all simple variables, with the data type and
address of each. If the variable is removed as a result of optimization, a double asterisk
( * *) appears in place of the address.
• Records: The record summary lists all record variables. It shows the address, the
structure that defines the fields of the individual records, and the total size of each
record.
• Arrays: The array summary is similar to the variable summary. In addition to data
type and address, the array summary gives the total size and dimensions of the array.
If the array is an adjustable array or assumed-size array, its size is shown as double
asterisks ( **), and each adjustable dimension bound is shown as a single asterisk ( *).
• Record Arrays: The record array summary is similar to the record summary. The
record array summary gives the dimensions of the record array in addition to address,
defining structure, and total size. If the record array is an adjustable array or assumedsize array, its size is shown as double asterisks ( ** ), and each adjustable dimension
bound is shown as a single asterisk ( *).
• Namelists: The namelist summary lists names of namelists.

3-32

Compiling FORTRAN Programs

• Labels: The label summary lists all user-defined statement labels. FORMAT statement labels are suffixed with an apostrophe ( '). If the label address field contains
double asterisks ( ** ), the label was not used or referred to by the compiled code.
• Functions and subroutines: The functions and subroutines summary lists all external
routine references made by the source program. This summary does not include references to routines that are dummy arguments; the actual function or subroutine name
is supplied by the calling program.

A heading for an information category is printed in the listing only when entries are
generated for that category.
Cross-reference information is optional. It is supplied only when you specify:
$

FDRTRAN/LIST/CRDSS_REFERENCE

When you request cross-referencing, the compiler supplies information on the following
entities:
• Parameter constants: The parameter constant summary lists all of the PARAMETER
constants along with the data type of each.
• Field scalars: The field scalar summary lists all of the scalar fields declared within a
structure block. It shows the starting offset within the structure for each scalar field,
the name of the structure containing each scalar field, and the datatype and size (in
bytes) of each scalar field.
• Field arrays: The field array summary lists all of the array fields declared within a
structure block. It shows the starting offset within the structure for each array field;
the name of the structure containing each array field; and the datatype, size (in
bytes), and dimensions of each array field.

The compiler also supplies attributes and line number references if you request crossreferencing, the attributes indicate whether a variable or array appears in common and
whether it appears in an EQUIVALENCE statement.
The compiler supplies the following reference information for each name:
• A source line number indicates where the name was referenced.

• An equal sign (=) next to a line number indicates that the value of a variable or array
was modified at that line.
• A number sign (#) next to a line number indicates the line where the symbol was
defined.

• An "A" next to a line number indicates an actual argument which may have been
modified.
• A "D" next to a line number indicates that data initialization occurred at that point in
the program.
• A number in parentheses (n) next to a line number indicates that the name appeared n
times on that line.
Compiling FORTRAN Programs

3-33

Figure 3-4 shows an example of a storage map section with cross-reference information.
PROGRAM SECTIONS

0 $CODE
3 $BLANK
Total SPace Allocated

B~·tes

Attributes

82
1000ll

PI C CON REL LCL
PI C DI.JR REL GBL

SHR
E)<E
SHR NDE>{E

RD NOWRT LONG
RD
WRT LONG

9=
1 ll
13 (al
13 (al
1 ll

1 ll =

1 ll
1 ll
15

15
15

10086

ENTRY POINTS
Address

TYPe

NaMe

References

RELA)-{2

0-00000000
1.JAR I ABLES
Address

TY Pe

Nar11e

**
AP-OOOOOOOll@
**
**
**

L*ll
R*ll
I *ll
I*ll
R*ll

DONE
EPS
I

Attributes

References
7

12=
11 =

)-{NEW

~3=

ARRAYS
Attributes
3-00000000
13(ll)
1ll

R*ll
15=

COMM

Bvtes

DiMensions

1000ll

(O:l!O I 0:60)

References

PARAMETER CONSTANTS
References

12
11

LABELS
Address

Label

0-0000000ll
**

References
9#
11

17
12

15#

Figure 3-4: Sample Storage Map Section
As shown in Figure 3-4, a section size is printed as a number of bytes, expressed in decimal.
A data address is specified as an offset from the start of a program section, expressed in
hexadecimal. The symbol AP can appear instead of a program section. When it does, the
3-34

Compiling FORTRAN Programs

address refers to a dummy argument, expressed as the offset from the argument pointer
(AP). Indirection is indicated by an at sign (@) following an address field. In this case, the
address specified by the program section (or AP) plus the offset points to the address of the
data, not to the data itself.

3. 7.4 Compilation Summary Section
The final entries on the compiler listing are the compiler qualifiers and compiler statistics.
The first line of qualifiers in this section echoes the command line that you used to invoke
the compiler. The next set of qualifiers shows which ones were in effect during the compilation. The compiler statistics are the machine resources used by the compiler.
If the /CROSS_REFERENCE qualifier is specified, an explanation of the reference flags
is printed before the qualifier summary.

Figure 3-5 shows how compiler options and command qualifiers and compilation statistics
appear on the listing.

+---------------------------------------------+
#

A
D
(n)

KEY TD REFERENCE FLAGS
l,lalue Modified
Definins Reference
Actual ArsuMent1 Possibly Modified
Data Initialization
NuMber of occurrences on line

+---------------------------------------------+
OPTIONS QUALIFIERS
/CHECK=CNDBOUNDS1DVERFLDW1NDUNDERFLDW>
/F77 /NOG_FLOATING /NOia
COMMAND QUALIFIERS
FORTRAN /LISTING/MACHINE_CODE/CRDSS_REFERENCE RELAX2
/CHECK=CNOBOUNDS1DVERFLDW1NDUNDERFLDW>
/DEBUG=CNDSYMBDLS1TRACEBACK>
/STANDARD=CNOSYNTAX1NDSDURCE_FORM)
/SHDW=CNOPREPROCESSDR1NOINCLUDE1MAP1NDDICTIONARY1SINGLE)
/WARNINGS=CGENERAL1NODECLARATIDNS>
/CDNTINUATIDNS=18 /CROSS_REFERENCE /NOD-LINES /NOEXTEND_SOURCE /F77
/NOG_FLDATING /Ia /MACHINE_CODE /OPTIMIZE
COMPILATION STATISTICS
Run Ti111e:
Elapsed Ti111e:
Pase Faults:
Dn·1a111ic Me1T1on·:

1.17 seconds
2.23 seconds
138
326 Pases

Figure 3-5: Sample Compilation Summary

Compiling FORTRAN Programs

3-35

Chapter 4

Linking and Running FORTRAN Programs
This chapter describes how to produce an executable image from a FORTRAN object file,
how to execute the resulting image, and how to isolate run-time errors.

4.1 Linking FORTRAN Programs
This section describes how to use the linker and object module libraries to combine object
modules into executable programs. It discusses:
• The functions performed by the linker
• The LINK command and its input and output files
The topics in this chapter are confined to areas of particular interest to FORTRAN programmers. For additional information on linker capabilities and detailed descriptions of
LINK command qualifiers and options, see the VAX/VMS Linker Reference Manual.

4.1.1 Functions of the Linker
The primary functions of the linker are to allocate virtual memory within the executable
image, to resolve symbolic references among modules being linked, to assign values to
relocatable global symbols, and to perform relocation. The linker's end product is an
executable image that you can run on a VAXNMS system.
For any FORTRAN program unit, the object module generated by the compiler may
contain calls and references to VAX FORTRAN run-time procedures, which the linker
locates automatically in the default system object module libraries. The libraries are described in the VAX/VMS Linker Reference Manual.

4-1

4.1.2 The LINK Command
The LINK command initiates the linking of the object file. The command has the form:
$ LINK[/command-qualifiers] file-spec[/file-qualifiers] ...

where:
/command-qualifiers

Specifies output file options.
file-spec

Specifies the input object file to be linked.
/file-qualifiers

Specifies input file options.
In interactive mode, you can issue the LINK command with no accompanying file specification. The system then requests the file specifications with the following prompt:
_File:

You can enter multiple file specifications by separating them with commas or plus signs.
When used with the LINK command, the comma has the same effect as the plus sign; that
is, a single executable image is created from the input files specified. If no output file is
specified, the linker produces an executable image with the same name as that of the first
object module and with a file type of EXE. Table 4-1 lists the linker qualifiers of particular.
interest to FORTRAN users. See the VAX/VMS Linker Reference Manual for details on
the linker.
Table 4-1: LINK Command Qualifiers
Function

Qualifiers

Defaults

Request output file and define a file specification.

/EXECUTABLE [=file-spec]
/SHAREABLE [=file-spec]

/EXECUTABLE=name.EXE,
where name is the name of the
first input file.
/NO SHAREABLE

Request and specify the contents of a memory allocation
listing.

/BRIEF
/[NOJCROSS__REFERENCE
/FULL
/[NOJMAP

/NOCROSS_REFERENCE
/NO MAP
(interactive)
/MAP=name.MAP (batch)
where, name is the name of the
first input

Specify the amount of debugging information.

/[NOJDEBUG
/[NOJTRACEBACK

/NODEBUG
/TRACEBACK

4-2

Linking and Running FORTRAN Programs

Table 4-1 (Cont.): LINK Command Qualifiers
Function

Qualifiers

Defaults

Indicate that input files are
libraries and to specifically
include certain modules.

/INCLUDE=(module-name ... )
/LIBRARY
/SELECTNE-8EARCH

Not applicable

Request or disable the
searching of default user libraries and system libraries.

/[NOJSYSLIB
/[NOJSYSSHR
/[NOJUSERLIBRARY[=table]

/SYS LIB
/SYSSHR
/USERLIBRARY=ALL

Indicate that an input file is a
linker options file.

/OPTIONS

Not applicable

4.1.2.1 Linker Output File Qualifiers
You can include qualifiers in the LINK command to influence the output of the linker. You
can also specify whether the debugging or the traceback facility is to be included.
The debugger and traceback qualifiers are:
/[NO] DEBUG
/[NO]TRACEBACK

The /DEBUG and /TRACEBACK qualifiers are described in Section 4.1.2.2.
Linker output consists of an image file and, optionally, a map file. The qualifiers that
control image and map files are described under the headings that follow.

Image File Qualifiers
The image file qualifiers are /[NOlEXECUTABLE and /[NOlSHAREABLE. The use and
effects of these two qualifiers are as follows:
•/EXECUTABLE Qualifier. If you do not specify an image file qualifier, the default is
/EXECUTABLE, and the linker produces an executable image.
To suppress production of an image, specify /NOEXECUTABLE. For example, in the
following command, the file CIRCLE.OBJ is linked, but no image is generated:
$

LINK/NDEXECUTABLE CIRCLE

The /NOEXECUTABLE qualifier is useful if you want to verify the results of linking
an object file without actually producing the image.
To designate a file specification for an executable image, use the /EXECUTABLE
qualifier in the form:
/EXECUTABLE=file-spec

Linking and Running FORTRAN Program!)

4-3

For example, in the following command, the file CIRCLE.OBJ is linked and the
executable image generated by the linker is named TEST.EXE:
LINK/EXECUTABLE=TEST CIRCLE

• /SHAREABLE Qualifier. A shareable image is an image that has all of its internal
references resolved, but it must be linked with one or more object modules to produce
an executable image. A shareable image file, for example, can contain a library of
routines or can be used by the system manager to create a global section for all users.
To create a shareable image, specify the /SHAREABLE qualifier, as shown in the
following example:
$

LINK/SHAREABLE CIRCLE

To include a shareable image as input to the linker, you can insert the shareable image
into a shareable-image library and specify the library as input to the LINK command.
By default, the linker automatically searches the system-supplied shareable-image
library SYS$LIBRARY:IMAGELIB.OLB after searching any libraries you specify on
the LINK command line. You can also include a shareable image by using a linker
options file. See the VAX/VMS Linker Reference Manual for more information.
If you specify (or default to) /NOSHAREABLE, the image produced cannot be linked
with other images.

Map File Qualifiers
The map file qualifiers tell the linker whether a map file is to be generated and, if so, what
information is to be included.
The map qualifiers are specified as follows:
/MAP[=file-spec] [ { /BRIEF}] [/CROSS_REFERENCE]
/FULL

The linker uses the following map file defaults: in interactive mode, the default is to
suppress the map; in batch mode, the default is to generate the map.
If you do not include a file specification with the /MAP qualifier, the map file has the name
of the first input file and a file type of MAP. It is stored on the default device in the default
directory.

The /BRIEF and /FULL qualifiers define the amount of information included in the map
file. They function as follows:
• /BRIEF produces a summary of the image's characteristics and a list of contributing
modules.
• /FULL produces a summary of the image's 'characteristics and a list of contributing
modules (as produced by /BRIEF). It also produces a list, in symbol-name order, of
global symbols and values (program, subroutine,· and common block names, and
names declared EXTERNAL) and a summary of characteristics of image sections in
the linked image.

4-4

Linking and Running FORTRAN Programs

If neither /BRIEF nor /FULL is specified, the map file, by default, contains a summary of
the image's characteristics, a list of contributing modules (as produced by /BRIEF), and a
list of global symbols and values, in symbol-name order.

You can use the /CROSS-REFERENCE qualifier with either the default or /FULL map
qualifiers to request cross-reference information for global symbols. This cross-reference
information indicates the object modules that define and/or refer to global symbols encountered during linking. The default is /NOCROSS_REFERENCE.

4.1.2.2 /DEBUG and /TRACEBACK Qualifiers
The /DEBUG qualifier indicates that the debugger (see Chapter 17) is to be included in the
executable image and that local symbol information contained in the object modules is to
be included. The default is /NODEBUG.
When you use the /TRACEBACK qualifier, run-time error messages will be accompanied
by a symbolic traceback that shows the sequence of calls that transferred control to the
program unit in which the error occurred. If you specify /NOTRACEBACK, this information is not produced. The default is /TRACEBACK.
If you specify /DEBUG, the traceback capability is automatically included, and the
/TRACEBACK qualifier is ignored. (See Section 4.3.1 for a sample traceback list.)

4.1.2.3 Linker Input File Qualifiers
Input file qualifiers affect the file specifications of input files. Input files can be object files,
shareable files previously linked, or library files.
The qualifiers that control linker input files are the /LIBRARY qualifier and the
/INCLUDE qualifier.
• The /LIBRARY qualifier has the form:
/LIBRARY

This qualifier specifies that the input file is an object-module or shareable-image
library that is to be searched to resolve undefined symbols referenced in other input
modules. The default file type is OLB.
• The /INCLUDE qualifier has the form:
/INCLUDE=module-name(s)
The qualifier specifies that the input file is an object-module or shareable-image
library and that the modules named are the only modules in the library to be explicitly
included as input. In the case of shareable-image libraries, the module is the shareable-image name.
At least one module name is required. To specify more than one, enclose the module
names in parentheses and separate the names with commas.
The default file type is OLB. The /LIBRARY qualifier can also be used, with the same
file specification, to indicate that the same library is to be searched for unresolved
references.
Linking and Running FORTRAN Programs

4-5

4.1.3 Linker Messages
If the linker detects any errors while linking object modules, it displays messages about
their cause and severity. If any errors or fatal conditions occur (severities E or F), the linker

does not produce an image file.
Linker messages are descriptive, and you do not normally need additional information to
determine the specific error. Some of the more common errors that occur during linking are
as follows:

• An object module has compilation errors. This error occurs when you attempt to link a
module that had warnings or errors during compilation. Although you can usually link
compiled modules for which the compiler generated messages, you should verify that
the modules will actually produce the output you expect.
• The modules that are being linked define more than one transfer address. The linker
generates a warning if more than one main program has been defined. This can occur,
for example, when an extra END statement exists in the program. The image file
created by the linker in this case can be run; the entry point to which control is
transferred is the first one that the linker found.
• A reference to a symbol name remains unresolved. This error occurs when you omit
required module or library names from the LINK command and the linker cannot
locate the definition for a specified global symbol reference.
If an error occurs when you link modules, you can often correct it simply by reentering the

command string and specifying the correct routines or libraries.

4.2 Running FORTRAN Programs
This section describes the following considerations for executing FORTRAN programs on
the VAXNMS operating system:
• Using the RUN command to execute programs interactively
• Passing status values to the command interpreter

4.2.1 The RUN Command
The RUN command initiates execution of a program.
The command has the form:
$ RUN[/[NO]DEBUG] file-spec

You must specify the file name. If you omit optional elements of the file specification, the
system automatically provides a default value. The default file type is EXE.

4-6

Linking and Running FORTRAN Programs

The /DEBUG qualifier allows you to use the debugger, even if you omitted this qualifier
from the FORTRAN and LINK commands. Refer to Section 4.3 for details.
Before the image is activated, the system initializes to zero all variables and arrays that are
not initialized by means of DATA statements. (Note: It is not considered a good programming practice to rely on this, however.)

4.2.2 System Processing at Image Exit
When the main program executes an END statement, or when any program unit in the
program executes a STOP statement, the image is terminated. In the VAX/VMS operating
system, the termination of an image, or image exit, causes the system to perform a variety
of clean-up operations during which open. files are closed, system resources are freed, and so
on.

4.2.3 Interrupting a Program
When you execute the RUN command interactively, you cannot execute any other program
images or DCL commands until the current image completes. However, if your program is
not performing as expected-if, for instance, you have reason to believe it is in an endless
loop-you can interrupt it. To do so, use the <CTRL/Y> key. (You may also use the
<CTRL/C> key, unless your program takes specific action in response to <CTRL/C>.) For
example:
$ RUN APPLIC
hy
$

This command interrupts the program APPLIC. After you have interrupted a program, you
can terminate it by entering a DCL command that causes another image to be executed or
by entering the DCL commands EXIT or STOP.
Following a <CTRLIY> interruption, you can also force an entry to the debugger by
entering the DEBUG command.
There are some other DCL commands you can enter that have no direct effect on the
image. After using them, you can resume the execution of the image with the DCL command CONTINUE. For example:
$ RUN APPLIC
.. y

$ SHOW TRANSLATION INFILE
INFILE =
(undefined)
$DEFINE INFILE DBAl:CTESTFILESJJANUARY,DAT
$ CONTINUE

Linking and Running FORTRAN Programs

4-7

For a complete list of the commands you can enter following a <CTRL/Y> interruption
without affecting the current image, see the VAX/VMS Command Definition Utility Reference Manual.
As noted above, you may use <CTRL/C> to interrupt your program; in most cases, the
effect of <CTRL/C> and <CTRL/Y> is the same. However, some programs (including
programs you may write) establish particular actions to take to respond to <CTRL/C>. If a
program has no <CTRL/C> handling routine, then <CTRL/C> is the same as <CTRL/Y>.

4.2.4 Returning Status Values to the Command Interpreter
If you run your program as part of a command procedure, it is frequently useful to return a
status value to the command procedure indicating whether the program actually executed
properly. To return such a status value, call the EXIT system subroutine rather than
terminating execution with a STOP, RETURN, or END statement. The EXIT subroutine
can be called from any executable program unit. It terminates your program and returns
the value of the argument as the return status value of the program. See Section D .4.4 for a
description of the EXIT subroutine.

When the command interpreter receives a status value from a terminating program, it
attempts to locate a corresponding message in a central system message file or a userdefined message file. Every possible message that can be issued by a system program,
command, or component, has a unique 32-bit numeric value associated with it. These 32bit numeric values are called condition symbols. Condition symbols are described in Section 6.9 of the VAX FORTRAN User's Guide.
The command interpreter does not display messages on completion of a program under the
following circumstances:
• The EXIT argument specifies the value 1, corresponding to SUCCESS.
• The program does not return a value. If the program terminates with a RETURN,
STOP, or END statement, a value of 1 is always returned and no message is displayed.

4.3 Finding and Correcting Run-Time Errors
Both the compiler and the VAX Run-Time Library include facilities for detecting and
reporting errors. You can use the VAX Symbolic Debugger and the traceback facility to
help you locate errors that occur during program execution.

4-8

Linking and Running FORTRAN Programs

4.3.1 Effects of Error-Related Command Qualifiers
At each step in compiling, linking, and executing your program, you can specify command
qualifiers that affect how errors are processed.
• At compile time, you can specify the /DEBUG qualifier on the FORTRAN command
to ensure that symbolic information is created for use by the debugger.
• At link time, you can also specify the /DEBUG qualifier on the LINK command to
make the symbolic information available to the debugger.
• At run time, you can specify the /DEBUG qualifier on the RUN command to invoke
the debugger.
Table 4-2 summarizes the /DEBUG and /TRACEBACK qualifiers.

Table 4-2: /DEBUG and /TRACEBACK Qualifiers
Qualifier

Command

Effect

Default

/DEBUG

FORTRAN

The FORTRAN compiler creates symbolic data debugger.

/DEBUG=
(NOSYMBOLS,
TRACEBACK)

/DEBUG

LINK

Symbolic data created by the
FORTRAN compiler is passed to
the debugger.

/NODEBUG

!TRACEBACK

LINK

Traceback information is passed
to the debugger. Traceback will
be produced.

trRACEBACK

/DEBUG

RUN

Invokes the debugger. The
DBG> prompt will be displayed.
Not needed if$ LINK/DEBUG
was specified.

/NODEBUG

RUN

If /DEBUG was specified in the
LINK command, RUN/NODEBUG starts program execution
without first invoking the debugger.

Linking and Running FORTRAN Programs

4-9

If these qualifiers are not specified at any point in the compile-link-execute sequence, a
traceback list is generated by default if an execution error occurs.

To perform symbolic debugging, you must use the /DEBUG qualifier with both the
FORTRAN and LINK commands, but you do not need to specify it with the RUN command. If /DEBUG is omitted from either the FORTRAN or LINK command, you can still
use it with the RUN command to invoke the debugger. However, any debugging you
perform must then be done by specifying virtual addresses rather than symbolic names.
If you linked your program with the debugger, but wish to execute the program without
debugger intervention, specify:
$ RUN/NODEBUG program-name

If you specify LINK/NOTRACEBACK, you receive no traceback in the event of errors. A
sample source program and a traceback are shown in Figure 4-1.
PROGRAM TRACE_TEST

0001
0002
0003
0004
0005

CALL SUB1<I>
END

0 001
0002
0003
0004
0005

SUBROUTINE SUB1<I>
I = I + 1
CALL SUB2
RETURN
END

0001
0002
0003
0004
0005
0006
0007
0008
0008

= 1

SUBROUTINE SUB2
COMPLE}{ W
COMPLE}{ Z
DATA W/(0. 10. )/
Z = LOG<W>
RETURN
END

%MTH-F-INVARGMAT1 invalid ar~ument to math library
user PC 00003404
%TRACE-F-TRACEBACK1 symbolic stacK dump follows
111odu1 e n a1t1 e

SUB2
SUB 1
TRACE_TEST

routine na1t1e

SUB2
SUB 1
TRACE_TEST

1 in e

relati1.1e PC

absolute PC

7
3
4

00001368
00002C51
000034D4
00000011
OOOOOOOC
00000014

00001368
00002C51
000034D4
00000439
00000424
00000414

Figure 4-1: Sample FORTRAN Program and Traceback

4-10

Linking and Running FORTRAN Programs

The traceback is interpreted as follows:
When the error condition is detected, you receive the appropriate message, followed by the
traceback information. The Run-Time Library displays a message indicating the nature of
the error and the address at which the error occurred (user PC). This is followed by the
traceback information, which is presented in inverse order to the calls. Note that values
can be produced for relative and absolute PC, with no corresponding values for routine
name and line. These PC values reflect procedure calls internal to the Run-Time Library.
Of particular interest are the values listed under "routine name" and "line." The names
under "routine name" show what routine or subprogram called the Run-Time Library,
which subsequently reported the error. The value given for "line" corresponds to the compiler-generated line number in the source program listing (not to be confused with editorgenerated line numbers). With this information, you can usually isolate the error in a short
time.
If you specify either LINK/DEBUG or RUN/DEBUG, the debugger assumes control of
execution and you do not receive a traceback list if an error occurs. To display traceback
information, you can use the debugger command SHOW CALLS.

You should specify the /NOOPTIMIZE qualifier on the FORTRAN command line whenever you use the debugger; see Section 3.2.3.15.

Linking and Running FORTRAN Programs

4-11

Chapter 5

Introduction to VAX FORTRAN
This chapter contains information on the following topics:
• The standards that VAX FORTRAN adheres to (Section 5.1)
• The elements that make up a VAX FORTRAN source program (Section 5.2)
• The character set supported by VAX FORTRAN (Section 5.3)
• The general rules for coding in VAX FORTRAN (Section 5.4)

5.1 VAX FORTRAN Language Definition
VAX FORTRAN is based on American National Standard FORTRAN-77 (ANSI X3.91978). It includes support for programs that conform to the previous standard (ANSI X3.91966). Extensions to the FORTRAN-77 standard are printed in blue in this manual.
VAX FORTRAN provides the following extensions to the ANSI standard:
o Relative file organization

o Indexed file organization

° Conformance with the VAX procedure-calling standard
o Records and structures
o DO WHILE statement
o Additional data types
0

Namelist-directed input/output

Hexadecimal constants and field descriptors

Symbolic debugging facility

VAX FORTRAN is also a compatible superset of PDP-11 FORTRAN-77. This means that
you can compile existing PDP-11 FORTRAN-77 source programs using the VAX
FORTRAN compiler (see Appendix Bin the VAX FORTRAN User's Guide).

5-1

5.2 Elements of FORTRAN Source Programs
This section provides an overview of the make up of a FORTRAN source program. It
describes the concept of a program unit and the rules governing the use of statements and
symbols within a program unit. It also describes the use of comments within programs.

5.2.1 Program Units
A program unit is a sequence of statements that defines a computing procedure and is
terminated by an END statement. A program unit can be either a main program or a
subprogram. An executable program consists of one main program and, optionally, one or
more subprograms.
A subprogram is a program unit that is separate from the main program. Subprograms are
invoked from the rµain program or another subprogram. There are two types of subprograms: function subprograms and subroutine subprograms. See Chapter 10 for detailed
information on subprograms.

5.2.2 Statements
Statements are grouped into two general classes: executable and nonexecutable. Executable statements describe the action of the program. Nonexecutable statements describe
data arrangement and characteristics, and provide editing and data-conversion information.
Statements are divided into physical sections called lines. A line is a string of up to 80
characters (optionally, 132; see Section 5.4.5). (Note: FORTRAN-77 limits the length to 72
characters.) If a statement is too long to fit on one line, you can continue it on one or more
additional lines called continuation lines. A continuation line is identified by a continuation character in the sixth column of that line. (For further information on continuation
characters, see Section 5.4.4.)
You can identify a statement with a statement label so that other statements can refer to
it, either to get the information it contains or to transfer control to it. A statement label
must be an integer, and it must appear in the first five columns of a statement's initial line.
Any statement can have a label; however, you can only refer to labels on executable
statements and FORMAT statements.

5.2.2.1 Order of Statements in a Program Unit
Figure 5-1 shows the required order of statements in a FORTRAN program unit. In this
figure, vertical lines separate statement types that can be interspersed. For example,
DATA statements can be interspersed with executable statements. On the other hand,
horizontal lines indicate statement types that cannot be interspersed. For example, type
declaration statements cannot be interspersed with executable statements.

5-2

Introduction to VAX FORTRAN

Statements included in the category of "executable statements" in Figure 5-1 are: ACCEPT, ASSIGN, assignment statements, BACKSPACE, CALL, CLOSE, CONTINUE,
DELETE, DO and END DO, ELSE, END, ENDFILE, FIND, GO TO (normal, computed,
and assigned), IF (arithmetic, logical, and block) and END IF, INQUIRE, OPEN, PAUSE,
PRINT, READ, RETURN, REWIND, REWRITE, STOP, TYPE, UNLOCK, and WRITE.
Statements included in the category of "other specification statements" in Figure 5-1 are:
COMMON, DICTIONARY, DIMENSION, EQUIVALENCE, EXTERNAL, INTRINSIC,
RECORD, SAVE, structure declarations, type declarations, and VOLATILE. (Note: The
statements STRUCTURE and END STRUCTURE, UNION and END UNION, and MAP
and END MAP are included in this category. They are used only in structure declaration
blocks.)
As a VAX FORTRAN extension, DATA statements can be freely interspersed with
PARAMETER statements and other specification statements.

OPTIONS Statement
PROGRAM,FUNCTION,SUBROUTINE, or BLOCK DATA Statements
IMPLICIT NONE Statement
IMPLICIT
Statements
Comment
Lines
and
INCLUDE
Statements

NAMELIST
FORMAT
and
ENTRY
Statements

Other
Specification
Statements

PARAMETER
Statements

Statement Function
Definitions

DATA
Statements

Executable
Statements

END Statement
ZK-615-82

Figure 5-1: Required Order of Statements and Lines

Introduction to VAX FORTRAN

5-3

5.2.3 Symbolic Names
Symbolic names identify entities within a FORTRAN program unit. These entities are
listed in Table 5-2.
A symbolic name is a string of letters, digits, and the special characters dollar sign ( $) and
underscore (_), The first character in a symbolic name must be a letter. The symbolic
name can contain a maximum of 31 characters. (Note: FORTRAN-77 limits the length of a
symbolic name to six characters.)
Examples of valid symbolic names are:
NUMBER

KB
\I

FIND_ IT

Examples of invalid symbolic names are:
50
B.4

$FREQ

(begins with a numeral)
(contains a special character other than_ or $)
(begins with $)

By convention, symbolic names containing a dollar sign ($) are reserved for use in DIGITAL-supplied software components. To avoid name conflicts, you should not define any
symbolic names in your program that contain a dollar sign.
In most cases, you cannot use the same symbolic name to identify two or more entities in
the same program unit. The exceptions are as follows:
o The names of structures can be used as the names. of fields of records (see Sections

8.15.1 and 8.15.2, respectively).
• Common block names can be used as variable or array names.
In an executable program consisting of two or more program units, the symbolic names of
the following entities must be unique within the entire program:
• Function subprograms
• Subroutine subprograms
• Common blocks
• l\1ain programs
• Block data subprograms
• Function entry points
• Subroutine entry points

5-4

Introduction to VAX FORTRAN

That is, if your program contains a function named BTU, you cannot use BTU as the
symbolic name of any other subprogram, entry, or common block in the program, even if
the name appears in a different program unit.
Table 5-1 lists those entities that can be given a symbolic name. It also indicates whether
the entities can be given a data type. Sections 6.2.2.1 and 6.2.2.2 discuss how to specify the
data type of a symbolic name.

Table 5-1: Entities Identified by Symbolic Names
Entity

Typed

Variables
Arrays
Structures
Records
Record elements
Statement functions
Intrinsic functions
Function subprograms
Subroutine subprograms
Common blocks
Namelist data groups
Main programs
Block data subprograms
Function entry points
Subroutine entry points
Parameter constants

Yes
Yes
No
No
Yes
Yes
Yes
Yes
No
No
No
No
No
Yes
No
Yes

5.2.4 Comments
Comments do not affect program processing in any way. They are merely a documentation
aid to the programmer. You can use them freely to describe the actions of the program, to
identify program sections and processes, and to provide greater ease in reading the source
program listing. The letter C or an asterisk (*) in the first column of a source line identifies
that line as a comment; a line containing only spaces is also a comment line. In addition, if
you place an exclamation point ( !) in column 1 or anywhere in the statement portion of a
source line, the remainder of that line is treated as a comment.

Introduction to VAX FORTRAN

5-5

5.3 FORTRAN Character Set
The character set supported by VAX FORTRAN consists of the following:
• All uppercase and lowercase letters (A through Z, a through z)
• The numerals 0 through 9
• The following special characters:

Character

Name

!::::,. or <TAB>

Space or tab
Equal sign

Plus sign
Minus sign

Asterisk

Slash

(

Left parenthesis
Right parenthesis
Comma
Period
Apostrophe
Quotation mark

Dollar sign
Underscore
Exclamation point
Colon

Left angle bracket

Right angle bracket

Percent sign

Ampersand

5-6

Introduction to VAX FORTRAN

You can use the space character to improve the legibility of a FORTRAN statement. The
compiler ignores all spaces in a statement field except those within a character or Hollerith
constant. For example, GO TO and GOTO are equivalent.
Other printable ASCII characters can appear in a FORTRAN statement only as part of a
character or Hollerith constant (see Appendix B for a list of printable characters). Any
printable character can appear in a comment. Nonprintable characters should not be used
in a FORTRAN source statement; if they are used, they appear as question marks.
Except in character and Hollerith constants, the compiler makes no distinction between
uppercase and lowercase -letters.

5.4 Format Requirements of FORTRAN Source Code
Each FORTRAN line has the following four fields:
• Statement label field
• Continuation indicator field
• Statement field
o Sequence number field

There are two ways to code a FORTRAN line: fixed format or tab format. You may prefer
to use the fixed format method when punching cards or using a coding form. The tab
format method is convenient when you are entering lines at a terminal with a text editor.

5.4.1 Fixed-Format Lines
As shown in Figure 5-2, a FORTRAN line is divided into fields for statement labels,
continuation indicators, statement text, and sequence numbers. Each column represents a
single character. Sections 5.4.3 through 5.4.6 describe the use of each field.

Introduction to VAX FORTRAN

5-7

OAT!

FORTRAN
NOILIM

COOING fQltM

CCo"""'""'~

1--- ~

FORTRAN STATEMENT

~~~--~&(' ~' !

oO!NTlf•CATION

' '..

I 2 ) . s . 7191011121l .. ISl61711192021222l2•2l26272129)0)1)2lll•lSJ6)7Jl)9'0"•2•lU•S•••7•1•9SOSISBJS-SH6S7SIS9000IOlOlO . . HMIOIOl6970nn1J7•7Ho77717'1C

lrHl S
D.Q

PRO~Ci_R.AM CP,,LCULA.T,E,S, 1P1R l,ME, ,N4MB,E 1R1S1 l,R,OM 1 1J.-i-:-T._,,0+-+5::+:0=-+--+--+-<>-+-+-+-+-+~>-+->-+-+-++-+~--+-<H--i

I =I I

J =I
4

u=J+2
IA.=.J

+-+-+--+--+-+-+-+-+-+-<>-+-+-+-+-+--+--<>-+-++-+-+-+-->-+-++-+-+-+--1-+-+-+-+-+-+--+++~-+--..........+-+-+-+-+--+-+-+-+-+->-+-++-+-i-+--+-+-++-+-+~

1-+->-+-<~~~-~--~l.~~'A,..........._.... -+--+-+-+-+-+-+-+-+-<->-+-<...........--+-+--+-+~~.......------+-+-t--+--<~~-+-+---+-+-+-+-+-+-+-+--+-+-+-+-+-+-+-+-+-+-....+->-+-<-+-+-+-+-i

a=.1~~---------+-+-+----+-+-<. . . . . . . .-+-+-<...-+-+--+-+-<-+-+-+-+-------+-+-+..................._._,___..__~-+-+----+-+--t-+-<-+-~--~

..............................._....._.-+--......_...............................+-+-...................-..-+-+-.._........,.........-~..........-+--..--.....-......-........................._.-+--...................-+-<-+-+-+-+-+-+-i

B=A-l
I F

.(BJ

5~-+-+-+-+---+-+-+-+_._.-+-•-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--+--+-+-+--+--+-+--+-+--+-+-+--+-+--+--+--+--+--+-+......+-+-+-+-+-+-1
.GO TO 4

I F J.J .J.,_T ~RT
TYPE 105
I

.i FLOAT J.l Jlj

~- J:QNTINUE
I 05

FOR;;y j) 4

S+-+pR !..ME: '.l

IFND

PG· 3

DIGITAL EQUIPMENT COR .. ORATION

•

MAYNARD, MASSACHUSETTS

ZK-613-82

Figure 5-2: FORTRAN Coding Form
To enter an item in a field, enter it in the column(s) in the coding form, as listed below:

Field

Column(s)

Statement label

1 through 5

Continuation indicator

Statement

7 through 72 (optionally, to 132)

Sequence number

73 through 80

5-8

Introduction to VAX FORTRAN

5.4.2 Tab-IFormai Lines
You can specify the statement label field, the continuation indicator field, and the statement field using tab formatting. However, you cannot specify a sequence number field
using this method of coding. Figure 5-3 illustrates FORTRAN lines coded using tab formatting and the equivalent lines with fixed formatting.
1

10 11 12 13 14 15 16 17 18 19 20

s T

C @ID FIRST VALUE

10 @ID I = J + 5*K +

1 0

1
@ID IVAL

= 1+2

L
I

v A L u E
+

* M

v A L

+ 2

ZK-614-82

Figure 5-3: Line Formatting Example
The statement label field consists of the characters that you type before the first tab
character. The statement label field cannot have more than five characters.
After you type the first tab character, you can type either the continuation indicator field
or the statement field.
To enter the continuation indicator field, type any nonzero digit after the first tab. If you
enter the continuation indicator field, the statement field consists of all the characters after
the digit to the end of the line.
To enter the statement field without a continuation indicator field, type the statement
immediately after the first tab. Note that no FORTRAN statement starts with a digit.
Many text editors and terminals advance the terminal print carriage to a predefined print
position when you press the TAB key. However, this action is not related to the FORTRAN
compiler's interpretation of the tab character described above.

Introduction to VAX FORTRAN

5-9

The compiler treats the tab character in a statement field the same as a space. In the
source listing that the compiler produces, the tab causes the character that follows to be
printed at the next tab stop (located at columns 9, 17, 25, 33, and so on).

NOTE
Do not use tabs when you are using sequence numbers. If you use tabs to
position your sequence numbers, the compiler may interpret the sequence numbers as part of the statement fields in your program.

5.4.3 Statement Label Field
Any statement can have a label. A statement label or statement number consists of from
one to five decimal digits in the statement label field of a statement's initial line. Spaces
and leading zeros are ignored. An all-zero statement label is invalid.
The only statements that can be referred to by other statements are labeled FORMAT
statements and labeled executable statements (see Section 5.2.2). FORMAT statements
are referred to only in the format specifier of an I/O statement or in an ASSIGN statement.
No two statements within a program unit can have the same label.
The first column of the label field can contain two special indicators: the comment indicator and the debugging statement indicator. These indicators are described in Sections
5.4.3.1 and 5.4.3.2.
The statement label field of a continuation line must be blank-except in the case of a
debugging statement (see Section 5.4.3.2).

5.4.3.1 Comment Indicator
You can use the letter C, an asterisk ( *), or an exclamation point ( ! ) in column 1 to indicate
that a line is a comment. The compiler prints that line in the source program listing and
then ignores the line. An all-blank line is also considered to be a comment. The exclamation point can also be used anywhere in the statement field (except when used in a Hollerith or character constant) to start an end-of-line comment.

5.4.3.2 Debugging Statement Indicator
You can use the letter D in column 1 to designate debugging statements. The initial line of
the debugging statement can contain a statement label in the remaining columns of the
label field. If a debugging statement is continued onto more than one line, every continuation line must begin with a D (in column 1) and a continuation indicator.
The compiler treats the debugging statement either as source text to be compiled or as a
comment, depending on the setting of the /D___LINES compiler command qualifier. If you
specify /D___LINES, debugging statements are compiled as a part of the source program. If
you do not specify /D___LINES, debugging statements are treated as comments.

5-10

Introduction to VAX FORTRAN

5.4.4 Continuation Indicator Field
A continuation indicator is any character, except zero or space, in column 6 of a FORTRAN
line, or any digit, except zero, after the first tab. The compiler considers the characters
after the continuation character to be the characters following the last character of the
previous line, as if there were no break at that point. If a continuation indicator is a zero or
space, the compiler considers the line to be an initial line of a FORTRAN statement.
Comment lines cannot be continued. They can occur between a statement's initial line and
its continuation line(s), or between successive continuation lines.

5.4.5 Statement Field
The text of a FORTRAN statement is placed in the statement field. Because the compiler
ignores the tab character and spaces (except in character and Hollerith constants), you can
space the text in any way desired for maximum legibility.
By default, the statement field extends to character position 72. If the default is in effect,
any text following position 72 is ignored and no warning message is printed. However, if the
/EXTEND_SOURCE qualifier is specified on the FORTRAN command (see Section
3.2.3.7), the statement field is extended to position 132. Any text beyond that position will
generate a fatal error and will cause immediate termination of the compilation.

5.4.6 Sequence rJumber !Field
By default, a sequence number or other identifying i:r:iformation can appear in columns 73
through 80 of any line in a FORTRAN program. The compiler ignores the characters in this
field. However, if the /EXTEND_SOURCE qualifier is specified on the FORTRAN command (see Section 3.2.3.7), a sequence number field does not exist because the statement
field is extended to position 132.

Introduction to VAX FORTRAN

5-11

Chapter 6

Data Types, Data Items, and Expressions
This chapter contains information on the following topics:
• Data types-integer, real, complex, logical, character, and Hollerith (Section 6.1)
• Data items-constants, variables, arrays, character substrings, and records (Section
6.2)

• Expressions-arithmetic, character, relational, and logical (Section 6.3)

6.1 Data Types
Each constant, variable, array, expression, or function reference in a FORTRAN statement
represents typed data. The data type of these items can be inherent in their constructions,
implied by convention, or explicitly declared. The data types available in FORTRAN, and
their definitions, are:
• Integer-a whole number.
• REAL (REAL*4)-a floating point number, that is, a whole number, a decimal fraction, or a combination of the two.
• DOUBLE PRECISION (REAL*8)-similar to REAL*4; has more than twice the degree of accuracy in its representation (the G_floating implementation also has an
extended range).
o REAL*16-similar to REAL*4; has an extended range, and more than four times the

accuracy in its representation.
• COMPLEX (COMPLEX*8)-a pair of REAL*4 values that represent a complex number; the first value represents the real part oHhat number, and the second represents
the imaginary part.
o DOUBLE COMPLEX (COMPLEX*l6)-similar to complex; its real and imaginary

parts are REAL*8.

6-1

• Logical-a logical value, .TRUE. or .FALSE.
• Character-a string of characters.
o Hollerith-a

string of printable characters preceded by a character count and the

letter H.
See Appendix C for descriptions of the VAX hardware representations of these data types.

6.1.1 Storage Requirements
An important attribute of each data type is the amount of memory required to represent a
value of that type. Variations on the basic types affect either the accuracy of the represented value or the allowed range of values.
ANSI FORTRAN defines a "numeric storage unit" as the amount of storage needed to
represent a REAL, INTEGER, or LOGICAL value. In VAX FORTRAN, a numeric storage
unit corresponds to four bytes of memory. REAL*8 and COMPLEX*8 values occupy two of
these numeric storage units, whereas REAL*16 and COMPLEX*l6 values occupy four.
ANSI FORTRAN defines a "character storage unit" as the amount of storage needed to
represent one character value. In VAX FORTRAN, a character storage unit corresponds to
one byte of memory.
VAX FORTRAN provides additional data types for optimum selection of performance and
memory requirements. Table 6-1 lists the data types available, the names associated with
each data type, and the amount of storage required (in bytes). The form *n appended to a
data type name is called a data type length specifier.
Table 6-1: Data Type Storage Requirements
Data Type

Storage Requirements
(in bytes)

BYTE
LOGICAL
LOGICAL*l
LOGICAL*2
LOGICAL*4

11
2 or 4 2
11
2
4

INTEGER
INTEGER*2
INTEGER*4

2 or 4 2
2
4

REAL
REAL*4
REAL*8
DOUBLE PRECISION
REAL*16

4
4
8
8

6-2

Data Types, Data Items, and Expressions

Table 6-1 (Cont.): Data Type Storage Requirements
Data Type
COMPLEX
COMPLEX*8
COMPLEX*16
DOUBLE COMPLEX
CHARACTER* len
CHARACTER*(*)

Storage Requirements
(in bytes)
8

8
16
16

len 3

The 1-byte storage area can contain the logical values true or false, a single character, or integers in
the range -128 to 127.
2

Either two or four bytes are allocated depending on the setting of the [NOJl4 qualifier. The default
allocation is four bytes.
3 The value of len is the number of characters specified, which can be in the range 1 to 65535. Passed-

length format, *( *), applies to dummy arguments or character functions, and indicates that the
length of the actual argument or function is used (see Chapter 10).

6.1.2 VAX Implementations of REAL •8
There are two implementations of the REAL*8 (and COMPLEX*l6) data type on VAX:
D_floating and G_floating. The G_floating implementation offers a greater range, but a
smaller number of significant digits of precision, than the D_floating implementation.
You select the G_floating implementation by compiling the program with the
/G_FLOATING qualifier in the FORTRAN command line or the OPTIONS statement;
the default implementation of REAL*8 is D_floating.
Some VAX processors do not implement one or more of the floating point data types. For
these processors, the data types not supported in hardware or microcode are emulated in
software. You should be aware of which data types are emulated on the system you use
because processing time with software emulation is much slower. The FORTRAN data
type you use-especially REAL*8-should be chosen with this in mind.
See Sections 6.2.1.2, C.4, C.4.2, and C.4.3 for more detailed information on the two implementations of the REAL*8 data type.

Data Types, Data Items, and Expressions

6-3

6.2 Data Items
Data items that you use in VAX FORTRAN statements are as follows:
• Constants-fixed, self-describing values.
• Variables-stored values represented by symbolic names.
• Arrays-groups of values that are stored contiguously and can be referred to individually or collectively. Individual values are called array elements.
• Character substrings-a contiguous segment of a character variable or character array
element.
0

Records-structured data items consisting of one or more elements (variables and
arrays) or one or more groups of these elements. Different record elements in the same
record can have unlike data types.

These data items are discussed in this order in Sections 6.2.1 through 6.2.5.

6.2.1 Constants
A constant is a data item with a fixed value; the value cannot be changed during program
execution. The value of a constant can be a numeric value, a logical value, or a character
string. There are eight types of constants:
·
• Integer
•Real
• Complex
o Octal
o Hexadecimal

• Logical
• Character
o Hollerith

Octal, hexadecimal, and Hollerith constants have no data type. They assume a data type
that conforms to the context in which they appear (see Sections 6.2.1.4 and 6.2.1.7, respectively).

NOTE
The generic term scalar reference is used throughout this manual to refer collec·
tively to all references that resolve to single, typed data items. All eight types of
constants fall into the scalar reference category.
Section 6.2.6 provides a thorough discussion of this new terminology.

6-4

Data Types, Data Items, and Expressions

6.2.1.1 Integer Constants
An integer constant is a whole number with no decimal point. It can have a leading sign
and is interpreted as a decimal number.
An integer constant has the form:
snn

where:
s
is an optional sign.
nn

is a string of decimal digits.
Leading zeros, if any, are ignored. A minus sign must appear before a negative integer
constant, whereas a plus sign is optional before a positive constant (an unsigned constant is
assumed to be positive). Except for a leading algebraic sign, an integer constant cannot
contain any character other than the numerals 0 through 9. The value of an integer constant must be within the range -2147483648 to 2147483647.
Examples of valid and invalid integer constants are:

Valid

Invalid (with explanation)
0

-127
+32123

99999999999

(too large)

3. 1 LI

(decimal point and
comma not allowed)

32t7G7

If the value of the constant is within the range -32768 to 32767, it represents a 2-byte signed
quantity and is treated as an INTEGER*2 data type. If the value is outside that range, it

represents a 4-byte signed quantity and is treated as an INTEGER*4 data type.
Integer constants can also be specified in octal form; see Section A.5.

6.2.1.2 Real Constants
A real constant is a number written with a decimal point or exponent (or both). The
constant can be positive, zero, or negative, and can have single precision (REAL*4), double
precision (REAL*8), or quad precision (REAL*16).
The different types of real constants (REAL*4, REAL*8, and REAL*l6) are described
under the headings that follow.

Data Types, Data Items, and Expressions

6-5

REAL •4 (REAL) Constants
A REAL*4 constant can be any one of the following:
• A basic real constant
• A basic real constant followed by a deCimal exponent
• An integer constant followed by a decimal exponent
Integer constants are defined in the preceding subsection. A basic real constant is a string
of decimal digits having one of the following forms:
s.nn
snn.nn
snn.

where:
s

is an optional sign.

nn
is a string of decimal digits.
The decimal point can appear anywhere in the string. The number of digits is not limited,
but typically only the leftmost seven digits are significant. Leading zeros (zeros to the left
of the first nonzero digit) are ignored in counting the leftmost seven digits. Thus, in the
constant 0.00001234567, all of the nonzero digits, and none of the zeros, are significant.
A decimal exponent has the form:
Esnn

where:

s
is an optional sign.

nn
is an integer constant.
The exponent represents a power of 10 by which the preceding real or integer constant is to
be multiplied (for example, 1.0E6 represents the value 1.0 * 10**6).
A REAL*4 constant occupies four bytes of VAX storage, and it is interpreted as a real
number with a degree of precision that is typically seven decimal digits (see Sections C.4
and C.4.1).
A minus sign must appear before a negative REAL*4 constant; a plus sign is optional
before a positive constant. Similarly, a minus sign must appear between the letter E and a
negative exponent, whereas a plus sign is optional between the letter E and a positive
exponent.

6-6

Data Types, Data Items, and Expressions

A REAL*4 constant cannot contain any character other than the numerals 0 through 9,
except for algebraic signs, a decimal point, and the letter E (if used).
If the letter E appears in a REAL*4 constant, an integer constant exponent field must
follow'. The exponent field cannot be omitted; it can, however, be zero.

The magnitude of a nonzero REAL*4 constant cannot be smaller than approximately
0.29E-38 or greater than approximately 1.7E38.
Examples of valid and invalid REAL*4 constants follow:

Valid

Invalid (with explanation)
3+1ll158

(commas not allowed)

1 t23llt567.
325E-ll5

(too small)

-ll7.Ell7

(too large)

+5.0E3

100

(decimal point missing)

2E-3

$25.00

(special character
not allowed)

621712+
-+00127

REAL•B (DOUBLE PRECISION) Constants
A REAL*8 constant is a basic real constant or an integer constant followed by a decimal
exponent of the form:
Dsnn

where:
s

is an optional sign.
nn

is a string of decimal digits.
There are two implementations of the REAL*8 constant: D_floating and G_floating.
Both implementations have the same syntax and storage requirements, but each has a
different number of significant digits and a different exponent range. The G_floating
implementation is invoked with the /G_FLOATING qualifier.
A REAL*8 constant occupies eight bytes of storage. The number of digits that precede the
exponent in a REAL*8 constant is not limited. However, the degree of precision is typically
only the leftmost 16 (for D_floating) or 15 (for G_floating) digits (see Sections C.4, C.4.2,
and C.4.3).
A minus sign must appear before a negative REAL*8 constant; a plus sign is optional
before a positive constant. Similarly, a minus sign must appear between the letter D and a
negative exponent, whereas a plus sign is optional between the letter D and a positive
exponent.
Data Types, Data Items, and Expressions

6-7

If the letter D appears in a REAL*8 constant, an integer constant exponent field must
follow. The exponent field following the letter D cannot be omitted; it can, however, be
zero.

The magnitude of a nonzero REAL*8 constant cannot be less than approximately 0.29D-38
or greater than approximately 1. 7D38 for the D_floating implementation; nor can it be
less than approximately 0.56D-308 or greater than approximately 0.9D308 for the G_
floating implementation.
Examples of valid and invalid D_floating and G_floating REAL*8 constants follow:
Valid

D_floating
Invalid (with explanation)

123£!5678800+5

123ll5678800ll5

(too large)

+2.718281828£!6182000

123£!567880.00-88

(too small)

-72.50-15
100

+2.71828128£!6182

(no Dsnn present;
this is a valid single-precision
constant)

G_floating
Invalid(with explanation)

Valid
123£!56788.00
+2.3£!5678801230-5
-10+300

123£!56788. oaoo
123£!56788. o-aoo

(too large)
(too small)

6.2.1.2.1 REAL•16 Constants
A REAL*16 constant is a basic real constant or an integer constant followed by a decimal
exponent of the form:
Qsnn

where:
s

is an optional sign.
nn

is a string of decimal digits.
A REAL*16 constant occupies 16 bytes of VAX storage. The number of digits that precede
the exponent is not limited; however, typically only the leftmost 33 digits are significant
(see Sections C.4 and C.4.4).

6-8

Data Types, Data Items, and Expressions

A minus sign must appear before a negative REAL*16 constant; a plus sign is optional
before a positive constant. Similarly, a minus sign is required between the letter Q and a
negative exponent, whereas a plus sign is optional between the letter Q and a positive
exponent.
If the letter Q appears in a REAL*16 constant, an integer constant exponent field must
follow. The exponent field following the letter Q cannot be omitted; however, it can be zero.

The magnitude of a nonzero REAL*16 constant cannot be less than approximately 0.84Q4932 or greater than approximately 0.59Q4932.
Examples of valid and invalid REAL*16 constants follow:
Valid

Invalid (with explanation)

123lJ567890lJOOO

1.05000

(too large)

-1.230-lJOO

1.0-5000

(too small)

+2.7200

6.2.1.3 Complex Constants
A complex constant consists of a pair of real or integer constants. The two constants are
separated by a comma and enclosed in parentheses. The first constant represents the real
part of that number, and the second constant represents the imaginary part.
VAX FORTRAN supports COMPLEX*8 and COMPLEX*16 complex constants. These
are described under the headings that follow.

COMPLEX•& (COMPLEX) Constants
A COMPLEX*8 constant is a pair of integer or REAL*4 constants that represents a
complex number.
A COMPLEX*8 constant has the form:
(c,c)

where:
c

is an integer or REAL*4 constant:
The parentheses and comma are part of the constant and are required. See Section 6.2.1.2
for the rules for forming REAL*4 constants.
A COMPLEX*8 constant occupies eight bytes of VAX storage and is interpreted as a
complex number (see Sections C.4 and C.4.5).

Data Types, Data Items, and Expressions

6-9

The following are examples of valid and invalid COMPLEX*8 constants.

Valid

Invalid (with explanation)

( 1. 7039 t-1+70391)

( 1. 23 t)

(second REAL constant is missing)

(+12739E3t0+)
( 1 t 2)

< 1 • O,

OQO >

(REAL*l6 constants are not allowed)

COMPLE}{•16 (DOUBLE COr.1PLEU) Constants
A COMPLEX*16 constant is a pair of constants that represent a complex number. One
constant must be REAL*8; the other must be an integer, REAL*4, or REAL*8. The two
constants are separated by a comma and enclosed in parentheses; the first constant represents the real part of the complex number, the second the imaginary part. There are two
implementations of COMPLEX*16, corresponding to the D_floating and G_floating implementations of REAL*8.
A COMPLEX*16 constant has the form:
(c,c)

where:
c
is an integer, a REAL*4, or a REAL*8 constant. (One of the pair must be a REAL*8
constant.)
The parentheses and the comma are part of the constant and are required. See Section
6.2.1.2 for the rules governing the formation of REAL*8 constants.
A COMPLEX*16 constant occupies 16 bytes of VAX storage and is interpreted as a complex number (see Sections C.4, C.4.6, and C.4.7).
Examples of valid and invalid COMPLEX*16 constants follow:

Valid

Invalid (with explanation)

(1,7039001-1.703900)

( 1 + 2300)

(second constant missing)

(+127390310.00)

(0,BQO tO.l!QOl

(REAL*16 constants not allowed)

<1.00300,-1,00300)

(both constants out of range
for D_floating implementation of REAL*8; valid for
G_floating implementation
of REAL*8)

6-10

Data Types, Data Items, and Expressions

6.2.1.4 Octal ancl Umcadecimal Constants
Octal and hexadecimal constants are alternative ways to represent numeric constants. You
can use them wherever numeric constants are allowed.
An octal constant is a string of octal digits enclosed by apostrophes and followed by the
alphabetic character 0. An octal constant has the form:
'C1C2C3···cn '0

where:
c

is a digit in the range 0 to 7.
A hexadecimal constant is a string of digits enclosed by apostrophes and followed by the
alphabetic character X. A hexadeeimal constant has the form:
'C1C2C3···cn

where:
c

is a digit in the range 0 to 9, or a letter in the range A to F or a to f.
Leading zeros are ignored in octal and hexadecimal constants. You can specify up to 128
bits (43 octal digits, 32 hexadecimal digits).
Examples of valid and invalid octal constants are:
Valid

Invalid (with explanation)

'07737'0

'7782'0

(invalid character)

1I0

7772'0

(no initial apostrophe)

'0737'

(no 0 after second apostrophe)

Examples of valid and invalid hexadecimal constants are:
Valid

Invalid (with explanation)

I AF9730 I){

'999

FFABC I){

F9>(

I)-(

(invalid character)
(no apostrophe before the X)

Data Types, Data Items, and Expressions

6-11

Octal and hexadecimal constants are "typeless" numeric constants. They assume data
types based on the way they are used (and thus are not converted before use), as follows:
0

When the constant is used with a binary operator, including the assignment operator,
the data type of the constant is the data type of the other operand. For example:
Statement

Data Type
of Constant

Length of
Constant

REAL*4
INTEGER*2
REAL*8
INTEGER*4

4
2
8
4

INTEGER*2 !COUNT
REAL*B DOUBLE
RAPHA = '99AF2 '}{
JC OU NT = I COUNT + '777 I 0
DOUBLE = I FFF99A I}-{
IFCN.EQ. '123'0GOT010)'

o When a specific data type (generally integer) is required, that type is assumed for the

constant. For example:

Statement

Data Type
of Constant

Length of
Constant

YCI}O = YC '15'0) + 3.

INTEGER*4

When the constant is used as an actual argument, no data type is assumed; however, a
length of four bytes is always used. For example:
Statement

Data Type
of Constant

CALL APAC ( '3l!BC2 I}-()

None

Length of
Constant
4

When the constant is used in any other context, an INTEGER*4 data type is assumed.
For example:
Statement
IF C 'AF77'}-() 1 ,z ,3
I = I 7777 I 0 - I A39 I}-{
J =.NOT. '73777 'O

Data Type
of Constant

Length of
Constant

INTEGER*4
INTEGER*4
INTEGER*4

4
4
4

An octal or hexadecimal constant specifies as much as 16 bytes of data. When the data type
implies that the length of the constant is more than the number of digits specified, the
leftmost digits have a value of zero. When the data type implies that the length of the
constant is less than the number of digits specified, the constant is truncated on the left.
An error results if any nonzero digits are truncated. Table 6-1 (in Section 6.1.1) lists the
number of bytes that each data type requires.

6-12

Data Types, Data Items, and Expressions

6.2.1.5 Logical Constants
A logical constant specifies a logical value, true or false. Thus, only the following two
logical constants are possible:
.TRUE .
.FALSE.
The delimiting periods are a required part of each constant.

6.2.1.6 Character Constants
A character constant is a string of printable ASCII characters enclosed by apostrophes.
A character constant has the form:
, C1C2C3 ... Cn,

where:
c

is a printable character.
Both delimiting apostrophes must be present.
The value of a character constant is the string of characters between the delimiting apostrophes. The value does not include the delimiting apostrophes, but does include all spaces
or tabs within the apostrophes.
Within a character constant, the apostrophe character is represented by two consecutive
apostrophes (with no space or other character between them).
The length of the character constant is the number of characters between the apostrophes,
except that two consecutive apostrophes represent a single apostrophe. The length of a
character constant must be in the range 1 to 2000.
Examples of valid and invalid character constants are:
Valid

Invalid (with explanation)

'WHAT?'

'HEADINGS

'TODAY"S DATE IS:
'HE SAID t "HELLO"

(character constant must contain
at least one character)

(no trailing apostrophe)

" Now / o R NE 1.1 ER "

(quota ti on marks cannot be used
in place of apostrophes)

If a character constant appears in a numeric context (for example, as the expression on the

right side of an arithmetic assignment statement), it is considered a Hollerith constant (see
next section).

Data Types, Data Items, and Expressions

6-13

6.2.1. 7 Hollerith Constants
A Hollerith constant is a string of printable characters preceded by a character count and
the letter H.
A Hollerith constant has the form:
riHc 1c 2c 3 ... cn

where:
n

is an unsigned, nonzero integer constant stating the number of characters in the string
(including spaces and tabs).
c

is a printable character.
A Hollerith constant can be a string of 1 to 2000 characters.
Hollerith constants are stored as byte strings, one character per byte.
Hollerith constants have no data type. They assume a numeric data type according to the
context in which they are used. Hollerith constants cannot assume a character data type
and cannot be used where a character value is expected.
Examples of valid and invalid Hollerith constants are:
Valid

Invalid (with explanation)

1 GHTODAY Is DATE Is:

3HABCD

(wrong number of characters)

1HB

(Hollerith constants
least one character)

must contain at

When Hollerith constants are used in numeric expressions, they assume data types according to the following rules:
o

When the constant is used with a binary operator, including the assignment operator,
the data type of the constant is the data type of the other operand. For example:
Statement

Data Type
of Constant

Length of
Constant

REAL*4
INTEGER*2
REAL*8
INTEGER*4

4
2
8
4

INTEGER*2 I COUNT
REAL*B DOUBLE
RALPHA = 4HABCD
JCOUNT = I COUNT + 2H>CY
DOUBLE = BHABCDEFGH
IF (N, EQ, !HZ) GO TD 10

6-14

Data Types, Data Items, and Expressions

When a specific data type is required, generally integer, that type is assumed for the
constant. For example:
Statement

Data Type
of Constant

Length of
Constant

Y <DO = Y < 1 HA) + 3.

INTEGER*4

When the constant is used as an actual arguqient, no data type i~ assumed. For
example:
Statement

Data Type
of Constant

CALL A PAC ( 8HABCDEFGH I)

None

Length of
Constant
9

When the constant is used in any other context, an INTEGER*4 data type is assumed.
For example:
Statement

Data Type
of Constant

Length of
Constant

IF ( 2HAB > 1 t 2 t 3
I = 1 HC - 1 HA
J =.NOT. 1HB

INTEGER*4
INTEGER*4
INTEGER*4

4
4
4

When the length of the constant is less than the length implied by the data type, spaces are
appended to the constant on the right. When the length of the constant is greater than the
length implied by the data type, the constant is truncated on the right. An error results if
any characters other than space characters are truncated.
Table 6-1 (in Section 6.1.1) lists the number of characters required for each data type.
Each character occupies one byte of storage.

6.2.2 Variables
A variable is represented by a symbolic name associated with a storage location. The value
of the variable is the value currently stored in that location; you can change that value by
assigning a new value to the variable. (See Section 5.2.3 for the form of a symbolic name.)
Variables are classified by data type, just as constants are. The data type of a variable
indicates the type of data it represents, its precision, and its storage requirements. When
data of any type is assigned to a variable, it is converted,.if necessary, to the data type of
the variable. You can establish the data type of a variable by type declaration statements,
IMPLICIT statements, or predefined typing rules.

Data Types, Data Items, and Expressions

6-15

NOTE
The generic term scalar reference is used throughout this manual to refer collectively to all references that resolve to single, typed data items. All types of
variables fall into the scalar reference category.
Section 6.2.6 provides a thorough discussion of this new terminology.
Two or more variables are associated with each other when each is associated with the same
storage location. They are partially associated when part (but not all) of the storage associated with one variable is the same as part or all of the storage associated with another
variable. Association and partial association occur when you use COMMON statements,
EQUIVALENCE statements, MAP declarations (within STRUCTURE declaration
blocks), or actual arguments and dummy arguments in subprogram references.
A variable is considered defined if the storage associated with it contains data of the same
type as that of the name. A variable can be defined before program execution by a DATA
statement or during execution by an assignment or input statement.
If variables of different data types are associated (or partially associated) with the same
storage location, and the value of one variable is defined (for example, by assignment), the
value of the other variable becomes undefined.

6.2.2.1 Data Type by Specification
Type declaration statements (see Section 8.4) specify that given variables are to represent
specified data types. For example:
COMPLEH lJAR 1
DOUBLE PRECISION VAR2

These statements indicate that the variable VARl is to be associated with an 8-byte
storage location that is to contain complex data, and that the variable VAR2 is to be
associated with an 8-byte double-precision storage location.
The IMPLICIT statement (see Section 8.8) has a broader scope. It states that, in the
absence of an explicit type declaration, any variable with a name that begins with a
specified letter, or any letter within a specified range, is to represent a specified data type.
You can explicitly specify the data type of a variable only once. An explicit data type
specification takes precedence over the type implied by an IMPLICIT statement.
Character type declaration statements (see Sections 8.4 and 8.4.2) specify that given variables are to represent character values with the length specified. For example:
CHARACTER*72 INLINE
CHARACTER NAME*12t NUMBER*8

These statements indicate that the variables INLINE, NAME, and NUMBER are to be
associated with storage locations containing character data of lengths 72, 12, and 9, respectively.

6-16

Data Types, Data Items, and Expressions

Passed-length character arguments are used within a single subprogram to process character strings of different lengths. The passed-length character argument has a length specification of asterisk ( *). For example:
CHARACTER*<*> CHARDUMMY

The passed-length character argument assumes the length of the actual argument (see
Chapter 10).

6.2.2.2 Data Type by Implication
In the absence of either IMPLICIT statements or explicit type statements, all variables
with names beginning with I, J, K, L, M, or N are assumed to be integer variables.
Variables with names beginning with any other letter are assumed to be REAL*4 variables.
For example:
Real Variables

Integer Variables

ALPHA
BETA
TOTAL

JCOUNT
ITEM

NTOTAL

6.2.3 Arrays
An array is a group of contiguous storage locations associated with a single symbolic name,
the array name. The individual storage locations (called array elements) are referred to by
a subscript appended to the array name. Section 6.2.3.2 discusses subscripts.
An array can have from one to seven dimensions. For example, a column of figures is a onedimensional array. A table of more than one column of figures is a two-dimensional array.
To refer to a specific value in this array, you must specify both its row number and its
column number. A table of figures that covers several pages is a three-dimensional array.
To locate a value in this array, you must specify the row number, column number, and a
page number.
The following FORTRAN statements establish arrays:
• Type declaration statements (see Section 8.4)
• The DIMENSION statement (see Section 8.5)
• The COMMON statement (see Section 8.2)
These statements contain array declarators (see Section 6.2.3.1) that define the name of
the array, the number of dimensions in the array, and the number of elements in each
dimension.
An element of an array is considered defined if the storage associated with it contains data
of the same data type as that of the array name (see Section 6.2.3.3). You can define an
array element or an entire array before program execution with a DATA statement. During
program execution, you can define an array element with an assignment or input statement; and an entire array with an input statement.
Data Types, Data Items, and Expressions

6-17

6.2.3.1 Array Declarators
An array declarator specifies the symbolic name that identifies an array within a program
unit and indicates the properties of that array.
An array declarator has the form:
a(d[,d] ... )

where:
a

is the symbolic name of the array, that is, the array name. (Section 5.2.3 gives the
form of a symbolic name.)
d

is a dimension declarator; d can specify both a lower bound and an upper bound as
follows:
[dl:]du

where:
di

is the lower bound of the dimension.
du

is the upper bound of the dimension. (An asterisk ( *) can also occur as an upper
bound, but only of the last dimensio.n.)
The number of dimension declarators indicates the number of dimensions in the array. The
number of dimensions can range from one to seven.
The value of the lower-bound dimension declarator can be negative, zero, or positive. The
value of the upper-bound dimension declarator· must be greater than or equal to that of the
corresponding lower-bound dimension declarator. The number of elements in the dimension is du-dl+l. If a lower bound is not specified, it is assumed to be one, and the value of
the upper bound specifies the number of elements in that dimension. For example, a
dimension declarator of 50 indicates that the dimension contains 50 elements. The upper
bound in the last dimension declarator in a list of dimension declarators may be an asterisk
( *); an asterisk marks the declarator as an assumed-size array declarator (see Section
10.1.1.2).
Each dimension bound is an integer arithmetic expression in which each operand is a
constant, a dummy argument, or a variable in a common block. The expression is converted to an integer if necessary.
The type of a variable used in a bound expression cannot be changed by a later type
declaration.

6-18

Data Types, Data Items, and Expressions

NOTE
Array references and references to user-defined functions should not be used in
dimension bounds expressions.
Dimension bounds that are not constant expressions can be used in a subprogram to define
adjustable arrays. You can use adjustable arrays within a single subprogram to process
arrays with different dimension bounds by specifying the array name as a subprogram
argument, and by either specifying the bounds as subprogram arguments or by placing the
bounds in a common block. See Section 10.1.1.1 for more information on adjustable arrays.
Dimension bounds that are not constant expressions are not permitted in a main program.
The number of elements in an array is equal to the product of the number of elements in
each dimension.
An array name can appear in only one array declarator within a program unit.

6.2.3.2 Array Subscripts
A subscript qualifies an array name. A subscript is a list of expressions, called subscript
expressions, enclosed in parentheses, that determine which element in the array is referred
to. The subscript is appended to the array name it qualifies.

NOTE
The generic term scalar reference is used throughout this manual to refer collectively to all references that resolve to single, typed data items. Subscripted array
references fall into the scalar reference category.
Section 6.2.6 provides a thorough discussion of this new terminology.
A subscript has the form:
(s[,s] ... )

where:
s
is a subscript expression.
A subscripted array reference must contain one subscript expression for each dimension
defined for that array (one for each dimension declarator).
Each subscript can be any valid arithmetic expression. However, noninteger subscript
expressions are converted to integers before use (any fractional parts are truncated).

6.2.3.3 Arrangement of Array Elements in Storage
As discussed earlier in this section, you can think of the dimensions of an array as rows,
columns, and levels or planes. However, FORTRAN always stores an array in memory as a
linear sequence of values. A one-dimensional array is stored with its first element in the

Data Types, Data Items, and Expressions

6-19

first storage location and its last element in the last storage location of the sequence. A
multidimensional array is stored so that the leftmost subscripts vary most rapidly. This is
called the "order of subscript progression." For example, Figure 6-1 shows array storage in
one, two, and three dimensions.
One-Dimensional Array BRC (6)

BRC(2)

BRC(3)

BRC(4)

BRC(S)

BRC(6)

...___ _ _......__ _ _ Memory Positions

Two-Dimensional Array BAN (3,4)

BAN(1,1)

BAN(1,2)

BAN(1,3)

10 BAN(1,4)

BAN(2,1)

BAN(2,2)

BAN(2,3)

BAN(3,1)

BAN(3,2)

BAN(3,3)

12 BAN(3,4)

BAN(2,4)

Memory Pos1t1ons

Three-Dimensional Array BOS (3,3,3)

BOS(1, 1,3)

BOS(1,2,3)

BOS(1,3,3)

BOS(2, 1,3)

BOS(2,2,3)

BOS(2,3,3)

BOS(3,3,3)

BOS(1, 1,2)

BOS(1,2,2)

16 BOS(1,3,2)

BOS(2,1,2)

BOS(2,2,2)

17 BOS(2,3,2)

BOS(1,1,1)

BOS(1,2,1)

BOS(1,3,1)

BOS(2,1,1)

BOS(2,2,1)

BOS(2,3,1)

BOS(3,1,1)

BOS(3,2,1)

BOS(3,3,1)

18 BOS(3,3,2)

Memory Pos1t1ons
ZK-616-82

Figure 6-1: Array Storage

6-20

Data Types, Data Items, and Expressions

6.2.3.4 Data Type of an Array
The data type of an array is specified in the same way as the data type of a variable; that
is, the data type of an array is specified implicitly by the initial letter of the name or
explicitly by a type declaration statement.
All the values in an array have the same data type. Any value assigned to an array element
is converted to the data type of the array. If an array is named in a DOUBLE PRECISION
statement, for example, the compiler allocates an 8-byte storage location for each element
of the array. When a value of any type is assigned to any element of that array, the value is
converted to double precision.

6.2.3.5 Array References Without Subscripts
In the following statements, you can specify an array name without a subscript to indicate
that the entire array is to be used (or defined):
• COMMON statement
• DATA statement
• EQUIVALEN CE statement
o NAMELIST statement

• SAVE statement

• VO statements
• Type declaration statements
You can also use unsubscripted array names as dummy arguments in FUNCTION,
SUBROUTINE, and ENTRY statements, and as actual arguments in references to external procedures. The use of unsubscripted array names is not permitted in all other types of
statements.

6.2.3.6 Adjustable Arrays
Adjustable arrays allow subprograms to manipulate arrays of variable dimensions. To use
an adjustable array in a subprogram, you specify the array bounds, as well as the array's
name, as subprogram arguments. The bounds may also be given in a common block. See
Section 10.1.1.1 for more information.
6.2.3. 7 Assumed-Size Arrays
Assumed-size arrays are similar to adjustable arrays. With assumed-size arrays, however,
an asterisk is used to specify the upper bound of the last dimension. Section 10.1.1.2
describes the rules governing the dimensions that are assumed.

Data Types, Data Items, and Expressions

6-21

.6.2.4 Character Substrings
A character substring is a contiguous segment of a character variable or character array
element.
A character substring reference has one of the following forms:
v([e1 ]:[e2])
a(s[,s] ... ) ([e1 ]:[e2])

where:
v

is a character variable name.
a

is a character array name.
s

is a subscript expression.
e1

is a numeric expression that specifies the leftmost character position of the
substring.
e2

is a numeric expression that specifies the rightmost character position of the substring.
Character positions within a character variable or array element are numbered from left to
right, beginning at one. For example, LABEL(2:7) specifies the substring beginning with
the second character position and ending with the seventh character position of the character variable LABEL. If the CHARACTER*8 variable LABEL has a value of XVERSUSY,
then the substring LABEL(2:7) has a value of VERSUS.
If the value of the numeric expression el or e2 is not of type integer, it is converted to an

integer value by truncating any fractional part before use.
The values of the numeric expressions el and e2 must meet the following conditions:
1 .LE. e1 .LE. e2 .LE. len

where:
len

is the length of the character variable or array element.

6-22

Data Types, Data Items, and Expressions

If el is omitted, FORTRAN assumes that el equals one. If e2 is omitted, FORTRAN
assumes that e2 equals len.

For example, NAMES(l,3)(:7) specifies the substring starting with the first character
position and ending with the seventh character position of the character array element
NAMES(l,3).

6.2.5 necords
The VAX FORTRAN record-handling capability is an extension to the FORTRAN-77
standard. It enables you to declare and operate on multifield records in your FORTRAN
programs. It also enables you to access records in the VAX Common Data Dictionary
(CDD) for use in your programs.

NOTE
A VAX FORTRAN record should not be confused with an RMS I/O record. A
VAX FORTRAN record is a named data entity, consisting of one or more fields,
that you create in your program.

6.2.5.1 Oucruiew of necords and Structures
A record is a composite, or aggregate, entity containing one or more record elements, or
fields. In this respect, it is similar to an array. It differs from an array, however, in the
following respects:
0

Unlike arrays, which are defined by means of a single declaration statement, creating
a record is a multistep process. Creating a record requires:
- A multistatement declaration, called a structure declaration, in which the form of
the record is defined.
-

A RECORD statement that establishes the referenced structure as a record in
memory, that is, as a named data entity. More that one RECORD statement can
refer to a given structure declaration.

o Unlike arrays, whose data elements must be of the same data type, records allow you

to organize heterogeneous data elements within one structure and to operate on them
either individually or collectively. Because they can be composed of heterogeneous
data elements, records are not typed as arrays are.
0

Unlike arrays, each element of a record can be-and usually is-named. References to
a record element consist of the name of the record and the name of the desired
element.

You define the form of a record with a group of statements called a structure declaration
block.
You establish a structure declaration in memory by specifying the name of the structure .
declaration in a RECORD statement.

Data Types, Data Items, and Expressions

6-23

A structure declaration block can include one or more of the following items:
o

Typed data declarations (variab,les or arrays): Typed data declarations in structure
declarations have the form of normal FORTRAN typed data declarations. Data items
with different types can be freely intermixed within a structure declaration; for example, INTEGER and LOGICAL data items can be declared in the same structure.
declarations: Substructures can be established with a structure by
means of either a nested structure declaration or a RECORD statement.

o Substructure

Structure declarations can be nested within structure declarations. A nested structure declaration must have one or more field names specified on its STRUCTURE
statement. A nested structure declaration can optionally be given a structure name
for later reference by a RECORD statement.

- The fields in another, previously declared, structure declaration can be incorporated in a structure by including a RECORD statement, naming the other structure, within a structure declaration. This feature enables you to create a structure
declaration and then include it, as necessary, as a substructure declaration within
other structure declarations. Depending on the needs of an application, this can
have advantages over the use of nested structure declarations, which are individually coded within a containing, outer structure.
field declarations: Mapped field declarations are made up of one or more
typed data declarations, substructure declarations (structure declarations and RECORD statements), or other mapped field declarations.

o Mapped

Mapped field declarations are defined by a block of statements called a union declaration. Unlike typed data declarations, all mapped field declarations that are made
within a single union declaration share a common location within the containing
structure. This capability is analogous to the ·use of EQUIVALENCE statements to
give names to variables. In other languages, it is called a "variant record" capability.
fields: Unnamed fields can be declared in a structure by specifying the
pseudo-name %FILL in place of an actual field name. You can use this mechanism to
generate empty space in a record for purposes such as alignment.

o Unnamed

For a detailed description of the syntax and use of RECORD statements and structure
declarations, see Sections 8.13 and 8.15, respectively.

6.2.5.2 Arrangement of Records in Storage
FORTRAN stores a record in memory as a linear sequence of values, with the record's first
element in the first storage location and its last element in the last storage location. No
gaps are left between elements. A record array is stored in a similar fashion, with no gaps
between array elements.

6-24

Data Types, Data Items, and Expressions

The following example contains a structure declaration and record statement, and shows
how the resulting records are stored in memory.
Source Code:
STRUCTURE /STRA/
CHARACTER*! CHR
INTEGER*Ll INT
END STRUCTURE

RECORD /STRA/ REC1AREC(2)

Memory Diagram:
5

(byte offset)

REC.INT

REC.CHA
v

Record REC
ZK-1844-84

0
AREC(1 ).CHR

AREC(1 ).INT

6
AREC(2).CHR

(byte offset)

AREC(2).INT

Record AREC(2)
ZK-1843-84

Data Types, Data Items, and Expressions

6-25

The next example is similar but involves a record that is more complex than the records in
the preceding example. The record in this example includes a substructure.
Source Code:
STRUCTURE /STRB/
REAL*B FLT
RECORD /STRA/ STRC2)
END STRUCTURE

RECORD /STRB/ NRD

Memory Diagram:
0

8
NAO.FLT

9
NRD.STR(1 ).CHA

NRD.STR(1).INT

Substructure
STRA (STR(1))

14
NRD.STR(2).CHR

(byte offset)

NRD.STR(2).INT

Substructure
STRA (STR(2))

}

~'===============~v===============~/
Record NRD

ZK-1842-84

Unions cause the storage of the associated mapped fields to be overlaid, as the following
example illustrates:
Source Code:
STRUCTURE I STR I
INTEGER*LI TAG
UNION
MAP
REAL*4 FLT
CHARACTER*2 CHR
END MAP
MAP
I NTEGER*2 I NT
END MAP
END UNION
LOGICAL*! LOG
END STRUCTURE

RECORD /STR/REC

6-26

Data Types, Data Items, and Expressions

Memory Diagram:
6

(byte offset)

l
FLT
TAG
INT

CHR

LOG
(unused)

Area for mapped fields
ZK-1845-84

The next section describes how to refer to records and to fields within records.

6.2.5.3 Record and Field Deferences
Fields are the atomic units of records; they correspond to substructures or to ordinary
variables or array elements. Fields within a record can be operated on collectively (that is,
as part of an operation involving an entire record) or individually.
There are two forms of record references: aggregate field and scalar field references.
0

An aggregate field reference refers to a composite, or structured, data item, that is, a
record structure or a record substructure.
·

o A scalar field

reference refers to a typed data item, that is, a variable or an array

element.
Aggregate: Field Reference:
record-name[.aggregate-field-name .... aggregate-field-name]

Scalar Field Reference:
record-name.aggregate-field-name[ .... aggregate-field-name].scalar-field-name

where:
record-name

The name used in a RECORD statement to identify a record. See Section 8.13 for a
description of the RECORD statement.

Data Types, Data Items, and Expressions

6-27

aggregate-field-name

The name of a field that is a substructure (that is, a record or a nested structure
declaration) within the record structure identified by the record name.
See Section 8.15 for a description of how fields are specified within structure declarations.
scalar-field-name

The name of a typed data item defined within a structure declaration.

NOTE
The generic term scalar reference is used throughout this manual to refer collectively to all references that resolve to single, typed data items. Scalar field
references fall into the scalar reference category.
The generic term aggregate reference is used throughout this manual to refer
collectively to all references that resolve to references to structured data items,
that is, records and nested structure declarations. Aggregate field references are
the only references that fall into this category.
Section 6.2.6 provides a thorough discussion of this new terminology.
The following considerations and restrictions apply to the various forms of record references:
o Aggregate Field References

An aggregate field reference consists of the name of a record (as specified in a
RECORD statement) and zero or more levels of aggregate field names.
Aggregate record assignments are permitted; that is, aggregate field references can be
specified on the left-hand side of an assignment statement.
o Scalar Field References

A scalar field reference consists of the name of a record (as specified in a RECORD
statement) and zero or more levels of aggregate field names followed by the name of a
scalar field.
A scalar field reference refers to a single, typed data item and can be treated like a
normal reference to a FORTRAN variable or array element. Scalar field references can
be used in statement functions and in executable statements. They cannot, however,
be used in COMMON, SAVE, NAMELIST, or EQUIVALENCE statements.
Type conversion rules for scalar field references are the same as those for variables and
array elements.

6-28

Data Types, Data Items, and Expressions

o Records in 1/0 Statements

Aggregate field references can be used in unformatted I/0 statements (one I/0 record
is written no matter how many aggregate and array name references appear in the I/0
list), but cannot be used in formatted and NAMELIST I/0 statements.
o Records as Arguments

Aggregate field references can be used as both dummy and actual arguments. The
declaration of the dummy record in the subprogram must match the form of the record
declared in the calling program unit, that is, each structure must have the same
number and types of fields in the same order. The ordering of map fields within a
union declaration is irrelevant.
Records are passed by reference. Aggregate field references are treated like normal
variables. Adjustable arrays are allowed in RECORD statements used as dummy
arguments.

NOTE
Because periods are used in record references to separate fields, you should not
use relational operators (for example, .EQ., .XOR.) logical constants (.TRUE. or
.FALSE.) and logical expressions (.AND., .NOT., .OR.) as field names in structure declarations.

Elcamples
The examples of record and field references shown here are based on the record structure
APPOINTMENT (described at length in Section 8.15.1) and the following RECORD statement:
RECORD /APPOINTMENT/ NEXT_APP1APP_LIST(10l

The preceding statement results in the creation of both a variable named NEXT_APP
and a 10-element array named APP_LIST. Both the variable and each element of the
array have the form of the structure APPOINTMENT.
The declarations of the record structure APPOINTMENT and its substructure DATE are
repeated here to show the fields used in the field references in the examples that follow.

Data Types, Data Items, and Expressions

6-29

Structure DATE:
STRUCTURE /DATE/
LOGICAL*l DAY, MONTH
INTEGER*2 YEAR
END STRUCTURE

Structure APPOINTMENT:
STRUCTURE /APPOINTMENT/
RECORD /DATE/
APP-DATE
STRUCTURE /TIME/ APP_TIME (2)
LOGICAL*l
HOUR1 MINUTE
END STRUCTURE
CHARACTER*20
APP_MEMO (4)
LOGICAL*l
APP_FLAG
END STRUCTURE

Each of the following examples of record and field references is introduced by ·a brief
description.
Aggregate Field References:
o The record NEXT_APP:

o The field APP_TIME(l), an array field of the record NEXT__APP:

NEXT_APP.APP_TIME<l>
o The field APP _DATE, a 4-byte array field in the record array APP __LIST(3):

APP_LISTC3) .APP-DATE

Scalar Field References:
0

The field APP _FLAG, a LOGICAL field of the record NEXT__APP:
NEXT-APP.APP-FLAG

The field HOUR, a LOGICAL*lsubfield of field APP _TIME(l) of record NEXT_
APP:
NEXT_APP.APP_TIMEC1).HOUR

6-30

Data Types, Data Items, and Expressions

o The

first character of APP _MEMO(l), a CHARACTER*20 field of the 'record
NEXT_APP:
NEXT_APP.APP_FLAG(20)(1:1)

The field MONTH, a LOGICAL*l subfield of field APP _l)ATE of ~ecord array
APP _LIST(l):
APP_LIST<l>.APP_DATE.MDNTH

6.2.6 Terminology Used to Refer to Data Items
Constants, variables, arrays, scalar fields, aggregate fields, character substrings, and expressions can be specified in many places in a FORTRAN program. FORTRAN statements
and expressions have individual restrictions governing which of these items can used in
· them and in what form. Thus, to avoid repeatedly enumerating lists of the various items
that can be specified with the various statements and expressions, the items are divided
into four general categories. The names of these categories are used throughout this manual
to identify what can be included in a particular statement or expression. The categories are
as follows:
• Scalar Reference-resolves itself to a reference to a single, typed data item: a variable,
array element, constant, character substring, or expression.
• Scalar Memory Reference-same as scalar reference, excluding constants and expressions.
• Array Name Reference-resolves itself to a reference to an array.
0

Aggregate Reference-resolves itself to a reference to a structured data item.

Data Types, Data Items, and Expressions

6-31

References formed from the following data declarations can be used to illustrate the three
types of reference:
INTEGER INTt INTARY C10)
STRUCTURE /STRA/
INTEGER I NTFLD , I NTFLDARY C10)
END STRUCTURE
STRUCTURE /STRB/
CHARACTER*20 CHARFLD
INTEGER I NTFLD, I NTFLDARY ( 10)
STRUCTURE STRUCFLD
COMPLEX CPXFLDt CPXFLDARY C10)
END STRUCTURE
RECORD _/STRA/ RECFLDt RECFLDARY C10)
END STRUCTURE
RECORD

/STRB/

RECt RECARY (10)

Examples of references, by category, that can be formed from the preceding data declarations are as follows:
• Scalar References:
INT
INTARY<1>
REC.INTFLD
REC.INTFLDARY(1)
REC.RECFLD.INTFLD
REC,STRUCFLD.CPXFLD
REC.RECFLD.INTFLDARY<1>
REC.RECFLDRAY<1> .INTFLD
REC.RECFLDRAY<1>.INTFLDARY(1)
REC. CHARFLD

REC,CHARFLDC5:10)
RECARY<1>.CHARF~D<5:10)

RECARYC1>.INTFLD
REC ARY ( 1 > , I NTFLDARY <1 >
RECARY<l>.RECFLO.INTFLD
RECARYC1) ,STRUCFLD.CPXFLD
RECARY<1>.RECFLO,INTFLDARY<1>
RECARY<1>.RECFLDRAYC1>.INTFLD
RECARYC1>.RECFLDRAY<1>.1NTFLDARYC1>

• Array Name References:
INTARY
REC ARY
REC.INTFLDARY
REC.RECFLDARY
REC.RECFLO.INTFLDARY
REC.RECFLDARY<l> .INTFLDARY
o Aggregate References:
REC
RECARY<1>
REC.RECFLD
REC.STRUCFLD
6-32

Data Types, Data Items, and Expressions

REC.STRUCFLD.CPXFLDARY
RECARY<l>.INTFLDARY
RECARY<l>.RECFLDARY
RECARYC1> .RECFLD,INTFLDARY
RECARYC1),STRUCFLD.CPXFLDARY
RECARY<l> .RECFLDARYC1),INTFLDARY
REC.RECFLDARYC1)
RECARY<l> .RECFLD
RECARYC1),STRUCFLD
RECARYC1),RECFLDARY<1>

Scalar reference, array name reference, and aggregate reference are used throughout this
manual to indicate where these various categories of data items can be specified. Note that
constants are included in the scalar reference category.

6.3 Expressions
An expression represents a single value. An expression can consist of a scalar field reference
or function reference; or combinations of these references plus certain other elements,
called operators. Operators specify computations to be performed on the values of the data
items and a single result is obtained.
Expressions are classified as arithmetic, character, relational, or logical. Arithmetic expressions produce numeric values; character expressions produce character values; and relational and logical expressions produce logical values.

6.3.1 Arithmetic Expressions
Arithmetic expressions are formed with arithmetic elements and arithmetic operators. The
evaluation of such an expression yields a single numeric value.

An arithmetic element can be any of the following:
• A numeric scalar reference

• An arithmetic expression enclosed in parentheses
• A numeric function reference
The term "numeric," as used above, includes logical data, because logical data is treated as
integer data when used in an arithmetic context.
Arithmetic operators specify a computation to be performed using the values of arithmetic
elements. They produce a numeric value as a result. The operators and their meanings are:
Operator

Function

**
*

Exponentiation

Division

Addition or unary plus

Multiplication

Subtraction or unary minus
These operators are called binary operators because each is used with two elements. The
plus ( +) and minus (- ) symbols are also unary operators: when they immediately precede
an arithmetic element and are not immediately preceded by an arithmetic element, they
denote a positive or negative value.
A variable or array element must have a defined value before it can be used in an arithmetic expression.
Data Types, Data Items, and Expressions

6-33

Any arithmetic operation whose result is not mathematically defined is not allowed. Examples of this are dividing by zero and raising a zero-valued base to a zero-valued or negativevalued power. Raising a negative-valued base to a real power is also not allowed.
Arithmetic expressions are evaluated in an order determined by a precedence associated
with each operator. The precedence of the operators is:
Operator

Precedence

First

*and I

Second

+and -

Third

When two or more operators of equal precedence (such as + and -) appear, they can be
evaluated in any order, as long as the order of evaluation is algebraically equivalent to a
left-to-right order of evaluation. Exponentiation, however, is evaluated from right to left.
For example, A**B**C is evaluated as A** (B**C); B**C is evaluated first, and then A is
raised to the resulting power.
Normally, two operators cannot be placed in succession. When the second operator is unary
( + or -) , as an extension to the ANSI standard, VAX FORTRAN allows two consecutive
operators within an expression. This extension can be illustrated by the following two
expressions:
1. A••B•C
2. A •• -8 • C

In the first example, the ** operator is evaluated first because it takes precedence over the
* operator. In the second example, the * operator is evaluated first. Normally, the **
operator would be evaluated first, but because VAX FORTRAN allows the combination of
the ** and - operators, the order of evaluation is affected. With the ** and - operators
combined, the ** operator cannot be evaluated until after the - operator. As a result, then,
the * operator is evaluated first in compliance with normal rules of precedence.

6.3.1.1 Use of Parentheses
You can use parentheses to force a particular order of evaluation. When part of an expression is enclosed in parentheses, that part is evaluated first, and the resulting value is used
in the evaluation of the remainder of the expression. In the following examples, the numbers below the operators indicate the order of the evaluations:
4+3•2-6/2=7
T T T T

(4+3) * ·2 - 6 I 2 = 11
T T T T
1 2 4 3

6-34

Data Types, Data Items, and Expressions

(4 + 3 * 2 - 6) I 2 = 2

T l

T
3

T
4

((4+3) * 2 - 6) I 2 = 4

T l

As shown in the third and fourth examples above, expressions within parentheses are
evaluated according to the normal order of precedence, unless you override the order by
using parentheses within parentheses.
Nonessential parentheses, as in the following expression, do not affect expression evaluation:
4 + (3•2) - (6/2)

The use of parentheses to specify the evaluation order is often important in high-accuracy
numerical computations. In such computations, evaluation orders that are algebraically
equivalent might not be computationally equivalent when processed by a computer.

6.3.1.2 Data Type of an Arithmetic Expression
If every element in an arithmetic expression is of the same data type, the value produced
by the expression is also of that data type. If elements of different data types are combined
in an expression, the evaluation of that expression and the data type of the resulting value
depend on a rank associated with each data type. The rank assigned to each data type is as
follows:

Data Type

Rank

Logical

1 (Lowest)

INTEGER*2

INTEGER*4

REAL*4 (REAL)

REAL*8 (DOUBLE PRECISION)

REAL*l6

COMPLEX*8 (COMPLEX)

COMPLEX*l6 (DOUBLE COMPLEX)

8 (Highest)

The data type of the value produced by an operation on two arithmetic elements of different data types is the data type of the highest-ranked element in the operation. For example, the data type of the value resulting from an operation on an integer and a real element
is real. However, an operation involving a COMPLEX*8 data type and either a REAL*S or
REAL*l6 data type produces a COMPLEX*16 result.

Data Types, Data Items, and Expressions

6-35

The data type of an expression is the data type of the result of the last operation in that
expression. The data type of an expression is determined according to the following conventions:
• Integer operations-Integer operations are performed only on integer elements. (Logical entities used in an arithmetic context are treated as integers.) In integer arithmetic, any fraction that can result from division is truncated, not rounded. For example:
1/4 + 1/4 + 1/4 + 1/4

The value of this expression is 0, not 1.
• Real operations-Real operations are performed only on real elements or combinations
of real, integer, and logical elements. Any integer elements present are converted to
the real data type by giving each a fractional part equal to zero. The expression is then
evaluated using real arithmetic. Note, however, that in the statement Y = (I/J)*X, an
integer division operation is performed on I and J, and a real multiplication is performed on that result and X.

• REAL*B and REAL*l6 operations-Any element in an operation in which there is a
higher-precision element is converted to the data type of the higher-precision element
by making the existing element the most significant portion of the higher-precision
data. The least significant portion of the binary representation is zero. The expression
is then evaluated in the higher-precision arithmetic.
• Converting a real element to a higher-precision element does not increase its accuracy.
For example, a REAL variable having the value
0.3333333

is converted to (approximately)
0.333333313465118400

not to either
0.333333300000000000

or
0 .3333333333333333 DO

• Complex operations-In an operation that contains any complex element, integer
elements are converted to the real data type, as previously described. The REAL or
REAL*8 element thus obtained is then designated as the real part of a complex
number; the imaginary part is assigned a value of zero. The expression is then evaluated using complex arithmetic and the resulting value is of a complex data type.
Operations involving COMPLEX*8 and REAL*8 elements are done as
COMPLEX*l6 operations; that is, the REAL*8 element is not rounded.
• When a constant defined by a PARAMETER statement is used in an arithmetic
expression, it is treated in some cases as a lower-order type even if it was explicitly
typed. For example, an INTEGER*4 constant could be treated as an
constant.
6-36

Data Types, Data Items, and Expressions

These rules also generally apply to arithmetic operations in which one of the operands is a
constant. However, if a real or complex constant is used in a higher-precision expression,
additional precision will be retained for the constant. The effect is as if a REAL*8 or
REAL*l6 representation of the constant had been given. For example, the expression
1.000 + 0.3333333

is treated as if it were
1.000 + 0.333333300000000000

6.3.2 Character Expressions
Character expressions consist of character elements and character operators. The evaluation of a character expression yields a single value of character data type.
A character element can be any one of the following:
• A character scalar reference
• A character substring
• A character expression, optionally enclosed in parentheses
• A character function reference
The only character operator is the concatenation operator ( //).
A character expression has the form:
character element [//character element] ...

The value of a character expression is a character string formed by successive left-to-right
concatenations of the values of the elements of the character expression. The length of a
character expression is the sum of the lengths of the character elements. For example, the
value of the character expression 'AB' //'CDE' is 'ABCDE ',which has a length of five.
Parentheses do not affect the value of a character expression. For example, the following
character expressions are equivalent:
I ABC I I I I DE I ) I I IF I
ABC I I I ( I DE I I I IF I)
I ABC I I I I DE I I I IF I

(

Each of these character expressions has the value 'ABCDEF '.
If a character element in a character expression contains spaces, the spaces are included in
the value of the character expression. For example, 'ABC '//'D E '//'F ' has a value of
'ABC DEF '.

Data Types, Data Items, and Expressions

6-37

6.3.3 Relational Expressions
A relational expression consists of two arithmetic expressions or two character expressions
separated by a relational operator. The value of the expression is either true or false,
depending on whether the stated relationship holds.
A relational operator tests for a relationship between two arithmetic expressions or between
two character expressions. These operators are:
Operator

Relationship

.LT.

Less than

.LE .

Less than or equal to

.EQ.

Equal to

.NE.

Not equal to

.GT.

Greater than

.GE.

Greater than or equal to

The delimiting periods are a required part of each operator.
Complex expressions can be related only by the .EQ. and .NE. operators. Complex entities
are equal if their corresponding real and imaginary parts are both equal.
In an arithmetic relational expression, the arithmetic expressions are first evaluated to
obtain their values. These values are then compared to determine whether the relationship
stated by the operator holds. For example:
APPLE+PEACH .GT. PEAR+ORANGE

This expression states the relationship, "The sum of the real variables APPLE and PEACH
is greater than the sum of the real variables PEAR and ORANGE." If that relationship
holds, the value of the expression is true; if not, the value of the expression is false.
Similarly, in a character relational expression, the character expressions are first evaluated
to obtain their values. These values are then compared to determine whether the relationship stated by the operator holds. In character relational expressions "less than" means
"precedes in the ASCII collating sequence," and "greater than" means "follows in the
ASCII collating sequence." For example:
AB I I zzz
LT. ccccc
I

•

This expression states that 'ABZZZ' is less than 'CCCCC '. Since that relationship does
hold, the value of the expression is true. If the relationship stated does not hold, the value
of the expression is false.
If the two character expressions in a relational expression are not the same length, the
shorter one is padded on the right with spaces until the lengths are equal. For example:
I

ABC

•

EQ.

ABC

'AB' .LT, 'C'

6-38

Data Types, Data Items, and Expressions

The first relational expression has a value of true even though the lengths of the expressions
are not equal, and the second has a value of true even though 'AB' is longer than 'C '.
All relational operators have the same precedence. However, arithmetic and character
operators have a higher precedence than relational operators.
As in any other expression, you can use parentheses to alter the order of evaluation of the
expressions in a relational expression. However, because arithmetic and character operators _are evaluated before relational operators, you need not enclose the entire arithmetic or
character expression in parentheses.
A relational expression can compare two numeric expressions of different data types. In
this case, the value of the expression with the lower.:.ranked data typ.e is converted to the
higher-ranked data type before the comparison is made.

6.3.4 Logical Expressions
A logical expression can be a single logical element or a combination of logical elements
and logical operators. A logical expression yields a single logical value, true or false.
A logic~l element can be any of the following:
• An integer or logical scalar reference

• A relational expression
• An integer or logical expression enclosed in parentheses
• An integer or logical function reference

The logical operators are:
Operator

Example

Meaning

.AND.

A • AND. B

Logical conjunction: The expression is true if, and
only if, both A and B are true .

.OR.

A • DR. B

Logical disjunction (inclusive OR): The expression
is true if either A or B, or both, are true.

.NEQV.

A • NEQ1.1. B

Logical exclusive OR: The expression is true if A
_and B have different logical values; but the expression is false if both elements have the same logical
value .

.XOR

Same as .NEQV .

.EQV.

A • EQt.1. B

Logical equivalence: The expression is true if, and
only if, both A and B have the same logical value,
whether true or false .

. NOT.

.NOT. A

Logical negation: The expression is true if, and
only if, A is false.

The delimiting periods of logical operators are required.
Data Types, Data Items, and Expressions

6-39

When a logical operator operates on logical elements, the resulting data type is logical.
When a logical operator operates on integer elements, the logical operation is carried out
bit-by-bit on the corresponding bits of the internal (binary) representation of the integer
elements. The resulting data type is integer. When a logical operator combines integer and
logical values, the logical value is first converted to an integer value, then the operation is
carried out as for two integer elements. The resulting data type is integer.
A logical expression is evaluated according to an order of precedence assigned to its operators. Some logical expressions can be evaluated before all their subexpressions are evaluated. For example, if A is .FALSE., the expression A .AND. (F(X,Y) .GT. 2.0) .AND. Bis
.FALSE. The value of the expression can be determined by testing A without evaluating
F(X, Y). Under these circumstances, the function subprogram F may not be called. Thus, it
is uncertain whether side-effects resulting from the call-for example, changing variables
in the common block-will occur.
The following list summarizes all the operators that can appear in a logical expression, in
the order in which they are evaluated:
Operator

Precedence

**
*,/

First (Highest)
Second

+,-,//

Third

Relational
Operators

Fourth

.NOT.

Fifth

.AND.

Sixth

.OR.

Seventh

.XOR.,.EQV.,.NEQV.

Eighth (Lowest)

Operators of equal rank are evaluated from left to right, except for exponentiation, which is
evaluated from right to left. For example:
A*B+C*ABC .EQ. X*Y+DM/ZZ .AND •• NOT. K*B .GT. TT

The sequence in which this logical expression is evaluated is:
(((A*B)+(C*ABC)) .EO. <<X*Y)+(DM/ZZ))) .AND. (.NOT. <<K*B>. GT. TT>>

As in arithmetic expressions, you can use parentheses to alter the normal sequence of
evaluation.
Two logical operators cannot appear consecutively, unless the second operator is .NOT.

6-40

Data Types, Data Items, and Expressions

Chapter 7

Assignment Statements
Assignment statements define the value of a data item-a variable, array element, record
(structured variable), record element, or character substring. The expression on the right
side of the assignment statement's equal sign is evaluated and the resulting value is
assigned to the data item.
The following statements perform assignments:
• Arithmetic assignment statement
• Logical assignment statement
• Character assignment statement
0

Aggregate assignment statement

• ASSIGN statement
These statements are discussed individually in the sections that follow.

7.1 Arithmetic Assignment Statement
The arithmetic assignment statement assigns the value of the expression on the right of the
equal sign to the numeric scalar memory reference on the left of the equal sign.
The arithmetic assignment statement has the form:
V=8

where:
v
is a numeric scalar memory reference.
e

is an arithmetic expression.

7-1

The equal sign does not mean "is equal to," as in mathematics. It means "is replaced by."
For example:
COUNT = COUNT + 1
This statement means, "replace the current value of the integer variable COUNT with the
sum of that current value and the integer constant 1."
Although the symbolic name on the left of the equal sign can be undefined, values must
have been previously assigned to all symbolic references in the expression on the right of
the equal sign.
The expression e must yield a value that conforms to the range requirements of v. For
example, a real expression that produces a value greater than 32767 is invalid if the entity
on the left of the equal sign is an INTEGER*2 variable. Significance may be lost if an
INTEGER*4 value, which can exactly represent values of approximately the range
-2*10**9 to +2*10**9, is converted to REAL*4 (including the real part of a complex
constant), which is accurate to only about seven digits.
If v has the same data type as that of the expression on the right, the statement assigns the
value directly. If the data types are different, the value of the expression is converted to the
data type of the entity on the left of the equal sign before it is assigned. Table 7-1
summarizes the data conversion rules for assignment statements.

Examples of valid and invalid assignment statements are:

Valid
PI= 3.14158
SUM = SUM + 1.
NEW= RECROD1.FIELD1
SYMBOL CI ) • DEF I NED = • TRUE.

Invalid
3+14=A-B

Entity on the left must be a numeric scalar
memory reference.

-J = I**4

Entity on the left must not be signed.

ALPHA = C( }{+G) *B*B/ CH-Y)

Left and right parentheses do not balance.

. !COUNT= A//BC3:7>

Expressions on the right cannot be of character
data type if the entity on the left is not of character data type.

7-2

Assignment Statements

Table 7-1: Conversion Rules for Assignment Statements
Variable
or Array
Element
(V)

Expre~on (E)

Integer or
Logical

REAL

REAL•S

REAL•l6

COMPLEX

COMPLEX•16

Integer
or Logical

Assign E to V

Trunca le E to
integer and
assign to V

Truncate E to
integer and
assign to V

Truncate real part
of E to integer and
assign to V;
imaginary part of E
is not used

Truncate real part of E
to integer and assign to
V; imaginary part of E
is not used

REAL

Append fraction
(.0) to E and
assign to V

Assign E to V

Assign MS• portion
ofE to V; LS•
portion of E is
rounded

Assign real part of
E to V; imaginary
part of E is not
used

Assign MS• portion
of the real part of
E to V; LS• portion
of the real part of
E is rounded;
imaginary part of
Eis not used

REAL•S

Append fra~tion
(.0) to E and
assign to V

Assign E to MS•
portion of V; LS•
portion of V is 0

Assign E to V

Same as above

Assign real part of
E to MS• ofV;
LS• portion of V
is O;imaginary part
of Eis not used

Assign real part of
E to V; imaginary
part of E is not used

REAL•J6

Same as above

Assign E to Ms•
portion ofV; LS•
portion of V is 0

Assign E to V

COMPLEX

Append fraction
(.0) to E and
assign to real
part ofV;
imaginary part of
Vis0.0

Assign E to real
part of V;
imaginary part
ofV isO.O

Assign MS• portion
of E to real part of
V; LS• portion of
E is rounded:
imaginary part of
VisO.O

Assign MS• portion
of E to real part of
V;·LS• portion of
Eis rounded:
imaginary part of
VisO.O

Assign E to V

Assign MS* portion
of real part of E to
real part of V:LS*
portion of real part
of E is rounded.
Assign MS* portion of
imaginary part of E
to imaginary part of
V:LS* portion of
imaginary part of E
is rounded.

Append fraction
(.0) to E and assign
to V;imaginary
part of V is 0.0

Assign E to MS•
portion of real
part ofV;
imaginary part
ofV is 0.0

Assign E to real
part of V;
imaginary part
isO.O

Sarne as ahnve

Assign real part of
E lo MS* portion
of real part ofV;
LS• portion of
real part is 0. Assign
imaginary part of E
to MS• portion of
imaginary part of V;
LS• portion of
imaginary part is 0.

Assign E lo V

Assign real part of
E to MS* portion
of V:LS* portion
of real part of V
is O.lmaginary ·part
of Eis not used

•MS ~ most significant (high order)
LS ~ least significant (low order)

7.2 Logical Assignment Statement
The logical assigment statement assigns the value of the logical expression on the right of
the equal sign to the logical scalar memory reference on the left of the equal sign. See Table
7-1 for conversion rules.

Assignment Statements

7-3

The logical assignment statement has the form:
V=0

where:
v

is a logical scalar memory reference.
e

is a logical expression.
Values must have been previously assigned to all symbolic references that appear in the
expression. The expression must yield a logical value.
Examples of logical assignment statements are:
PAGEND =.FALSE.
PRNTOK = LINE .LE. 132 .AND .. NOT. PAGEND
ABIG = A.GT.B .AND. A.GT.C .AND. A.GT.D

7.3 Character Assignment Statement
The character assignment statement assigns the value of the character expression on the
right of the equal sign to the character scalar memory reference on the left of the equal sign.
The character assignment statement has the form:
V=9

where:
v

is a character scalar memory reference.
e

is a character expression.
If the length of e is greater than the length of v, the character expression is truncated on the

right.
If the length of e is less than the length of v, the character expression is filled on the right

with spaces.
The expression e must be of character data type. You cannot assign a numeric value to a
character scalar memory reference.

7-4

Assignment Statements

Note that by assigning a value to a character substring you do not affect character positions
in the character scalar memory reference not included in the substring. If a character
position outside of the substring has a value previously assigned, it remains unchanged; if
the character position is undefined, it remains undefined.
Examples of valid and invalid character assignment statements follow. Note that all scalar
memory references in the examples are assumed to be of character data type.

Valid
FILE= 'PRDG2'
REt.JOL(l) = 'MAR'//'CIA'
LDCA(3:8) = 'PLANTS' TE}<T( I tJ+l) (2:N-1> =NAME/I}-{

Invalid
I

ABC I = CHARS

Element on the left must be a character variable, array element, or substring reference.

CHARS = 25

Expression on the right must be of character
data type.

STRING= 5HBEGIN

Expression on the right must be of character
data type; Hollerith constants are numeric,

The aggregate assignment statement assigns the value of each field of the aggregate on the
right of the equal sign to the corresponding field of the aggregate on the left. Note that both
aggregates must be declared with the same structure.
The aggregate assignment statement has the form:
V=S

where:
v

is an aggregate reference (see Section 6.2.5.3) with the same structure as the aggregate
represented by e.
e

is an aggregate reference lsee Section 6.2.5.3) with the same structure as the aggregate
represented by v.

Assignment Statements

7-5

Examples:
RECORD /DATA/ TDDAYt THIS_WEEKC7)
STRUCTURE /APPOINTMENT/
RECORD /DATA/ APP_DATE
END STRUCTURE
RECORD /APPOINTMENT/ MEETING
GET _DATE <TODAY)
DO I = 1 , 7
TH I S_WEEK (I) = TODAY
THIS_WEEK III.DAY= TODAY.DAY+ 1
END DD
MEETING+APP_DATE = TODAY

7.5 ASSIGN Statement
The ASSIGN statement assigns a statement label value to an integer variable. The variable can then be used as either a transfer destination in a subsequent assigned GO TO
statement or a format specifier in a formatted I/O statement.
The ASSIGN statement has the form:
ASSIGN s TO v

where:
s

is the label of an executable statement or a FORMAT statement in the same program
unit as the ASSIGN statement.
v

is an integer variable.
The ASSIGN statement assigns the statement number to the variable. It is similar to an
arithmetic assignment statement, with one exception: the variable becomes defined for use
as a statement label reference and becomes undefined as an integer variable.
The ASSIGN statement must be executed before the statement(s) in which the assigned
variable is to be used. Moreover, the ASSIGN statement and the statement(s) in which the
assigned variable is used must occur in the same program unit. For example:
ASSIGN 100 TD NUMBER

This statement associates the variable NUMBER with the statement label 100. Arithmetic
operations on the variable, as in the following statement, then become invalid because
arithmetic on label values is undefined:
NUMBER = NUMBER + 1

7-6

Assignment Statements

The next statement dissociates NUMBER from statement 100, assigns it an integer value
10, and returns it to its status as an integer variable:
NUMBER = 10
The variable NUMBER can no longer be used in an assigned GO TO statement.
Examples of ASSIGN statements are:
ASSIGN 10 TD NSTART
ASSIGN 99999 TD KSTDP
ASSIGN 250 TD ERROR

(Note: ERROR must be previously defined as an integer variable.)

Assignment Statements

7-7

Chapter 8

Specification Statements
Specification statements are nonexecutable statements that are used to allocate and initialize variables, arrays, records, and structures and to define other characteristics of the
symbolic names used in the program.
The specification statements, in alphabetical order, are:
• BLOCK DATA statement-establishes and defines common blocks and assigns initial
values to entities contained in those common blocks.
• COMMON statement-defines one or more contiguous areas of storage.
• DATA statement-assigns initial values to variables, arrays, and array elements before program execution.
• Data type declaration statement-explicitly defines the data type of specified symbolic names.
• DIMENSION statement-defines the number of dimensions in an array and the number of elements in each dimension.
• EQUIVALEN CE statement-associates two or more entities with the same storage
location.
• EXTERNAL statement-allows use of user-supplied procedures as arguments to subprograms. (See Appendix A for a version of the EXTERNAL statement that is compatible with earlier versions of FORTRAN produced by DIGITAL.)
• IMPLICIT statement-overrides the implied data type of symbolic names.
• INTRINSIC statement-allows use of FORTRAN intrinsic functions as arguments to
subprograms.
o NAMELIST statement-specifies lists of entities whose values may be read or written

in namelist-directed I/0 statements and associates the list with specified groupnames.
• PARAMETER statement-assigns a symbolic name to a constant value. (See Appendix A for a version of the PARAMETER statement that is compatible with earlier
versions of FORTRAN produced by DIGITAL.)

8-1

• PROGRAM state~ent-assigns a symbolic name to a main program unit.
o RECORD statement-establishes a record with the structure defined by the block of

statements in a structure declaration.
• SAVE statement-retains values of local variables after a return from a subprogram.
o Structure declaration block-specifies the form, or structure, of a record.
0

VOLATILE statement-prevents optimization from being performed on specified variables, arrays, and common blocks.

The following sections detail these statements, giving their forms and showing their use.

8.1 BLOCK DATA Statement
The BLOCK DATA statement, followed by a series of specification statements, assigns
initial values to entities in named common blocks and, at the same time, establishes and
defines those blocks.
The BLOCK DATA statement has the form:
BLOCK DATA [nam]

where:
nam

is a symbolic name.
You can use COMMON, DATA, DIMENSION, EQUIVALENCE, IMPLICIT, PARAMETER, RECORD, SAVE, structure declaration, and type declaration statements following a
BLOCK DATA statement.
The specification statements that follow the BLOCK DATA statement establish and define
common blocks, assign variables, arrays, and records to these blocks, and assign initial
values to the variables, arrays, and records.
A BLOCK DATA statement and its associated specification statements comprise a special
kind of program unit. A block data program unit must not contain any executable statements. As with other types of program units, the last statement in a block data program
unit is an END statement.
If you use a BLOCK DATA statement to initialize any entity in a labeled common block,
you must provide a complete set of specification statements to establish the entire block,
even though some of the entities in the block do not appear in a DATA statement. You can
use the same block data program unit to define initial values for more than one common
block.

You can include the name of a block data subprogram in an EXTERNAL statement of a
different program unit to force the VAX Linker to search object libraries for the block data
subprogram at link time.

8-2

Specification Statements

An example of a block data program unit follows:
BLOCK DATA BLKDAT
INTEGER St}{
LOGICAL TtW
DOUBLE PRECISION U
DIMENSION R(3)
COMMON IAREAllRtStTtU IAREA21WtXtY
DATA Rl1.0t2*2+01t Tl.FALSE.It UI0,214537D-71t WI.TRUE.It Yl3.51
END

8.2 COMMON Statement
A COMMON statement defines one or more contiguous areas, or blocks, of storage. COMMON statements also define the order in which variables, arrays, and records are stored in
each common block.
A symbolic name identifies each block. However, you can omit a symbolic name for one
block in a program unit. The block without a name is known as the blank common block.
The COMMON statement has the form:
COMMON [/[cb]/]nlist[[,] /[cb]/nlist] ...

where:
Cb

is a symbolic name, called a common block name. Cb can be blank. If the first cb is
blank, you can omit the first pair of slashes.
nllst

is a list of variable names, array names, array declarators, and records separated by
commas.
Any common block name cb or an omitted cb for blank common can occur more than once
in one or more COMMON statements in a program unit. The list nlist following each
successive appearance of the same common block name is treated as a continuation of the
list for that common block name.
A common block name can have the same name as that of a variable, array, or record.
However, it cannot be the same as a function, subroutine, or entry name in the executable
program.
When you declare common blocks of the same name in different program units, these
blocks all share the same storage area when the program units are combined into an
executable program.
Entities are assigned storage in common blocks on a one-for-one basis. Thus, the entities
assigned by a COMMON statement in one program unit should agree with the data type of

Specification Statements

8-3

entities placed in a common block by another program unit. For example, if one program
unit contains the statement
COMMON CENTS

and another program unit contains the statements
INTEGER*Z MONEY
COMMON MONEY

when these program units are combined into an executable program, incorrect results may
occur because the 2-byte integer variable MONEY is made to correspond to the loweraddressed two bytes of the real variable CENTS.
The following program segments show a common block in a main program and a corresponding common block in a subprogram:
Main Program

Subprogram

COMMON HEAT t}{ /BLK 1 /KILO tO

SUBROUTINE FIGURE
COMMON /BLK 1 I LI MA t R I I ALFA t BET

CALL FIGURE
RETURN
END

The COMMON statement in the main program puts HEAT and X in the blank common
block, and KILO and Q in a named common block, BLKl. The COMMON statement in
the subroutine makes ALFA and BET correspond to HEAT and X in the blank common
block, and makes LIMA and R correspond to KILO and Q in BLKl.
You can use array declarators in the COMMON statement to define arrays.

8.3 DATA Statement
The DATA statement assigns initial values to variables and array elements before program
execution.
The DATA statement has the form:
DATA nlist/clist/[[,] nlist/clist/] ...

where:
nlist

is a list of one or more variable names, array names, array element names, character
substring names, or implied-DO lists, separated by commas. Subscript expressions

8-4

Specification Statements

and expressions in substring references must be integer expressions containing integer
constants and implied-DO variables. The form of an implied-DO list in a DATA
statement is:
(dlist, i=n1 ,n2[,n3])

where:
dlist

is a list of one or more array element names, character substring names, or impliedDO lists, separated by commas.
is the name of an integer variable.
n1 ,n2,n3

are each an integer constant expression, except that the expression can contain implied-DO variables of other implied-DO lists that can have this implied-DO list
within their ranges.
clist

is a list of constants; clist constants have one of the following forms:

where:
c
is a constant or the symbolic name of a constant.
n

defines the number of times the same value is to be assigned to successive entities in
the associated nlist; n is a nonzero, unsigned integer constant or the symbolic name of
an integer constant.
The DATA statement assigns the constant values in each clist to the entities in the preceding nlist. Values are assigned one by one in order as they appear, from left to right.
Therefore, the number of constants must correspond exactly to the number of entities in
the preceding nlist.
When an unsubscripted array name appears in a DATA statement, values are assigned to
every element of that array. The associated constant list must therefore contain enough
values to fill the array. Array elements are filled in the order of subscript progression.
The relationship of nlist items to clist items is described in the following list.
1. If both the constant value in clist and the entity in nlist have numeric data types,
conversion is based on the following rules:

• The constant value is converted, if necessary, to the data type of the variable being
initialized.
Specification Statements

8-5

When an octal or hexadecimal constant is assigned to a variable or array element,
the number of digits that can be assigned depends on the data type of the data
item. If the constant contains fewer digits than the capacity of the variable or array
element, the constant is extended on the left with zeros; if the constant contains
more digits than can be stored, the constant is truncated on the left.

2. If the constant value in clist and the entity in nlist are both of character data type,
the conversion is based on the following rules:
• If the constant contains fewer bytes than the length of the entity, the rightmost
character positions of the entity are initialized with spaces.
• If the c_onstant contains more bytes than the length of the entity, the character
constant is truncated on the right.

3. If the constant value in clist is of numeric data type and the entity in nlist is of
character data type, the constant and the entity must conform to the following
restrictions:
o The character entity must have a length of one character.
0

The constant must be an integer, octal, or hexadecimal constant and must have a
value in the range 0 through 255.

4. If the constant value in clist is a Hollerith or character constant and the entity in
nlist is a numeric variable or numeric array element, the number of characters that
can be assigned depends on the data type of the data item (see Table 6-1). If the
Hollerith or character constant contains fewer characters than the capacity of the
variable or array element, the constant is extended on the right with spaces. If the
constant contains more characters than can be stored, the constant is truncated on
the right.
When the constant and the entity conform to these restrictions, the entity is initialized
with the character that has the ASCII code specified by the constant. This permits a
character entity to be initialized to any 8-bit ASCII code.
The first DATA statement in the following example assigns zero to all 10 elements of array
A and 4 asterisks followed by 2 spaces to the character variable STARS. The second DATA
statement assigns ASCII control character codes to the character variables BELL, TAB,
LF, and FF.
INTEGER AC10)
CHARACTER BELL1 TAB1 LF1 FF1 STARS*B
DATA A1STARS /10*01'****'/
DATA BELL1TAB1LF1FF /718110112/

8-6

Specification Statements

8.4 Data Type Declaration Statements
Type declaration statements explicitly define the data type of specified symbolic names.
There are two forms of type declaration statements: numeric type declarations (see Section
8.4.1) and character type declarations (see Section 8.4.2).
You can initialize data in either form of type declaration statement by placing values
bounded by slashes immediately after the symbolic name of the variable or array to be
initialized. The way that initial values are assigned parallels the way that initial values are
assigned in DATA statements.
The following rules apply to type declaration statements:
• Type declaration statements must precede all executable statements.
• The data type of a symbolic name can be declared only once.
• A type declaration cannot change the type of a symbolic name that has been used in a
context that implicitly assumes a different type.

8.4.1 Numeric Type Declaration Statements
Numeric type declaration statements have the form:
type v[/clist/][,v[/clist/]] ...

where:
type

is any of the following data type specifiers:
LOGICAL, INTEGER, REAL,
DOUBLE PRECISION, COMPLEX, or DOUBLE COMPLEX. Note that BYTE and
LOGICAL*l are equivalent.
v

is the symbolic name of a constant, variable, array, statement function or function
subprogram, or array declarator.
clist

is a list of constants, as in a DATA statement. (See Section 8.3.)
You can use a numeric data type declaration statement to define arrays by including array
declarators (see Section 6.2.3.1) in the list.
A symbolic name can be followed by a data type length specifier of the form *S, where s is
one of the acceptable lengths for the data type being declared. Such a specification overrides the length attribute that the statement implies and assigns a new length to the
specified item. If you specify a data type length specifier with an array declarator, the data
type length specifier goes immediately after the array name.

Specification Statements

8-7

You can use a type declaration statement to assign initial values to variables or arrays.
This is done by specifying a list of constants (clist) in the type declaration statement. The
constants specified initialize only the variable or array that immediately precedes them.
The constant list cannot consist of more than one element unless it is being used to
initialize an array. The list of constants used to initialize an array must contain a value for
every element in the array.
Examples of numericJype declaration statements are:
INTEGER COUNT t MATR !}{ (a ta) t SUM
REAL MANt MU
LOGICAL SWITCH
INTEGER*2 It Jt Kt M12*4t CJt Il..1EC*4(10)
REAL*B WX1 t WXZt WX3*4t WX5t WXB*B
REAL*16 PI/3,14158CJO/ t E/2,7200/ t OARRAYl10)/5*0+0r5*1+9/

8.4.2 Character Type Declaration Statements
Character type declaration statements have the form:
CHARACTER[•len[,]] v[•len][/clist/][,v[•len][/clist/]] ...

where:
v

is the symbolic name of a constant, variable, array, statement function, or function
subprogram or array declarator.
len

is an unsigned integer constant, an integer constant expression enclosed in
parentheses, or an asterisk enclosed in parentheses. The value of len specifies the
length of the character data elements.
clist

is a list of constants, as in a DATA statement. (See Section 8.3.)
If you use CHARACTER* len, len is the default length specification for that list. If an item
in that list does not have a length specification, the item's length is len. However, if an item
does have a length specification, it overrides the default length specified in
CHARACTER* len.

A length specification of asterisk-for example, CHARACTER*(*)-specifies that a function name or dummy argument assumes the length specification of the corresponding
function reference or actual argument (see Chapter 6). A length specification of asterisk for
the symbolic name of a constant specifies that the symbolic constant name is to assume the
actual length of the constant that it represents.
The length specification must be in the range 1 to 65535. If you do not specify a length, a
length of one is assumed. Note that a length specification of zero is invalid. You can use a

8-8

Specification Statements

character type declaration statement to define arrays by including array declarators (see
Section 6.2.3.1) in the list. If you specify both an array declarator and a length, the array
declarator goes first:
Specifying a list of constants (clist) allows you to assign initial values to variables or arrays.
The constants specified initialize only the variable or array that immediately precedes
them. The constant list cannot consist of more than one element unless it is being used to
initialize an array. The list of constants used to initialize an array must contain a value for
every element in the array.
Examples of character type declaration statements follow.
1. The following statement specifies an array NAMES comprising one hundred 32character elements, an array SOCSEC comprising one hundred 9-character elements, and a variable NAMETY, which is 10 characters long with an initial value of
'ABCDEFGHIJ ':
CHARACTER*32NAMES<100) t SOCSECC 100)*9 t NAMET'1'*10/ 'ABCDEFGHIJ ' I

2. The following statement specifies two 8-character variables, LAST and FIRST:
PARAMETER

<LENGTH=4)

CHARACTER*C4+LENGTH>

LASTt

FIRST

(Note: The PARAMETER statement is described in Section 8.11.)
3. The following statement specifies an array LETTER comprising twenty-six 1-character elements and a dummy argument, BUBBLE, which has a passed length (it is
defined by the calling program):
SUBROUTINE S1CBUBBLE>
CHARACTER LETTER< 28) t

BUBBLE*<*)

4. The following statement is invalid; the value specified for BIGCHR is too large and

the length specifier for QUEST is not an integer constant expression:
CHARACTER* 18 BI GCHR* < 80000*28) t QUEST*< 5* I NT< A))

8.5 DIMENSION Statement
The DIMENSION statement defines the number of dimensions in an array and the number of elements in each dimension.
The DIMENSION statement has the form:
DIMENSION a(d)[,a(d)] ...

where:
a(d)

is an array declarator. (See Section 6.2.3.1.)

Specification Statements

8-9

The DIMENSION statement allocates a number of storage elements to each array named
in the statement. One storage element is assigned to each array element in each dimension,
and the length of each storage element is determined by the data type of the array. The
total number of storage elements assigned to an array is equal to the number produced by
multiplying together the number of elements in each dimension in the array declarator. For
example:
DIMENSION ARRAYUl tll), MATRl}-((5 ,5 ,5)

This statement defines ARRAY as having 16 real elements of 4 bytes each and defines
MATRIX as having 125 integer elements of 4 bytes each.
The VIRTUAL statement has the same form and effect as the DIMENSION statement.
VAX FORTRAN supports the VIRTUAL statement in order to be compatible with PDP-11
FORTRAN.
For further information on arrays and the storage of array elements, see Section 6.2.3.
You can also use array declarators in type declaration and COMMON statements. However, in each program unit, you can use an array name in only one array declarator.
Examples of DIMENSION statements are:
DIMENSION BUDC1212ll110)
DIMENSION )-((5 ,5 ,5), YCll 185), ZC 100)
DIMENSION MARKCll1ll1lltll>
SUBROUTINE APROCCA1 tA2 tNl tN2 tN3)
DIMENSION Al CN1 :NZ>, A2CN3:*>

8.6 EQUIVALENCE Statement
The EQUIVALENCE statement partially or totally associates two or more entities in the
same program unit with the same storage location.
The EQUIVALEN CE statement has the form:
EQUIVALENCE (nlist)[,(nlist)] ...

where:
nlist

is a list of variables, array elements, arrays, or character substring references, separated by commas. You must specify at least two of these entities in each list.
Each expression in a subscript or a substring reference must be an integer constant
expression. Records and record fields cannot be specified in EQUIVALENCE statements.
The EQUIVALENCE statement causes all of the entities in one parenthesized list to be
allocated storage beginning at the same storage location.

8-10

Specification Statements

You can equivalence variables of different data types. If you do, multiple components of
one data type can share storage with a single component of a higher-ranked data type. For
example, if you make an integer variable equivalent to a complex variable, the integer
variable shares storage with the real part of the complex variable.
Examples of EQUIVALENCE statements:
1. The following EQUIVALENCE statement makes the four elements of the integer
array IARR occupy the same storage as that of the double-precision variable DVAR.
DOUBLE PRECISION DVAR
INTEGER*2 IARR(a)
EQUIVALENCE (DVAR1 IARR(i))

2. The following EQUIVALEN CE statement makes the first character of the character
variables KEY and STAR share the same storage location. The character variable
STAR is equivalent to the substring KEY (1:10).
CHARACTER KEY*161 STAR*10
EQUIVALENCE (KEY1 STAR)

8.6.1 Making Arrays Equivalent
When you make an element of one array equivalent to an element of another array, the
EQUIVALEN CE statement also sets equivalences between the other elements of the two
arrays. Thus, if the first elements of two equal-sized arrays are made equivalent, both
arrays share the same storage space. If the third element of a 7-element array is made
equivalent to the first element of another array, the last five elements of the first array
overlap the first five elements of the second array.
You must not attempt to use the EQUIVALENCE statement to assign the same storage
location to two or more elements of the same array. You also must not attempt to assign
memory locations in a way that is inconsistent with the normal linear storage of array
elements. For example, you cannot make the first element of one array equivalent to the
first element of another array, and then attempt to set an equivalence between the second
element of the first array and the sixth element of the other array.
For example:
DIMENSION TABLE (212) 1 TRIPLE (21212)
EQUil,IALENCE (TABLE(212) 1 TRIPLE( 112 12))

As a result of these statements, the entire array TABLE shares part of the storage space
allocated to array TRIPLE. Figure 8-1 shows how these statements align the arrays.

Specification Statements

·8-11

Array TRIPLE
Array
Element

Element
Number

TRIPLE(l,1,1)
TRIPLE(2,l,l)
TRIPLE(l,2,1)
TRIPLE(2,2,1)
TRIPLE(l,1,2)
TRIPLE(2,1,2)
TRIPLE(l,2,2)
TRIPLE(2,2,2)

1
2
3
4
5
6
7

Array TABLE
Array
Element

TABLE(l,1)
TABLE(2,l)
TABLE(l,2)
TABLE(2,2)

Element
Number

1
2
3
4

Figure 8-1: Equivalence of Array Storage
Each of the following statements also aligns the two arrays as shown in Figure 8-1:
EQUIVALENCE <TABLE, TRIPLEC21211))
EQUIVALENCE <TRIPLE< 1t112), TABLEC2 11 > >

Similarly, you can make arrays equivalent with nonunity lower bounds. For example, an
array defined as A(2:3,4) is a sequence of eight values. A reference to A(2,2) refers to the
third element in the sequence. To make array A(2:3,4) share storage with array B(2:4,4),
you can use the following statement:
EQUil.IALENCE CAC31£1), 5(2 1£1))

The entire array A shares part of the storage space allocated to array B. Figure 8-2 shows
how these statements align the arrays.
Each of the following statements also aligns the arrays as shown in Figure 8-2:
EQUIVALENCE CA, 5(£111>>
EQUilJALENCE <BC312), AC212) >

8-12

Specification Statements

Array B

Array A

Array
Element

Element
Number

B(2,1)
B(3,1)
B(4,1)
B(2,2)
B(3,2)
B(4,2)
B(2,3)
B(3,3)
B(4,3)
B(2,4)
B(3,4)
B(4,4)

1
2
3
4
5
6

7
8
9
10
11
12

Array
Element

Element
Number

A(2,1)
A(3,1)
A(2,2)
A(3,2)
A(2,3)
A(3,3)
A(2,4)
A(3,4)

1
2
3
4
5
6

7
8

Figure 8-2: Equivalence of Arrays with Nonunity Lower Bounds
Only in the EQUIVALENCE statement can you identify an array element with a single
subscript (that is, the linear element number), even though the array was defined as a
multidimensional array. For example, the following statements align the two arrays as
shown in Figure 8-1:
DIMENSION TABLE C2 t2), TRIPLE C2 r2 r2)
EQUIVALENCE CTABLE Cll > , TR I PLE C7 > >

8.6.2 Making Substrings Equivalent
When you make one character substring equivalent to another character substring, the
EQUIVALENCE statement also sets equivalences between the other corresponding characters in the character entities.
For example:
CHARACTER NAME*lGr ID*S
EQUIVALENCE CNAMEC10:13) t

IDC2:5))

As a result of these statements, the character variables NAME and ID share space as
illustrated in Figure 8-3.

Specification Statements

8-13

The following statement also aligns the arrays as shown in Figure 8-3:
EQUIVALENCE <NAME<8:8) t ID<l:lll

If the character substring references are array elements, the EQUIVALEN CE statement
sets equivalences between the other corresponding characters in the complete arrays.

NAME
Character
Position

1
2

3
4

5
6
7

Character
Position

8
9
ZK-618-82

Figure 8-3: Equivalence of Substrings
Character elements of arrays can overlap at any character position. For example:
CHARACTER FIELDS<lOO>*at STAR(5)*5
EQUIVALENCE <FIELDS< 1 >(2:l!) t STAR<2l (3:5) >

As .a result of these statements, the character arrays FIELDS and STAR share storage
space as shown in Figure 8-4.
8-14

Specification Statements

STAR
Character
Position

Subscript

1
2

3
4

FIELDS

5
Subscript

Character
Position

1
2

3
4

1
2

~
100
2

3
4
ZK-619-82

Figure 8-4: Equivalence of Character Arrays
Specification Statements

8-15

You cannot use the EQUIVALENCE statement to assign the same storage location to two
or more substrings that start at different character positions in the same character variable
or character array.
You also cannot use the EQUIVALENCE statement to assign memory locations in a way
that is inconsistent with the normal linear storage of character variables and arrays.

8.6.3 EQUIVALENCE and COMMON Interaction
If you make variables or arrays equivalent to entities stored in a common block, the
common block can be extended beyond its original boundaries. However, you can only
extend the block beyond its last element; the extended portion cannot precede the first
element in the block. The following examples show valid and invalid extensions of the
common block:

Valid
A(l)

DIMENSION A(ll), B<G>
COMMON A
EQU I l.JALENCE <A ( 2) , B ( 1) >

A(2)

A(3)

A(4)

B(l)

B(2)

B(3)

B(4)

B(5)

B(6)

. . . ._. .__ _ _v,,,..._ __.J''-.......--.v,,,....__.J'
Existing
Common

Extended
Portion
ZK-1944-84

Invalid
DIMENSION AUl), B<G>

B(l)

COMMON A
EQU !l.'ALENCE (A ( 2) , B ( 3))

A(l)

A(2)

8(2)

B(3)

A(3)

A(4)

B(4)

B(5)

B(6)

"'-v-"
Extended Existing Common Extended
Portion
Portion
~......__

ZK-1945-84

If you assign two variables or arrays to common blocks, you cannot make them equivalent
to each other.

8. 7 EXTERNAL Statement
The EXTERNAL statement allows you to use the names of external procedures as arguments to other subprograms.
The subprograms mentioned in the EXTERNAL statement can never be FORTRAN intrinsic functions; they can only be user-supplied functions, subroutines, or block data
subprograms. The INTRINSIC statement discussed in Section 8.9 allows intrinsic function
names to be used as arguments.
The EXTERNAL statement has the form:
EXTERNAL v[,v] ...

8-16

Specification Statements

where:
v

is the symbolic name of a user-supplied subprogram or the name of a dummy argument associated with the name of a subprogram.
The EXTERNAL statement declares each symbolic name included in it to be the name of
an external procedure, even if a name is the same as that of an intrinsic function. For
example, if SIN is specified in an EXTERNAL statement (EXTERNAL SIN), all subsequent references to SIN are to a user-supplied function named SIN, not to the intrinsic
function of the same name (see Section 10.3.3).
A name specified in an EXTERNAL statement can be used as an actual argument to a
subprogram, and the subprogram can then use the corresponding dummy argument in a
function reference or a CALL statement.
You can include the name of a block data subprogram in the EXTERNAL statement in
order to force the VAX Linker to search the object module libraries for the block data
subprogram. However, the name of the subprogram must not be used in a type declaration
statement.
Note that a complete function reference used as an argument-for instance, FUNC(B) in
CALL SUBR (A, FUNC(B), C)-represents a value, not a subprogram. A complete function reference is not, therefore, defined in an EXTERNAL statement.
The interpretation of the EXTERNAL statement described herein is different from that of
earlier versions of FORTRAN produced by DIGITAL. See Appendix A for the earlier
interpretation.
See Section 8.9 for an example of EXTERNAL statements.

8.8 IMPLICIT Statement
By default, all names beginning with the letters I through N are assumed to be of integer
data type, and all names beginning with any other letter are assumed to be of REAL*4 data
type. The IMPLICIT statement overrides implied data typing of symbolic names.
The IMPLICIT statement has two forms:
{

IMPLICIT typ (a[,a] ... )[,typ(a[,a] ... )] ... }
NONE

where:
typ

is one of the data type specifiers. (See Chapter 6, Table 6-1.)
a

is an alphabetic specification in either of the general forms: c or cl-c2, where c is an
alphabetic character. The latter form specifies a range of letters, from cl through c2,
where cl precedes c2 in alphabetical order.
Specification Statements

8-17

When you specify typ as CHARACTER* len, len specifies the length for character data
type. Len is an unsigned integer constant or an integer constant expression enclosed in
parentheses and must be in the range 1 through 65535.
The IMPLICIT statement assigns the specified data type to all symbolic names that begin
with any specified letter, or any letter ih a specified range, and that have no explicit data
type declaration. For example:
IMPLICIT INTEGER CI1J1K1L1M1Nl
IMPLICIT REAL CA-Ht 0-Z)

These statements represent the default in the absence of any data type specifications.
Examples of IMPLICIT statements are:
IMPLICIT
IMPLICIT
IMPLICIT
IMPLICIT

DOUBLE PRECISION CD)
COMPLE)-( CS ,y), LOGICAL*! CL 1A-Cl
CHARACTER*32 CT-Vl
CHARACTER*2 CW)

You use an IMPLICIT NONE statement to override all implicit defaults. You must then
explicitly declare the data types of all symbolic names in the program unit. If you specify
IMPLICIT NONE, no other IMPLICIT statement can be included in the program unit.
The IMPLICIT statement has no effect on the default types of intrinsic functions.
By using the /WARNINGS= DECLARATIONS qualifier in the FORTRAN command line,
you can get the benefit ofIMPLICIT NONE (that is, be issued warnings when variables are
used but not declared) without having to use the IMPLICIT NONE statement, a VAX
FORTRAN language extension.

8.9 INTRINSIC Statement
The INTRINSIC statement allows you to use names of intrinsic functions as arguments to
subprograms. See the appendixes for the names and descriptions of the individual
FORTRAN intrinsic functions; for further information on intrinsic functions, see Chapter
10.
The INTRINSIC statement has the form:
INTRINSIC v[,v) ...

where:

v
is the symbolic name of an intrinsic function.
The INTRINSIC statement declares each symbolic name included in it to be the name of
an intrinsic procedure. This name can then be used as an actual argument to a subprogram, and the subprogram can then use the corresponding dummy argument in a function
reference or a CALL statement.

8-18

Specification Statements

An example of the use of the EXTERNAL and INTRINSIC statements follows.
Main Program

DnERNAL CTN
INTRINSIC SIN, COS

CALL TRIGCANGLEtSINtSINE>

CALL TRIGCANGLEtCOStCOSINE>

CALL TRIGCANGLEtCTNtCOTANGENT>

Subprograms
SUBROUTINE TR I G0{ , F , Y)
Y =FOO
RETURN
END
FUNCTION CTN ( }-{ >
CTN= COSOO/SINOO
RETURN
END
In the preceding example, when TRIG is called with a second argument of SIN or COS, the
function reference F(X) references the FORTRAN library functions SIN and COS; but
when TRIG is called with a second argument of CTN, F(X) references the user function
CTN.

Specification Statements

8-19

The NAMELIST statement defines a list of variables or array names and associates that
list of names with a unique group-name. The group-name is used in the namelist-directed
I/0 statement to identify the variables or arrays that are to be read or written.
The NAMELIST statement has the form:
NAMELIST /group-name/ namelist[[,] /group-name/ namelist] ...

where:
group-name

is a symbolic name.
namelist

is a list of variable or array names, separated by commas, that is to be associated with
the preceding group-name.
The namelist associates a group of entities (variables or arrays) with a single group-name,
which is used by namelist-directed I/0 statements in lieu of an I/0 list. The unique groupname identifies a list whose entities can be modified or transferred.
The namelist entities can be of any data type and can be explicitly or implicitly typed.
Array elements, character substrings, records, and record fields are not permitted in a
namelist, but you can use namelist-directed I/0 to assign values to elements of arrays or
substrings of character variables that appear in namelists.
Only the entities specified in the namelist can be read or written in name list-directed I/0.
It is not necessary for the input records in a namelist-directed input statement to define
every entity in the associated namelist.
The order of entities in the namelist controls the order in which the values are written in
the namelist-directed output. Input of namelist values can be in any order.
A variable or an array name can appear in several namelists. Dummy arguments cannot
appear in a namelist.
An example of a NAMELIST statement follows:
CHARACTER*30 NAMEC25l
NAMELIST /INPUT/ NAME1 GRADE1 DATE /OUTPUT/ TOTAL, NAME

'
In the preceding example, the NAMELiST statement defines two group-names: (1) INPUT
with the entities NAME, GRADE, and DATE and (2) OUTPUT with the entities TOTAL
and NAME.
Refer to Sections 11.4.1.3 and 11.5.1.3 for more information on namelist-directed I/O.

8-20

Specification Statements

8.11 PARAMETER Statement
The PARAMETER statement assigns a symbolic name to a constant.
The PARAMETER statement has the form:
PARAMETER (p=c[,p=c] ... )

where:
p

is a symbolic name.
c

is a constant, a compile-time constant expression, or the symbolic name of a constant.
Compile-Time Constant Expressions

A compile-time constant expression can be a compile-time logical expression, a compiletime character expression, or a compile-time arithmetic expression.
A compile-time logical expression is a logical expression in which:
• Each operand is either a constant; the symbolic name of a constant; one of the functions IAND, IOR, NOT, IEOR, ISHFT, LGE, LGT, LLE, LLT with constant
operands; or another compile-time constant expression.
• Each operand has a data type of logical or integer.
• Each operator is a Boolean or relational operator.
A compile-time character expression is a character expression in which:
• Each operand is either a constant, the symbolic name of a constant, the function
CHAR with a constant operand, or another compile-time constant expression.
• Each operand has a data type of character.
• Each operator is the concatenation operator //.
A compile-time arithmetic expression is an arithmetic expression in which:
• Each operand is either a constant; the symbolic name of a constant; one of the functions MIN, MAX, ABS, MOD, !CHAR, NINT, DIM, DPROD, CMPLX, CONJG,
!MAG with constant operands; or another compile-time constant expression.
• Each operand has a data type of integer, real, or complex.
• Each operator is a +, -, *, /, or ** operator. (The ** operator is evaluated at compile
time only if the exponent has a data type of integer.)

Specification Statements

8-21

Symbolic Names
The data type of a symbolic name defined to be a constant is determined as follows:
• By an explicit type declaration statement preceding the defining PARAMETER statement
• By the same rules for implicit declarations that determine the data type of any other
symbolic name
For example, the following PARAMETER statement is interpreted as MU=l, unless the
PARAMETER statement is preceded by an appropriate type declaration or IMPLICIT
statement, for example, REAL*8 MU:
PARAMETER (MLJ=i.23>

Once a symbolic name is defined to be a constant, it can appear anywhere in a program
that any other constant can appear-except in FORMAT statements (where constants can
only be used in variable format expressions) and as the character count for Hollerith
constants. For compilation purposes, writing the name is the same as writing the value.
The following rules govern the use of symbolic constant names:
• If the symbolic name is used as the length specifier in a CHARACTER declaration, it
must be enclosed in parentheses. If it is used as a numeric item in a FORMAT edit

description, it must be enclosed in angle brackets.
• The symbolic name of a constant cannot appear as part of another constant,
it can appear as either the real or imaginary part of a complex constant.
• A symbolic name defined to be a constant can be used only within the program unit
containing the defining PARAMETER statement. Also, a symbolic name can be defined only once within the same program unit.
The form and the interpretation of the PARAMETER statement described herein are
different from those of the PARAMETER statement provided in earlier versions of
FORTRAN produced by DIGITAL. However, VAX FORTRAN provides support for both
the FORTRAN-77 and the earlier form of the PARAMETER statement; see Appendix A
for information on the earlier form and interpretation.
The following sequence of statements demonstrates the use of the FORTRAN-77 P ARAMETER statement:
REAL*4 PI , PI 01.12
REAL*B DPI, DPIOl.12
LOGICAL FLAG
CHARACTER*(*) LONGNAME
PARAMETER (PI=3.1415827r DPI=3.141582653588783238DO>
PARAMETER (PIOV2=PI/2r DPIOV2=DPI/2)
PARAMETER (FLAG=.TRUE., LONGNAME='A STRING OF 25 CHARACTERS')

8-22

Specification Statements

8.12 PROGRAM Statement
The PROGRAM statement assigns a symbolic name to a main program unit.
The PROGRAM statement has the form:
PROGRAM nam

where:
nam

is the symbolic name of a source file.
The PROGRAM statement is optional. The default name for a main program unit is
filename$MAIN, where filename is the name of your source file. If filename is larger than
26 characters and a name is not specified in a PROGRAM or BLOCK DATA statement,
the name is truncated to 26 characters and $MAIN is appended to form the program name.
If you use the PROGRAM statement, it must be the first statement in the main program;

however, it is the second statement in a main program that begins with an OPTIONS
statement. The symbolic name must not be the name of any entity within the main
program; it also must not be the same as the name of any subprogram, entry, or common
block in the same executable program.

The RECORD statement creates a record of the form specified in a previously declared
structure.
The effect of a RECORD statement is comparable to that of an ordinary FORTRAN type
declaration except that composite, or aggregate, data items are declared instead of scalar
data items.
The format of a RECORD statement is as follows:
RECORD /structure-name/record-namelist
[,/structure-name/record-namelist]

[,/structure-name/record-namelist]

where:
structure;.name

is the name of a previously declared structure. See Section 8.15.1 for a description of
structure declarations.

Specification Statements

8-23

record-name list

is a list of one or more variable names, array names, or array declarators, separated by
commas. All of the records named in this list have the same structure and are allocated separately in memory.
Record names can be used in COMMON and DIMENSION statements. They cannot be
used in DATA, EQUIVALENCE, NAMELIST, or SAVE statements.
Records initially have undefined values unless you have defined their values in structure
declarations.

E1camples
The following RECORD statement creates a pair of records with the form of structure
declaration DATE:
RECORD/DATE/ TODAY1YESTERDAY

The preceding example creates the variables TODAY and YESTERDAY-each with the
same structure-in separate areas of memory.
The following RECORD statement creates a record and an array of records with the
structure CHECK.
RECORD /CHECK/ CURRENT_CHECK1 CHECKBOOKl1000)

8.14 SAVE Statement
The SAVE statement causes the definition of data entities to be retained after execution of
a RETURN or END statement in a subprogram.
The SAVE statement has the form:
SAVE [a[,a] ... ]

where:
a

is one of the following entities: a common block name (preceded and followed by a
slash), a variable name, or an array name.

An entity specified by a SAVE statement within a program unit does not become undefined
upon execution of a RETURN or END statement in that program unit. If the entity is in a
common block, however, it may become undefined (or redefined) in another program unit.
Procedure names, blank common blocks, names of entities in a common block, and names
of dummy arguments cannot be used in a SAVE statement.
A SAVE statement that does not explicitly contain a list is treated as though it contained a
list of all allowable items in the program unit that contains the SAVE statement.

8-24

Specification Statements

NOTE
It is not necessary to use SA VE statements in VAX FORTRAN programs. The
definitions of data entities are retained automatically by VAX FORTRAN, making the use of SAVE statements a redundant exercise. However, its use is required by the ANSI FORTRAN Standard for programs that depend on such
retention for their correct operation. If you want your programs to be transportable, you should include SA VE statements where your programs would otherwise require them. Note that the omission of SAVE statements in necessary
instances is not flagged, even when you specify the /STANDARD qualifier on
your FORTRAN command, because the compiler has no way to determine
whether such dependencies exist.

The structure, or form, of a record is defined by a multistatement declaration. This declaration is composed of the following elements:
o STRUCTURE statement: This statement indicates the beginning of a structure decla-

ration.
o Declaration body: The body of a structure declaration is composed of one or more field

declarations. The order of the declarations determines the order of the fields within a
structure.
o END STRUCTURE statement: This statement indicates the end of a structure decla-

ration.
Field declarations within structure declarations consist of the following:
1. Typed data declaration statements. Ordinary FORTRAN type declaration; see Sec-

tion 8.4. Fields can be any data type and can be dimensioned in the normal way.
2. Substructure declarations. A field within a structure can be a substructure composed
of atomic fields and/or other substructures. There are two ways to declare substructures:
-

RECORD statements specifying names of other, previously declared, structure
declarations to be incorporated as substructures; see Section 8.13.

Other, nested structure declarations, that is, one or more levels of structure declarations contained within a structure declaration.

3. Union declarations. A union declaration declares groups of fields that logically share
a common location within a structure. Each group of fields within a union declaration is declared by a map declaration, with one or more fields per map declaration.
You use union declarations when you want to use the same area of memory to
alternately contain two or more groups of fields. Whenever one of the fields declared
by a union declaration is referenced in your program, that field and any other fields

Specification Statements

8-25

in its map declaration become defined. Then, when a field in one of the other map
declarations in the union declaration is referenced, the fields in that map declaration
become defined, superseding the fields that were previously defined.
4. PARAMETER statements. A structure declaration block containing a
PARAMETER statement has no effect on the meaning of the PARAMETER statement declaration. (Note: Because the PARAMETER statement is not conceptually
related to the topic of structure declarations, its inclusion in a structure declaration
block is not noted elsewhere in this section.)
The names specified in these statements are not the names of variables and the statements
in a structure declaration do not create variables. The names are field names, and the
information provided in the statements describes the layout, or form, of the structure. The
ordering of both the statements and the field names within the statements is important
because this ordering determines the order of the fields in records.
Sections 8.15.1 through 8.15.3 describe structure declarations, substructure declarations,
and union declarations.

A VAX FORTRAN record comprises one or more fields. The field(s) within a VAX
FORTRAN record are defined by means of a structure declaration. This declaration defines
the field names, the types of data within fields, and the order and alignment of fields
within a record.
Unlike type declaration statements, structure declarations do not create variables. Structured variables (referred to as "records") are created when you use a RECORD statement
containing the name of a previously declared structure. The RECORD statement can be
considered as a kind of type statement. The difference is that aggregate items, rather than
single items, are being defined.
The form of a structure declaration is as follows:
STRUCTURE [/structure-name/][field-namelist]
field-declaration
[field-declaration]

[field-declaration]
END STRUCTURE

where:
structure-name

The name used to identify a structure. A structure name is enclosed by slashes. If the
slashes are present, a name must be specified between them.
The structure name is used in subsequent RECORD statements to refer to a structure.
8-26

Specification Statements

Structure declarations can be nested; that is, a structure declaration can contain one
or more other structure declarations. A structure name is required on the structured
declaration at the outermost level of nesting. A structure name is optional for nested
declarations. A nested structure declaration requires a name only when you wish to
reference it elsewhere in your program in a RECORD statement.
A structure name must be unique among structure names. However, structure names
can also be used to name either variables (simple or array) or fields. Thus, it is
possible to have a variable named X, a structure named X, and one or more fields
named X.
Structure, field, and variable names are all local to the defining program unit. When
records are passed as arguments, the fields must match in type, order, and dimension.
field-namelist

A list of fields having the structure of the associated structure declaration. A field
namelist is allowed only in nested structure declarations. Nested structure declarations are described in Section 8.15.2.
field-declaration

Field declarations can consist of any combination of the following types of declarations:
Substructure declarations
Union declarations
Typed data declarations
These declarations are described under the headings that follow.

Substructure declaration
A field within a structure can be a substructure composed of atomic fields and/or other
substructures. See Section 8.15.2 for a description of substructure declarations.

Union declaration
A union declaration is composed of one or more mapped field declarations. The mapped
fields logically share a common location within a structure. See Section 8.15.3 for a more
complete description of union declarations.

Typed data declaration
The syntax of a typed data declaration within a record structure is identical to that of a
normal FORTRAN type statement; that is, it includes a type (for example, INTEGER),
one or more names of variables or arrays, and, optionally, one or more data initialization
values.

Specification Statements

8-27

The following rules apply to typed data declarations in record structures:
o The pseudo-name %FILL can be specified in place of a field name to create empty

space in a record for purposes such as alignment. This creates an unnamed field.
o Initial values can be supplied in the field declaration statements. These initial values

are supplied for all records that are declared using this structure. Fields not initialized
will have undefined values when variables are declared by means of RECORD statements. Unnamed fields cannot be initialized; they are always undefined. See Sections
8.4.1and8.4.2 for detailed descriptions of numeric and character typed declarations.
0

All field names must be explicitly typed and there are no default names. The
IMPLICIT statement has no effect on statements within a structure declaration.

All VAX FORTRAN data types are allowed in the data declarations.

Any required array dimensions must be specified in the field declaration statements;
DIMENSION statements cannot be used to define field names.

Adjustable or assumed sized arrays and passed length CHARACTER declarations are
not allowed in field declarations.

° Field names within the same declaration level must be unique, but an inner structure
declaration (substructure declaration) can include field names used in an outer structure declaration without conflict.
In a structure declaration, each field offset is the sum of the lengths of the previous fields;
the length of the structure therefore is the sum of the lengths of its fields. The structure is
packed; you must explicitly provide any alignment that is needed by including, for example, unnamed fields of the appropriate length.

l;m1mplns
The following examples illustrate the use and form of structure declarations:
1. The structure named DATE is defined by the following declaration:
STRUCTURE /DATE/
LDGICAL*1 DAYt MONTH
INTEGER*2 YEAR
END STRUCTURE

This structure contains three scalar fields:
(LOGICAL*l), and YEAR (INTEGER*2).

DAY (LOGICAL*l), MONTH

The following diagram shows the memory mapping of any record or record array
element with the structure DATE.

8-28

Specification Statements

? + 0

field DAY

? + 1

field MONTH

? + 2

i------i}

field YEAR

? + 4
ZK-1849-84

2. The structure named APPOINTMENT is defined by the following declaration:
STRUCTURE /APPOINTMENT/
RECORD /DATE/
APP_DATE
STRUCTURE /TIME/ APP_TIME (2)
LOGICAL*!
HOUR1 MINUTE
END STRUCTURE
APP_MEMO (l!)
CHARACTER*20
APP_FLAG
LOGICAL*!
END STRUCTURE

APPOINTMENT contains the structure DATE (field APP _DATE) as a substructure. It also contains a substructure named TIME (field APP _TIME, an array), a
CHARACTER*20 array named APP _MEMO, and a LOGICAL*l variable named
APP _FLAG. (Note: The use of substructures is described in the Section 8.15.2.)
The length of any instance of structure APPOINTMENT is 89 bytes. The following
diagram shows the memory mapping of any record or record array element with the
structure APPOINTMENT.

Specification Statements

8-29

? + 0

field DAY of field APP _DATE

? + 1

field MONTH of field APP _DATE

? + 2

}

field YEAR of field APP _DATE

? + 3

? +4

field HOUR of field APP_TIME(1}

? + 5

field MINUTE of field APP_TIME(1}

? +6

field HOUR of field APP_TIME(2}

? +7

field MINUTE of field APP_TIME(2}

? + 8

field APP _MEM0(1}
0
0
0

field APP _MEM0(2}

?+28
0
0
0

field APP_MEM0(3}

?+48
0
0
0

field APP_MEM0(4}

?+68
0
0
0

?+88

field APP _FLAG

?+89
ZK-1848-84

8-30

Specification Statements

o.·u 5.2 ~~~~:mUrn~fL~wa [!]c~~ornU~mm
A field within a stru~ture can itself be a structured item composed of atomic fields and/or
other structured items. There are two ways of declaring substructures:
o

Nested structure declaration:
A structure declaration contained within either a structure declaration or a union
declaration. For obvious reasons, a structure cannot, at any level of nesting, include
itself as a substructure in structure or union declarations.
One or more field names must be defined in the STRUCTURE statement for the
substructure because all fields in a structure must be named and, in this case, a
structure-the substructure-is being used as a field within a structure or union.
Field names within the same declaration nesting level must be unique, but an inner
structure declaration can include field names used in an outer structure declaration
without conflict.
The pseudo-name %FILL can be specified in place of a field name to create empty
space in a record for purposes such as alignment.

o RECORD statement declaration:

A RECORD statement specifying another, previously defined, record structure to be
included in the structure being declared.
See the second example in the preceding section for a sample structure declaration containing both a nested structure declaration (TIME) and an included structure (DATE).

A union declaration is a multistatement declaration defining a data area that can be shared
intermittently during program execution by one or more fields or groups of fields.
A union declaration is initiated by a UNION statement and terminated by an END
UNION statement. Enclosed within these statements are two or more map declarations,
initiated and terminated by MAP and END MAP statements, respectively. Each unique
field or group of fields is defined by a separate map declaration.
The form of a union declaration is as follows:
UNION
map-declaration
map-declaration
[map-declaration]

[map-declaration]
END UNION

Specification Statements

8-31

where map-declaration is:
MAP
field-declaration
[field-declaration]

[field-declaration]
END MAP

where:
field-declaration

is a structure declaration or RECORD statement contained within a union declaration, a union declaration contained within a union declaration, or the declaration of a
typed data field within a union. See Section 8.15.1 for a more detailed description of
what can be specified in field declarations.
As with normal FORTRAN type declarations, data can be initialized in field declaration
statements in union declarations. Note, however, that if fields within multiple map declarations in a single union are initialized, the data declarations are initialized in the order in
which the statements appear. As a result, only the final initialization takes effect and all of
the preceding initializations are overwritten.
The size of the shared area established for a union declaration is the size of the largest map
defined for that union. The size of a map is the sum of the sizes of the field(s) declared
within it.
As the variables or arrays declared in map fields in a union declaration are assigned values
during program execution, the values are established in a record in the field shared with
other map fields in the union. The fields of only one of the map declarations is defined
within a union at any given point in the execution of a program. Note, however, if you
overlay one variable with another variable that is smaller, that portion of the initial variable that is not overlaid is retained. Depending on the application, the retained portion of an
overlaid variable may or may not contain meaningful data and be utilized at a later point
in the program.
Manipulating data using union declarations is similar to what happens using
EQUIVALENCE statements. The difference is that data entities specified within EQUIVALENCE statements are concurrently associated with a common storage location and the
data residing there; whereas, union declarations enable you to use one discrete storage
location to alternately contain a variety of fields (arrays or variables). With union declarations, only one map declaration within a union declaration can be associated at any point
in time with the storage location that they share. Whenever a field within another map
declaration-in the same union declaration-is referenced in your program, the fields in
the prior map declaration become undefined and are succeeded by the fields in the map
declaration containing the newly referenced field.

8-32

Specification Statements

Em1mples
In the following example, the structure WORDS_LONG is defined. This structure contains a union declaration defining two map fields. The first map field consists of three
INTEGER*2 variables (WORD_O, WORD_l, and WORD-2), and the second, an
INTEGER*4 variable, LONG.
STRUCTURE /WORDS_LONG/
UNION
MAP
INTEGER*2
END MAP
MAP
INTEGER*a
END MAP
END UNION
END STRUCTURE

WORD_Ot WORD_l t WORD_2
LONG

The length of any record with the structure WORDS_LONG is six bytes. The following
diagram shows the memory mapping of any record with the structure WORDS_LONG:

? + 0

{

Variable LONG
I

? +4

Unused space

? + 6

ZK-1846-84

Specification Statements

8-33

The VOLATILE statement prevents all optimization operations from being performed on
the variables, arrays, or common blocks that it identifies. As a result, for example, a
variable that is declared but never referenced will still be retained if it has been declared as
volatile.
VOLATILE nlist

nlist

is a list of one or more variable names, common block names, or array names, separated by commas.
If array names or common block names are used, the entire array or common block be-

comes volatile.
For example:
PROGRAM TEST
LOGICAL*1 IPICll)
INTEGER*ll A1B1C1D1E1ILOOK
INTEGER*ll Pi 1P2 ,p3 ,p4
COMMON /BLK1/A1B1C

t.JOLATILE /BLK1/ 1D 1E
EOU Il.'ALENCE (I LOOK tI PI)
EOLJil.IALENCE CA 1P1)
EOU I l.JALENCE ( P 1 , Pl!)

In this example, the named common block, BLKl, and the variables D, and E are volatile.
In addition, variables Pl and P4 ~ecome volatile; a direct equivalence (as in the case of Pl)
or indirect equivalence (as in the case of P4) causes the equivalenced variables to assume a
volatile attribute.
See the VAX FORTRAN User's Guide for information about the optimizations performed
by the VAX FORTRAN compiler and the circumstances in which you should use the
VOLATILE declaration.

8-34

Specification Statements

Chapter 9

Control Statements
Statements are normally executed in the order in which they are written. However, you can
interfere with normal program flow by transferring control to another section of the program unit or to a subprogram. The transfer of control can be conditi9nal or unconditional;
that is, it can occur as a result of specified conditions being met at a certain point in the
program unit or it can occur unconditionally each time a certain point is reached.
You use the FORTRAN control statements to transfer control to a point within the same
program unit or to another program unit. These statements also govern iterative processing, suspension of program execution, and program termination.
The control statements and their effects are as follows:
• CALL statement-invoke a subroutine subprogram
• CONTINUE statement-transfer control to the next executable statement
• DO and DO WHILE statements-execute a block of statements .repetitively
• END statement-mark the end of a program unit
o END DO statement-terminate DO and DO WHILE loops

• GO TO statement-transfer control within a program unit
• IF statement-transfer control or execute a statement (conditional)
• IF THEN, ELSE IF THEN, ELSE, and END IF statements-execute a block of
statements (conditional)
• PAUSE statement-temporarily suspend program execution
• RETURN statement-return control from a subprogram to the calling program unit
• STOP statement-terminate program execution
The following sections describe these statements, in alphabetical order, giving their forms
as well as examples of how they are used.

9-1

9.1 CALL Statement
The CALL statement executes a subroutine subprogram or other external procedure. It can
also specify an argument list for the subroutine. (See Chapter 10 for greater detail on the
definition and use of subroutines.)
The CALL statement has the form:
CALL sub[([a][,[a]) ... ))

)

where:
sub

is the name of either (1) a subroutine subprogram or other external procedure or (2) a
dummy argument associated with a subroutine subprogram or other external procedure.
a

is an actual argument. (Section 10.1 describes actual arguments.)
If you specify an argument list, the CALL statement associates the values in the list with
the dummy arguments in the subroutine. It then transfers control to the first executable
statement following the SUBROUTINE or ENTRY statement referenced by the CALL
statement.

The arguments in the CALL statement must agree in number, order, and data type with
the dummy arguments in the subroutine. They can be variables, arrays, array elements,
records, record elements, record arrays, record array elements, substring references, constants, expressions, Hollerith constants, alternate return specifiers, or subprogram names.
An unsubscripted array name or record array name in the argument list refers to the entire
array.
Examples of CALL statements are:
CALL CURVECBASE13.1a158+X1Y1LIMIT1RCLT+2))
CALL PNTOUTCA1N1'ABCD'>
CALL D{IT
RECORD /GETJPI/ GETJPIARG

CALL SYS$GET JPI C,, tGET JPIARG,,,)
CALL MULTIA1B1*101*201C)

The last example illustrates the use of statement label identifiers in CALL statement
argument lists. The asterisks in the last CALL statement indicate that *10 and *20 are
statement label identifiers. Label identifiers that are prefixed by asterisks (or ampersands
(&)) are called alternate return specifiers (see Section 10.1.1.5).
9-2

Control Statements

9.2 CONTINUE Statement
The CONTINUE statement transfers control to the next executable statement. It is used
primarily as the terminal statement of a labeled DO loop when that loop would otherwise
end improperly, that is, with either a GO TO, arithmetic IF, or any other prohibited control
statement.
The CONTINUE statement has the form:
CONTINUE

9.3 DO Statement
The two types of DO statements are:
• Indexed DO (DO)
o Pretested indefinite DO (DO WHILE)

DO is discussed in Section 9.3.1 and DO WHILE in,Section 9.3.2.

9.3.1 Indexed DO Statement
The indexed DO statement controls iterative processing; that is, the statements in its range
are repeatedly executed a specified number of times.
The DO statement has the form:
DO s[,] v=e1 ,e2[,e3]

where:
s

is the label of an executable statement. The statement must physically follow in the
same program unit. VAX FORTRAN allows the label to be omitted.
v

is a variable with an integer or real data type.
e1 ,e2,e3

are arithmetic expressions,
The variable vis the control variable; el, e2, and e3 are the initial, terminal, and increment
parameters, respectively. If you omit the increment parameter, a default increment value
of 1 is used.

Control Statements

9-3

The optional label that appears in the DO statement identifies the terminal statement of
the DO loop. If no label appears in the DO statement, the DO loop must be terminated by
the END DO statement as discussed in Section 9.4. The terminal statement must not be
one of the following statements:
• Unconditional or assigned GO TO statement
• Arithmetic IF statement
• Any block IF statement
• END statement
• RETURN statement
• .DO statement
The range of the DO statement includes all the statements that follow the DO statement,
up to and including the terminal statement or END DO.
·
The DO statement first evaluates the expressions el, e2, and e3 to determine values for the
initial, terminal, and increment parameters, respectively. The increment parameter (e3)
cannot be zero.
The value of the initial parameter is assigned to the control variable. If the data type of the
initial, terminal, and increment parameters are not the same as the data type of the control
variable, they are converted before they are used.
The number of executions of the DO range, called the iteration count, is given by:
[(e2 - el + e3)/e3]
where the notation [X] represents the largest integer whose magnitude does not exceed the
magnitude of X and whose sign is the same as the sign of X.
If the iteration count is zero or negative, the body of the loop is not executed.
If the /NOF77 qualifier is specified on the FORTRAN command and the iteration count is

zero or negative, the body of the loop is executed once.

9.3.1.1 DO Iteration Control
After each iteration of the DO range, the following steps are executed:
1. The value of the increment parameter (e3) is algebraically added to the control
variable.

2. The iteration count (el) is decremented.
3. If the iteration count is greater than zero, control transfers to the first executable
statement after the DO statement for another iteration of the range.
4. If the iteration count is zero, execution of the DO statement terminates. The final
value of the control variable is the value determined by step 1.

9-4

Control Statements

Note that if the data type of the control variable is real, the number of iterations of the DO
range, because of rounding errors, might not be what is expected.
You can also terminate execution of a DO statement by using a statement within the range
that transfers control outside the loop. The control variable of the DO statement remains
defined with its current value.
When execution of a DO loop terminates and other DO loops share its terminal statement,
control transfers outward to the next most enclosing DO loop in the DO nesting structure
(see Section 9.3.1.2). If no other DO loop shares the terminal statement or if the DO
statement is outermost, control transfers to the first executable statement after the terminal statement.
You cannot alter the value of the control variable within the range of the DO statement.
However, you can use the control variable for reference as a variable within the range.
You can modify the initial, terminal, and increment parameters within the loop without
affecting the iteration count.
·
The range of a DO statement can contain other DO statements, as long as these nested DO
loops meet certain requirements. Section 9.3.1.2 describes these requirements.
You can transfer control out of a DO loop, but not into a loop from elsewhere in the
program. Exceptions to this rule are described in Sections 9.3.1.3 and 9.3.1.4.
Examples of DO iteration control follow.
1. The following statement specifies 25 iterations; K=49 during the final iteration,
K=51 after the loop.
DO 100 K=i 15012

2. The following statement specifies 27 iterations; J=-2 during the final iteration, J=-4
after the loop.
DO 350 J=501-21-2

3. The following statement specifies 5 iterations; IVAR=5 during the final iteration,
IVAR=6 after the loop.
DO 25 ll,JAR=1 ,5

4. The following statement specifies 9 iterations; NUMBER=37 during the final iteration, NUMBER=41 after the loop. The terminating statement of the DO loop must
be END DO.
DO NUMBER=51l!01ll

The following example illustrates how a common typing error can cause errors with DO
loops; a decimal point is typed in place of a comma.
DO l!O M=2,10

Control Statements

9-5

9.3.1.2 Nested DO Loops
A DO loop can contain one or more complete DO loops. The range of an inner nested DO
loop must lie completely within the range of the next outer loop. Nested loops can share a
labeled terminal statement but not an unlabeled END DO statement.
Figure 9-1 illustrates nested loops.
Correctly Nested

Incorrectly Nested

DOll5K=1t10

D015K=1t10

DO 35 L=2 t50 t2

DO 25 L=1 t20

CONTINUE

DO as M= 1 t20

CONTINUE

Correctly Nested
DO Loops

CONTINUE

DO 30 M= 1 t5

CONTINUE

Incorrectly Nested
DO Loops

DO 10 I=1 t20

DO 10 I=1 t5

DOJ=1t5

DOJ=1t10

CONTINUE

END DO

CONTINUE

Figure 9-1: Nested DO Loops

9-6

Control Statements

9.3.1.3 Control Transfers in DO Loops
In a nested DO loop, you can transfer control from an inner loop to an outer loop. However,
a transfer into a loop from outside that loop is not permitted.
If two or more nested DO loops share the same terminal statement, you can transfer control

to that statement only from within the range of the innermost loop. Any other transfer to
that statement constitutes a transfer from an outer loop to an inner loop because the shared
statement is part of the range of the innermost loop.

9.3.1.4 EJdended Range
A DO loop has an extended range if it contains a control statement that transfers control
out of the loop and if, after execution of one or more statements, another control statement
returns control back into the loop. Thus, the range of the loop is extended to include all
executable statements between the destination statement of the first transfer and the
statement that returns control to the loop.
The following rules govern the use of a DO statement extended range:
1. A transfer into the range of a DO statement is permitted only if the transfer is made
from the extended range of that DO statement.

2. The extended range of a DO statement must not change the control variable of the
DO statement.
Figure 9-2 illustrates valid and invalid extended range control transfers.

Control Statements

9-7

Valid
Control Transfers

Invalid
Control Transfers

35 K=l tlO

GO TO 20

15 L=2 t20

D050K=1t10

GO TO 20

CONTINUE

A = 5 + C

D = E/F

CONTINUE

35M=1t15

DO 35 L=2 t20

GO TO ao

GO TO 50

A = 5 + C

)-( = A

CONTINUE

'"' = A * o

D = E/F

ll5

CONTINUE

GO TO 30

CONTINUE

DOll5M=1t15

Loop

Extended
Ranae

GO TO 30

Figure 9-2: Control Transfers and Extended Range

9-8

Control Statements

9.3.2 [D)«Jl um-m.. !E SRaiemen~
The DO WHILE statement is similar to the DO statement discussed in the preceding
section. The difference between them is as follows:
0

The DO WHILE statement executes for as long as a logical expression contained in the
statement continues to be true.

The DO statement executes for a fixed number of iterations.

The DO WHILE statement has the form:
DO [s[,]] WHILE (e)

where:
s

is the label of an executable statement that must physically follow in the same
program unit.
e
is a logical expression.
The DO WHILE statement tests the logical expression at the beginning of each execution
of the loop, including the first. If the value of the expression is true, the statements in the
body of the loop are executed; if the expression is false, control transfers to the statement
following the loop.

If no label appears in a DO WHILE statement, the DO WHILE loop must be terminated ·
with an END DO statement (see Section 9.4).
The following example demonstrates the use of the DO WHILE statement:
CHARACTER*132 LINE
I

= 1

LINE< 132: > = 'x'
DD WHILE <LINE<I:I>
I

= I

.Eo.

+ 1

END DO

You can transfer control out of a DO WHILE loop but not into a loop from elsewhere in the
program.

The END DO statement terminates the range of a DO or DO WHILE statement. The END
DO statement must be used to terminate a DO block, if the DO or DO WHILE statement
defining the block does not contain a terminal-statement label. The END DO statement
may also be used as a labeled terminal statement if the DO or DO WHILE statement does
contain a terminal-statement label.

Control Statements

9-9

The END DO statement has the form:
END DO

Examples of the use of the END DO statement are:
DD WHILE CI .GT. J)
ARRAYCI 1J) = 1.0
I = I - 1
END DD

DD 10 WHILE CI
ARRAYCI1J)
I = I - 1
END DO

• GT,

= 1. 0

9.5 END Statement
The END statement marks the end of a program unit. It must be the last source line of
every program unit.
The END statement has the form:
END

In a main program, if control reaches the END statement, program execution terminates.
In a subprogram, a RETURN statement is implicitly executed.
If an initial line contains END in the statement field, and nothing else, it is treated as an
END statement even if there are continuation lines that follow.

9.6 GO TO Statements
GO TO statements transfer control within a program unit. Depending on the value of an
expression, control is transferred either to the same statement every time GO TO is executed or to one of a set of statements.
The three types of GO TO statement are:
• Unconditional GO TO
• Computed GO TO
• Assigned GO TO

9.6.1 Unconditional GO TO Statement
The unconditional GO TO statement transfers control to the same statement every time it
is executed.

9-10

Control Statements

The unconditional GO TO statement has the form:
GO TO s

where:
s

is the label of an executable statement that is in the same program unit as the GO TO
statement.
The unconditional GO TO statement transfers control to the statement identified by the
specified label. The label must identify an executable statement that is in the same program unit as the GO TO statement.
Examples of unconditional GO TO statements are:
GO

TD 773£1

TD 88888

9.6.2 Computed GO TO Statement
The computed GO TO statement transfers control to a statement based on the value of an
expression within the statement.
The computed GO TO statement has the form:
GO TO (slist)[,] e

where:
slist

is a list of one or more labels of executable statements separated by commas. The list
of labels is called the transfer list.
e

is an arithmetic expression in the range 1 to n (where n is the number of statement
labels in the transfer list).
The computed GO TO statement evaluates the expression e and, if necessary, converts the
resulting value to integer data type. Control is transferred to the statement label in position
e in the transfer list. For example, if the list contains (30,20,30,40), and the value of e is 2,
control is transferred to statement 20.
If the value of e is less than 1 or greater than the number of labels in the transfer list,

control is transferred to the first executable statement after the computed GO TO.
Examples of computed GO TO statements are:
GO

C12 12£1138),

C320133013li0135013GO>,

!NOD(
SITUCJ1K>

+ 1

Control Statements

9-11

9.6.3 Assigned GO TO Statement
The assigned GO TO statement transfers control to a statement label that is represented
by a variable. An ASSIGN statement must establish the relationship between the variable
and a specific statement label. Thus, the transfer destination can be changed, depending
on the most recently executed ASSIGN statement.
The assigned GO TO statement has the form:
GO TO v[[,](slist)]

where:
v

is an integer variable.
slist

is a list of one or more labels of executable statements separated by commas; slist
does not affect statement execution and can be omitted.
The assigned GO TO statement transfers control to the statement whose label was most
recently assigned to the variable v. The variable v must be of integer data type and must
have a statement label value assigned to it by an ASSIGN statement (not an arithmetic
assignment statement) before the GO TO statement is executed.
The assigned GO TO statement and its associated ASSIGN statement(s) must exist in the
same program unit. Also, statements to which control is transferred must be in this same
program unit and must be executable statements.
Examples of assigned GO TO statements are:
ASSIGN 200 TO IGO
GO TO IGO

This is equivalent to GO TO 200.
ASSIGN 450 TO !BEG
GO TO IBEG1 (300145011000125)

This is equivalent to GO TO 450.

9. 7 IF Statements
IF statements conditionally transfer control or conditionally execute a statement or block
of statements. The three types of IF statement are:
• Arithmetic IF
• Logical IF
•Block IF (IF THEN, ELSE IF THEN, ELSE, END IF)

9-12

Control Statements

For each type, the decision to transfer control or to execute the statement or block of
statements is based on the evaluation of an expression within the IF statement.

9. 7.1 Arithmetic IF Statement
The arithmetic IF statement conditionally transfers control to one of three statements,
based on the current value of an arithmetic expression.
The arithmetic IF statement has the form:
IF (e) s1 ,s2,s3

where:
e

is an arithmetic expression.
s1 ,s2,s3
are labels of executable statements in the same program unit.

All three labels (sl,s2,s3) are required; however, they need not refer to three different
statements.
The arithmetic IF statement first evaluates the expression e. It then transfers control to one
of the three statement labels in the transfer list, as follows:
If the value is:

Control passes to:

Less than 0
Equal to 0
Greater than 0

Label sl
Label s2
Label s3

Examples of arithmetic IF statements follow.
IF <THETA-CHI> 50t50t100

This statement transfers control to statement 50 if the real variable THETA is less than or
equal to the real variable CHI. Control passes to statement 100 only if THETA is greater
than CHI.
IF CNUMBER/2*2-NUMBER> 20taOt20

This statement transfers control to statement 40 if the value of the integer variable NUMBER is even; it transfers control to statement 20 if the value is odd.

9. 7.2 Logical IF Statement
A logical IF statement conditionally executes a single FORTRAN statement, based on the
current value of a logical expression within the logical IF statement.

Control Statements

9-13

The logical IF statement has the form:
IF (e) st

where:
e

is a logical expression.
st

is a complete FORTRAN statement. The statement can be any executable statement
except a DO statement, an END DO statement, an END statement, a block IF
statement, or another logical IF statement.
The logical IF statement first evaluates the logical expression e. If the value of the expression is true, the statement st is executed. If the value of the expression is false, control
transfers to the next executable statement after the logical IF, and the statement st is not
executed.
Examples of logical IF statements are:
IF

(J,GT.ll

.OR,

(REF(J1K)

(ENDRLJN)

J,LT.1>

.NE.

HOLD)

GO TO 250
REF(J1K)

= REF(J1K) * (-1.500)

CALL EXIT

9. 7.3 Block IF Statements
Block IF statements conditionally execute blocks, or groups, of statements.
The four block IF statements are:
•IF THEN
• ELSE IF THEN
•ELSE
•END IF

9-14

Control Statements

These statements are used in block IF constructs. The block IF construct has the form:
IF (e) THEN

block

ELSE IF (e1) THEN
block

ELSE
block
END IF

where:
e

is a logical expression.
block

is a sequence of zero or more complete FORTRAN statements. This sequence is called
a statement block.
Figure 9-3 shows the flow of control for four examples of block IF constructs.
Each block IF statement, except the END IF statement, has an associated statement
block. The statement block consists of all the statements following the block IF statement
up to, but not including, the next block IF statement in the block IF construct. The
statement block is conditionally executed based on the value(s) of the logical expression(s)
in the preceding block IF statements.
The IF THEN statement begins a block IF construct. The block following it is executed if
the value of the logical expression in the IF THEN statement is true.
The ELSE IF THEN statement is an optional statement that specifies a statement block to
be executed if no preceding statement block in the block IF construct has been executed,
and if the value of the logical expression in the ELSE IF THEN statement is true. A block
IF construct can contain any number of ELSE IF THEN statements.
The ELSE statement specifies a statement block to be executed if no preceding statement
block in the block IF construct has been executed. The ELSE statement is optional.
However, if the ELSE statement is present, the ELSE statement block must be immediately followed by the END IF statement.
The END IF statement terminates the block IF construct.

Control Statements

9-15

Construct

Flow of Control

IF (e) THEN
block
END IF

IF (e) THEN
block1
ELSE
block2
ENDIF

IF (e,) THEN
block 1
ELSE IF (e2) THEN
block2
ENDIF

IF (e,) THEN
block1
ELSE IF (e2) THEN
block2
ELSE IF (e3) THEN
block3
ELSE
block4
ENDIF

False

Execute
block 4

ZK-617-82

Figure 9-3: Examples of Block IF Constructs

9-16

Control Statements

After the last statement in a statement block is executed, control passes to the next
executable statement following the END IF statement. Consequently, no more than one
statement block in a block IF construct is executed each time that the IF THEN statement
is executed.
ELSE IF THEN and ELSE statements can have statement labels, but the labels cannot be
referenced. The END IF statement can have a statement label to which control can be
transferred, but only from within the immediately preceding block.
Section 9.7.3.1 describes restrictions on statements in a statement block. Section 9.7.3.2
describes examples of block IF constructs. Section 9.7.3.3 describes nested block IF constructs.

9.7.3.1 Statement Blocks
A statement block can contain any executable FORTRAN statement except an END
statement. You can transfer control out of a statement block, but you must not transfer
controi into a block. Thus, you must not transfer control from one statement block to
another.
DO loops cannot partially overlap statement blocks. When a statement block contains a
DO statement, it must also contain the DO loop's terminal statement, and vice versa.

9.7.3.2 Block IF Examples
The following examples illustrate four variations of block IF constructs.
1. The simplest block IF construct consists of the IF THEN and END IF statements;
this construct conditionally executes one statement block. For example:

Form

Example

IF (e) THEN
block

TOTERR = TDTERR + ABS ( ADJU >

IF (ABS(ADJU) .GE. 1.0E-G) THEN
QUEST = ADJU I FNDt.lAL

END IF

The statement block consists of all the statements between the IF THEN and the
END IF statements.
The IF THEN statement first evaluates the logical expression e, or ABS(ADJU)
.GE. 1.0E-6. If the value of e is true, the statement block is executed. If the value of e
is false, control transfers to the next executable statement after the END IF statement, and the block is not executed.

Control Statements

9-17

2. The following example contains a block IF construct with an ELSE IF THEN statement:
Form

Example

IF (el) THEN
blockl

IF <A .GT. 5) THEN

ELSE IF (e2) THEN
block2

ELSE IF <A .GT. B/2.) THEN

END IF

D= B
F =A - B
D=B/2.
F=A-B/2,
END IF

Blockl consists of all the statements between the IF THEN and the ELSE IF THEN
statements; block2 consists of all the statements between the ELSE IF THEN and
the END IF statements.
If A is greater than B, blockl is executed. If A is not greater than B but A is greater

than B/2, block2 is executed. lfA is not greater than Band A is not greater than B/2,
neither blockl nor block2 is executed; control transfers directly to the next executable statement after the END IF statement.
3. The following example contains a block IF construct with an ELSE statement:
Form

Example

IF (e) THEN
blockl

IF (NAME • LT. IN I) THEN

ELSE
block2
END IF

ELSE

I FRONT = I FRONT + 1
FRLET ( I FRONT> = NAME< 1: 2)

I BACK = !BACK + 1
END IF

Blockl consists of all the statements between the IF THEN and ELSE statements;
block2 consists of all the statements between the ELSE and the END IF statements.
If the value of the character variable NAME is less than 'N ', blockl is executed. If

the value of NAME is greater than or equal to 'N ', block2 is executed.

9-18

Control Statements

4. The following example contains a block IF construct with several ELSE IF THEN
statements and an ELSE statement:
Form

Example

IF (el) THEN
blockl

IF (A .GT. 5) THEN
D= B
F = A- B
ELSE IF <A .GT. C) THEN
D= C
F = A- C
ELSE IF <A • GT. Z) THEN
D - ...,,_
F = A- Z
ELSE
D = 0, 0
F = A
END IF

ELSE IF (e2) THEN
block2
ELSE IF (e3) THEN
block3
ELSE
block4
END IF

There are four statement blocks in this example. Each consists of all the statements
between the block IF statements listed below.
Block

Delimiting Block IF Statements

blockl
block2
block3
block4

IF THEN and first ELSE IF THEN
First ELSE IF THEN and second ELSE IF THEN
Second ELSE IF THEN and ELSE
ELSE and END IF

If A is greater than B, blockl is executed. If A is not greater than B but is greater
than C, block2 is executed. If A is not greater than B or C but is greater than Z,
block3 is executed. If A is not greater than B, C, or Z, block4 is executed.

9. 7.3.3 Nested Block IF Constructs
A block IF construct can be included in a statement block of another block IF construct.
But the nested block IF construct inust be completely contained within a statement block;
it must not overlap statement blocks.

Control Statements

9-19

The following example contains a nested block IF construct:
Form

Example

IF (el) THEN

IF <A .LT. 100) THEN
INRAN = INRAN + 1

IF (e2) THEN
block la
ELSE
blocklb
END IF
ELSE
block2
END IF

IF <ABS<A-At.IG) +LE. 5. >THEN
I NAt.IG = I NAl.IG + 1
ELSE
OUTAt.JG = OUTAt.JG + 1
END IF
ELSE
OUTRAN = OUTRAN + 1
END IF

If A is less than 100, the code immediately after the IF is executed. This code contains a
nested block IF construct. If the absolute value of A minus AVG is less than or equal to 5,
blockla is executed. If the absolute value of A minus AVG is greater than 5, blocklb is

executed.
If A is greater than or equal to 100, block2 is executed, and the nested IF construct (blockl)

is not executed.

9.8 PAUSE Statement
The PAUSE statement displays a message on the terminal and temporarily suspends
program execution in order to permit you to take some action.
The PAUSE statement has the form:
PAUSE [disp]

where:
disp

is a character constant or a string of decimal numbers (one to five digits).
The disp argument is optional. The effect of a PAUSE statement depends on how your
program is being executed. If your program is running as a batch job or detached process,
the contents of disp are written to the system output file, but the program is not suspended.

9-20

Control Statements

If the program is running in interactive mode, the contents of disp are displayed at your

terminal, followed by the prompt sequence, indicating that the program is suspended and
that you should enter a command. For example, if the following statement is executed in
interactive mode:
PAUSE 'ERRONEOUS RESULT DETECTED'

you will see the following display at the terminal:
ERRONEOUS RESULT DETECTED
$

If you do not specify a value for disp, the following message is displayed by the system:
FORTRAN PAUSE

You can respond by typing one of the following commands:
CONTINUE

Execution resumes at the next executable statement.

EXIT

Execution is terminated.

DEBUG

Execution resumes under control of the VAX Symbolic Debugger.

9.9 RETURN Statement
The RETURN statement transfers control from a subprogram to the program that called
the subprogram. You can use RETURN statements only in subprogram units.
The RETURN statement has the form:
RETURN [i]

The optional argument, i, indicates an alternate return from the subprogram and can be
specified only in subroutine subprograms; it cannot be specified in function subprograms.
When specified, the value of i indicates that the ith alternate return in the actual argument
list is to be taken (see the second example that follows in this section).
The value of i can be any integer constant or expression, for example, 2 or I+J. The system
converts the type of the value to integer, if necessary.
When a RETURN statement is executed in a function subprogram, control is returned to
the calling program at the statement that contains the function reference (see Chapter 10).
When a RETURN statement is executed in a subroutine, control is returned either to the
first executable statement following the CALL statement that initiated the subroutine, or
to the statement label that was specified as the ith alternate return in the CALL argument
list.
Examples of RETURN statements follow.

Control Statements

9-21

1. In the following example, control is returned to the calling program at the first

executable statement following the CALL CONVRT statement.
SUBROUTINE CONVRTCN1ALPH1DATA1PRNT1K)
INTEGER ALPH<*> 1 DATA(*) 1 PRNT<*>
IF CN .GE. 10) THEN
DATACK+Z>
N-CN/lO>*N
N = N/1C>

DATACK+1)
PRNTCK+2)
PRNTCK+1)

ALPHCDATACK+2)+1)
ALPHCDATACK+1)+1)

ELSE
PRNTCK+2)
END IF
RETURN
END

ALPHCN+1)

2. The following example shows how alternate returns can be included in a subroutine.
SUBROUTINE CHECKCX1Y1*1*1C)

50
GO
70
BO

IF CZ> 60170180
RETURN
RETURN 1
RETURN 2
END

If the value computed for Z is less than zero, a normal return is taken, and the calling
program continues at the first executable statement following CALL CHECK. If Z equals
zero, however, the first alternate return (RETURN 1) is taken; and if Z is greater than zero,
the second alternate return (RETURN 2) is taken. Control is returned to the statement
specified as the first or second alternate return argument in the CALL statement argument
list. For example, if the CALL statement has the form:
CALL CHECKCA1B1*l01*Z01C)

RETURN 1 transfers control to statement label 10, and RETURN 2 transfers control to
statement label 20.
Note that if a subroutine includes an alternate return that specifies a value either less than
1 or greater than the number of alternate return arguments, control is returned to the next
executable statement after the CALL statement. That is, the alternate returns are ignored.
Therefore, you should ensure that the value of i is within the range of alternate return
arguments.

9-22

Control Statements

9.1 O STOP Statement
The STOP statement terminates program execution.
The STOP statement has the form:
STOP [disp]

where:
disp

is a character constant or a string of decimal numbers (one to five digits).
The disp argument is optional. If you specify it, the STOP statement displays the contents
of disp at your terminal, terminates program execution, and returns control to the operating system. If you do not specify a value for disp, the following message is sent by the
system:
FORTRAN STOP

Examples of STOP statements are:
STOP 98
STOP 'END OF RUN'

Control Statements

9-23

Chapter 10

Subroutines and Functions - Subprograms
Subprograms are program units that can be invoked from another program unit, usually to
perform some commonly used computation on behalf of the other program unit. Subprograms are either supplied by the user or supplied as part of the VAX FORTRAN system.
User-supplied subprograms include the following:

• Statement functions-a computing procedure defined by a single statement that is
similar in form to an assignment statement. A statement function is invoked by a
function reference in a main program unit or a subprogram unit.
• Function subprograms-a program unit, also called a function, that contains a set of
commonly used computations. A function subprogram's first statement is a
FUNCTION statement, optionally preceded by an OPTIONS statement. A function
subprogram is invoked by a function reference in a main program unit or a subprogram
unit.
• Subroutine subprograms-a program unit, also called a subroutine, that contains a set
of commonly used computations. A subroutine subprogram's first statement is a
SUBROUTINE statement, optionally preceded by an OPTIONS statement. A subroutine subprogram receives control when it is invoked with a CALL statement and
returns control with a RETURN statement.
Subprograms supplied with the FORTRAN system include the following:
• Intrinsic mathematical functions
• Intrinsic character functions
• Miscellaneous intrinsic functions
Normally, the program invoking the subprogram passes values, known as actual arguments, to the subprogram, which uses the actual arguments to compute the results and
then returns the results to the calling program.

10-1

10.1 Subprogram· Arguments
Subprogram arguments are either dummy arguments or actual arguments:
• Dummy arguments are specified when you write the subprogram.
• Actual arguments are specified when you invoke the subprogram.
When control is transferred to a subprogram, each dummy argument takes on the value of
the corresponding actual argument. When control is returned to the calling program unit,
the last value assigned to a dummy argument is assigned to the corresponding actual
argument.

10.1.1 Actual Argument and Dummy Argument Association
Actual arguments must agree in order, number, and data type (or structure, for record
arguments) with their corresponding dummy arguments. Actual arguments can be scalar
references, array name references, aggregate references, alternate return specifiers, or subprogram names. The dummy arguments specified in subprogram definitions, representing
corresponding actual arguments, appear as unsubscripted names.
Although dummy arguments are not actual variables, arrays, records, or subprograms,
each dummy argument can be declared as though it were a variable, array, record, or
subprogram.
• A dummy argument declared as an array can be associated only with an actual argument that is an array or array element of the same data type. The actual argument
must not be placed in parentheses. If a dummy argument is an array, it must be no
larger than the array that is the actual argument. You can use adjustable arrays (see
Section 10.Ll.1) to process arrays of different sizes in a single subprogram.
• A dummy argument declared as a record can be associated only with an actual argument that is an aggregate reference for an entity with a matching structure.
o A dummy argument referenced as a subprogram must be associated with an actual

argument that has been declared EXTERNAL or INTRINSIC in the calling routine.
The length of a dummy argument with a data type of character must not be greater than
the length of its associated actual argument. Note that if the character dummy argument's
length is specified as * ( *), the length used is exactly the length of the associated actual
argument. (This is known as a passed-length character argument. See .Section 10.1.1.3.)
The following topics are discussed in Sections 10.1.1.1 through 10.1.1.5.
• Adjustable array arguments
• Assumed-size array arguments
• Passed-length character arguments
• Character and Hollerith constants as actual arguments
• Alternate return arg:uments
10-2

Subroutines and Functions - Subprograms

10.1.1.1 Adjustable Arrays
Adjustable arrays are dummy arguments in subprograms. The dimensions of an adjustable
array are determined in the reference to the subprogram. The array declarator (see Section
6.2.3.1) for an adjustable array can contain integer variables that are either dummy arguments or variables in a common block.
When the subprogram is entered, each dummy argument used in the array declarator must
be associated with an actual argument, and each variable in a common block used in an
array declarator must have a defined value. The dimension declarator is evaluated using
the values of the actual arguments, variables in common blocks, and constants specified in
the array declarator.
The size of the adjustable array must be less than or equal to the size of the array that is its
corresponding actual argument.
The function in the following example computes the sum of the elements of a two-dimensional array. Note the use of the dummy arguments M and N to control the iteration.
FUNCTION SUM(A1M1N>
DIMENSION A(M1N>
SUM = O.O
DD 10 J=11N
DD 10 1=11M
SUM=SUM+A(l1J)
RETURN
END

The following statements are sample calls on SUM:
DIMENSION Al ( 10 ,35) 1 A2(3 158)
SUM1
SUM(A1t10135)
SUM2 = SUM(A21315G)
SUM3 = SUM(A1 t10 t10)

The upper- and lower-dimension bound values are determined once each time a subprogram is entered. These values do not change during the execution of that subprogram even
if the values of variables contained in the array declaration are changed. For example:
DIMENSION ARRAY(8,5)
L = 8
M = 5

CALL SUB(ARRAY1L1M>
END
SUBROUTINE SUB(X1I ,J)
DIMENSION X(-I/2:1/21J)
}-((!/2,J) = 888
J
I

= 1
= 2

END

In this example, the adjustable array X is declared as X(-4:4,5) on entry to subroutine
SUB. The assignments to I and J do not affect that declaration.

Subroutines and Functions - Subprograms

10-3

Once a variable is used in an array declarator for an adjustable array, it must not appear in
a type declaration that changes the· variable's data type. Thus, the following program
segment is invalid:
SUBROUTINE SUB11A1X)
DIMENSION AO()
INTEGER }{

An adjustable array is undefined if a dummy argument array is not currently associated
with an actual argument array. It is also undefined if any of the variables in the adjustable
array declarator are either not currently associated with an actual argument or not in a
common block. Note that argument association is not retained between one reference to a
subprogram and the next reference to that subprogram.
This is illustrated by the following example of a subroutine subprogram and the sample
statements of a calling program unit:
1. Subroutine subprogram:
SUBROUTINE S(A tI ,}0
DIMENSION A(I)

A(I>

= }{

RETURN
ENTRY Sl(I1A1K1L>
A(I) = A(I) + 1.0
RETURN
END

2. Statements in the program unit that calls the subroutine subprogram:
DIMENSION B( 10)

CALL S<B 12 13.<))

CALL S1(51Br3r2)

In the preceding example, the calling program unit defines B as a real array with 10
elements. The first call to subroutine S sets array element B(2) equal to the value 3.0. The
second call to subroutine S (at entry point Sl) increments array element B(5) by the value
1.0. RECORD statements not contained within structure declaration blocks can also declare adjustable arrays.

10.1.1.2 Assumed-Size Arrays
An assumed-size array is a dummy array for which the upper bound of the last dimension is
specified as an asterisk (*). For example:
SUBROUTINE SUB(ArN)
DIMENSION A( 1 :N t1 :*)

10-4

Subroutines and Functions - Subprograms

The size of an assumed-size array and the number of elements that can be referenced are
determined as follows:
• If the actual argument corresponding to the dummy array is a name of a noncharacter
array, the size of the dummy array is the size of the actual-argument array.
• If the actual argument corresponding to the dummy argument is a name of a noncharacter array element, with a subscript value of s in an array of size a, the size of the
dummy array is a+l-s.
• If the actual argument is a name of a character array, character array element, or

character array element substring and begins at character storage unit b of an array
with n character storage units, the size of the dummy array is INT(n+l-b)/y, where y
is the length of an element of the dummy array.
Because the actual size of an assumed-size array is not known, an assumed-size array name
cannot be used as any of the following:
• An array name in the list of an 1/0 statement
• A unit identifier for an internal file in an 1/0 statement
• A run-time format specifier in an 1/0 statement
RECORD statements not contained within structure declaration blocks can also declare
adjustable arrays.

10.1.1.3 Passed-Length Character Arguments
A passed-length character argument is a dummy argument that assumes the length attribute of the corresponding actual argument. An asterisk is used to specify the length of the
dummy character argument.
When control transfers to the subprogram, each dummy argument assumes the length of its
corresponding actual argument.
A character array dummy argument can also have a passed length. The length of each
element in the dummy argument is the length of the elements in the actual argument. The
passed length and the array declarator together determine the size of the passed-length
character array. A passed-length character array can also be an adjustable or assumed-size
array.
The following example of a function subprogram uses a passed-length character argument.
The function finds the position of the character with the highest ASCII code value; it uses
the length of the passed-length character argument to control the iteration. (Note that the
processor-defined function LEN is used to determine the length of the argument. See
Section 10.3.4.1 for a description of the LEN function.)

INTEGER FUNCTION ICMAX(CVAR>
CHARACTER*(*) CVAR
ICMA}{ = 1
DO 10 I=21LEN(CVAR)
IF (Cl,IAR(l:Il +GT+ Cl,IAR(ICMM(:ICMA>()) ICMA>(=I
RETURN
END

Subroutines and Functions - Subprograms

10-5

The length of the dummy argument is determined each time control transfers to the
function. The length of the actual argument can be the length of a character variable, array
element, substring, or expression. Each of the following function references specifies a
different length for the dummy argument:
CHARACTER VAR*lOt CARRAY(315l*20

Il
I2
I3
Ia

ICMAX(l,JARl
ICMAX(CARRAY(212l)
ICMAX(VAR(3:8ll
ICMA}-((CARRAY( 1 ,3) (5: 151 l
ICMAX(VAR(3:al//CARRAY(315l l

10.1.1.4 Character and Hollerith Constants as Actual Arguments
Actual arguments and their corresponding dummy arguments must agree in data type. If
the actual argument is a Hollerith constant (for example, 4HABCD), the dummy argument
must be of numeric data type. In VAX FORTRAN, if an actual argument is a character
constant (for example, 'ABCD '), the corresponding dummy argument can have either a
numeric or a character data type. If the dummy argument has a numeric data type, the
character constant 'ABCD ' is, in effect, converted to a Hollerith constant by the
FORTRAN compiler and the linker.
An exception to this occurs when the function or subroutine name is itself a dummy
argument. It is not possible to determine at compile time or link time whether a character
constant or Hollerith constant is required. In this case, a character constant actual argument can correspond only to a character dummy argument. For example:
SUBROUTINE S(CHARSUB1HOLLSUB1A1Bl
EXTERNAL CHARSUB1HOLLSUB

CALL CHARSUB(A1'STRING')
CALL HOLLSUBCBtGHSTRINGl

In this example, the subroutine names CHARSUB and HOLLSUB are themselves dummy
arguments of the subroutine S. Therefore, the actual argument 'STRING' in the call to
CHARSUB must correspond to a character dummy argument, whereas the actual argument 6HSTRING in the call to HOLLSUB must correspond to a Hollerith dummy argument.

10.1.1.5 Alternate Return Arguments
To specify an alternate return argument in a dummy argument list, place asterisks in the
list. For example:
SUBROUTINE MINN(A1B1*1*1Cl

10-6

Subroutines and Functions - Subprograms

The actual argument list passed in the CALL must include alternate return arguments in
the corresponding positions. These arguments have the form:
•label

or
&label

You can use either an asterisk or an ampersand to indicate an alternate return argument in
an actual argument list. The value you specify for label must be the label of an executable
statement in the program that issued the CALL.

10.1.2 IBuiH-ln Functions
Built-in functions perform utility operations that are useful in communicating with subprograms written in languages other than FORTRAN. The two kinds of built-in functions are:
o

Argument list built-in functions

%LOC built-in function

10.1.2.1 Argument List Built-In Functions
To call subprograms (such as VAXNMS system services) written in languages other than
FORTRAN, you may need to pass the actual arguments in a form different from that used
by FORTRAN. To change the form of the argument, you can use the built-in functions
%VAL, %REF, and %DESCR in the argument list of a CALL statement or function
reference. These built-in functions specify the way the argument should be passed to the
subprogram. You can use them only in the actual argument list of a CALL statement or
function reference. You cannot use them in any other context.
The argument list built-in functions are:
Function

Effect

%VAL(a)

Pass the argument as a 32-bit immediate value (if the actual argument is
shorter than 32 bits, it is sign-extended to a 32-bit value)

%REF( a)

Pass the argument by reference

%DESCR(a)

Pass the argument by descriptor

In these functions, a is an actual argument.
See the VAX FORTRAN User's Guide for more information on argument-passing mechanisms.
Table 10-1 lists the FORTRAN argument-passing defaults and the allowed uses of %VAL,
%REF, and %DESCR.

Subroutines and Functions - Subprograms

10-7

Table 10-1: Argument List Built-In Functions and Defaults
Actual Argument
Data Type

Functions Allowed
Default

%VAL

%REF

DES CR

REF
REF
REF
REF
REF
REF
DES CR
REF
REF

Yes 1
Yes 1
Yes
No
No
No
No
No
No

Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
Yes

Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
No

REF
DES CR
REF

No
No
No

Yes
Yes
Yes

Yes
Yes
No

REF
DES CR

No
No

Yes
Yes

Expressions
Logical
Integer
REAL*4
REAL*8
REAL*l6
Complex
Character
Holerith
Aggregate
Array Name
Numeric
Character
Aggregate
Procedure Name
Numeric
Character

1 If a bgical or integer value occupies less than 32 bits of storage, it is converted to a 32-bit value by

sign extension. Use the ZEXT function if zero extension is desired.

10.1.2.2 %LDC Built-In Function
The %LOC built-in function computes the .internal address of a storage element. It has the
form:
%LOC(arg)

where:
arg

is a scalar memory reference, array name reference, aggregate reference, or external
procedure name.
The %LOC built-in function produces an INTEGER*4 value that represents the location of
its argument. The INTEGER*4 value can be used as an element in an arithmetic expression.

10-8

Subroutines and Functions -

Subprograms

See the VAX FORTRAN User's Guide for more information on the %LOC built-in function.

10.2 User-Written Subprograms
A user-written subprogram is a FORTRAN statement or group of FORTRAN statements
that performs a computing procedure. The computing procedure can be either a series of
arithmetic operations or a series of FORTRAN statements. You can use a single subprogram to perform a computing procedure in several places in your program, and thus avoid
duplicating the series of operations or statements in each place.
There are three types of subprograms. Table 10-2 lists each type of subprogram, the
statements needed to define the subprogram, and the method of transferring control to it.

Table 10-2: Types of User-Written Subprogram
Subprogram Type

Defining Statements

Control Transfer
Method

Statement function

Statement function definition

Function reference

Function

FUNCTION
ENTRY

Function reference

Subroutine

SUBROUTINE
ENTRY

CALL statement

A function reference is used in an expression and consists of the function name and the
function arguments. A function reference returns a value that is used in evaluating the
expression in which the function appears.
Function and subroutine subprograms can change the values of their arguments, and the
calling program can use the changed values.
A subprogram can refer to other subprograms; but it cannot, either directly or indirectly,
refer to itself.

10.2.1 Statement Functions
A statement function is a computing procedure defined in the same program unit in which
it is referenced. It is defined by a single statement that is similar in form to an assignment
statement. The computation is performed each time you refer to the statement function.
The resulting value is then made available to the expression that contains the statement
function reference.

Subroutines and Functions - Subprograms

10-9

The statement function definition statement has the form:
fun([p[,p] ... ]) = e

where:
fun

is the symbolic name of the statement function.
p

is a dummy argument.
e
is an expression.
The expression (e) is an arithmetic, logical, or character expression that defines the computation to be performed.
A statement function reference has the form:
f([p[,p] ... ])

where:

is the symbolic name of the function.
p

is an actual argument.
Rules governing the use of statement function definitions and references are as follows:
• When a statement function reference appears in an expression, the values of the actual
arguments are associated with the dummy arguments in the statement function definition. The expression in the definition is then evaluated. The resulting value is used
to complete the evaluation of the expression containing the function reference.
• The data type of a statement function is determined either implicitly by the initial
letter of the function name, or explicitly in a type declaration statement. The data
type can be any of the data types, including the character data type.
• Dummy arguments in a statement function indicate only the number, order, and data
type of the actual arguments. You can use the names of the dummy arguments to
represent other entities elsewhere in the program unit. Note that, except for data type,
declarative information associated with an entity is not associated with· the dummy
arguments in the statement function. That is, declaring an entity to be an array or to
be in a common block does not affect a dummy argument with the same name.
• Actual arguments must agree in number, order, and data type with their corresponding dummy arguments.

10-10

Subroutines and Functions -

Subprograms

• You cannot use the name of the statement function to represent any other entity
within the same program unit.
• The expression in a statement function definition can contain function references. If a
reference to another statement function appears in the expression, you must have
previously defined that function in the same program unit.
• Any reference to a statement function must appear in the same program unit as the
definition of that function.
• A statement function reference must appear as, or be part of, an expression. You
cannot use the reference as the left side of an assignment statement.
Examples
• Examples of statement function definitions:

= a.188*RADIUS**3

VOLUME(RADIUS>
SINH(X)

= (EXP(X>-EXP(-X))*0+5

CHARACTER*lO CSFtAtB
CSF(A15) = A(G:l0)//5(1:5)

The following definition is invalid. A constant cannot be used as a dummy argument.
A1.1 G( A t B , C , 3 • )

= ( A+ B+ C ) I 3 •

• Examples of statement function references:
Given the definition:
AVG(A1B1C)

= (A+B+C)/3.

The references are:

GRADE = AVG(TEST11TEST21XLAB>
IF (At.JG(P1D10) +LT. At.JG()-{,y,z)) GO TO 300

The following reference is invalid. The data type of the third argument does not agree
with the dummy argument.
FINAL= AVG(TEST31TEST41LAB2>

10.2.2 Function Subprograms
A function subprogram is a program unit consisting of a FUNCTION statement followed
by a series of statements that define a computing procedure. You use a function reference
to transfer control to a function subprogram, and a RETURN or END statement to return
control to the calling program unit.

Subroutines and Functions - Subprograms

10-11

A function subprogram returns a single value to the calling program unit by assigning that
value to the function's name. The function's name determines the data type of the value
returned.

10.2.2.1 Logical and Numeric Functions
The FUNCTION statement has the form:
[typ] FUNCTION nam(*m](([p(,p] ... ])]

where:
typ

is one of the logical or numeric data type specifiers. See Section 8.4.1 for a list of these
specifiers.
nam

is the symbolic name of the function.
m

is an unsigned, nonzero integer constant specifying the length of the data type; it
must be one of the valid length specifiers for the data type given by typ.
p

is a dummy argument.

10.2.2.2 Character Functions
The CHARACTER FUNCTION statement has the form:
CHARACTER[•n] FUNCTION nam[*n] (([p[,p] ... ])]

where:
n

is an unsigned, nonzero integer constant, or parenthetical asterisk (*) indicating a
passed-length function name. If you specify CHARACTER*(*), the function assumes
the length declared for it in the program unit that invokes it. A passed-length character function can have different lengths when it is invoked by different program units.
If n is an integer constant, the value of n must agree with the length of the function
specified in the program unit that invokes the function. If you do not specify n, a
length of one is assumed. If the length has already been specified following the keyword CHARACTER, the optional length specification following nam is not permitted.
nam

is the symbolic name of the function.
p

is a dummy argument.

10-12

Subroutines and Functions -

Subprograms

10.2.2.3 Function Reference
A function reference that transfers control to a function subprogram has the form:
nam([p[,p] ... ])

where:
nam

is the symbolic name of the function.
p

is an actual argument.
When control transfers to a function subprogram, the values of the actual arguments (if
any) in the function reference are associated with the dummy arguments (if any) in the
FUNCTION statement. The statements in the subprogram are then executed and the
resulting value is assigned to the name of the function. Finally, the function returns control
to the calling program unit. The value assigned to the function's name is now available to
the expression containing the function reference and is used to complete the evaluation of
that expression.
The data type of a function name can be specified explicitly in the FUNCTION statement
or in a type declaration statement, or it can be specified implicitly. The function name
defined in the function subprogram must have the same data type as the function name in
the calling program unit.
The FUNCTION statement must be the first statement of a function subprogram, unless
an OPTIONS statement is used. A function subprogram cannot contain a SUBROUTINE
statement, a BLOCK DATA statement, a PROGRAM statement, or another FUNCTION
statement. ENTRY statements can be included to provide multiple entry points to the
subprogram (see Section 10.2.4).
Examples of function subprograms follow.
1. In the following example
FUNCTION ROOT(A)
2

)-( = 1. 0
E}-( = E}-( p ( )-( )
EMINl-( = 1,/E)-(
ROOT= ((EX+EMINXl*+5+COSIX)-A)/((EX-EMINX)*,5-SINIX))
IF IABSO(-ROOT) ,LT, lE-6) RETURN
)-( = ROOT
GO TO

END

the function uses the Newton-Raphson iteration method to obtain the root of the
function:
F(X) = cosh(X) + cos(X) - A =

Subroutines and Functions - Subprograms

10-13

The value of A is passed as an argument. The iteration formula for this root is:
cosh(XFcos(Xi)-A )
Xi+1 =X1 -

(

sinh(Xi)-sin(Xi)

This is calculated repeatedly until the difference between Xi and Xi+l is less than
1.0E-6. The function uses the FORTRAN intrinsic functions EXP, SIN, COS, and
ABS (see Section 10.3).
2. The following example is a passed-length character function. It returns the value of
its argument, repeated to fill the length of the function.

CHARACTER*(*) FUNCTION REPEAT(CARG)
CHARACTER*l CARG
DD 10 I=l 1LEN(REPEAT)
REPEAT(I:I) = CARG
RETURN
END

3. Within any given program unit all references to a passed-length character function
must have the same length. In the following example, the REPEAT function has a
length of 1000:
CHARACTER*lOOO REPEAT, MANYASt MANYZS
MANYAS = REPEAT ( I AI)
MANYZS = REPEAT ( I z I)

However, another program unit within the executable program can specify a different
length. In the following example, the REPEAT function has a length of 2:
CHARACTER HDLD*Gt REPEAT*2
HOLD= REPEAT( 'A')//REPEAT( 'B')//REPEAT( 'C')

10.2.3 Subro1:1tine Subprograms -

SUBROUTINE Statement

A subroutine subprogram is a program unit consisting of a SUBROUTINE statement
followed by a series of statements that define a computing procedure. You use a CALL
statement to transfer control to a subroutine subprogram, and a RETURN or END statement to return control to the calling program unit.
The SUBROUTINE statement has the form:
SUBROUTINE sub [([p[,p] ... ])]

where:
sub

is the symbolic name of the subroutine.
p

is a dummy argument. You can specify a dummy argument as an alternate return
argument by placing an asterisk in the argument list.
Section 9.1 describes the CALL statement.
10-14

Subroutines and Functions - Subprograms

When control transfers to the subroutine, the values of the actual arguments (if any) in the
CALL statement are associated with the corresponding dummy arguments (if any) in the
SUBROUTINE statement. The statements in the subprogram are then executed.
The SUBROUTINE statement must be the first statement of a subroutine, unless an
OPTIONS statement is used.
A subroutine subprogram cannot contain a FUNCTION statement, a BLOCK DATA
statement, a PROGRAM statement, or another SUBROUTINE statement. ENTRY statements are allowed to specify multiple entry points in the subroutine (see Section 10.2.4).
Examples
The following example contains a subroutine that computes the volume of a regular
polyhedron, given the number of faces and the length of one edge. It uses the computed GO
TO statement to determine whether the polyhedron is a tetrahedron, cube, octahedron,
dodecahedron, or icosahedron. The GO TO statement also transfers control to the proper
procedure for calculating the volume. If the number of faces is not 4, 6, 8, 12, or 20, the
subroutine sends an error message to the user's terminal.
Main Program
COMMON NFACES, EDGE, l,JOLUME
ACCEPT *, NFACES, EDGE
CALL PL yt,JOL
TYPE*' 'l,JOLUME=

I' l,JOLUME

STOP
END

Subroutine
SUBROUTINE PL Yl,JOL
COMMON NFACES, EDGE, 1,IOLUME
CUBED = EDGE**3
GO TO (61616t1161216,3161616tl!1616161616161615), NFACES
GO TO 6
l,JOLUME = CUBED

* 0 • 11 785

RETURN
2

1,IOLUME = CUBED

RETURN

* 0 • ll 71 £10

RETURN

l.IOLUME = CUBED

* 7. 66312

RETURN
5

1,IOLUME = CUBED

* 2. 181 70

RETURN
6

TY PE 100, NFACES

100

FORMAT ( I NO REGULAR POLYHEDRON HAS

'I 3 ' I FACES t

1,IOLUME = 0, 0
RETURN
END

Subroutines and Functions - Subprograms

10-15

The following example illustrates the use of alternate return specifiers to determine where
control is to be transferred on completion of the subroutine. The SUBROUTINE statement
argument list contains two dummy alternate return arguments corresponding to the actual
arguments *10 and *20 in the CALL statement argument list. The decision about which
RETURN statement to execute depends on the value of Z, as computed in the subroutine.
Thus, if Z is less than zero, the normal return is taken; if Z is equal to zero, the return is to
statement label 10 in the main program; if Z is greater than zero, the return is to statement
label 20 in the main program.
Main Program

Subroutine

CALL CHECKCAtBt*10t*20tC)

SUBROUTINE CHECKCXtYt*t*tO)

TYPE * t 'l,IALUE LESS THAN ZERO I
GO TD 30
10 TY PE * t '1,IALUE EQUALS ZERO I
GO TO 30

50 IF CZ> GO 170 180

20 TY PE * t '1,IALUE MORE THAN ZERO I

GO RETURN

30 CONT I NUE

70 RETURN 1

80 RETURN 2
END

10.2.4 ENTRY Statement
The ENTRY statement provides multiple entry points within a subprogram. It is not
executable and can appear within a function or subroutine program after the FUNCTION
or SUBROUTINE statement. Execution of a subprogram referred to by an entry name
begins with the first executable statement after the ENTRY statement.
The ENTRY statement has the form:
ENTRY nam[([p[,p] ... ])]

where:
nam

is the symbolic name of an entry point.
p

is a dummy argument.
Considerations/Restrictions
• Use the CALL statement to refer to entry names within subroutine subprograms. Use
function references to refer to entry names within function subprograms.
• An entry name within a function subprogram can appear in a type declaration statement.
10-1.6

Subroutines and Functions - Subprograms

• You can specify an entry name in an EXTERNAL statement and use it as an actual
argument; you cannot use it as a dummy argument.
• You cannot use entry names in executable statements that physically precede the
appearance of the entry name in an ENTRY statement.
• You can include alternate return arguments in ENTRY statements by placing asterisks in the dummy argument list. ENTRY statements that specify alternate return
arguments can be used only in subroutine subprograms.
• You can use dummy arguments in ENTRY statements that differ in order, number,
type, and name from the dummy arguments you use in the FUNCTION, SUBROUTINE, and other ENTRY statements in the same subprogram. However, each reference to a function, subroutine, or entry must use an actual argument list that agrees in
order, number, and type with the dummy argument list in the corresponding FUNCTION, SUBROUTINE, or ENTRY statement.
• A dummy argument can be referred to only in executable statements that follow the
first SUBROUTINE, FUNCTION, or ENTRY statement in which the dummy argument is specified. A dummy argument is undefined if it is not currently associated
with an actual argument. An argument association is not retained from one reference
of a subprogram to the next.
• You cannot use an ENTRY statement within a block IF construct or a DO loop.

10.2.4.1 ENTRY in Function Subprograms
All entry names within a function subprogram are associated with the name of the function
subprogram. Therefore, defining any entry name or the name of the function subprogram
defines all the associated names of the same data type; all associated names that are of
different data types become undefined. The function and entry names do not need to be of
the same data type, but they all must be consistent within one of the following groups of
data types:
Group 1:

BYTE, INTEGER*2, INTEGER*4, LOGICAL*2, LOGICAL*4, REAL*4,
REAL*8, COMPLEX*8

Group 2:

COMPLEX*l6, REAL*l6

Group 3:

CHARACTER

When either a RETURN statement or the implied return at the end of a subprogram is
executed, the symbolic name used to refer to the function subprogram must be defined.
If the function is of character data type, all entry names must also be of character data type

and must have the same length specification as that of the function. Note that the length
specified must also agree with the length specified in the program unit referring to the
entry name. If an asterisk enclosed in parentheses is used to specify the length of the entry
name, the entry name has a passed length (see Section 10.1.1.3).

Subroutines and Functions - Subprograms

10-17

Figure 10-1 illustrates a function subprogram that computes the hyperbolic functions sinh,
cosh, and tanh.
REAL FUNCTION TANH(X)
C

StateMent function to coMPUte twice sinh

TSINH(Y) = EXP(Y) - EXP(-Y)
C

StateMent function to coMPute twice cosh

TCOSH(Yl
C

= EXP(Yl

EXP(-Yl

CoMPute tanh

TANH = TSINH(X)/TCOSH(Xl
RETURN
C

CoMPute sinh

ENTRY SINHO()
SINH = TSINH(Xl/2.0
RETURN
C

CoMPute cosh

ENTRY COSH ( }{ l
COSH = TCOSH(Xl/2.0
RETURN
END

Figure 10-1: Multiple Functions in a Function Subprogram

10.2.4.2 ENTRY in Subroutine Subprograms
To refer to an entry point name in a subroutine, issue a CALL statement that includes the
entry point name defined in the ENTRY statement. For example:
Main Program
CALL SUBA (A 1B 1C l

Subroutine
SUBROUTINE SUB ( }{, Y ,z)

ENTRY SUBA ( Q 1R 15 l

10-18

Subroutines and Functions - Subprograms

In this example, the CALL is to an entry point (SUBA) within the subroutine (SUB).
Execution begins with the first statement following ENTRY SUBA (Q,R,S), using the
actual arguments (A,B,C) passed in the CALL statement. Note that alternate returns can
be specified in ENTRY statements. For example:
SUBROUTINE SUBCK1*1*)

ENTRY SUBCCJ1K 1*1*1Xl

RETURN 1
RETURN 2
END

If you issue a CALL to entry point SUBC, you must include actual alternate return
arguments. For example:
CALL SUBCCM1N1*l001*2001Pl

In this case, RETURN 1 transfers control to statement label 100 and RETURN 2 transfers
control to statement label 200 in the calling program.

10.3 FORTRAN Intrinsic Functions
Intrinsic functions, supplied in the VAXNMS FORTRAN library, perform commonly used
mathematical computations.
Function references to FORTRAN intrinsic functions are written in the same way that
function references to user-defined functions are written. For example:
R = 3.14159 * ABSCX-ll

As a result of this reference, the absolute value of X-1 is calculated and multiplied by the
constant 3.14159; the result is assigned to the variable R.
Appendix D lists the intrinsic functions, their data types, and the data types of their actual
arguments.· For descriptions of the intrinsic function algorithms, refer to the VAX/VMS
Run-Time Library Reference Manual.
The two methods of referencing intrinsic functions are described in the sections that follow.

10.3.1 Intrinsic Function References
FORTRAN library function names are called intrinsic function names. Normally, a name
in the table of intrinsic function names (Table D-1) refers to the FORTRAN library
function with that name. However, the name can refer to a user-defined function when the
name appears in an EXTERNAL statement (see Section 8.7).

Subroutines and Functions - Subprograms

10-19

Except when they are used in an EXTERNAL statement, intrinsic function names are
local to the program unit that refers to them. Thus, they can be used for other purposes in
other program units. In addition, the data type of an intrinsic function does not change if
you use an IMPLICIT statement to change the implied data type rules.
Note that you cannot have an intrinsic function and a user-defined function with the same
name in the same program unit.

10.3.2 Generic Function References
Many of the intrinsic functions supplied with VAX FORTRAN are generic functions,
which means that you refer to them by a common name and the selection of the actual
library routine to be used is based on the data type of the argument in the function
reference. For example, there are five intrinsic functions that calculate cosines. All of them
can be referred to by the generic name COS. Their names are COS, DCOS, QCOS, CCOS,
and CDCOS. These functions differ in that they return REAL*4, REAL*8, REAL*l6,
COMPLEX*8, and COMPLEX*l6 values, respectively. To invoke the cosine function, you
can refer to it generically as COS, and the compiler selects the appropriate routine, based
on the arguments that you specify. For example, if the argument is REAL*4, COS is
selected; if it is REAL*8, DCOS is selected; and if COMPLEX*8, CCOS is selected.
Note, however, that you can explicitly refer to a particular routine if you wish. Thus, to
invoke the double-precision cosine function, you could specify DCOS rather than use the
generic name.
The compiler lists the internal names of the intrinsic functions it has selected in the
"FUNCTIONS AND SUBROUTINES REFERENCED" section of the listing.
Generic function selection occurs independently for each function reference. Thus, you can
use a generic function reference repeatedly, in the same program unit, to access different
intrinsic functions.
Table 10-3 lists the generic function names. If you use the names in Table 10-3 in any of
the following ways, you c·annot use them for generic function selection:
• As the name of a statement function
• As a dummy argument name, a common block name, or a variable or array name
Using a generic name in an INTRINSIC statement (see Section 8.9) does not affect function references. When you use a generic function name in an actual argument list as the
name of a function to be passed, generic function selection does not occur because there is
no argument list on which to base a selection. The name is treated according to the rules for
nongeneric FORTRAN functions described in Section 10.3.
Generic function names are local to the program unit that refers to them. Thus, they can be
used for other purposes in other program units.

10-20

Subroutines and Functions - Subprograms

Table 10-3: Generic Function Name Summary
Data Type
of Argument

Data Type
of Result

ABS

Integer
Real
COMPLEX*8
COMPLEX*16

Integer
Real
REAL*4
REAL*8

AINT, ANINT

Real

NINT

Real

Integer

INT

Integer
Real
Complex

Integer
Integer
Integer

REAL

Integer
Real
Complex

REAL*4
REAL*4
REAL*4

DBLE

Integer
Real
Complex

REAL*8
REAL*8
REAL*8

QEXT

Integer
Real
Complex

REAL*16
REAL*l6
REAL*16

CMPLX

Integer
Real
Complex

COMPLEX*8
COMPLEX*8
COMPLEX*8

DCMPLX

Integer
Real
Complex

COMPLEX*16
COMPLEX*16
COMPLEX*16

MOD, MAX, MIN, SIGN, DIM

Integer
Real

EXP, LOG, SIN, COS, SQRT

Real
Complex

LOGlO, SIND, COSD, TAN, TAND,
ATAN, ATAND, ATAN2, ATAN2D, ASIN,
ASIND, ACOS, ACOSD, SINH, COSH,
TANH

Real

Generic Name

Subroutines and Functions - Subprograms

10-21

10.3.3 Intrinsic and Generic Function Usage
Figure 10-2 shows the use of intrinsic and generic function names. In this figure, a single
executable program uses the name SIN in four distinct ways:
• As the name of a statement function
• As the name of a generic function
• As the name of a specific intrinsic function
• As the name of a user-defined function
Using the name in these four ways emphasizes the local and global properties of the name.
In Figure 10-2, the circled numbers are keyed to the notes that follow the figure.
C

CoMPare ways of coMPutinS sine.
PROGRAM SINES
REAL*zB }-(, PI
PARAMETER (PI=3.1a1582653588783238DO>
COMMON t.1 ( 3)

Define SIN as a stateMent function

SIN(X) = COS(P!/2-X)
DO 10 }-( = -PI, PI, Z*PI/100
CALL COM PUT ( }-()
C

Reference the stateMent function SIN

10
100

WRITE ( G t100) }-(,
FORMAT (5F10.7)
END

t.1,

SIN 0( >

SUBROUTINE COMPUT(Y)
REAL*B Y
C

Use intrinsic function SIN as actual arSuMent
INTRINSIC SIN
COMMON t.1 ( 3)

Generic reference to double-Precision sine
t.l(l)

= SIN<Yl

Figure 10-2: Multiple Function Name Usage

10-22

Subroutines and Functions - Subprograms

INTRINSIC FUNCTION SINE AS ACTUAL ARGUMENT

CALL SUB(REAL(Y) 1SIN)
END
SUBROUTINE SUB(A1S)
C

Declare SIN as naMe of user function

E}-{TERNAL SIN
C

Declare SIN as tYPe REAL*B

REAL*B SIN
COMMON lJ ( 3)
C

Evaluate intrinsic function SIN

l,l(2) = S(A)
C

Evaluate user-defined SIN function

l.J(3) = SIN(A)
END
C

Define the user SIN function

REAL*B FUNCTION SIN(X)
INTEGER FACTOR
SIN
X - X**3/FACTOR(3) + X**5/FACTOR(5)
1
- X**7/FACTOR(7)
END

INTEGER FUNCTION FACTOR(N)
FACTOR = 1
DO 10 I=N i11-1
FACTOR = FACTOR * I
END

Figure 10-2 (Cont.): Multiple Function Name Usage

Notes:
0 A statement function named SIN is defined in terms of the generic function name COS.
Since the argument of COS is double precision, the double-precision cosine function
will be evaluated. The statement function SIN is itself single precision.
@

The statement function SIN is called.

6> The name SIN is declared intrinsic so that the single-precision intrinsic sine function
can be passed as an actual argument at 0.

The generic function name SIN is used to refer to the double-precision sine function.

The single-precision intrinsic sine function is used as an actual argument.

Subroutines and Functions - Subprograms

10-23

Notes (Cont.)
0 The name SIN is declared a user-defined function name.
0

The type of SIN is declared double precision.

The single-precision sine function passed at 0 is evaluated.

The user-defined SIN function is evaluated.

The user-defined SIN function is defined as a simple Taylor series using a user-defined
function FACTOR to compute the factorial function.

10.3.4 Character and Lexical Comparison Library Functions
Character library functions are functions that take character arguments and return integer,
ASCII, or character values; lexical comparison library functions are functions that take
character arguments and return logical values.

10.3.4.1 Character Functions
FORTRAN provides four character functions: LEN, INDEX, I CHAR, and CHAR.
LEN Function
The LEN function returns the length of a character expression. The LEN function has the
form:
LEN(c)

where:
c

is a character expression. The value returned indicates how many bytes there are in
the expression.

INDEX Function
The INDEX function searches for a substring (c2) in a specified character string (cl), and,
if it finds the substring, returns the substring's starting position. If c2 occurs more than
once in cl, the starting position of the first (leftmost) occurrence is returned. If c2 does not
occur in cl, the value zero is returned. The INDEX function has the form:
INDEX(c1 ,c2)

10-24

Subroutines and Functions -

Subprograms

where:
c1

is a character expression specifying the string to be searched for the substring specified by c2.
c2

is a character expression specifying the substring for which the starting location is to
be determined.

ICHAR Function
The ICHAR function converts a character expression to its equivalent ASCII code and
returns the ASCII value. ICHAR has the form:
ICHAR (c)

where:
c

is the character to be converted to an ASCII cc:>de. If c is longer than one byte, only the
value of the first byte is returned; the remainder is ignored.

CHAR Function
The CHAR function converts an ASCII integer value to a character value and returns the
character value. CHAR has the form:
CHAR (i)

where:
is an integer expression.

Examples
Examples illustrating the LEN and INDEX functions follow.
LEN Function Example:
SUBRDUT I NE REt.lERSE CS)
CHARACTER T, S* C*)
J = LENCS)
DD 10 !=1 tJ/2
T =SCI:!)
SCI:!)= SCJ:J)
SCJ:J> = T
10

n
J=J-1
CONTINUE
RETURN
END

Subroutines and Functions - Subprograms

10-25

INDEX Function Example:
SUBROUTINE FIND_SUBSTRINGS(SUBtS)
CHARACTER*<*) SUB t S
CHARACTER*132 MARKS

I = 1
MARKS =
10

J=INDE>{CSCI:>tSUB)
IF <J • NE. 0) THEN
I=I+CJ-1)
MARKSCI:I> =

':f:I:'

=I + 1

IF (I .LE. LEN CS>) GO TO 10
END IF
WRITE CG t91) St MARKS
91

FORMAT C2<1U< tA))
END

10.3.4.2 Lexical Comparison Functions
The four lexical comparison functions provided with FORTRAN are:
• LLT, where LLT(X,Y) is equivalent to (X .LT. Y)
• LLE, where LLE(X,Y) is equivalent to (X .LE. Y)
• LGT, where LGT(X,Y) is equivalent to (X .GT. Y)
• LGE, where LGE(X,Y) is equivalent to (X .GE. Y)
The lexical functions have the form:
func(c,c)

where:
func

is one of the symbolic names: LLT, LLE, LGT, or LGE.
c

is a character expression.

10-26

Subroutines and Functions -

Subprograms

The lexical comparison functions defined by the FORTRAN-77 standard are guaranteed to
make comparisons according to the ASCII collating sequence, even on non-ASCII processors. On VAX systems, the lexical comparison functions are identical to the corresponding
character relationals.
An example of the use of the lexical comparison functions is:
CHARACTER*10 CH2
IF (LGT(CH2' 'SMilH I))

STOP

The IF statement in this example is equivalent to the following:
IF

( c H2

• GT •

s MITH

)

.s TO p

Subroutines and Functions - Subprograms

10-27

Chapter 11

VAX FORTRAN Input/Output
This chapter describes FORTRAN input/output (I/0) as implemented for VAX FORTRAN
and provides information about FORTRAN I/0 in relation to the VAX Record Management Services (RMS) and the VAX Run-Time Library (RTL).
The topics covered include:
• Overview of FORTRAN I/0 (Section 11.1)
• Elements of I/0 Processing (Section 11.2)
• Components of I/0 statements (Section 11.3)
• READ statements (Section 11.4)
• WRITE statements (Section 11.5)
0

REWRITE statement (Section 11.6)

o ACCEPT statement (Section 11.7)
0

TYPE and PRINT statements (Section 11.8)

The statements listed here initiate data transfer operations. Other FORTRAN statements,
which influence I/0 processing but do not directly initiate data transfers, are described in
Chapter 12, FORMAT Statements, and in Chapter 13, Auxiliary Input/Output Statements.

11.1 Overview of VAX FORTRAN 1/0
This section introduces the concept of logical units, briefly describes the scope of interprocess communications, and lists and describes the different types of 1/0 statements and the
optional forms of I/0 statements.

11-1

11.1.1 Identifying Logical Input/Output Units
Logical unit numbers are integers from 0 to 99. For example:
READ

C2t100)

!1){,y

This READ statement specifies that data is to be entered from the device or file corresponding to logical unit 2, in the format specified by the FORMAT statement labeled 100.
The association between the logical unit number and the physical device or file occurs at
execution time. If necessary, you can change this association at execution time to match
the needs of the program and the available resources. You do not need to change the logical
unit numbers specified in the program. FORTRAN programs, therefore, are inherently
device independent.
READ, WRITE, and REWRITE statements refer explicitly to a logical unit from or to
which data is to be transferred. The logical unit can be connected to a device or file by
means of an OPEN statement (see Section 13.1).
ACCEPT, TYPE, and PRINT statements do not refer explicitly to a logical unit (a file or
device) from or to which data is to be transferred; they refer implicitly to a default logical
unit. The ACCEPT statement is normally connected to the default input device, and the
TYPE and PRINT statements are normally connected to the default output device. These
defaults can be overridden with appropriate logical name assignments (see Section
13.3.1.1).

11.1.2 Types of 1/0 Statements
The type of an 1/0 statement depends on the organization of the file being accessed. The
various types of I/0 are as follows:
• Sequential 1/0-transfers records sequentially to or from files or 1/0 devices such as
terminals.
• Direct Access 1/0-transfers records, selected by record number, to and from direct
access files.

° Keyed I/0-transfers records, based on data values (keys) contained in the records, to
and from indexed files.
• Internal 1/0-transfers data between variables and arrays defined within a program.

11-2

VAX FORTRAN Input/Output

11.1.3 Interprocess Communication
You can use standard FORTRAN I/0 statements to communicate between processes on
either the same computer or different computers.
• Mailboxes permit interprocess communication on the same computer.
• DECnet network facilities are used for interprocess communication on different computers. DECnet can also be used to process files on different computers.
Information on the preceding types of operations is provided in the VAX FORTRAN User's
Guide.

11.1.4 Forms of 1/0 Statements
Each type of 1/0 statement can be coded in a variety of forms. The form you select depends
on the nature of your data and how you want it treated. The 1/0 statement forms are
formatted, unformatted, list-directed, and namelist-directed.
• Formatted 1/0 statements contain explicit format specifiers that are used to control
the translation of data from internal (binary) form within a program to external
(readable character) form in the records, or vice versa.
• List-directed and namelist-directed 1/0 statements are similar to formatted statements in function. However, they use different mechanisms to control the translation
of data: formatted I/0 statements use explicit format specifiers, and list-directed and
namelist-directed I/0 statements use data types.
• Unformatted 1/0 statements do not contain format specifiers and therefore do not
translate the data being transferred. Unformatted I/0 is especially appropriate where
the output data will subsequently be used as input data. Unformatted 1/0 saves
execution time by eliminating the data translation process, preserves greater precision
in the external data, and usually conserves file storage space.
1/0 statements transfer all data as records; that is, that which is read or written is a record.
The amount of data that one of these records can contain depends on whether unformatted
or formatted 1/0 is used to transfer the data. With unformatted 1/0, the 1/0 statement
alone specifies the amount of data to be transferred; with formatted 1/0, the 1/0 statement
and its associated format specifier jointly determine the amount of data to be transferred.
Normally, the data transferred by an 1/0 statement is read from or written to a single
record. It is possible, however, for formatted, list-directed, and namelist-directed 1/0 statements to transfer data from or to more than one record.
Table 11-1 shows the various I/O statements, by category, that can be used in FORTRAN
programs.

VAX FORTRAN Input/Output

11-3

Table 11-1: Available 1/0 Statements
Statement
Category

Statement Name
READ

WRITE

REWRITE

TYPE

Yes
Yes
Yes
Yes

No
No
No
No

Yes
Yes
Yes
No

Yes
Yes

No
No

Yes
Yes

No
No

Yes
Yes
No

No
No
No

Sequential
Formatted
List-Directed
N amelist-Directed
Unformatted
Direct
Formatted
Unformatted
Indexed
Formatted
Unformatted
Internal
Formatted
List-Directed
Unformatted

11.2 Elements ol 110 Processing
The following sections describe in general terms the elements of FORTRAN 1/0 processing.
The topics covered include:
• VAXNMS file specifications (Section 11.2.1)
• Logical names, as used in FORTRAN, and logical unit numbers (Section 11.2.2)
• FORTRAN file organizations, I/0 record formats, and access modes (Section 11.2.3)

11.2.1 File Specifications
VAXNMS file specifications are described in detail in Chapter 1. The discussion of file
specifications is abbreviated in this section, concentrating on how to identify files in I/0
statements.
A complete VAXNMS file specification has the form:
node::device:[directory]filename.filetype;version

For example:
BOSTON::USERD:CSMITHJTEST.DATi2

11-4

VAX FORTRAN Input/Output

You can associate a file specification with a logical unit by using a logical name assignment
(see Section 11.2.2) or by using the OPEN statement (see Section 11.2.3). If you do not
specify such an association or if you omit elements of the file specification, the system
supplies default values, as follows:
• If you omit the node, the local computer is used.
• If you omit the device or directory, the current user default is used.
• If you omit the file name, the system supplies FOROnn, where nn is the logical unit
number.
• If you omit the file type, the system supplies DAT.
• If you omit the version number, the system supplies either the highest current version
number (for input) or the highest current version number plus 1 (for output).

For example, if your default device is USERD and your default directory is SMITH, and
you specify:
READ C8 t100 >

WRITE C9t200)

The default input and output file specifications are respectively:
USERD:[SMITH]FOR008.DAT;n

and
USERD:[SMITH]FOR009.DAT;m

Where n equals the highest current version number of FOR008.DAT and m is 1 greater
than the highest existing version number of FOR009.DAT.

11.2.2 Logical Names and Logical Unit Numbers
You can use the logical name mechanism of the VMS operating system to associate logical
units with file specifications. A logical name is an alphanumeric string, up to 63 characters
long, that you can use instead of a file specification.
The operating system supplies a number of predefined logical names that are already
associated with particular file specifications. Table 11-2 lists the logical names of special
interest to FORTRAN users. FORTRAN logical unit names are shown in Table 11-3.

VAX FORTRAN Input/Output

11-5

Table 11-2: Predefined System Logical Names
Name

Meaning

Default

SYS$COMMAND

Default command stream

For an interactive user, the default is the
terminal; for a batch job, the default is
the batch job input command file.

SYS$DISK

Default disk device

As specified by the user.

SYS$ERROR

Default error stream

For an interactive user, the default is the
terminal; for a batch job, the default is
the batch job log file.

SYS$INPUT

Default input stream

For an interactive user, the default is the
terminal; for a batch job, the default is
the batch command file.

SYS$0UTPUT

Default output stream

For an interactive user, the default is the
terminal; for a batch job, the default is
the batch log file.

You can dynamically create a logical name and associate it with a file specification by
means of the VAXNMS ASSIGN command. For example, before program execution, you
can associate the logical names in your program with the file specification appropriate to
your needs.
For example:
$ASSIGN USERD:ESMITHJTEST+DATi2 LOGNAM

The preceding command creates the logical name LOGNAM and associates it with the file
specification USERD:[SMITHJTEST.DAT;2. As a result, this file specification is used
whenever the logical name LOGNAM is encountered during program execution.
Logical names provide great flexibility because they can be associated not only with a
complete file specification, but with a portion of a file specification (that is, either a device
or a device and a directory), or even another logical name.

11.2.2.1 FORTRAN Logical Names
Usually, FORTRAN 1/0 is performed by associating a logical unit number with a device or
file. VAXNMS logical names provide an additional level of association; a user-specified
logical name can be associated with a logical unit number.

11-6

VAX FORTRAN Input/Output

VAX FORTRAN provides predefined logical names in the form:
FOROnn

where:
nn

corresponds to the logical unit number.
By default, each FORTRAN logical name is associated with a file named FOROnn.DAT,
which is assumed to be located on your default disk under your default directory. For
example:
WRITE (171200)

If you enter the preceding statement without including an explicit file specification, the
data is written to a file named FOROl 7 .DAT on your default disk under your default
directory.

You can change the file specification associated with a FORTRAN logical unit number by
using the ASSIGN command to change the file associated with the corresponding
FORTRAN logical name. For example:
$ASSIGN USERD:[SMITHJTEST.DAT;z FOR017

The preceding command associates the FORTRAN logical name FOROl 7 (and therefore
logical unit 17) with file TEST .DAT;2 on device USERD in directory [SMITHJ.
You can also associate the FORTRAN logical names with any of the predefined system
logical names, as shown in the following two examples:
1. The following command associates logical unit 5 with the default input device, for
example, the batch input stream.
$ ASSIGN SYSSINPUT FOR005

2. The following command associates logical unit 6 with the default output device, for
example, the batch output stream.
$ ASSIGN SYSSDUTPUT FOROOG

VAX FORTRAN provides default logical name assignments for logical units 5 and 6, as
shown in the preceding examples.

11.2.2.2 Implied FORTRAN Logical Unit Numbers
The ACCEPT, PRINT, and TYPE statements, and optionally the READ and WRITE
statements, do not include an explicit logical unit number. Each of these FORTRAN
statements uses an implicit logical unit number and logical name. Each logical name is, in
turn, associated by default with one of the system's predefined logical names. Table 11-3
shows these relationships.

VAX FORTRAN Input/Output

11-7

Table 11-3: Implicit FORTRAN Logical Units
Statement

FORTRAN
Logical Name

System
Logical Name

READ (*,f) list

FOR$READ

SYS$INPUT

READ f,list

FOR$READ

SYS$INPUT

ACCEPT f,list

FOR$ACCEPT

SYS$INPUT

WRITE (*,f) list

FOR$PRINT

SYS$0UTPUT

PRINT f,list

FOR$PRINT

SYS$0UTPUT

TYPE f,list

FOR$TYPE

SYS$0UTPUT

You can change the file specifications associated with these FORTRAN logical names, as
you would any other FORTRAN logical name, by means of the VMS ASSIGN command.
For example:
$ ASSIGN USERD:ESMITHJTEST.DATi2 FOR$READ

Following execution of the preceding command, the READ statement's logical name
(FOR$READ) refers to the file TEST.DAT;2 on device USERD in directory [SMITH].
11.2.2.3 File Specification in the OPEN Statement
You can use the FILE and DEFAULTFILE keywords of the OPEN statement to specify the
complete definition of a particular file to be opened on a logical unit. (Section 13.1 describes the OPEN statement in greater detail.) For example:
OPEN <UNIT=a, FILE='USERD:ESMITHJTEST.DATi2', STATUS='OLD'l

In the preceding example, the file TEST.DAT;2 on device USERD in directory SMITH is
to be opened on logical unit 4. Neither the default file specification (FOR004.DAT) nor the
FORTRAN logical name FOR004 is used. The value of the FILE keyword can be a character constant, variable, or expression.
In the following interactive example, the file name is supplied by the user and the
DEFAULTFILE keyword supplies the default values for the file specification string.
CHARACTER*B DOC
TYPE*' 'ENTER FILE NAME <WITHIN APOSTROPHES)'
ACCEPT *' DOC
OPEN <LINIT=2, FILE=DOC,
DEFAULTFILE='USERD:EARCHIVEJ,TXT',
STATUS='OLD'l

In the preceding example, the file that is to be opened is located on device USERD in
directory ARCHIVE, with the file name supplied in DOC and the file type TXT. The
DEFAULTFILE specification overrides your process default device and directory.

11-8

VAX FORTRAN Input/Output

You can also specify a logical name as the value of the FILE keyword, if the logical name is
associated with a file specification. For example:
$ASSIGN USERD:[SMITHJTEST.DAT LOGNAM

The preceding command assigns the logical name LOGNAM to the file specification
USERD:[SMITHJTEST.DAT. The logical name can then be used in an OPEN statement,
as follows:
OPEN

CUNIT=181FILE='LOGNAM'1 STATUS='OLD'l

When an I/0 statement refers to logical unit 19, the system uses the file specification
associated with logical name LOGNAM.
If the value specified for the FILE keyword has no associated file specification, it is regarded as a true file name rather than as a logical name. That is, if LOG NAM had not been
previously associated with the file specification USERD:[SMITHJTEST.DAT by means of
an ASSIGN command, then the above OPEN statement indicates that a file named
LOGNAM.DAT is located on the default device, in the default directory.

A logical name specified in an OPEN statement must not contain brackets, semicolons, or
periods. The system treats any name containing these punctuation marks as a file specification, not as a logical name.

11.2.2.4 Assigning Files to Logical Units-Summary
As described in the preceding sections, you can assign files to logical units in any of three
ways:
• By using default logical names. In the following example, the READ statement causes
the logical unit FOR007 to be associated with the file FOR007 .DAT by default, and the
TYPE statement causes the logical unit FOR$TYPE to be associated with
SYS$0UTPUT by default.
READ

C7 t100 l

TYPE

100

• By specifying a logical name in an OPEN statement. For example:
OPEN

(UN IT=7' FI LE= I LOGNAM I '

STATUS= I OLD I)

• By supplying a file specification in an OPEN statement. For example:
OPEN

CUNIT=71 FILE='FILNAM,DAT'1

STATUS='OLD'l

You can use the ASSIGN command to cha~ge the association of logical names and file
specifications.
A logical name used with the FILE keyword of the OPEN statement must be associated
with a file specification,· and the character expression specified for the FILE keyword must
contain no punctuation marks. Otherwise, the logical name is treated as a true file specification.
VAX FORTRAN Input/Output

11-9

You use the VAXNMS SHOW LOGICAL command to determine the current associations
of logical names and file specifications.
To remove the association of a logical name and a file specification, use the DEASSIGN
command, in the form:
$ DEASSIGN logical-name

11.2.3 File Organizations, 1/0 Record Formats, and Access Modes
A distinction must be made between the way in which files are organized and the way in
which records are accessed. The term "file organization" applies to the way records are
physically arranged on a storage device. "Record access" refers to the method used to read
records from or write records to a file, regardless of its organization. A file's organization is
specified when the file is created, and cannot be changed. In contrast, record access is
specified each time the file is opened, and can be different each time.
The following sections describe in general terms the elements of FORTRAN 1/0 processing:
files, internal files, 1/0 records, and access modes.

11.2.3.1 File Organizations
A file is a collection of logically related records that are arranged in a specific order and
treated as a unit. The arrangement or organization of a file is determined when the file is
created.
VAX FORTRAN supports three kinds of file organization: sequential, relative, and indexed. The organization of a file is specified by means of the ORGANIZATION keyword in
the OPEN statement, as described in Section 13.1.19.
Files are normally stored on disk. Sequential files, however, can be stored on either magnetic tape or disk. Other peripheral devices, such as terminals, card readers, and line
printers, are treated as sequential files.
The three kinds of file organization are discussed individually under the headings that
follow.

Sequential Organization
A sequentially organized file consists of records arranged in the sequence in which they are
written to the file (the first record written is the first record in the file, the second record
written is the second record in the file, and so on). As a result, records can be added only at
the end of the file.
Sequential file organization is permitted on all devices supported by the VMS operating
system.

Relative Organization
A relative file consists of numbered positions, called cells. These cells are of fixed equal
length and are consecutively numbered from 1 to n, where 1 is the first cell, and n is the last
available cell in the.file. Each cell either contains a single record or is empty.
11-10

VAX FORTRAN Input/Output

Records in a relative file are accessed according to cell number. A cell number is a record's
relative record number, that is, its location relative to the beginning of the file. By specifying relative record numbers, you can directly retrieve, add, or delete records regardless of
their locations.
Relative files are supported only on disk devices.

lndmced Organization
An indexed file consists of two or more separate sections: one section contains the data
records, and the other(s) contain the index( es). When an indexed file is created, each index
is associated with a specification defining a field, called a key field, within each record. A
record in an indexed file must contain at least one key. This mandatory key, called the
primary key, determines the location of the records within the body of the file.
The keys of all records are collected to form one or more structured indexes, through which
records are always accessed. The structure of the index(es) allows a program to access
records in an indexed file either randomly, by specifying particular key values, or sequentially, by retrieving records with increasing key values. In addition, keyed access and
sequential access can be mixed. The term Indexed Sequential Access Method (ISAM)
refers to this dynamic access feature.
Indexed files are supported only on disk devices. See Chapter 15 for more information on
indexed files.

11.2.3.2 Internal Files
An internal file is designated internal storage space that is manipulated to facilitate internal 1/0. Its use with formatted and list-directed sequential READ and WRITE statements
eliminates the need to use the ENCODE and DECODE statements for internal 1/0 (see
Appendix A).
An internal file consists of a character variable, a character array element, a character
array, or a character substring; a record in an internal file consists of any of these data
items except a character array.

If an internal file is made up of a single character variable, array element, or substring, that
file comprises a single record whose length is the same as the length of the variable, array
element, or substring. If an internal file is made up of a character array, that file comprises
a sequence of records, with each record consisting of a single array element. The sequence
of records in an internal file is determined by the order of subscript progression.
A record in an internal file can be read only if the character variable, array element, or
substring comprising the record has been defined; that is, a value has been assigned to the
record.
Prior to data transfer, an internal file is always positioned at the beginning of the first
record.

VAX FORTRAN Input/Output

11-11

11.2.3.3 110 Record Formats
An I/O record is a collection of data items, called fields, that are logically related and are
processed as a unit.

NOTE
I/0 records are not to be confused with record entities declared in a program as
structured data items. There is no relationship between structured data items
and I/O records. Structured data items are described in Section 6.2.5.
Generally, each FORTRAN I/O sta~ement transfers one record. The exceptions are formatted, list-directed, and namelist-directed I/0 statements, which can transfer additional
records.
If an input statement does not use all of the data fields in a record, the remaining fields are
ignored. If an input statement requires more data fields than the record contains, either an
error condition occurs or, in the case of formatted input, all fields are read as spaces.
If an output statement attempts to write more data fields than the record can contain, an
error condition occurs. If an output statement transfers less data than is required to fill a
fixed-length record, the record is filled with spaces (if it is a formatted record) or zeros (if it
is an unformatted record).

Records are stored in one of four formats:
• Fixed-length
• Variable-length
• Segmented
• Stream
Fixed-length and variable-length formats can be used with sequential, relative, or indexed
file organization. Segmented format is unique ta FORTRAN; it is not used by other VMSsupported languages. It can only be used with sequential file organization, and only for
unformatted sequential access. You should not use segmented records for files that are read
by programs written in languages other than FORTRAN. Stream format can only be used
with sequential file organization.
The various kinds of I/0 record formats are discussed individually under the headings that
follow.

Fixed-Length Records
When you specify fixed-length records (see Section 13.1.23), you are specifying that all
records in the file contain the same number of bytes. When you create a file that is to
contain fixed-length records, you must specify the record size (see Section 13.1.21). A
sequentially organized file opened for direct access must contain fixed-length records, to
allow the record number to be computed correctly.

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VAX FORTRAN Input/Output

Variable-Length Records
Variable-length records can contain any number of bytes, up to a specified maximum.
These records are prefixed by a count field, indicating the number of bytes in the record.
The count field comprises two bytes on a disk device and four bytes on magnetic tape. The
value stored in the count field indicates the number of data bytes in the record. Variablelength records in relative files are actually stored in fixed-length cells, the size of which
must be specified by means of the RECL keyword of the OPEN statement (see Section
13.1.21). This RECL value specifies the largest record that can be stored in the file.
The count field of a variable-length record is available when you read the record by issuing
a READ statement with a Q format descriptor. You can then use the count field information to determine how many bytes should be in an I/0 list.

Segmented Records
A segmented record is a single logical record consisting of one or more variable-length,
unformatted records in a sequentially organized file. Each variable-length record constitutes a segment. The length of a segmented record is arbitrary. Segmented records are
useful when you want to write exceptionally long records but cannot or do not wish to
define one long variable-length record. Unformatted data written to sequentially organized
files using sequential access is stored as segmented records by default.
Because there is no limit on the size of a segmented record, each variable-length record in
the segmented record contains control information to indicate that it is one of the following:
• The first segment
• The last segment
• The only segment
• None of the above
This control information is contained in the first two bytes of each segment of a segmented
record. Therefore, when you wish to access an unformatted sequential file that contains
variable-length records, you must specify RECORDTYPE= 'VARIABLE' when you open
the file. Otherwise, the first two bytes of each record will be mistakenly interpreted as
control information, and errors will probably result.

Stream Records
A stream-type record is a variable-length record whose length is indicated by explicit
record terminators embedded in the data, not by a count. These terminators are automatically added when you write records to a stream-type file and are removed when you read
records.

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11-13

There are three varieties of stream-type files, each using a different record terminator:
• STREAM files use the 2-character sequence consisting of a carriage-return and a linefeed as the record terminator.
• STREAM_CR files use only a carriage-return as the terminator.
• STREAM_LF files use only a line-feed as the terminator.

11.2.3.4 Record Access Modes
Access mode is the method a program uses to retrieve and store records in a file. The access
mode is specified as part of each I/O statement. VAX FORTRAN supports three record
access modes:
• Sequential
• Direct

° Keyed
Your choic~ of record access mode is affected by the organization of the file to be accessed.
For example, the sequential access mode can be used with sequential, relative, and indexed
files; but the keyed access mode can be used only with indexed organization files.
Table 11-4 shows all the valid combinations of access mode and file organization.

Table 11-4: Valid Combinations of Record Access Mode
Access Mode

File
Organization

Sequential

Direct

Keyed

Sequential

Yes

Yes 1

Relative

Yes

Indexed

Yes

Fixed-length records only.

The three kinds of access mode are discussed individually under the headings that follow.

Sequential Access Mode
If you select sequential access mode for files with sequential or relative organization,
records are written to or read from the file starting at the beginning and continuing through
the file, one record after another. For files with indexed organization, sequential access can
be used to read or write all records according to ascending key values. Sequential access to
indexed files can also be used with keyed access to read or write a group of records at a
specified point in the file.

When you use sequential access for files with sequential and relative organization, a particular record can be retrieved only after all the records preceding it have been read.
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VAX FORTRAN Input/Output

Writing records by means of sequential access also varies according to the file organization.
• For a file with sequential organization, new records can be written only at the end of
the file.
• For a file with relative organization, a new record can be written at any point, replacing the existing record in the specified cell. For example, if two records are read from a
relative file and then a record is written, the new record occupies cell 3 of the file.

° For a file with indexed organization, records can be written in any order, and READ
operations refer to the next record with the same or next higher specified key value.

Direct Access Mode
If you select direct access mode, you determine the order in which records are read or
written. Each READ or WRITE statement must include the relative record number, indicating the record to be read or written.

You can access relative files directly. You can also access a sequential disk file directly if it
contains fixed-length records. Because direct access uses cell numbers to find records, you
can issue successive READ or WRITE statements requesting records that either precede or
follow previously requested records. For example, the following statements, appearing in a
program in the order shown here, read record 24 and then read record 10.
READ (121REC=2a) I
READ (121REC=10) J

tCeyed Access Mode
If you select keyed access mode, you determine the order in which records are read or
written by means of character values or integer values called keys. Each READ statement
contains the key that locates the record. The key value in the 1/0 statement is compared
with index entries until the record is located.
When you insert a new record, the values contained in the key fields of the record determine the record's placement in the file; you do not have to indicate a key.
You can use keyed access only for files with an indexed organization.
Your program can mix keyed access and sequential access I/0 statements on the same file.
You can use keyed 1/0 statements to position the file to a particular record and then use
sequential 1/0 statements to access records with increasing key values in the current keyof-reference.

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11-15

11.3 Components of 1/0 Statements
1/0 statements are composed of three basic components: the statement keyword, the control list, and the l/O list.
The six statement keywords that represent input and output operations are:

Input Operations

Output Operations

READ
ACCEPT

WRITE
REWRITE
TYPE
PRINT

These statements are fully described in Sections 11.4 through 11.8.
The control list and the 1/0 list are discussed in Sections 11.3.1 and 11.3.2, respectively.

11.3.1 Control List
The control list of an 1/0 statement is a list of one or more parameters that specify the
following:
• The logical unit to be acted upon
• The internal file to be acted upon
• Whether formatting is to be used for data editing, and, if it is, the format specification
o The NAMELIST group-name specification

• The cell number of a direct access record to be accessed
0

The key and key-of-reference of a keyed access record to be accessed

• The name of a variable to contain the completion status of an 1/0 operation
• The label of a statement to which control is transferred in the event of an error or endof-file condition
The type of a statement can always be determined by the contents of its control list. For
example, the control list of a formatted 1/0 statement always contains a format specifier
(FMT=f or f), whereas that of a list-directed 1/0 statement always contains an asterisk in
place of a format specifier.
The control list has the form:
(p[,p] ... )

where:
p

is of the form:
[keyword =] value

The keywords and values are explained in the following sections.
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VAX FORTRAN Input/Output

11.3.1.1 Logical Unit Specmer
The logical unit specifier is a parameter that specifies the logical unit to be accessed.
The logical unit specifier has one of the following forms:
[UNIT=]U
[UNIT=]*

where:
u

is an integer expression with a value in the range 0 through 99 that refers to a specific
file or I/0 device. If necessary, the value is converted to integer data type before being
used.
1t

specifies that the default input or output unit is to be accessed.
The keyword UNIT is optional only if the logical unit specifier is the first parameter in the
control list.
A logical unit number is assigned to a file or device in one of two ways:
• Explicitly through an OPEN statement (see Section 13.1)
• Implicitly by the system (see Section 11.2.2.2)

11.3.1.2 Internal File Specifier
An internal file specifier is a parameter that specifies the internal file to be used.
The internal file specifier has the form:
[UNIT=]cv

where:
CV

is a character scalar memory reference or a character array name reference.
The external logical unit specifier and the internal file specifier are mutually exclusive. The
keyword UNIT is optional if the internal file specifier is the first parameter in the control
list.
See Section 11.2.3.2 for more information on internal files.

11.3.1.3 Format Specifiers
The format specifier is a parameter that specifies that explicit or list;.directed formatting is
to be used and, in the case of explicit formatting, identifies the parameter that will control
the formatting.

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The format specifier has the forms:
[FMT =]f
[FMT =)*

where:

is the statement label of a FORMAT statement, an integer variable that has been
assigned a FORMAT statement label with an ASSIGN statement, or the name of an
array, array element, or character expression containing a run-time format.
*

specifies list-directed formatting.
The keyword FMT is optional only if the format specifier is the second parameter in the
control list, and the first parameter is a logical unit or internal file specifier without the
optional keyword UNIT.
Chapter 12 describes FORMAT statements. Section 12.7 describes the interaction between
formats and I/0 statements.
In sequential I/O statements, you can use an asterisk instead of a format specifier to denote
list-directed formatting. See Sections 11.4.1.2 and 11.5.1.2.
11.3.1.4 rJamelist Specifier
The namelist specifier is a parameter that specifies that namelist-directed I/0 is being used
and identifies the group-name of the list of entities that may be modified on input or
written on output.

The namelist specifier has the form:
[NML=]group-name

where:
group-name

is the name of a list previously defined in a NAMELIST statement.
The keyword NML is optional only if (1) the namelist specifier is the second parameter in
the control list and (2) the first parameter is a logical unit specifier without an optional
keyword UNIT. A namelist specifier cannot be used in a statement that contains a format
specifier.

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VAX FORTRAN Input/Output

11.3.1.5 Record Specifier
The record specifier is a parameter that specifies the number of the record to be accessed in
a file with relative organization.
The record specifier has the forms:

{RECd !

where:
r

is a numeric expression with a value that represents the position in a direct access file
of the record to be accessed. The value must be greater than or equal to one, and less
than or equal to the maximum number of record cells allowed in the file. If necessary,
a record number is converted to integer data type before being used.

11.3.1.6 tCey-Field-Ualue Specifier
The key-field-value specifier is a parameter that specifies the key field value of a record to
be accessed in an indexed file. Indexed files are composed of records that have one or more
fields in common; that is, the byte offset, type, and length of the field(s) are the same in
each record in any given indexed file.
The key-field-value specifier has two components:
0

An expression, which specifies the key field value to be used in locating the record to
be transferred

A match criterion, which specifies the selection conditions

A key-field-value specifier has one of the following forms:
KEY=val
KEYEQ=val
KEYGE=val
KEYGT=val

where:
val

is a character expression or an integer expression. Character expressions must be used
with character key fields, and integer expressions must be used with integer key
fields.
An integer expression in a key-field-value specifier cannot contain real and complex values.
A character expression in a key-field-value specifier can be an ASCII string in one of the
following forms:
o A character expression
o A BYTE (LOGICAL* 1) array name containing Hollerith data

VAX FORTRAN Input/Output

11-19

The length of the character expression is the length of the character key field value or the
length of the BYTE array. If the length of the expression is greater than the length of the
key field, an error occurs. If the length of the expression is less than the length of the key
field, a generic key value search rather than an exact key field value search is made.
The match criterion specifies which key values in the record can match the expression.
There are three possible criteria:
0

Equal. The key field value must be equal to the expression specified.

Greater. The key field value must be greater than the expression specified.

Greater than or equal. The. key field value must be greater than or equal to the
expression specified.

The following parameters are used to establish the desired match criterion:
KEY=val
} specifies an equal match.
KEYEQ=val
specifies a greater than match.
KEYGT=val
specifies a greater than or equal match.
KEYGE=val
For character expressions, the comparison is made according to the ASCII collating sequence.
For integer expressions, the comparison is made according to the signed integer value.
For character keys, either generic match or exact match can be used. Generic match
applies if the expression in the 1/0 statement's key specifier is shorter than the key field in
the record. In this case, only the leftmost characters of the key field are used for the match.
For example, if the expression is 'ABCD' and the key field is 10 characters long, then an
equal match i.s obtained for the first record containing 'ABCD' as the first 4 bytes of the
key field. The remaining six characters are arbitrary.
An approximate-generic match occurs when approximate match (KEYGT or KEYGE) is
selected in addition to generic match. In that case, only the leftmost characters are used for
comparison.
For example, if the expression is 'ABCD ', the key field is five characters long, and a
greater-than match is selected, then the value 'ABCDA' does not match; 'ABCEx' does
match.

11.3.1.7 ltey-of-Reference Specifier
The key-of-reference specifier may optionally be included with a key-field-value specifier;
it is used to specify the key field index that is to be searched for the specified key field
value.

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VAX FORTRAN Input/Output

The key-of-reference specifier has the form:
KEYID=kn

where:
Im

is an integer expression, called the key-of-reference number, that designates the key
field index to be searched.
The key-of-reference number is an integer value in the range zero to the maximum key
number defined for the file. A value of zero specifies the primary key, a value of one
specifies the first alternate key, and so forth.
If no key-of-reference number is given, it defaults to the last specification given in a keyed

I/0 statement for that logical unit.

11.3.1.8 110 Status Specifier
The I/O status specifier. designates a variable in which a value is stored that indicates
whether an error or end-of-file condition exists. If the value is zero, no error or end-of-file
condition exists. If the value is positive, an error condition exists. If the value is negative,
an end-of-file condition exists, but an error condition does not.
The I/0 status specifier has the form:
IOSTAT=ios

where:
ios

is an integer scalar memory reference.
Refer to Section 18.3 for more information on the error numbers returned by IOSTAT.

11.3.1.9 Transfer-of-Control Specifiers
The transfer-of-control specifiers are parameters that transfer control of the program to a
specific statement in the event of an end-of-file condition or an error condition.
The transfer-of-control specifiers have the form:
END=s
ERR=s

where:
s
is the label of the executable statement to which control is to be transferred.
A sequential· READ statement can include either or both of the above specifications, in any
order. WRITE, REWRITE, direct access READ, and keyed access READ statements can
include only the ERR=s specification.

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11-21

The statement label in the END=s or ERR=s specification must refer to ·an executable
statement within the same program unit as that of the I/0 statement.
An end-of-file condition occurs when no more records exist in a file during a sequential
read, or when an end-file record produced by the ENDFILE statement is encountered (see
Section 9.6). End-of-file conditions do not occur in direct access or keyed access READ
statements. If a READ statement encounters an end-of-file condition during an I/0 operation, it transfers control to the statement named in the END=s specification; if there is no
END=s specification and no IOSTAT specifier, an error occurs.
If a READ, WRITE, or REWRITE statement encounters an error condition during an I/0
operation, it transfers control to the statement whose label appears in the ERR=s specification. If neither an ERR specifier nor an IOSTAT specifier is present, the I/0 error terminates program execution.

The VAX FORTRAN User's Guide describes system subroutines that you can use to
control error processing. To obtain information from the I/0 system on the type of error
that occurred, use the IOSTAT parameter discussed in Section 11.3.1.8.
Examples of I/O statements follow:
1. The following READ statement transfers control to statement 550 if an end-of-file
condition occurs on logical unit 8.
RE AD ( 8 t END =5 5 0 l ( MAT RI )-( ( K). , K= 1 , 1 0 0 l

2. The following WRITE statement transfers control to statement 390 if an error occurs

while it is being executed.
WRITE (Gt50tERR=380l VAR1 t VAR2t VAR3

3. The following READ statement transfers control to statement 150 (if an error occurs
while it is being executed) or to statement 200 (if an end-of-file condition occurs).
READ (1 tFORMtERR=150tEND=200l ARRAY

11.3.1.1 O Rules for Specifying Control List Parameters-Summary
The FORTRAN I/0 statements described in Sections 11.4 through 11.8 are subject to the
following syntactical rules:
1. For the keyword form of control-list parameters (that is, when the control-list parameter is specified with a keyword and equal sign):
-

11-22

The control-list parameters can appear in any order in the control list. An exception to this rule occurs when keyword and nonkeyword forms are intermixed in
the same I/0 statement. In this case, the provisions of the rules for nonkeyword
form take precedence.

VAX FORTRAN Input/Output

2. For the nonkeyword form of control-list parameters (that is, when the control-list
parameter is specified without a keyword and equal sign):
-

Either the logical unit specifier or the internal file specifier must occupy the first
(leftmost) position in the control list.

When used with a logical unit specifier or internal file specifier, the nonkeyword
form of the format or namelist specifier must occupy the second position in the
control list; the unit or internal file specifier must also be in nonkeyword form
(and therefore occupy the first position in the control list).

- The nonkeyword form of the direct access record specifier must immediately
follow the nonkeyword form of the logical unit specifier.

11.3.2 1/0 List
The I/0 list in an input or output statement contains the scalar references, array name
references, and aggregate references specifying the memory locations from which or to
which data will be transferred. (See Section 6.2.6 for a description of the different types of
references.)
The I/0 list in an input statement cannot contain constants and expressions because these
do not specify named memory locations that can be referenced later in the program. The
I/0 list in an output statement can contain constants and expressions, however, because
the compiler can use temporary memory locations to hold these values during the execution
of the I/0 statement.
An I/0 list has the following form:
s[,s] ...

where:
s

is a simple list element or an implied-DO list.
The I/O statement assigns values to, or transfers values from, the list elements in the order
in which they appear, from left to right.

11.3.2.1 Simple List Elements
A simple I/O list element can be a scalar reference, scalar array name reference, or aggregate reference. For example:
WRITE

C5t10>

J, KC3),

CL+L!)/2t N

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When you use an array name reference or an aggregate reference in an 1/0 list, an input
statement reads enough data to fill every element of the array or aggregate; an output
statement writes all of the values in the array or aggregate. Data transfer begins with the
initial element of the array and proceeds in the order of subscript progression, with the
leftmost subscript varying most rapidly. For example, the following defines a two-dimensional array:
DIMENSION ARRAY(313)

If the name ARRAY, with no subscripts, appears in a READ statement, that statement
assigns values from the input record(s) to ARRAY(l,l), ARRAY(2,l), ARRAY(3,1), ARRAY(l,2), and so on through ARRAY(3,3).

In an input statement, variables in the 1/0 list can be used in array subscripts later in the
list. For example:
READ (111250) J, Kt ARRAYCJ1K)
1250 FORMAT (Ilt1}{1Il1rn1F6.2)

The input record contains the following values: 1,3,721.73
When the READ statement is executed, the first input value is assigned to J and the
second to K, thereby establishing the actual subscript values for ARRAY(J,K). Then the
value 721.73 is assigned to ARRAY(l,3). Variables that are to be used as subscripts in this
way must appear before (to the left of) their use as the array subscripts in the 1/0 list.
An output statement 1/0 list may contain any valid expression. However, this expression
must not attempt any further 1/0 operations on the same logical unit. For example, an
output statement 1/0 list expression must not refer to a function subprogram that performs
1/0 on the same logical unit.

An input statement 1/0 list must not contain a constant or an expression, except as a
subscript'expression in an array reference or as an expression in a substring reference.
Aggregate references can be used only in unformatted input and output statements. When
multiple array names or aggregate references are used in the 1/0 list of an unformatted
input or output statement, only one record is read or written regardless of how many array
name references or aggregate references appear in the list.

11.3.2.2 Implied-DO Lists in 1/0 Statements
An implied-DO list is an 1/0 list element that functions as though it were a part of an 1/0
statement within a DO loop. Implied-DO lists can be used to:
• Specify iteration of part of an 1/0 list
• Transfer part of an array
• Transfer array elements in a sequence different from the order of subscript progression
An implied-DO list has the form:
(list, i=e1 ,e2[,e3])

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VAX FORTRAN Input/Output

where:
list

is an 1/0 list.
is an integer or real variable.
e1,e2,e3

are arithmetic expressions.
The variable i and the parameters el, e2, and e3 have the same forms and the same
functions that they have in the DO statement (see Section 9.3). The list immediately
preceding the DO loop parameter is the range of the implied-DO loop. Elements in that list
can reference i, but they must not alter the value of i. Some examples of the use of impliedDO lists follow.

Examples
1. The following two WRITE statements have the same effect.
WRITE

C3t200)

CAtBtCt I=1t3)

C3t200)

AtBtCtAtBtCtAtBtC

and
WRITE

2. In the following example, the I/0 list consists of an implied-DO list containing
another implied-DO list nested within it.
WRITE

CG)

CI t

CJ t PC I ) t QC I t J) t J = 1 t U

I= 1 t M)

Together, the implied-DO lists write a total of (1+3*L)*M fields, varying the Js for
each value of I.
3. In a series of nested implied-DO lists, the parentheses indicate the nesting (see
Section 9.3.1.2). Execution of the innermost lists is repeated most often. For example:
150

WRITE CG t150) CCFORMCK tU t L=1 t10) t K=1 t10 /z)
FORMAT CF10.2)

Because the inner DO loop is executed 10 times for each iteration of the outer loop,
the second subscript, L, advances from 1 through 10 for each increment of the first
subscript. This is the reverse of the order of subscript progression. In addition, K is
incremented by 2; thus, only the odd-numbered rows of the array are output.
4. The entire list of an implied-DO list is transmitted before the control variable is
incremented. For example:
READ

C5t989)

CPCI) t

CQCI tJ) t J=1 t10) t

I=1 t5)

In this example, P(l), Q(l,1), Q(l,2) .. .,Q(l,10) are read before I is incremented to 2.
VAX FORTRAN Input/Output

11-25

5. When processing multidimensional arrays, you can use a combination of fixed subscripts and subscripts that vary according to an implied-DO list. For example:
READ

(3 t5555)

(BO}-(( 1 tJ)

t J=1 t10)

This statement assigns input values to BOX(l,1) through BOX(l,10) and then terminates without affecting other elements of the array.
6. The value of the control variable can also be output directly. For example:
WR I TE

( G tl 111 )

(I t

I= 1 t 20)

This statement simply prints the integers 1 through 20.
If the 1/0 statement containing an implied-DO list terminates abnormally (that is, with an

END= or ERR= transfer or with an IOSTAT value other than zero), the loop control
variable becomes undefined.

11.4 READ Statements
The READ statements transfer input data to internal storage from records contained in
external logical units or to internal storage from internal files.
The four types of READ statement-sequential, direct, indexed, and internal-are described in Sections 11.4.1 through 11.4.4.

11.4.1 Sequential READ Statements
Sequential READ statements transfer input data to internal storage from external records
accessed under the sequential mode of access.
The formats of the four forms of sequential READ statement-formatted, list-directed,
namelist-directed, and unformatted-are as follows:

Formatted
READ (extu,fmt[,iostat][,err][,end]) [iolist]
READ f[,iolist]

List-Directed
READ (extu,•[,iostat][,err][,end]) [iolist]
READ *[,iolist]

rJamelist-Directed
READ (extu,nml[,iostat][,eri][,end])
READ n

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VAX FORTRAN Input/Output

Unformatted
READ (extu[,iostat][,err][,end]) [iolist]

The meanings of the symbolic abbreviations used to represent control-list parameters in
the preceding command lines are as follows:
• extu-a logical unit specifier.
• fmt-a format specifier.
• f-the nonkeyword form of a format specifier. See fmt, above.
• *-specifies list-directed formatting. You can also use FMT=*·
o nml-a namelist specifier.
o

n-the nonkeyword form of a namelist specifier. See nml, above.

• iostat-an 1/0 status specifier.
• err/end-transfer-of-control specifiers.
The I/0-list parameter is represented by the symbolic abbreviation iolist.
All of the parameters used in 1/0 statements are described in Sections 11.3.1 (control-list
parameters) and 11.3.2 (l/0-list parameter). The rules for specifying control-list parameters are summarized in Section 11.3.1.10.
The uses and effects of the four forms of sequential READ statements are described in
Sections 11.4.1.1 through 11.4.1.4.

11.4.1.1 Formatted Sequential READ Statement
The formatted sequential READ statement performs the following operations:
• Reads character data from one or more external records accessed under the sequential
or keyed mode of access.
• Translates the data from character to binary form using format specifications to provide editing.
• Assigns the translated data to the elements in the 1/0 list, in the order, from left to
right, in which those elements appear in the list.
If the number of 1/0 list elements in a statement is less than the number of fields in an
input record, the statement ignores the excess fields.

See Section 11.4.3 for information about the combined use of formatted sequential READ
statements and indexed READ statements under the keyed mode of access.

VAX FORTRAN Input/Output

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11.4.1.2 List-Directed Sequential READ Statement
The list-directed sequential READ statement performs the following operations:
• Reads character data from records accessed under the sequential mode of access.
• Translates the data from external to binary form using the data types of the elements
in the I/0 list, and the forms of the data, to provide editing.
• Assigns the translated data to the elements in the 1/0 list in the order, from left to
right, in which those elements appear in the list.
The external records from which list-directed .READ statements read data contain a sequence of values and value separators.
A value in one of these records may be any one of the following:

• A constant-each constant has the form of the corresponding FORTRAN constant.
Input constants can be any of the following data types: integer, real, logical, complex,
and character. The data type of the constant determines the data type of the value and
the translation from external to internal form.
A numeric list element can correspond only to a numeric constant, and a character list
element can correspond only to a character constant. If the data types of a numeric list
element and its corresponding numeric constant do not match, conversion is performed according to the rules for arithmetic assignment (see Table 7-1).
A complex constant has the form of a pair of real or integer constants separated by a
comma and enclosed in parentheses. Spaces can occur between the opening parenthesis and the first constant, before and after the separating comma, and between the
second constant and the closing parenthesis.
A logical constant represents true or false values, that is, .TRUE. or any value beginning with T, .T, t, or .t; or .FALSE. or any value beginning with F, .F, f, or .f.
A character constant is delimited by apostrophes. An apostrophe occurring within a
character constant is represented by two consecutive apostrophes.
Hollerith, octal, and hexadecimal constants are not permitted.

• A null value-a null value is specified by two consecutive commas with no intervening
constant, or by an initial comma or trailing comma. Spaces can occur before or after
the commas. A null value indicates that the corresponding list element remains unchanged. A null value can represent an entire complex constant, but cannot be used
for either part of a complex constant.
• A repetition of constants in the form r*c-the form r*c indicates r occurrences of c,
where r is a nonzero, unsigned integer constant and c is a constant. Spaces are not
permitted except within the constant c as specified above.
• A repetition of null values in the form r*-the form r* indicates r occurrences of a null
value, where r is an unsigned integer constant.

11-28

VAX FORTRAN Input/Output

A value separator in a record can be any one of the following:
• One or more spaces or tabs
• A comma, with or without surrounding spaces or tabs
• A slash, with or without surrounding spaces or tabs
The slash terminates processing of the input statement and the record, leaving all remaining I/0 list elements unchanged.
When any of the above appear in a character constant, they are considered part of the
constant, not value separators.
The end of a record is equivalent to a space character except when it occurs in a character
constant. In this case, the end of the record is ignored, and the character constant is
continued with the next record. That is, the last character in the previous record is followed
immediately by the first character of the next record.
Spaces at the beginning of a record are ignored unless they are part of a character constant
continued from the previous record. In this case, the spaces at the beginning of the record
are considered part of the constant.
Each input statement reads one or more records as required to satisfy the I/0 list. If a slash
separator occurs or the I/0 list is exhausted before all the values in a record are used, the
remainder of the record is ignored.
An example of the use of list-directed READ statements follows.
A program unit consists of:
CHARACTER*1Ll C
DOUBLE PRECISION T
COMPLE){ D tE
LOGICAL LtM
READ (1,*) ItRtDtEtLtMtJtKtS1TtCtAtB

And the external record to be read contains:
a G.3 <3.a ,a.2>, <3, 2 > , r ,F, ,3*1a.s , 'ABC ,oEF/GHI' 'JK '1

VAX FORTRAN Input/Output

11-29

Upon execution of the program unit, the following values are assigned to the 1/0 list
elements:

1/0 List
Element
I
R
D
E
L
M
K

Value
4
6.3

(3.4,4.2)
(3.0,2.0)
.TRUE.
.FALSE.
14
14.6
14.6DO

ABC,DEF/GHI 'JK

A, B, and J are unchanged.

11.4.1.3 fJamelist-Directed Sequential READ Statement
The namelist-directed sequential READ statement performs the following operations:
o Reads data from external records accessed under the sequential mode of access until it

finds the specified group-name.
0

Translates the data from external to internal form using the data types of the entities
in the corresponding NAMELIST statement, and the forms of the data, to provide
editing.

o Assigns the translated data to the specified namelist entities in the order in which the

entities appear in the input records.
An example of the namelist-directed READ statement follows.
NAMELIST /CONTROL/ TITLE, RESET1 START, STOP, INTERVAL
CHARACTER*10 TITLE
REAL*B START1 STOP
LOGICAL*ll RESET
INTEGER*ll INTERVAL
READ (UN IT= 1 , NML= CONTROL>

In this example, the NAMELIST statement associates the group-name CONTROL with a
list of five entities. The corresponding READ statement reads input data and assigns
values to specified namelist entities.
The input for a namelist-directed READ consists of a record or records delimited by the
special symbol dollar sign ( $ ) , which starts in the second column of the first record.

11-30

VAX FORTRAN Input/Output

The namelist input has the form:
column 2

•

$group-name entity = value [,entity = value ,... ] $[END]

where:
$

is the special symbol used to indicate the beginning or end of input. The ampersand
( & ) can be used in place of the dollar sign.
group-name

is the name of the namelist that contains the entity or entities to be given values. The
namelist must have been previously defined in a NAMELIST statement in the program unit.
entity

is a namelist-defined entity. The entity can be a variable, array name, subscripted
variable, variable with a substring, or subscripted variable with a substring.
value

is a constant, a list of constants, a repetition of constants in the form r*c, or a
repetition of values in the form r* (see Section 11.4.1.2).
END

is an optional part of the last delimiter.
Information on syntax rules for namelist input, prompting for current values, and assigning
values is presented separately under the headings that follow.

Svntmc Rules for rJamelisi Input
The following syntax rules apply to creating namelist input:
1. The group-name cannot contain spaces or tabs and must be contained within a
single record.

2. The entities appearing on the left side of the equal sign in a value assignment cannot
contain spaces or tabs except within the parentheses of a subscript or substring
specifier. Each entity must be contained in a single record.
3. Each constant that appears in a value assignment has the form of the corresponding
FORTRAN constant. A complex constant has the form of a pair of real or integer
constants separated by a comma and enclosed in parentheses. Spaces can occur
between the opening parenthesis and the first constant, before and after the separating comma, and between the second constant and the closing parenthesis.
4. A logical constant represents true or false values, that is, .TRUE. or any value
beginning with T, .T, t, or .t; or .FALSE. or any value beginning with F, .F, f, or .f. A

VAX FORTRAN Input/Output

11-31

character constant is delimited by apostrophes. An apostrophe occurring within a
character constant is represented by two consecutive apostrophes. Hollerith, octal,
and hexadecimal constants are not permitted.
5. The valid separators in a list of constants are spaces, tabs, and commas. Except
within a character constant, any number of consecutive spaces and tabs is equivalent
to a single space. A null value is specified by two consecutive commas, by an initial
comma, or by a trailing comma. A separating comma preceded or followed by spaces
is equivalent to a single comma. A null value indicates that the corresponding
namelist array element is unchanged. A null value can represent an entire complex
constant, but it cannot be used for either part of a complex constant.
6. The form r*c indicates r occurrences of c, where r is a nonzero, unsigned integer
constant and c is a constant. Spaces are not permitted except within the constant c
in complex or character constants.
7. The form r* indicates r occurrences of a null value, where r is an unsigned integer
constant.
8. The valid separators in a list of value assignments are spaces, tabs, and commas.
Any number of consecutive spaces and tabs is equivalent to a single space. A
separating comma preceded or followed by spaces is equivalent to a single comma.
Consecutive commas are not permitted.
9. The equal sign in a value assignment can be preceded and followed by any number of
spaces or tabs.
10. The end of a record in namelist input is equivalent to a space character except when
the end of the record occurs in a character constant. If this occurs, the end of the
record is ignored, and the character constant is continued with the next record. That
is, the last character in the previous record is followed immediately by the second
character of the next record. The first character is used for carriage control.

Prompting ior Current Ualues
If your program is executing a namelist READ statement, you may prompt it for the group
name and namelist entities that it will accept. To do this, enter a question mark ( ? ) record
character. The group name and current values of the namelist entities for that group will
then be displayed as in name list output (see Section 11.5.1.3).

Assigning Ualues
Input values can be assigned in any order using an assignment of the form: entity=value.
Each new li~e of input may begin in column 2 or in any column thereafter. Column 1 of
each record is assumed to contain a FORTRAN carriage-control character, and any data
placed in that column is ignored.
Assigned values, array subscripts, and substring specifiers must be constant values; use of
symbolic (PARAMETER) constants is not permitted.

11-32

VAX FORTRAN Input/Output

Input values can be any of the following data types: integer, real, logical, complex, and
character. If the data type of a name list entity and its assigned constant value do not
match, conversion is performed according to the rules for arithmetic assignment (see Table
7-1). Conversion between numeric and character data types is not permitted.
An example of namelist-directed data input follows.
co 1 ur11n 2

$CONTROL
@m TITLE= I TESTT002AA I '
@m INTERl,JAL=l 1
@m RESET=, TRUE, ,
@m START=10.21
@m STOP =!t'.l.5
$END

Upon program execution, values are assigned to list entities with the following results:

Entity

Value

TITLE
RESET
START
STOP
INTERVAL

TESTT002AA
T
10.2

14.5
1

In this example, values were assigned to all of the namelist entities previously associated
with the group-name CONTROL. However, it is not necessary to assign values to all of the
list entities defined in the corresponding NAMELIST group-name.
The namelist-directed READ statement does not change the values of namelist entities
that do not appear in the input data. Similarly, when character substrings and array
elements are specified, only the values of the specified variable substrings and array elements are changed. For example, if the next input to the character variable TITLE used in
the last example contains
C 0 1 Ul1ll"I

$CONTROL6TITLE(8:10)='BB'6$END

then its new value is TESTT002BB; the first eight positions of the variable do not change.
When a list of values is assigned to an array name, the first value in that list is assigned to
the first element of the array, the second value is assigned to the second element of the
array, and so on. The number of array elements assigned must be less than or equal to the
size of the array. Consecutive commas within a list indicate that the values of the array
elements remain unchanged. An example follows.

VAX FORTRAN Input/Output

11-33

A program unit contains:
DIMENSION ARRAYC20l
NAMELIST /ELEM/ ARRAY
READ <UNIT=l 1NML=ELEMl

and the input contains:
colur1in 2

$ELEM
ARRAY=l +1, 1.2, , 1,ll$END

Upon program execution, the READ statement assigns values to array elements with the
following results:

Array Element

Value

ARRAY(l)
ARRAY(2)
ARRAY(3)
ARRAY(4)
ARRAY(5) - ARRAY(20)

1.1
1.2
unchanged
1.4
unchanged

When a list of values is assigned to an array element, the assignment begins with the
specified array element, rather than with the first element of the array. For example, if the
next input to ARRAY consists of the following:
colur1in 2

v
$ELEM
ARRAYC3l=3l!.5ll1 ll5+3llt 87.631 3*20.00
$END

Upon program execution, the READ statement assigns new values only to ARRAY elements 3 through 8; it does not alter unspecified elements.

11.4.1.4 Unformatted Sequential READ Statement
The unformatted sequential READ statement reads an external record accessed under the
sequential or keyed mode of access; it assigns the fields of binary data contained in that
record to the elements in the 1/0 list, in the order, from left to right, in which those
elements appear in the list. The data is not translated. The amount of data assigned to
each element is determined by the element's data type.
The unformatted sequential READ statement reads exactly one record. If the VO list does
not use all the values in a record, the remainder of the record is discarded; this happens
when there are more values in the record than elements in the list. If the number of list
elements is greater than the number of values in the record, an error occurs.
If a statement contains no 1/0 list, it skips over one full record, positioning the file to read

the following record on the next execution of a READ statement.

11-34

VAX FORTRAN Input/Output

Some examples of the use of the unformatted sequential READ statement follow.
1. In the following example, the READ statement reads one record from the file connected to logical unit 1 and assigns values of binary data to variables FIELDl and
FIELD2, in that order.
READ

(LJNIT=1 l

FIELD11 FIELD2

2. In the following example, the READ statement advances the file connected to logical
unit 8 by one record.
READ

( 8)

11.4.2 Direct Access READ Statements
Direct access READ statements transfer input data to internal storage from external records accessed under the direct mode of access.
The formats of the two forms of direct access READ statement-formatted and unformatted-are as follows:

Formatted
READ (extu,rec,fmt[,iostat][,err]) [iolist]

Unformatted
READ (extu,rec[,iostat][,err]) [iolist]

The meanings of the symbolic abbreviations used to represent control-list parameters in
the preceding command lines are as follows:
• extu-a logical unit specifier
• rec-a record specifier
• fmt-a format specifier
• iostat-an I/0 status specifier
• err-transfer-of-control specifier
The 1/0-list parameter is represented by the symbolic abbreviation iolist.
All of the parameters used in I/O statements are described in Sections 11.3.1 (control-list
parameters) and 11.3.2 (I/0-list parameter). The rules for specifying control-list parameters are summarized in Section 11.3.1.10.
The uses and effects of the two forms of direct access READ statements are described in
Sections 11.4.2.1 and 11.4.2.2.

VAX FORTRAN Input/Output

11-35

11.4.2.1 Formatted Direct Access READ Statement
The formatted direct access READ statement performs the following operations:
• Reads character data from one or more external records accessed under the direct
mode of access.
• Translates the data from character to binary form using format specifications to provide editing.
• Assigns the translated data to the elements in the I/0 list, in the order, from left to
right, in which those elements appear in the list.
If the I/0 list and formatting do not use all the characters in a record, the remainder of the

record is discarded; if the I/O list and formatting require more characters than are contained in the record, the remaining fields are read as spaces.
An example of the use of the formatted direct access READ statement is:
READ (21REC=351FMT=10)
FORMAT <1012)

<NUM<Kl,

K=l t10)

In this example, the READ and FORMAT statements read thefirst 10 fields from record 35
in the file connected to logical unit 2, translate the values to binary form, and then assign
the translated values to the internal storage locations of the 10 elements of the array NUM.

11.4.2.2 Unformatted Direct Access READ Statement
The unformatted direct access READ statement reads an external record accessed under
the direct mode of access; it assigns the fields of binary data contained in that record to the
elements in the I/O list, in the order, from left to right, in which those elements appear in
the list. The data is not translated. The amount of data assigned to each element is
determined. by that element's data type.
The unformatted direct access READ statement reads exactly one record. If that record
contains more fields than there are elements in the I/0 list of the statement, the unused
fields are discarded; if there are more elements than fields, an error occurs.
Examples of the use of unformatted direct access READ statements follow.
1. In the following example, the READ statement reads record 10 in the file connected
to logical unit 1 and assigns binary integer values to elements 1 and 8 of the array
LIST.
READ

( 1'10)

LIST( 1), LIST(8)

2. In the following example, the READ statement reads record 58 in the file connected
to logical unit 4 and assigns binary values to five elements of the array RHO.
READ

11-36

Ul 1REC=58 t!DSTAT=K 1ERR=500)

VAX FORTRAN Input/Output

(RHO(N), N=l 15)

11.4.3 lndemad rllEAD SiaRemenis
The indexed READ statement transfers input data to internal storage from external records accessed under the keyed mode of access. There are two classes: formatted and
unformatted.
A series of records in an indexed file can be read in key value sequence by using a sequential READ statement in conjunction with an indexed READ statement. The first record in
the sequence is read using the indexed statement; the rest are read using sequential statements.
The forms of the two classes of indexed READ statement are as follows:

Formatted
READ (extu,fmt,key[,keyid][,iostat][,err]} [iolist]

Unformatted
READ (extu ,key[,keyid][,iostat][,err]} [iolist]

The meanings of the symbolic abbreviations used to represent control-list parameters in
the preceding command lines are as follows:
o

extu-a logical unit specifier

o fmt-a format specifier
o key-a key specifier

o keyid-a key-of-reference specifier
0

iostat-an I/0 status specifier

o err-transfer-of-control specifier

The I/0-list parameter is represented by the symbolic abbreviation iolist.
All of the parameters used in I/0 statements are described in Sections 11.3.1 (control-list
parameters) and 11.3.2 (I/0-list parameter). The rules for specifying control-list parameters are summarized in Section 11.3.1.10.
The uses and effects of the two forms of indexed READ statements are described in
Sections 11.4.3.1 and 11.4.3.2.

VAX FORTRAN Input/Output

11-37

11.4.3.1 Formatted lndmred READ Statement
The formatted indexed READ statement performs the following operations:
o Reads character data from

one or more external records accessed under the keyed

mode of access.
0

Translates the data from character to binary form using format specifications to provide editing.

o Assigns the translated values to the elements in the 1/0 list, in the order, from left to

right, in which they appear in the list.
The formatted indexed READ statement may be used only on indexed files. If the 1/0 list
and format specifications specify that additional records are to be read, the statement
reads those additional records sequentially using the current key-of-reference value.
If the KEYID parameter is omitted, the key-of-reference remains unchanged from the most
recent specification. If the KEYID parameter is omitted from the first keyed read, the keyof-reference is the primary key.
If the specified key value is shorter than the key field referred to, the key value is matched
against the leftmost characters of the appropriate key field until a match is found; the
record supplying the match is then read. If the key value is longer than the key field
referred to, an error occurs.

An example of the use of the formatted indexed READ statement is:
READ

(31KAT<25l1KEY='ABCD'l

A1B1C1D

In this example the READ statement retrieves a record with a key value of 'ABCD' in the
primary key, and then uses the format contained in the array item KAT(25) to read the
first four fields from the record into variables A,B,C, and D.

11.4.3.2 Unformatted lnde1ced READ Statement
The unformatted indexed READ statement reads an external record accessed under the
keyed mode of access; it assigns the fields of binary data contained in that record to the
elements in the 1/0 list, in the order, from left to right, in which those elements appear in
the list. The data is not translated. The amount of data assigned to each element is
determined by the element's data type.
The unformatted indexed READ statement reads exactly one record, and may be used only
on indexed files. If the number of 1/0 list elements is less than the number of fields in the
record being read, the unused fields in the record are discarded. If the number of 1/0 list
elements is greater than the number of fields, an error occurs.
If a specified key value is shorter than the key field referred to, the key value is matched
against the leftmost characters of the appropriate key field until a match is found; the
record supplying the match is then read. If the specified key value is longer than the key
field referred to, an error occurs.

11-38

VAX FORTRAN Input/Output

Some examples of the use of the unformatted indexed READ statement follow.
OPEN
2
3

CUNIT=31 STATUS='OLD' 1
ACCESS= 'KEYED I ' ORGANIZATION= I INDE>:ED I '
FORM='UNFORMATTED',
KEY=C1:5130:37'18:23))

READ

(31KEY='SMITH')

ALPHA1

BETA

In this example, the READ statement reads from the file connected to logical unit 3 and
retrieves the record with the value 'SMITH' in the primary key field (bytes 1 to 5). The
first two fields of the record retrieved are placed in variables ALPHA and BETA, respectively.
READ

(3 1KEYGE= '){YZOEF' 1KEYID=2 1ERR=88)

IKEY

In this example, the READ statement retrieves the first record having a value equal to or
greater than 'XYZDEF' in the second alternate key field (bytes 18 to 23). The first field of
that record is placed in the variable IKEY.

11.4.4 Internal READ Statement
The internal READ statement transfers input data to internal storage from an internal file.
The DECODE statement discussed in Appendix A may be used as an alternative to the
internal READ statement. There are two classes of internal READ statement: formatted
and list-directed.
The forms of the two classes of internal READ statement are as follows:

Formatted
READ (in tu ,fmt[,iostat][,err][,end]) [iolist]

List-Directed
READ (in tu, *[,iostat][,err][,end]) [iolist]

The meanings of the symbolic abbreviations used to represent control-list parameters in
the preceding command lines are as follows:
• intu-an internal file specifier.
• fmt-a format specifier.
• *-the list-directed formatting specifier. You can also use FMT=*.
• iostat-an I/0 status specifier.
• err/end-transfer-of-control specifiers.
The I/0-list parameter is represented by the symbolic abbreviation iolist.

VAX FORTRAN Input/Output

11-39

All of the parameters used in 1/0 statements are described in Sections 11.3.1 (control-list
parameters) and 11.3.2 (1/0-list parameter). The rules for specifying control-list parameters are summarized in Section 11.3.1.10.
The uses and effects of the two forms of internal READ statements are described in
Sections 11.4.4.1 and 11.4.4.2.

11.4.4.1 Formatted Internal READ Statement
The formatted internal READ statement performs the following operations:
• Reads character data from an internal file.
• Translates the data from character to binary form using format specifications to provide editing.
. • Assigns the translated data to the elements in the 1/0 list, in the order, from left to
right, in which those elements appear in the list.

11.4.4.2 List-Directed Internal READ Statement
The list-directed internal READ statement performs the following operations:
o Reads character data from an internal file.

o Translates the data from external to binary form using the data types of the elements

in the 1/0 list and the forms of the data to provide editing.
0

Assigns the translated data to the elements in the 1/0 list, in the order, from left to
right, in which those elements appear in the list.

Namelist-directed formatting is not permitted with an internal READ statement. Refer-to
Section 11.2.3.2 for information on the characteristics and use of internal files.
The following program segment demonstrates the use of internal-file reads:
INTEGER I l,IAL
CHARACTER TYPEt RECORD*BO
CHARACTER*(*) AFMTt IFMTt OFMTt ZFMT
PARAMETER <AFMT='(OtA) I t IFMT= '(110) I ' OFMT=
1
ZFMT= '(Z8)')
ACCEPT AFMT1 ILEN1 RECORD
TYPE = RECORD(l:l)
IF <TYPE ,EQ, 'D') THEN
READ <RECORD ( 2: MIN (I LEN, 11) ) 1 I FMTl 11.'AL
ELSE IF (TYPE ,EQ, '0') THEN
READ (RECORD ( 2: MIN (I LEN, 12) ) , OFMTl 11.'AL
ELSE IF (TYPE t EQ t ')-(I) THEN
READ <RECORD(2:MIN( ILEN 1 8)) 1ZFMTl ll.'AL
ELSE
PR I NT *' I ERROR I
END IF
END

11-40

VAX FORTRAN Input/Output

'(011) I t

This program segment reads a record and examines the first character to determine
whether the remaining data should be interpreted as decimal, octal, or hexadecimal. It
then uses internal-file reads to make appropriate conversions from character string representations to binary.

11.5 WRITE Statements
The WRITE statements transfer output data from internal storage to user-specified external logical units (disks, printers, terminals, mailboxes) or to internal files.
WRITE statements can be used in sequential, direct, keyed, or internal access modes.
These forms of the WRITE statement are discussed in Sections 11.5.1 through 11.5.4.
WRITE statements cannot write to existing records in an indexed file. For statements that
can perform this function in indexed files, refer to the REWRITE statement discussed in
Section 11.6.

11.5.1 Sequential WRITE Statements
Sequential WRITE statements transfer output data from internal storage to external records accessed under the sequential mode of access. See Section 11.2.3.4 for descriptions of
the various access modes.
The formats of the four forms of sequential WRITE statement are as follows:

Formatted
WRITE (extu,fmt[,iostat][,err]) [iolist]

List-Directed
WRITE (extu,*[,iostat][,err]) [iolist]

rJamelist-Directed
WRITE (extu,nml[,iostat][,err])

Unformatted
WRITE (extu[,iostat][,err]) [iolist]

The meanings of the symbolic abbreviations used to represent control-list parameters in
the preceding command lines are as follows:
• extu-a logical unit specifier.
• fmt-a format specifier.
• *-the list-directed formatting specifier. You can also use FMT=*.

VAX FORTRAN Input/Output

11-41

o nml-a namelist specifier.

• iostat-an I/0 status specifier.
• err-a transfer-of-control specifier.
The I/0-list parameter is represented by the symbolic abbreviation iolist.
All of the parameters used in I/0 statements are described in Sections 11.3.1 (control-list
parameters) and 11.3.2 (I/0-list parameter). The rules for specifying control-list parameters are summarized in Section 11.3.1.10.
The uses and effects of the four forms of sequential WRITE statements are described in
Sections 11.5.1.1 through 11.5.1.4.

11.5.1.1 Formatted Sequential WRITE Statement
The formatted sequential WRITE statement performs the following operations:
• Retrieves specified data from internal storage.
• Translates the data from binary to character form using format specifications to provide editing.
• Writes the translated values to an external record accessed under the sequential mode
of access.
· The length of the records written to a user-specified output device (for example, a line
printer) must not exceed the maximum record length which that device can process. In the
case of a line printer, this maximum is usually 132 characters.
Using an appropriate format specification, a statement can write more than one record.
Because numeric data transferred by formatted output statements is always rounded during its conversion from binary to character form, a loss of precision may result if this data is
subsequently used as input. It is recommended, therefore, that whenever numeric output is
to be used subsequently as input, unformatted output and input statements be used for
data transfer.
Some examples of the use of formatted sequential WRITE statements follow.
1. In the following example, the WRITE statement writes one record to logical unit 6.
The record consists of the character constant defined in the FORMAT statement.
650

WRITE <G1G50)
FORMAT (' HELLO THERE')

2. In the following example, the WRITE statement writes one record consisting of fields
AYE, BEE, and CEE to logical unit 1.
85

11-42

WRITE ( 1185) AYE, BEE, CEE
FORMAT C3F8.5)

VAX FORTRAN Input/Output

3. In the following example, the WRITE statement writes three separate records to
logical unit 1; each record consists of only one field.
800

WRITE ( 1 t800)
FORMAT (F8.5)

DEE, EEE, EFF

11.5.1.2 List-Directed Sequential WRITE Statement
The list-directed sequential WRITE statement performs the following operations:
• Retrieves specified data from internal storage.
• Translates that data from binary to character form using the data type of the elements
in the 1/0 list to provide editing.
• Writes the translated values to an external record accessed under the sequential mode
of access.
The values transferred as output by the list-directed WRITE statement have the same
forms as those of the constant values transferred as input by the list-directed READ and
ACCEPT statements, with the following exception: character constants are transferred
without delimiting apostrophes, and each internal apostrophe is represented by only one
apostrophe instead of two. As a consequence of this exception, records containing listdirected character output data can be printed, but cannot be used for list-directed input.
(Refer to Section 11.4.1.2 for a full discussion of list-directed value forms.)
Table 11-5 shows the default output formats for each data type.

Table 11-5: List-Directed Output Formats
Data Type

Output Format

LOGICAL*l(BYTE)
LOGICAL*2
LOGICAL*4
INTEGER*2
INTEGER*4
REAL
REAL*8
REAL*8(/G__FLOATING)
REAL*16
COMPLEX
COMPLEX*16
COMPLEX*16(/G__FLOATING)
CHARACTER

15
L2
L2
I7
112
1PG15.7E2
1PG24.16E2
1PG24.15E3
1PG43.33E4
'( ',1PG14.7E2, ', ', 1PG14.7E2, ')'
' ( ',1PG23.16E2, ', ',1PG23.16E2, ')'
'( ',1PG23.15E3, ', ',1PG23.15E3, ')'
An (where n is the length of the character expression)

VAX FORTRAN Input/Output

11-43

Note that:
• List-directed output statements do not produce octal values, null values, slash separators, or repeated forms of values.
• List-directed output edits a complex value so that there are no embedded spaces in the
value.
• Each output record begins with a space for carriage control.
• Each output statement writes one or more complete records.
• Each individual output value is contained within a single record, with the exception of
character constants longer than one record length and complex constants that can be
split after the comma.
An example of the use of the list-directed WRITE statement follows.
DIMENSION ACL!l
DATA A/ll*3+ll/
WR I TE ( 1 '*) I ARRAY l.JALUES FOLLOW I
WRITE (11*) Aili

In this example, the WRITE statements write the following records to logical unit 1:
ARRAY VALUES FOLLOW

3,l!OOOOO

3.l!OOOOO

3+l!OOOOO

3.l!OOOOO

11.5.1.3 rJamelist-Directed Sequential WRITE Statement
The namelist-directed sequential WRITE statement performs the following operations:
o Retrieves data specified by the namelist specifier from internal storage.
0

Translates that data from internal to external form using the data type of the list
entities in the corresponding NAMELIST statement.

Writes the translated values to external records accessed under the sequential mode of
access.

The namelist-directed WRITE statement transfers as output the current values of all list
entities associated with the specified name list specifier. These values are written in a form
that can be read as input by the namelist-directed READ and ACCEPT statements.
The order of data output is dictated by the sequence in which namelist entities are defined
in a NAMELIST statement; the first list entity and its value are written first, the second
list entity and its value are written second, and so on. Each value display begins on a new
line.

11-44

VAX FORTRAN Input/Output

An example of the namelist-directed WRITE statement follows.
A program unit consists of:
CHARACTER*19 NAMEC2)/2*' '/
REAL PITCH1 ROLL1 YAW1 POSITION(3)
LOGICAL DIAGNOSTICS
INTEGER ITERATIONS
NAMELIST /PARAM/ NAME1 PITCH, ROLL1 YAW, POSITION1
DIAGNOSTICS, ITERATIONS

READ (LJNIT=11NML=PARAMl
WRITE CUNIT=11NML=PARAM)

And the input contains:
LSPARAM#NAMEC2)(10: )='HEISENBERG',
LPITCH=s.o, YAW=o.o, ROLL=s.o,
LDIAGNOSTICS=,TRLJE,
LITERATIONS=10SEND

The WRITE statement writes the following:
L$PARAM
I
LNAME
LP ITCH
5.000000
LRDLL
5+000000
LYAW
o.oooooooE+oo,
LPOSITION
3*0,0000000E+OO,
LDIAGNOSTICS
T1
LITERATIONS
10
L$END
I

HEISENBERG

Notice that character values are enclosed in apostrophes. The value of POSITION is not
defined in the namelist-directed input. It may be defined elsewhere in the program or be
undefined. The namelist-directed WRITE statement prints the current contents of POSITION.

11.5.1.4 Unformatted Sequential WRITE Statement
The unformatted sequential WRITE statement transfers specified binary data from internal storage to an external record accessed under the sequential mode of access. The data is
not translated.

VAX FORTRAN Input/Output

11-45

The unformatted sequential WRITE statement writes exactly one record; if there is no I/0
list, the statement writes one null record.
Some examples of the use of the unformatted sequential WRITE statement follow.
WRITE

(1)

CLISTCK), K=l 15)

In this example, the WRITE statement writes a record to the file connected to logical unit 1
containing the values, in binary form, of elements 1 through 5 of the array LIST.
WRITE

(l!)

In this example, the WRITE statement writes one null record to the file connected to
logical unit 4.

11.5.2 Direct Access WRITE Statements
Direct access WRITE statements transfer output data from internal storage to external
records accessed under the direct mode of access. The OPEN statement is used to establish
the attributes of a direct access file.
The formats of the two forms of direct access WRITE statement-formatted and unformatted-are as follows:

Formatted
WRITE (ex tu ,rec, fmt[, iostat][,err]) [iolist]

Unformatted
WRITE (extu,rec[,iostat][,err]) [iolist]

The meanings of the symbolic abbreviations used to represent control-list parameters in
the preceding command lines are as follows:
• extu-a logical unit specifier
• rec-a record specifier
• fmt-a format specifier
• iostat-an I/O status specifier
• err-transfer-of-control specifier
The I/0-list parameter is represented by the symbolic abbreviation iolist.
All of the parameters used in I/0 statements are described in Sections 11.3.1 (control-list
parameters) and 11.3.2 (I/0-list parameter). The rules for specifying control-list parameters are summarized in Section 11.3.1.10.
The uses and effects of the two forms of direct access WRITE statements are described in
Sections 11.5.2.1 and 11.5.2.2.

11-46

VAX FORTRAN Input/Output

11.5.2.1 Formatted Direct Access WRITE Statement
The formatted direct access WRITE statement performs the following operations:
• Retrieves binary values from internal storage.
• Translates those values to character form using format specifications to provide editing.
• Writes the translated data to a user-specified external record accessed under the direct
mode of access.
If the values specified by the 1/0 list and formatting do not fill the output record being
written, the unused portion of the record is filled with space characters. If the values
overfill the record, an error occurs.

11.5.2.2 Unformatted Direct Access WRITE Statement
The unformatted direct access WRITE statement retrieves binary values from internal
storage and writes those values to a user-specified external record accessed under the direct
mode of access. The values are not translated.
If the values specified by the I/O list do not fill the output record being written, the unused
portion of the record is filled with zeros. If the values do not fit in the record, an error
occurs.

11.5.3 huhmed WnlTlE SiaiemenRs
The indexed WRITE statements transfer output data from internal storage to external
records accessed under the keyed mode of access.
The indexed WRITE statement always writes a new record. The REWRITE statement (see
Section 11.6) is used to update an existing record.
.
The OPEN statement is used to establish the attributes of an indexed file.
The syntactic form of the indexed WRITE statement is identical to that of the sequential
WRITE statement; the two statements differ only in that the indexed WRITE statement
refers to a logical unit connected to an indexed file, whereas the sequential WRITE statement refers to a logical unit connected to a sequential file.
The formats of the two forms of indexed WRITE statement-formatted and unformatted-are as follows:

Formatted
WRITE (extu,fmt[,iostat][,err]) [iolist]

Unformatted
WRITE (extu[,iostat][,err]) [iolist]

VAX FORTRAN Input/Output

11-47

The meanings of the symbolic abbreviations used to represent control-list parameters in
the preceding command lines are as follows:
o extu-a logical unit specifier

o fmt-a format specifier
o iostat-an I/O status specifier
o err-transfer-of-control specifier

The I/0-list parameter is represented by the symbolic abbreviation iolist.
All of the parameters used in I/0 statements are described in Sections 11.3.1 (control-list
parameters) and 11.3.2 (I/0-list parameter). The rules for specifying control-list parameters are summarized in Section 11.3.1.10.
The uses and effects of the two forms of indexed WRITE statements are described in
Sections 11.5.3.1 and 11.5.3.2.

11.5.3.1 Formatted lndelted WRITE Statement
The formatted indexed WRITE statement performs the following operations:
0

Retrieves binary values from internal storage.

o Translates those values to character form using format specifications to provide edit-

ing.
o Writes the translated data to one or more external records accessed under the keyed

mode of access.
No key parameters are required in the list of control parameters because all necessary key
information is contained in the output record.
If the values specified by the I/O list and formatting do not fill a fixed-length record being
written, the unused portion of the record is filled with space characters. If additional
records are specified, they are inserted in the file logically according to the key values
contained in each record.

An example of the use of formatted indexed WRITE statement follows.
WRITE
100

FORMAT

CL! t100)

KEYl,JAL,

<RDATA< I),

I=l 120)

CA10t20F15,7)

This example assumes that the first 10 bytes of a record are a character key. In this
example, the WRITE statement writes the translated values of each of the 20 elements of
the array RDATA to a new formatted record in the indexed file connected to logical unit 4,
with KEYVAL being the key by which the record is accessed.
When you write an INTEGER key using the formatted indexed WRITE statement, the key
is translated from internal binary form to external character form. A subsequent attempt to
read the record using an integer key may not match the key field in the record.

11-48

VAX FORTRAN Input/Output

11.5.3.2 Unformatted lndmced WnlTE Statement
The unformatted indexed WRITE statement retrieves binary values from internal storage
and writes those values to an external record accessed under the keyed mode of access. The
values are not translated.
No key parameters are required in the list of control parameters because all necessary key
information is contained in the output record.
If the values specified by the I/O list do not fill a fixed-length record beiilg written, the

unused portion of the record is filled with zeros; if the values specified overfill the record,
an error occurs. The use of records, or structured data items, (see Section 6.2.5) is advantageous when writing to indexed files. Such files usually have a fixed record format. By using
a structure declaration that models the file record format, I/0 can be accomplished with a
single record variable-instead of a potentially long I/0 list. For an example, see Section
14.3.

11.5.4 Internal WRITE Statement
The internal WRITE statement transfers output data from internal storage to an internal
file. You can also use the ENCODE statement discussed in Appendix A to control internal
output.
Refer to Section 11.2.3.2 for information on the characteristics and use of internal files.
The formats of the two forms of internal WRITE statements-formatted and list-directed-are as follows:

Formatted
WRITE (intu,fmt[,iostat][,err]) [iolist]

List-Directed
WRITE (intu,*[,iostat][,err]) [iolist]

The meanings of the symbolic abbreviations used to represent control-list parameters in
the preceding command lines are as follows:
• intu-an internal file specifier.
• fmt-a format specifier.
• *-the list-directed formatting specifier. You can also use FMT=*·
• iostat-an I/0 status specifier.
• err-transfer-of-control specifier.
The I/0-list parameter is represented by the symbolic abbreviation iolist.

VAX FORTRAN Input/Output

11-49

All of the parameters used in I/0 statements are described in Sections 11.3.1 (control-list
parameters) and 11.3.2 (l/0-list parameter). The rules for specifying control-list parameters are summarized in Section 11.3.1.10.
Namelist-directed formatting is not permitted with internal WRITE statements.
The uses and effects of the two forms of internal WRITE statements are described in
Sections 11.5.4.1 and 11.5.4.2.

11.5.4.1 Formatted Internal WRITE Statement
The formatted internal WRITE statement performs the following operations:
• Retrieves data from internal storage.
• Translates that data from binary to character form using format specifications to
provide editing.
• Writes the translated values to an intern~l file.

11.5.4.2 List-Directed Internal WRITE Statement
The list-directed internal WRITE statement performs the following operations:
0

Retrieves data from internal storage.

o Translates that data from binary to character form using the data type of the elements

in the 1/0 list to provide editing.
0

Writes the translated values to an internal file.

The REWRITE statement transfers output data from internal storage to the current record
in a file with indexed or relative organization.
The REWRITE statement transfers output data from internal storage to a specified record
in a file, with indexed or relative organization, which was most recently accessed by a
READ statement. The OPEN statement establishes the attributes of the file.
The formats of the two forms of REWRITE statement-formatted and unformatted-are
as follows:

Formatted
REWRITE (extu,fmt[,iostat][,err]) [iolist]

Unformatted
REWRITE (extu[,iostat][,err]) [iolist]

11-50

VAX FORTRAN Input/Output

The meanings, of the symbolic abbreviations used to represent control-list parameters in
the preceding command lines are as follows:
o

extu-a logical unit specifier

fmt-a format specifier

iostat-an I/0 status specifier

o err-transfer-of-control specifier

The I/0-list parameter is represented by the symbolic abbreviation iolist.
All of the parameters used in I/O statements are described in Sections 11.3.1 (control-list
parameters) and 11.3.2 (I/0-list parameter). The rules for specifying control-list parameters are summarized in Section 11.3.10.
The uses and effects of the two forms of REWRITE statements are described in Sections
11.6.1 and 11.6.2.

11.5.1 Liormaiiad n!EtrumYIE Sia~emen~
The formatted REWRITE statement performs the following operations:
0

Retrieves binary values from internal storage.

Translates those values to character form using format specifiers to provide editing.

Writes the translated data to an existing record in a file with indexed or relative
organization.

The record written to is the current record in the file, that is, the last record to be accessed
by a preceding indexed or sequential READ statement. Note that changing the primary
key value usually results in an error, and that attempting to rewrite more than one record
in a single REWRITE statement operation causes an error. Any unused space in a rewritten
fixed-length record is filled with spaces; if the record is too long, an error occurs.
An example of the use of a formatted REWRITE statement follows.
10

REWRITE C31101ERR=88l NAME1 AGE1 BIRTH
FORMAT CA161I21A8l

In this example, the REWRITE statement updates the current record contained in the
indexed organization file connected to logical unit 3 with the values represented by NAME,
AGE, and BIRTH.

11.5.2 UJniormaRied R!EtrumilE Siaiemeni
The unformatted REWRITE statement retrieves binary values from internal storage and
writes those values to an existing record in a file with indexed or relative organization. The
values are not translated.

VAX FORTRAN Input/Output

11-51

The record written to is the current record in the file, that is, the last record to be accessed
by a preceding indexed or sequential READ statement. Note that changing the primary
key value usually results in an error. Any unused space in a rewritten fixed-length record is
filled with zeros; if the record is too long, an error occurs.

The ACCEPT statement transfers input data to internal storage from external records
accessed under the sequential mode of access. ACCEPT statements can only be used on
implicitly connected logical units.
The formats of the ACCEPT statement are as follows:
ACCEPT f[,iolist]
ACCEPT *[,iolist]
ACCEPT n

The meanings of the symbolic abbreviations used to represent control-list parameters in
the preceding command lines are as follows:
0

f-the nonkeyword form of a format specifier

*-the list-directed formatting specifier

n-the nonkeyword form of a namelist specifier

The I/0-list parameter is represented by the symbolic abbreviation iolist.
All of the parameters used in 1/0 statements are described in Sections 11.3.1 (control-list
parameters) and 11.3.2 (1/0-list parameter). The rules for specifying control-list parameters are summarized in Section 11.3.1.10.
The ACCEPT statement functions exactly as the sequential READ statements discussed in
Sections 11.4.1.1 through 11.4.1.3, with the following important exception: the ACCEPT
statement can never be connected to user-specified logical units.
An example of the use of the formatted ACCEPT statement follows.

200

CHARACTER*10 CHARAR15l
ACCEPT 200, CHARAR
FORMAT C5A10l

In this example, the ACCEPT statement reads character data from the implicit unit and
assigns binary values to each of the five elements of the array CHARAR.

11-52

VAX FORTRAN Input/Output

11.8 1VfP>fE and PRINT Statements
The TYPE and PRINT statements transfer output data from internal storage to external
records accessed under the sequential mode of access.
The formats of the TYPE and PRINT statements are as follows:
TYPE f[,iolist]
PRINT f[,iolist]
TYPE •[,iolist]
PRINT *[,iolist]
TYPE n
PRINT n

The meanings of the symbolic abbreviations used to represent control-list parameters in
the preceding command lines are as follows:
• f-the nonkeyword form of a format specifier
• *-the list-directed formatting specifier
o n-the nonkeyword form of a namelist specifier

The 1/0-list parameter is represented by the symbolic abbreviation iolist.
All of the parameters used in 1/0 statements are described in Sections 11.3.1 (control-list
parameters) and 11.3.2 (1/0-list parameter). The rules for specifying control-list parameters are summarized in Section 11.3.1.10.
TYPE and PRINT statements function exactly as the formatted sequential WRITE statement discussed in Section 11.5.1.1, with the following important exception: The formatted
sequential TYPE and PRINT statements can never be used to transfer data to userspecified logical units.
An example of the use of a formatted sequential PRINT statement follows.

aoo

CHARACTER*1G NAMEt JOB
PRINT aoo, NAMEt JOB
FORMAT ('NAME=' ,A,' JOB=' ,A>

In this example, the PRINT statement writes one record to the implicit output device; the
record consists of four fields of character data.

VAX FORTRAN Input/Output

11-53

Chapter 12

FORMAT Statements
A FORMAT statement specifies the format in which data is to be transferred as well as the
data conversion (editing) required to achieve that format. FORMAT statements are nonexecutable statements used with formatted I/0 statements, ASSIGN statements, and with
ENCODE and DECODE statements.
Information related to the FORMAT statement is organized as follows in this chapter:
• The syntax of FORMAT statements (Section 12.1)
• The FORMAT statement's field and edit descriptors (Section 12.2)
• The carriage control options for output records (Section 12.3)
• The functions of the field separators (comma and slash) (Sections 12.4 and 12.5)
• The use of a run-time format instead of a FORMAT statement to create a format
dynamically during program execution (Section 12.6)
• The interaction between the format specifier and the I/O list (Section 12.7)
• A summary of the rules for writing FORMAT statements (Section 12.8)

12.1 Syntax of FORMAT Statement
FORMAT statements have the form:
FORMAT (q 1f 1s 1f 2s 2 ... fnqn)

where:
q

is zero or more slash (I) record terminators.
is a field descriptor or a group of field descriptors enclosed in parentheses.
s

is a field separator.

12-1

The entire list of field descriptors and field separators, including the parentheses, is called
the format specification.
A field descriptor in a format specification has one of the following forms:
[r]c

[r]cw

[r]cw.m

[r]cw.d[Ee]

where:

is the repeat count for the field descriptor. If you omit r, the repeat count is assumed
to be 1.
c

is a format code (1,0,Z,F,E,D,G,L,A,H,X,T,P,Q,$,:,BN,BZ,S,SP,SS, TL, or TR).
w

is the external field width, in characters.

m
is the minimum number of characters that must appear within the field (including
leading zeros).
d

is the number of characters to the right of the decimal point.
E

in this context, identifies an exponent field.
e

is the number of characters in the exponent.
The terms r, w, m, and d must all be unsigned integer constants or variable format
expressions. The values of r and w must be greater than zero and less than or equal to
32767, and the values of m, d, and e must be greater than zero and less than or equal to 255.
The r term is optional; however, you cannot use it in some field descriptors (see Section
12.2.1). The d and e terms are required in some field descriptors and are invalid in others.
You are not allowed to use PARAMETER constants for the terms r, w, m, d, ore.
The field descriptors are:
• Integer-Iw, Ow, Zw, lw.m, Ow.m, Zw.m
• Logical-Lw
• Real and complex-Fw.d, Ew.d, Dw.d, Gw.d, Ew.dEe, Gw.dEe
• Character-Aw
• Editing, and character and Hollerith constants-nH, ' ... ', nX,Tn, TLn, TRn, nP, Q,
$, :, BN, BZ, S, SP, SS (n is the number of characters or character positions).

12-2

Format Statements

12.2 Field and Edit Descriptors
A field descriptor describes the size and format of a data item or of several data items; each
data item in the external medium is called an external field. An edit descriptor specifies an
editing function to be performed on a data item or items.
The numeric field descriptors ignore leading spaces in the external field. Embedded and
trailing spaces are ignored only if the BN edit descriptor is specified or if
BLANK= 'NULL' is in effect for the logical unit. Otherwise, embedded and trailing spaces
are treated as zeros.
At the beginning of the execution of each formatted input statement, the BLANK attribute
for the relevant logical unit determines the interpretation of spaces; the VAX FORTRAN
defaults are BLANK= 'NULL' when an OPEN has been done and BLANK= 'ZERO'
when no explicit OPEN has been done. During the execution of a formatted input statement, the BN and BZ edit descriptors may supersede the default interpretation of blanks.
The BN and BZ edit descriptors affect only the formatted 1/0 statement of which they are
a part (as do the S, SP, and SS edit descriptors).
Sections 12.2.1 through 12.2.12 describe each of the field and edit descriptors in detail.

12.2.1 Repeat Counts and Group Repeat Counts
You can apply the field descriptors I, 0, Z, F, E, D, G, L, and A to a number of successive
data fields by preceding the field descriptor with an unsigned integer constant (parameter
constants not allowed) specifying the number of repetitions. This constant is called a
repeat count. For example, the following two statements are equivalent:
20

FORMAT

CE12.a 1E12.a tE12.a tl5 t15 tl5 tl5)

FORMAT

C3E12.lltlll5)

Similarly, you can apply a group of field descriptors repeatedly to data fields by enclosing
these field descriptors in parentheses and preceding them with an unsigned integer constant (parameter constants not allowed). The integer constant is called a group repeat
count. For example, the following two statements are equivalent:·
50

FORMAT

C2IB 13CFB.3 1E15, 7) 12( 15))

FORMAT

( IB tlB 1F8.3 1E15, 7 1F8.3 1E15, 7tFB,31E15, 7 tl5 tl5)
~~~

An H or Q field descriptor, which could not otherwise be repeated, can be enclosed in
parentheses and treated as a group repeat specification. Thus, it could be repeated a
desired number of times.
If you do not specify a group repeat count, a default count of 1 is assumed.

Section 12.7 discusses how to use parentheses when the number of values to be formatted is
greater than the number of format specifications.
Format Statements

12-3

12.2.2 Uariable rForma~ fEnprtlss~ons
By enclosing an arithmetic expression in angle brackets, you can use it in a FORMAT
statement wherever you can use an integer (except as the specification of the number of
characters in the H field). For example:
FORMAT

( I<J+l:>l

When the format is scanned, the preceding statement performs an I (integer) data transfer
with a field width of J+l. The expression is reevaluated each time it is encountered in the
normal format scan.
The following rules govern the use of variable format expressions:
0

If the expression is not of integer data type, it is converted to integer data type before
being used.

o The expression can be any valid FORTRAN expression, including function calls and

references to dummy arguments.
o The

value of a variable format expression must obey the restrictions on magnitude
applying to its use in the format, or an error occurs.

o Variable format expressions are not permitted in run-time formats.

Variable format expressions are evaluated each time they are encountered in the scan of
the format. If the value of the variable used in the expression changes during the execution
of the 1/0 statement, the new value is used the next time the format item containing the
expression is processed. See Section 12.7 for a description of the synchronization ofl/0 lists
with formats.
Figure 12-1 shows an example of a variable format expression.
DIMENSION A(5)
DATA A/1,,2,,3,,a,,5,;

100
10

101
20

12-4

DD 10 I=1 t10
WRITE (G t100l I
FORMAT ( I<MA>(( I 15) >l
CONTINUE
DD 20 I=1 ,5
WRITE (G t101) (A( I), J=1 t!)
FORMAT (<I>F10.<I-1>l
CONTINUE
END

Format Statements

On execution, these statements produce the following output:
2
3
LI

5
G

7
8

9
10
1•

2.0
3.00
LJ.ooo
5.0000

2.0
3.00
LJ.000
5.0000

3.00
Ll.000
5.0000

Ll.000
5.0000

5.0000

Figure 12-1: Variable Format Expression Example

12.2.3 Blank Control Editing
The treatment of embedded and trailing blanks within numeric input files is controlled by
BN and BZ edit descriptors.
12.2.3.1 BN Edit Descriptor
The BN descriptor causes the processor to ignore all the embedded and trailing blanks it
encounters within a numeric input field. It has the form:

BN
The effect is that of actually removing the blanks and right-justifying the remainder of the
field. A field of all blanks is treated as zero. The BN descriptor affects only I, 0, Z, F, E, D,
and G editing during the execution of an input statement.
12.2.3.2 BZ Edit Descriptor
The BZ descriptor causes the processor to treat all the embedded and trailing blanks it
encounters within a numeric input field as zeros. It has the form:
BZ

The BZ descriptor affects only I, 0, Z, F, E, D, and G editing during the execution of an
input statement.

Format Statements

12-5

12.2.4 Sign Control Editing
The treatment of optional plus characters in output data is controlled by SP, SS, and S
edit descriptors.

12.2.4.1 SP Edit Descriptor
An SP descriptor causes the processor to produce a plus character ( +) in any position
where this character would otherwise be optional. It has the form:
SP

The SP descriptor affects only I, F, E, D, and G editing during the execution of an output
statement.

12.2.4.2 SS Edit Descriptor
The SS descriptor causes the processor to suppress a leading plus character from any
position where this character would normally be produced as an optional character; it has
the opposite effect of the SP field descriptor described above. The SS descriptor has the
form:
SS

The SS descriptor affects only I, F, E, D, and G editing during the execution of an output
statement.

12.2.4.3 S Edit Descriptor
The S edit descriptor reinvokes optional plus characters ( + ) in numeric output fields. It
has the form:

s
The S descriptor counters the action of either the SP or SS descriptor by restoring to the
processor the discretion of producing plus characters on an optional basis.
The same restrictions apply as for the SP and SS descriptors.

12.2.5 Integer Editing
Integer editing is controlled by I (decimal), 0 (octal), and Z (hexadecimal) field descriptors.

12.2.5.1 I Field Descriptor
The I field descriptor transfers decimal integer values. It has the form:
Iw[.m]

The corresponding I/0 list element must be of either integer or logical data type.

12-6

Format Statements

Input Processing
In an input statement, the I field descriptor transfers w characters from the external field
and assigns them to the corresponding 1/0 list element as an integer value. The external
data must have the form of an integer constant; it cannot contain a decimal point or
exponent field.
If the value of the external field exceeds the range of the corresponding list element, an
error occurs. If the first nonblank character of the external field is a minus sign, the field is
treated as a negative value. If the first nonblank character is a plus sign, or if no sign
appears in the field, the field is treated as a positive value. An all-blank field is treated as a
value of zero.

Input Example:
Format

External Field

Internal Value

2788
-28
f::ll:::.f:,f::,/::,t:,312

2788
-26
312

Output Processing
In an output statement, the I field descriptor transfers the value of the corresponding I/0
list element, right-justified, to an external field that is w characters long. If the value does
not fill the field, leading spaces are inserted; if the value is too large for the field, the entire
field is filled with asterisks. If the value of the list element is negative, the field will have a
minus sign as its leftmost, nonblank character. The term w must therefore be large enough
to provide for a minus sign, when necessary. If m is present, the external field consists of at
least m digits, and is zero-filled on the left, if necessary.

Input Example:
Format

Internal Value

External Representation

13
I4
I5
I2
I3
I7
I4.2
I4.4

284
-284
174
3244
-473
29.812
1
1

28a
-28a
t:,t:,17a

**
***

Not Perrrlitted: error

t:,t:,O 1
0001

Note that if m is zero, and the internal representation is zero, the external field is blankfilled.

Format Statements

12-7

12.2.5.2 0 field Descriptor
The 0 field descriptor transfers octal (base 8) values and can be used with any data type. It
has the form:
Ow[.m]

Input Processing
In an input statement, the 0 field descriptor transfers w characters from the external field
and assigns them as an octal value to the corresponding I/0 list element. The external field
can contain only the numerals 0 through 7; it cannot contain a sign, a decimal point, or an
exponent field. An all-blank field is treated as a value of zero. If the value of the external
field exceeds the range of the corresponding list element, an error occurs.
Input Example:
Format

External Field

32787

04
03

1G23l1
976

Internal
Octal Value

32767
1623
Not permitted: error

Output Processing
In an output statement, the 0 field descriptor transfers the octal value of the corresponding
1/0 list element, right-justified, to an external field that is w characters long. No signs are
transmitted; a negative value is transmitted in internal form. If the value does not fill the
field, leading spaces are inserted; if the value is too large for the field, the entire field is
filled with asterisks. If m is present, the external field consists of at least m digits, and is
zero-filled on the left if necessary.
Output Example:
Format

Internal (Decimal) Value

External Re pre sen ta ti on

06
06

32767
-32767
14261
27

677777

05
04.2
04.4

10.5
7
7

100001

.6.633
l11050
.6.607

0007

Note that if m is zero, and the external representation is zero, the external field is blankfilled.

12-8

Format Statements

12.2.5.3 Z Field Descriptor
The Z field descriptor transfers hexadecimal (base 16) values, and can be used with any
data type. It has the form:
Zw[.m]

Input Processing
In an input statement, the Z field descriptor transfers w characters from the external field
and assigns them as a hexadecimal value to the corresponding I/0 list element. The external field can contain only the numerals 0 through 9 and the letters A (a) through F (f); it
cannot contain a sign, a decimal point, or an exponent field. An all-blank field is treated as
a value of zero. If the value of the external field exceeds the range of the corresponding list
element, an error occurs.

Input Example:
Internal
Hexadecimal Value

Format

External Field

A9ll

A94

Z5
Z5

A23DEF

A23DE

95.AF2

Not permitted: error

Output Processing
In an output statement, the Z field descriptor transfers the hexadecimal value of the
corresponding I/0 list element, right-justified, to an external field that is w characters long.
No signs are transmitted; a negative value is transmitted in internal form. If the value does
not fill the field, leading spaces are inserted; if the value is too large for the field, the entire
field is filled with asterisks. If m is present, the external field consists of at least m digits,
and is zero-filled on the left if necessary.

Output Example:
Format

Internal (Decimal) Value

External Representation

Z4
Z5

32767
-32767

68001

Z2
Z4

16
-10.5

Z3.3

2708
2708

Z6.4

7FFF
1 (l

C228
A9ll
660A9ll

Note that if m is zero, and the internal representation is zero, the external field is blankfilled.

Format Statements

12-9

12.2.6 Real Editing
Editing performed on data with a real data type is controlled by F, E, D, and G field
descriptors.

NOTE
When attempting to parse textual input, you should not mix in the use of F, E,
D, or G format descriptors. These descriptors accept some forms that are purely
textual as valid numeric input values. For example, the input values D, E, El,
plus sign ( + ) , minus sign ( - ) , and period ( . ) are all treated as 0.0.

12.2.6.1 F Field Descriptor
The F field descriptor transfers real values. It has the form:
Fw.d

The corresponding I/O list element must be of real data type, or it must be either the real or
the imaginary part of a complex data type.

Input Processing
In an input statement, the F field descriptor transfers w characters from the external field
and assigns them, as a real value, to the corresponding I/0 list element. If the first non-

blank character of the external field is a minus sign, the field is treated as a negative value.
If the first nonblank character is a plus sign, or if no sign appears in the field, the field is
treated as a positive value. An all-blank field is treated as a value of zero. A field with only
an exponent or decimal point is treated as a value of zero.
If the field contains neither a decimal point nor an exponent, it is treated as a real number
of w digits, in which the rightmost d digits are to the right of the decimal point, with
leading zeros assumed if necessary. If the field contains an explicit decimal point, the
location of that decimal point overrides the location specified by the field descriptor. If the
field contains an exponent, that exponent is used to establish the magnitude of the value
before it is assigned to the list element.

Input Example:
Format

External Field

Internal Value

F8.5
F8.5
F8.5
F5.2

123a5G789
-123a.5G7
2a77E+2
123.a5

123.45678
-1234.56
2477.0
123.45

12-10

Format Statements

Output Processing
In an output statement, the F field descriptor transfers the value of the corresponding VO
list element, rounded to d decimal positions and right-justified, to an external field that is
w characters long. If the value does not fill the field, leading spaces are inserted; if the
value is too large for the field, the entire field is filled with asterisks.
The term w must be large enough to include all of the following: a minus sign when
necessary (plus signs are optional); at least one digit to the left of the decimal point; the
decimal point; and d digits to the right of the decimal. Therefore, w must be greater than or
equal to d+3.

Output Example:
Format

Internal Value

External Representation

F8.5
F9.3
F2.1
Fl0.4
F5.2
F5.2

2.3547188
8789.7361
51.44
-23.24352
325.013

.62.35ll72
.68789.736

-.2

-0.20

.6.6-23. 2ll35

******

12.2.6.2 E Field Descriptor
The E field descriptor transfers real values in exponential form. It has the form:
Ew.d[Ee]

The corresponding I/0 list element must be of real data type, or it must be either the real or
the imaginary part of a complex data type.

Input Processing
In an input statement, the E field descriptor transfers w characters from the external field
and assigns them as a real value to the corresponding VO list element. The F field descriptor interprets and assigns data in exactly the same way.
Input Example:
Format

External Field

Internal Value

E9.3
E12.4
E15.3
E12.5

73ll.ll32E3
.6.61022.ll3E-6

734432.0
1022.43E-6
52.3759663
210.5271E10

52.3759663~~~~

210.52710+10

Note that in the last example, the E field descriptor treats the D exponent field indicator as
an E indicator if the I/0 list element is single precision.

Format Statements

12-11

Output Processing
In an output statement, the E field descriptor transfers the value of the corresponding 1/0
list element, rounded to d decimal digits and right-justified, to an external field that is w
characters long. If the value does not fill the field, leading spaces are inserted; if the value
is too large for the field, the entire field is filled with asterisks.
When you use the E field descriptor, data output is transferred in a standard form. This
form consists of the following: a minus sign when nece.ssary (plus signs are optional); a zero;
a decimal point; d digits to the right of the decimal point; and an e+2-character exponent.
The exponent has one of the following forms:
E+nn}
{ E-nn
+nnn}
{

Ew.d (for: exponent .LE. 99)

Ew.d (for: 99 .GT. exponent .LE. 999)

-nnn

E+n1n2 ... ne}
{ E-n n2".ne

Ew.dEe

The exponent field width specification is optional; if it is omitted, the value of e defaults to
two. If the exponent value is too large to be converted into one of the preceding forms, an
error occurs.
The d digits to the right of the decimal point represent the entire value, scaled to a decimal
fraction.
The term w must be large enough to include all of the following: a minus sign when
necessary (plus signs are optional); a zero; a decimal point, d digits; and an exponent.
Therefore, w must be greater than or equal to d+7, or to d+e+5 if e is present.
Output Example:
Format

Internal Value

External Representation

E9.2
El2.5
E12.3
El0.3
E5.3
E14.5E4
El4.3E6

475867.222
475867.222
0.00069
-0.5555
56.12
-1.001
0.000123

.6.0.llBF+OG
.6.0.ll7587E+OG
.6..6..6.0. G90E-03
-0.55GE+OO

12-12

Format Statements

*****
-0.10010E+0001
.6.0.123E-000003

12.2.6.3 D Field Descriptor
The D field descriptor transfers real values in -exponential form. It has the form:
Dw.d

The corresponding 1/0 list element must be of real data type, or it must be either the real or
the imaginary part of a complex data type.

Input Processing
In an input statement, the D field descriptor transfers w characters from the external field
and assigns them as a real value to the corresponding 1/0 list element. The F and E field
descriptors interpret and assign data in exactly the same way.
Input Example:
Format

External Field

Internal Value

BZ,Dl0.2
Dl0.2
D15.3

1 2 3 4 5 .6.6.6.6.6
.6.6 1 2 3 • 4 5 .6.6

12345000.0DO
123.45DO
3.674981763D+06

387.49817830+04

Output Processing
In an output statement, the D field descriptor has the same effect as the E field descriptor,
except that the D exponent field indicator is used in place of the E indicator.
Output Example:
Format

Internal Value

External Representation

D14.3
D23.12
D9.6

0.0363
5413.87625793

t::,.t::,.t::,.t::,.t::,.O, 383001

1.2

*********

t::,.t::,.t::,.t::,.t::,.O, 5413876257930+04

12.2.6.4 G Field Descriptor
The G field descriptor transfers real values in a form that, in effect, combines the F and E
field descriptors. It has the form:
Gw.d[Ee]

The corresponding 1/0 list element must be of real data type, or it must be either the real or
the imaginary part of a complex data type.

Format Statements

12-13

Input Processing
In an input statement, the G field descriptor transfers w characters from the external field
and assigns them as a real value to the corresponding 1/0 list element. The F, D, and E
field descriptors interpret and assign data in exactly the same way.

Output Processing
In an output statement, the G field descriptor transfers the value of the corresponding I/O
list element, rounded to d decimal positions and right-justified, to an external field that is
w characters long. The form in which the value is written is a function of the magnitude of
the value, as described in Table 12-1.

Table 12-1: Effect of Data Magnitude on G Format Conversions
Data Magnitude
m .LT. 0.1

Effective Conversion
Ew.d[Ee]

0.1 .LE. m .LT. 1.0

F(w-4).d, n(' ')

1.0 .LE. m .LT. 10.0

F(w-4).(d-1), n(' ')

lO**d-2 .LE. m .LT. lO**d-1

F(w-4).1, n(' ')

lO**d-1 .LE. m .LT. lO**d

F(w-4).0, n(' ')

m .GE. lO**d

Ew.d[Ee]

Then( ' ') field descriptor, which is, in effect, inserted by the G field descriptor for values
within its range, specifies that four or e+2 spaces are to follow the numeric data representation.
The term w must be large enough to include all of the following: a minus sign when
necessary (plus signs are optional); a decimal point; one digit to the left of the decimal
point; d digits to the right of the decimal point; and either a 4-character or e+2-character
exponent. Therefore, w must be greater than or equal to l+d+7 or l+d+5+e.

12-14

Format Statements

Output Example:
Format

Internal Value

External Representation

G13.6
G13.6
G13.6
G13.6
G13.6
G13.6
G13.6
G13.6
G13.6

0.01234567
-0 .12345678
1.23456789
12 .34567890
123.45678901
-1234 .56789012
12345 .67890123
123456. 78901234
-1234567.89012345

60.123457E-01
-0.123457.6..6..6..6.
661. 23456.6..6..6..6.
6612.3457.6..6..6..6.
66123. 457.6..6..6..6.
6-1234.57.6..6..6..6.
6612345. 7.6..6..6..6.
66123457 +.6..6..6..6.
-0.123457E+07

Compare the above example with the following example, which shows the same values
output using an equivalent F field descriptor.
Format

Internal Value

External Representation

F13.6
F13.6
F13.6
F13.6
F13.6
F13.6
F13.6
F13.6
F13.6

0.01234567
-0.12345678
1.23456789
12 .34567890
123.45678901
-1234 .56789012
12345 .67890123
123456. 78901234
-1234567.89012345

666660.012346
6666-0. 123457
666661. 234568
666612 +345679
666123 +456789
6-1234.567890
612345.678901
123456+789012

*************

12.2.6.5 Complex Data Editing
A complex value is an ordered pair of real values. Therefore, input or output of a complex
value is governed by two real field descriptors, using any combination of the forms Fw.d,
Ew.dEe, Dw.d, or Gw.dEe.

Input Processing
In an input statement, the two successive fields are read and assigned to a complex I/O list
element as its real and imaginary parts, respectively.

Input Example:
Format

External Field

Internal Value

F8.5,F8.5
E9.1,F9.3

1234567812345.67
734.432E8123456789

123.45678, 12345.67
734.432E8, 123456.789

Format Statements

12-15

Output Processing
In an output statement, the two parts of a complex value are transferred under the control
of repeated or successive field descriptors. The two parts are transferred consecutively,
without punctuation or spacing, unless the format specifier states otherwise.

Output Example:
Format

Internal Value

External Representation

2F8.5
E9.2, '.6.,.6. ',E5.3

2.3547188, 3.456732
47587 .222, 56.123

.6.2.35ll72

~3.ll5G73

.6.0.llBE+OG~.~*****

12.2. 7 Scale Factor Editing-P Edit Descriptor
The scale factor lets you alter, during input or output, the location of the decimal point in
real values and in the two parts of complex values.
The scale factor has the form:
nP

where:

n
is a signed or unsigned integer constant in the range -128 through 127. It specifies the
number of positions, to the left or right, that the decimal point is to move.
A scale factor can appear anywhere in a format specification, but must precede the first
field descriptor that is to be associated with it. For example:
nPFw.d

nPEw.d

nPDw.d

nPGw.d

Input Processing
On input, the scale factor in any of the above field descriptors multiplies the data by
lO**-n and assigns it to the corresponding I/O list element. For example, a 2P scale factor
multiplies an input value by .01, moving the decimal point two places to the left. A -2P
scale factor multiplies an input value by 100, moving the decimal point two places to the
right. However, if the external field contains an explicit exponent, the scale factor has no
effect.

Input Exa~ple:
Format

External Field

Internal Value

3PE10.5
3PE10.5
-3PE10.5

.6..6..6. 3 7 • G1 ll b.
.6..6.37. G1 llE2
.6..6..6..6. 3 7 • G1 ll

.037614
3761.4
37614.0

12-16

Format Statements

Output Processing
On output, the effect of the scale factor depends on the type of field descriptor associated
with it. For the F field descriptor, the value of the I/0 list element is multiplied by lO**n
before transfer to the external record. Thus, a positive scale factor moves the decimal point
to the right; a negative scale factor moves the decimal point to the left.
For the E or D field descriptor, the basic real constant part of the I/0 list element is
multiplied by lO**n, and n is subtracted from the exponent. For a positive scale factor, n
must be less than (d + 2) or an output conversion error occurs. Thus, a positive scale factor
moves the decimal point to the right and decreases the exponent; a negative scale factor
moves the decimal point to the left and increases the exponent.

Output Example:
Format

Internal Value

External Representation

1PE12.3
1PE12.2
-1PE12.2

-270.139
-270.139
-270.139

t::.t::.-2.701E+02
t::.t::.t::.-2. 70E+02
t::.t::.t::.-0. 03E+Ot'.l

The effect of the scale factor for the G field descriptor is suspended if the magnitude of the
data to be output is within the effective range of the descriptor, because the G field
descriptor supplies its own scaling function. The G field descriptor fUnctions as an E field
descriptor if the magnitude of the data value is outside its range. In this case, the scale
factor has the same effect as for the E field descriptor.
On input, and on output under F field descriptor control, a scale factor actually alters the
magnitude of the data. On output, a scale factor under E, D, or G field descriptor control
merely alters the form in which the data is transferred. In addition, on input, a positive
scale factor moves the decimal point to the left, and a negative scale factor moves the
decimal point to the right; on output, the effect is the reverse.
If you do not specify a scale factor with a field descriptor, a default scale factor of zero is
assumed. Once you specify a scale factor, however, it applies to all subsequent real field
descriptors in the same FORMAT statement, unless another scale factor appears. For
example:

10
100

DIMENSION A(G)
DO 10 I=1 tG
A(I) = 25.
TYPE 1001A
FORMAT(
tFB.2 t2PFB.2 tFB.2)
I

produces the following:
25.00 2500.00 2500.00
2500.00 2500.00 2500.00

If a second scale factor appears in the FORMAT statement, it takes control from the first
scale factor.

Format reversion has no effect on the scale factor (see Section 12. 7). A scale factor of zero
can be reinstated only by an explicit OP specification.
Format Statements

12-17

12.2.8 Logical Editing-L Edit Descriptor
The L field descriptor transfers logical data. It has the form:
Lw

The corresponding 1/0 list element must be of either integer or logical data type.

Input Processing
In an input statement, the L field descriptor transfers w characters from the external field.
If the first nonblank characters of the field are T, t, .T, or .t, the value .TRUE. is assigned
to the corresponding 1/0 list element; if the first nonblank characters are F, f, .F, or .f, the
value .FALSE. is assigned. An all-blank field is assigned the value .FALSE. Any other
value in the external field produces an error. Note that the logical constants .TRUE. and
.FALSE. are acceptable input forms.
Output Processing
In an output statement, the L field descriptor transfers either the letter T (if the value of
the corresponding 1/0 list element is .TRUE.) or the letter F (if the value is .FALSE.) to an
exter~al field that is w characters long. The letter Tor Fis in the rightmost position of the
field, preceded by w-1 spaces.
Output Example:
Format

Internal Value

External Representation

L5
Ll

.TRUE.
.FALSE.

6666 T

12.2.9 C.haracter Editing
Editing data with a character data type is controlled by the A and H field descriptors.

12.2.9.1 A Field Descriptor
The A field descriptor transfers character or Hollerith values. It has the form:
A[w]

The corresponding 1/0 list element can be of any data type. If it is of character data type,
character data is transmitted. If it is of any other data type, Hollerith data is transmitted.
The value of w must be less than or equal to 32767.

12-18

Format Statements

Input Processing
In an input statement, the A field descriptor transfers w characters from the external
record and assigns them to the corresponding 1/0 list element. The maximum number of
characters that can be stored depends on the size of the 1/0 list element. For character 1/0
list elements, the size is the length of either the character variable, the character substring
reference, or the character array element. For numeric 1/0 list elements, the size depends
on the data type, as follows:
Maximum
Number of Characters

1/0 List Element
BYTE
LOGICAL* I
LOGICAL*2
LOGICAL*4
INTEGER*2
INTEGER*4
REAL
REAL*S(DOUBLE PRECISION)
REAL*16
COMPLEX
COMPLEX*l6(DOUBLE COMPLEX)

1
1

2
4
2
4
4
8
16
gl
161

Because complex values are treated as pairs of real numbers, complex data editing requires two
format codes. See Section 12.2.6.5.

If w is greater than the maximum number of characters that can be stored in the corresponding 1/0 list element, only the rightmost characters are assigned to that element. The
leftmost excess characters are ignored. If w is less than the number of characters that can
be stored, w characters are assigned to the list element, left-justified, and trailing spaces
are added to fill the element.

Input Example:
Format

External Field

Internal Representation

A6
A6
A6
A6
A6
A6
A6
A6

PAGE6#
PAGE6#
PAGE6#
PAGE6#
PAGE6#
PAGE6#
PAGE6#
PAGE6#

#
ED.#
PAGED.#
PAGED.#66
#
6#
GED.#
PAGED.#66

(CHARACTER*l)
(CHARACTER*3)
(CHARACTER*6)
(CHARACTER*8)
(LOGICAL* I)
(INTEGER*2)
CREAL)
(REAL*8)

Format Statements

12-19

Output Processing
In an output statement, the A field descriptor transfers the contents of the corresponding
I/0 list element to an external field w characters long. If w is greater than the list element
size, the data appears in the field, right-justified, with leading spaces. If w is less than the
list element, only the leftmost w characters are transferred.
Output Example:
Format

Internal Value

External Representation

A5
A5
A5

OHMS
VOLTS
AMPERES

60HMS

l.JOL TS
AMP ER

If you omit win an A field descriptor, a default value is supplied. If the I/O list element is
of character data type, the default value is the length of the I/O list element. If the I/0 list
element is of numeric data type, the default value is the maximum number of characters
that can be stored in a variable of that data type.

12.2.9.2 H Field Descriptor
The H field descriptor transfers data between the external record and the H field descriptor
itself. It has the form of a Hollerith constant:
nHc 1c 2c 3 ... en

where:
n

is the number of characters to be transferred.
c

is an ASCII character.

Input Processing
In an input statement, the H field descriptor transfers n characters from the external field
to the field descriptor. The first character appears immediately after the letter H. Any
characters in the field descriptor before input are replaced by the input characters.
Output Processing
In an output statement, the H field descriptor transfers n characters following the letter H
from the field descriptor to the external field.
12.2.9.3 Character Constants
You can use a character constant instead of an H field descriptor; both types of format
specifier function identically.

12-20

Format Statements

In a character constant, the apostrophe is written as two apostrophes. For example:
50

F 0 RM AT

( I T 0 DA y I I S6D AT E6 I s : 6 I ' I 2 ' I I I ' I 2 ' I I I ' I 2 )

A pair of apostrophes used this way is considered a single character.

12.2.1 O Deiauli ~ield llllescriptors
If you write the field descriptors I, 0, Z, L, F, E, D, G, or A without specifying a field width

value, default values for w, d, and e are supplied based on the data type of the I/0 list
element.
Table 12-2 lists the default values for w, d, and e.
Table 12-2: Default Field Descriptor Values

REAL*8, COMPLEX*16

F,E,G,D

REAL*16

LOGICAL*l

LOGICAL*2,INTEGER*2

LOGICAL*4,INTEGER*4

REAL*4,COMPLEX*8

REAL*8,COMPLEX*16

REAL*l6

CHARACTER*n

Field IJescriptor

List Element

I,O,Z

BYTE

I,O,Z

INTEGER*2,LOGICAL*2

I,O,Z

INTEGER*2,LOGICAL*4

O,Z

REAL*4

O,Z

REAL*8

O,Z

REAL*l6

LOGICAL

F,E,G,D

REAL, COMPLEX*S

F,E,G,D

Note that for the A field descriptor, the default is the actual length of the corresponding I/0
list element.

Format Statements

12-21

12.2.11 Positional Editing
Positional editing is controlled by the X, T, TL and TR edit descriptors.
On output, a T, TL, TR, or X edit descriptor does not by itself cause characters to be
transmitted and therefore does not by itself affect the length of the record. If characters are
transmitted to positions at or after the position specified by a T, TL, TR, or X edit
descriptor, positions skipped and not previously filled are filled with blanks. The result is
as if the entire record were initially filled with blanks.

12.2.11.1 X Edit Descriptor
The X edit descriptor is a positional specifier. It has the form:
nX

The term n specifies how many character positions are to be passed over. The value of n
must be greater than or equal to one.

Input Processing
In an input statement, the X field descriptor specifies that the next n characters in the
input record are to be skipped.
Output Processing
In an output statement, the X field descriptor tabs right n spaces; it does not write over
anything already written on the same record. For example:
80

WRITE 16180) NPAGE
FORMAT ( '1PAGE6NUMBER6' 1IZ1l6X1'GRAPHIC6ANALYSIS16CONT, ')

The preceding WRITE statement would print a record similar to:
PAGE NUMBER nn

GRAPHIC ANALYSIS, CONT,

The term nn is the current value of the variable NPAGE. The numeral 1 in the first
character constant is not printed; it is used to advance the printer paper to the top of a new
page. Section 12.3 describes printer carriage control.
Note that a trailing X format on a record will not write any characters unless it is followed
by another field that does. For example:
88

WRITE 16 188) K
F 0 RM AT ( 6K = I 6 '5 ){ )
I

The preceding example will write a record of only 9 characters. To cause n trailing blanks
to be written at the end of a record, use the format n( '6 ').

12.2.11.2 T Edit Descriptor
The T edit descriptor is a positional tabulation specifier. It has the form:
Tn

12-22

Format Statements

The term n indicates the character position of the external record. The value of n must be
greater than or equal to one.

Input Processing
In an input statement, the T field descriptor positions the external record to its nth
character position. For example, if an input statement reads a record containing:
ABC.t:..t:.L:~.XYZ

and this record is under the control of the FORMAT statement:
10

FORMAT

(T7 1A3 1T11A3>

on execution, the input statement would first read the characters XYZ and then read the
characters ABC.

Output Processing
In an output statement, the T field descriptor specifies that subsequent data transfer is to
begin at the nth character position of the external record. The first position of a record to be
printed is usually reserved for a carriage control character, which is not printed (see Section
12.3). For example:
25

PRINT 25
FORMAT (T51, 'COLUMN 2' 1T21, 'COLUMN

1 ')

These statements would print the following line (assuming normal carriage control processing):
Position 20

COLUMN 1

Position 50

COLUMN 2

12.2.11.3 TL Edit Descriptor
The TL edit descriptor is a relative tabulation specifier. It has the form:
TLn

The term n indicates that the next character to be transferred from or to a record is the nth
character to the left of the current character. The value of n must be greater than or equal
to one. If the value of n is greater than or equal to the current character position, the first
character in the record is specified.

12.2.11.4 TR Edit Descriptor
The TR edit descriptor is also a relative tabulation specifier. It has the form:
TRn

The term n indicates that the next character to be transferred from or to a record is the nth
character to the right of the current character. The value of n must be greater than or equal
to one.

Format Statements

12-23

12.2.12 Miscellaneous Editing Operations
Edit descriptors that fall into the miscellaneous category are Q, dollar sign ( $ ) , and colon
(:)
0

The Q edit descriptor obtains the number of characters remaining following a partial
read operation.
The $ edit descriptor controls carriage returns.

• The : edit descriptor terminates format control if no more items are in the I/O list.
These descriptors are discussed, in this order, in the subsections that follow.

12.2.12.1 Q Edit Descriptor
The Q edit descriptor obtains the number of characters in the input record remaining to be
transferred during a read operation. It has the form:
Q

The corresponding I/0 list element must be of integer or logical data type.
For example:
READ (l! '1000) >:RAY, KK t NCHRS,
1000 FORMAT (E15.71Ill10180A1)

( ICHR(I) t

I=11NCHRS)

The preceding input statements read two fields into the variables XRAY and KK. The
number of characters remaining in the record is stored in NCHRS, and exactly that many
characters are read into the array ICHR. By placing the Q descriptor first in the format
,specification, you can determine the actual length of the input record.
In an output statement, the Q edit descriptor has no effect except that the corresponding
I/O list element is skipped.

12.2.12.2 Dollar Sign Descriptor
The dollar sign character ( $ ) in a format specification modifies the carriage control specified by the first character of the record. It only affects those files for which the
'FORTRAN' carriage control attribute (see Section 12.3) is in effect.
In an input statement, the $ descriptor is ignored.
In an output statement, if the first character of the record is a space, the $ descriptor
suppresses the carriage return. For terminal I/O, this means that a typed response will
follow the output on the same line. If the first character of the record is a plus sign ( + ) , the
$ descriptor causes the output to begin at the end of the previous line and leaves the print
position at the end of the line. If the first character of the record is 0 or 1, the$ descriptor is
ignored.

12-24

Format Statements

Thus, the statements
100
200

TYPE 100
FORMAT (I ENTER RADIUS 1.JALUE
ACCEPT 2001 RADIUS
FORMAT (FG,2)

1$)

produce a message on the terminal in the form:
ENTER RADIUS VALUE

Your response (for example, "12.") can then go on the same line:
ENTER RADIUS VALUE

12,

12.2.12.3 Colon Descriptor
The colon character ( : ) in a format specification terminates format control if no more
items are in the I/O list. The: descriptor has no effect if I/O list items remain. For example:

PRINT113
PRINT 21ll
FORMAT(' I='t!21' J='t!2)
FORMAT(' K='1I21:1' L='rI2)

These statements print the following two lines:
I =b.3.6.J =

K =boll

Section 12.7 describes format control in detail.

12.3 Carriage Control
Whenever the default for the OPEN statement's CARRIAGECONTROL keyword is in
effect ('FORTRAN'), the first character of every record transferred to a printer is not
printed. Instead, it is interpreted as a carriage control character (except when overridden
by the OPEN statement keyword CARRIAGECONTROL = 'LIST' or 'NONE'). The I/0
system recognizes certain characters as carriage control characters. Table 12-3 lists these
characters and their effects.
Table 12-3: Carriage Control Characters
Character Meaning
'+ '

Overprinting: starts output at the beginning of the current line and returns to
the left margin after printing

'6'

Single spacing: starts output at the beginning of the next line

'O'

Double spacing: skips a line before starting output

Format Statements

12-25

Table 12,...3 (Cont.): Carriage Control Characters
Character Meaning

'1 '

Paging: starts output at the top of a new page

'$'

Prompting: starts output at the beginning of the next line, and suppresses
carriage return at the end of the line

ASCII NUL Overprinting with no advance: starts output at the beginning of the current
line and does not return to the left margin after printing
Any character other than those listed in Table 12-3 is treated as a space and is deleted from
the print line. Note that if you accidentally omit the carriage control character, the first
character of the record is not printed.

12.4 Format Specification Separators
Field descriptors in a format specification are generally separated by commas. You can also
use the slash ( I) record terminator to separate field descriptors. A slash terminates input
or output of the current record and initiates a new record. For example:
40

WRITE (6140) K1L1M1N1D1P
FORMAT C3I6.61I612F8.4)

The preceding statements are equivalent to the following statements.
40
50

WRITE (6140) K1L1M
FORMAT C3I6.G)
WRITE (6150) N1D1P
FORMAT CI612F8.4)

You can use multiple slashes to bypass input records or to output blank records. If n
consecutive slashes appear between two field descriptors, (n-1) records are skipped on
input, or (n-1) blank records are output. The first slash terminates the current record; the
second slash terminates the first skipped or blank record, and so on.
However, n slashes at the beginning or end of a format specification result inn skipped or
blank records. This is because the opening and closing parentheses of the format specification are themselves a record initiator and t~rminator, respectively. For example:
99

WRITE (6 199)
FORMAT ( '1' tT51 t 'HEADING LINE

I IT51 ''SUBHEADING.

The above statements produce the following output:
Column 50, top of page
~

HEAD I NG LI NE

(blank line)
SUBHEAD I NG LI NE

(blank line)
(blank line)
12-26

Format Statements

LINE

11)

12.5 External Field Separators
A field descriptor such as Fw .d specifies that an input statement is to read w characters
from the external record. If the data field in the external record contains fewer than w
characters, the input statement would read characters from the next data field in the
external record, unless the short field is padded with leading zeros or spaces.
When the field descriptor is numeric, you can avoid padding the input field by using a
comma to terminate the field. The comma overrides the field descriptor's field width
specification. This is called short field termination. It is particularly useful when you are
entering data from a terminal keyboard. You can use it with the I, 0, Z, F, E, D, G, and L
field descriptors. For example:
100

READ (51100) ItJ1A1B
FORMAT C2IG12F10.2l

If the preceding statements read the following record:
1,-2,1.0,35

Based on this input, the following assignments would occur:

I= 1
J = -2
A= 1.0

B = 0.35
Note that the physical end of the record also serves as a field terminator and that the d part
of a w.d specification is not affected by an external field separator.
You can use a comma to terminate only fields less than w characters long. If a comma
follows a field of w or more characters, the comma is considered part of the next field.
Two successive commas, or a comma after a field of w characters, constitutes a null (zerolength) field. Depending on the field descriptor specified, the resulting value assigned is 0,
0.0, O.DO, O.QO, or .FALSE ..
You cannot use a comma to terminate a field that is controlled by an A, H, or character
constant field descriptor. However, if the record reaches its physical end before w characters are read, short field termination occurs and the characters that were read are assigned
successfully. Trailing spaces are appended to fill the corresponding 1/0 list element or the
field descriptor.

12.6 Run-Time Format
You can store format specifications in character scalar references, numeric array references,
numeric scalar field references (see Section 6.2.5.3), or numeric array references. Such a
format specification is called a run-time format, and can be constructed or altered during
program execution.
Format Statements

12-27

A run-time format in an array has the same form as a FORMAT statement, without the
word FORMAT and the statement label. The opening and closing parentheses are required.
Variable format expressions are not permitted in run-time formats.
In the following example, the DATA statement assigns a left parenthesis to the character
array element FORCHR(O), and assigns a right parenthesis and three field descriptors to
four character variables for later use. Next, the proper field descriptors are selected for
inclusion in the format specification. The selection is based on the magnitude of the
individual elements of the array TABLE. A right parenthesis is then added to the format
specification just before the WRITE statement uses it. Thus, the format specification
changes with each iteration of the DO loop.
SUBROUTINE PRINTCTABLE>
REAL TABLEC1015)
CHARACTER*5 FORCHR<0:5), RPAR*1,
DATA FORCHRCO) ,·RPAR I I ( I ' I) I I

FBIGt

FMEDt

FSML

DATA FBIG 1FMED 1FSML I 'F8.2' I ' 'FS.t'.l ' I ' 'FS+G' I I
DO 20 I=1 t10
DO 18 J=1 ,5
IF <TABLE< I tJ) .GE, 100,) THEN
ELSE

FORCHRCJ) = FBIG
IF CTABLECI1J) +GT,
FORCHR < J >

FMED

FORCHR ( J)

FSML

0,1)

THEN

ELSE

END IF
CONTINUE
FORCHRC5)(5:5)
WRITE CG tFORCHR>

RPAR
(TABLE< I 1J),

J=115)

CONTINUE
END

NOTE
Format specifications stored in arrays are recompiled at run time each time they
are used. If a Hollerith or character run-time format is used in a READ statement to read data into the format itself, that data is not copied back into the
original array. Thus, it will not be available subsequently for using that array as
a run-time format specification.

12.7 Format Control Interaction with 1/0 Lists
Format control begins with the execution of a formatted 1/0 statement. The action taken
by format control depends on information provided jointly by the next element of the VO
list (if one exists) and the next field descriptor of the format specification. Both the 1/0 list
and the format specification are interpreted from left to right, except when repeat counts
and implied-DO lists are specified.

12-28

Format Statements

If the I/0 statement contains an I/0 list, you must specify at least one I, O, z, F, E, D, G,
L, A, or Q field descriptor in the format specification. An error occurs if a field descriptor is
not specified in this case.

On execution, a formatted input statement reads one record from the specified unit and
initiates format control. Thereafter; additional records can be read as indicated by the
format specification. Format control requires that a new record be read when a slash occurs
in the format specification, or when the last closing parenthesis of the format specification
is reached and I/0 list elements remain to be filled. Any remaining characters in the
current record are discarded when the new record is read.
On execution, a formatted output statement transmits a record to the specified unit as
format control terminates. Records can also be written during format control if a slash
appears in the format specification or if the last closing parenthesis is reached and more I/0
list elements remain to be transferred.
The I, O, z, F, E, D, G, L, A, and Q field descriptors each correspond to one element in the
I/O list. No list element corresponds to an H, X, P, T, TL, TR, SP, SS, S, BN, BZ, $, :, or
character constant field descriptor. In H and character constant field descriptors, data
transfer occurs directly between the external record and the format specification.
When an I/0 list element is to be transferred, format field descriptors are processed,
beginning with the current format item, until a descriptor is found that corresponds to an
I/0 list element. The I/0 list element is then transferred under control of the field descriptor.
Format execution continues until one of the following is encountered: an element-transferring field descriptor; a colon (:) edit descriptor; or the end of the format. These also
terminate format execution when no I/0 list elements are to be transferred.
When the last closing parenthesis of the format specification is reached, format control
determines whether more I/0 list elements are to be processed. If not, format control
terminates. However, if additional list elements remain, part or all of the format specification is reused in a process called format reversion.
In format reversion, the current record is terminated, a new one is initiated, and format
control reverts to the group repeat specification whose opening parenthesis matches the
next-to-last closing parenthesis of the format specification. If the format does not contain a
group repeat specification, format control returns to the initial opening parenthesis of the
format specification. Format control continues from that point.

12.8 Summary of Rules for FORMAT Statements
The following sections summarize the rules for constructing and using the format specifications and their components and for constructing external fields and records. Table 12-4
summarizes the FORMAT codes.

Format Statements

12-29

Table 12-4: Summary of FORMAT Codes
Code

Form

Effect

Alwl

Transfers character or Hollerith values.

Specifies that embedded and trailing blanks in a numeric
input field are to be ignored.

Specifies that embedded and trailing blanks in a numeric
input field are to be treated as zeros.

Dw.d

Transfers real values (D exponent field indicator).

Ew.d[Ee]

Transfers real values (E exponent field indicator).

Fw.d

Transfers real values.

Gw.d[Eel

Transfers real values: on input, acts like F code; on output,
acts like E code or F code, depending on the magnitude of
the value.

nHc ... c

Transfers data between the H field descriptor and an external record.

lw[.m]

Transfers decimal integer values.

Transfers logical data: on input, transfers characters; on
output, transfers Tor F.

Ow[.m]

Transfers octal values.

Obtains the number of characters remaining to be transferred in an input record.

Reinvokes optional plus characters in numeric output
fields: counters the action of SP and SS.

Writes plus characters that would otherwise be optional
into numeric output fields.

Suppresses optional plus characters in numeric output
fields.

Specifies positional tabulation.

TLn

Specifies relative tabulation (left).

TRn

Specifies relative tabulation (right).

Specifies that n characters are to be skipped.

Zw[.m]

Transfers hexadecimal values.

Suppresses carriage return during interactive 1/0.
Terminates format control if the VO list is exhausted.

12-30

Format Statements

12.8.1 General Rules
1. A FORMAT statement must always be labeled.
2. In a field descriptor such as rlw[.m] or nX, the terms r, w, m, and n must be unsigned
integer constants or variable format expressions whose values are greater than or
equal to zero. The values of r and w must be greater than zero and less than or equal
to 32767, and the values of m and n must be greater than zero and less than or equal
to 255. (They cannot be names assigned to constants in PARAMETER statements.)
You can omit the repeat count and field width specification.
3. In a field descriptor such as Fw.d, the term d must be an unsigned integer constant

or variable format expression. You must specify d with F, E, D, and G field descriptors even if d is zero. The decimal point is also required. Y6u must either specify both
w and d, or omit them both. In a field descriptor such as Ew .dEe, the term e must
also be an unsigned integer constant.
4. In a field descriptor such as nHc 1c 2 ... en, exactly n characters must follow the H

format code. You can use any printing ASCII character in this field descriptor.

5. In a scale factor of the form nP, n must be an integer constant or variable format
expression in the range -128 through 127 inclusive. The scale factor affects the F, E,
D, and G field descriptors only. Once you specify a scale factor, it applies to all
subsequent real field descriptors in that format specification until another scale
factor appears. You must explicitly specify OP to reinstate a scale factor of zero.
Format reversion does not affect the scale factor.

6. No repeat count is permitted in BN, BZ, S, SS, SP, H, Q, X, T, TR, TL, $, :, or
character constant field descriptors unless these descriptors are enclosed in
parentheses and treated as a group repeat specification.
7. If the associated I/O statement contains an I/0 list, the format specification must

contain at least one field descriptor. This descriptor must be I, 0, Z, F, E, D, G, L,

A, or Q.
8. A format specification in a character variable, character substring reference, character array element, character array, character expression, numeric array, or numeric
array element must be constructed in the same way as a format specification in a
FORMAT statement, including the opening and closing parentheses.
9. If a character-constant format includes apostrophes, those apostrophes must be represented by double apostrophes.

Format Statements

12-31

12.8.2 Input Rules
1. A minus sign must precede a negative value in an external input field; a plus sign is
optional before a positive value.
2. On input, an external field under I field descriptor control must be an integer constant. It cannot contain a decimal point or an exponent. An external field under 0
field descriptor control must contain only the numerals 0 through 7. An external field
input under Z field descriptor control must contain only the numerals 0 through 9
and the letters A(a) through F(f). An external field under 0 or Z field descriptor
control must not contain a sign, a decimal point, or an exponent. You cannot use
octal and hexadecimal constants in the form '777 'O or 'AF9 'X in external records.
3. On input, an external field under F, E, D, or G field descriptor control must be an
integer constant or a real constant. It can contain a decimal point and/or an E(e),
D(d), or Q(q) exponent field.
4. If an external field contains a decimal point, the actual size of the fractional part of
the field, as indicated by that decimal point, overrides the d specification of the
corresponding real field descriptor.
5. If an external field contains an exponent, the scale factor (if any) of the corresponding field descriptor is inoperative for the conversion of that field.
6. The field width specification must be large enough to accommodate both the numeric character string of the external field and any other characters that are allowed
(algebraic sign, decimal point, and/or exponent).
7. A comma is the only character you can use as an external field separator. It terminates the input of fields (for noncharacter data types) that are shorter than the
number of characters expected. It also designates null (zero-length) fields.

12.8.3 Output Rules
1. A format specification cannot specify more output characters than the external
record can contain. For example, a line printer record cannot contain more than 133
characters, including the carriage control character.
2. The field width specification (w) must be large enough to accommodate all characters that the data transfer can generate, including an algebraic sign, decimal point,
and exponent. For example, the field width specification in an E field descriptor
should be large enough to contain d+7 or d+e+5 characters.
3. The first character of a record transmitted to a line printer or terminal is typically
used for carriage control; it is not printed. The first character of such a record should
be a space, 0, 1, $, +, or ASCII NUL. Any other character is treated as a space.

12-32

Format Statements

Chapter 13

Auxiliary Input/Output Statements
The auxiliary I/0 statements perform file management functions. These statements are:
• OPEN-associates FORTRAN logical units with files. OPEN establishes a connection
between a logical unit and a file or device, and declares the attributes required for read
and write operations.
• CLOSE-terminates the connection between a logical unit and a file or device.
• INQUIRE-inquires about specified properties of a file or a logical unit.
• REWIND and BACKSPACE-perform file-positioning functions.
• ENDFILE-writes a special form of record that causes an end-of-file condition (and
END= transfer) when an input statement reads the record.
0

DELETE-deletes a record from a file.

UNLOCK-unlocks a currently accessed record, permitting access by other programs.

The statements are described, in the order shown here, in the sections that follow.

13.1 OPEN Statement
An OPEN statement either connects an existing file to a logical unit or creates a new file
and connects it to a logical unit. In addition, OPEN can specify file attributes that control
file creation and/or subsequent processing.
The OPEN statement has the form:
OPEN (par[,par] ... )

where:
par

is a keyword specification in one of the following forms:
keywd
keywd = value

13-1

where:
keywd

is a keyword, as described below.
value

depends on the keyword, as described below.
Keywords are divided into several categories based on function:
• Keywords that identify the unit and the file:
UNIT
FILE or NAME
DEFAULTFILE
or TYPE
DISPOSE

-logical unit number to be used
-file-name specification for the file
-default file-name specification for the file
-file existence status at OPEN
-file existence status after CLOSE

• Keywords that describe the file processing to be performed:
ACCESS
ORGANIZATION
READO NL Y

-FORTRAN access method to be used
-logical file structure
-write protection

• Keywords that describe the records in the file:
BLOCKSIZE
CARRIAGECONTROL
FORM
RECL or RECORDSIZE
RECORDTYPE
BLANK
KEY

-physical block size
-printer control type
-type of FORTRAN record formatting
-logical record length
-logical record format
-blank interpretation for numeric input
-positions of key fields within records in an indexed file

• Keywords that describe file storage allocation when a file is created:
INITIAL SIZE
EXTENDSIZE

-initial file allocation
-file allocation increment size

• Keywords that provide additional capability for direct access I/0:
ASSOCIATEVARIABLE -the next record number value
MAXREC
-maximum direct access record number
• Optional keywords that provide improved performance or special capabilities. These
options are generally transparent to I/O processing:
BUFFERCOUNT
NOSPANBLOCKS
SHARED
US ERO PEN

13-2

-number of 1/0 buffers to be used
-records are not to be split across physical blocks
-other programs can simultaneously access the file
-user program option to provide additional OPEN capability

Auxiliary Input/Output Statements

ERR

-statement to which control is transferred if an error occurs during execution of the OPEN statement
-status value that indicates whether an error condition
exists

IOSTAT

Table 13-1 lists the values accepted for each keyword.
Table 13-1: OPEN Statement Keyword Values
Values 1

Keyword

Function

Default

ACCESS

'SEQUENTIAL'
'DIRECT'
'KEYED'
'APPEND'

Access mode

ASSOCIATEVARIABLE

asv

Next direct access
record

BLANK

'NULL'
'ZERO'

Interpretation
blanks

'SEQUENTIAL'

'NULL'

BLOCKSIZE

Physical block size

System default

BUFFERCOUNT

Number of 1/0
buffers

System default

Print control

'FORTRAN'
(formatted)
'NONE'
(unformatted)

CARRIAGECONTROL

DEFAULTFILE
DISPOSE
DISP

'FORTRAN'
'LIST'
'NONE'

cl
'KEEP' or 'SA VE'
'DELETE'
'PRINT'
'PRINT' /DELETE'
'SUBMIT'
'SUBMIT/DELETE'

Default file specification
File disposition at
close

'KEEP'

ERR

Error transfer label

EXTEND SIZE

File allocation increment

Volume or system
default

Format type

Depends on
ACCESS keyword

FORM

'FORMATTED'
'UNFORMATTED'

Auxiliary Input/Output Statements

13-3

Table 13-1 (Cont.): OPEN Statement Keyword Values
Values 1

Keyword

Function

FILE
NAME

File-name specificati on

INITIAL SIZE

File allocation

IOSTAT

I/0 status

KEY

el :e2 [:INTEG ERJ
[:CHARACTER]

MAXREC

'SEQUENTIAL'
'RELATIVE'
'INDEXED'

RECORDTYPE

'FIXED'
'VARIABLE'
'SEGMENTED'
'STREAM'
'STREAM_CR'
'STREAM_LF'

File structure

Record length

As specif~ed at file
creation

Record structure

Depends on
ORGANIZATION,
ACCESS, and
FORM keywords

'OLD'
'NEW'
'SCRATCH'
'UNKNOWN'

File status at open

UNIT

Logical unit number

USEROPEN

User program option

Key: v
e
s
c

13-4

'SEQUENTIAL'

File sharing allowed

SHARED
STATUS
TYPE

Direct access record
limit

Write protection

READONLY
RECL
RECORDSIZE

Key field definitions

Records do not span
blocks

NOSPANBLOCKS
ORGANIZATION

Default

'UNKNOWN'

is an integer scalar memory reference.
is a numeric expression.
is a statement label.
is a character scalar reference, numeric scalar memory reference, or numeric array name
reference.
cl is a character expression.
el is the first byte position of a key.
e2 is the last byte position of a key.
p is an external function.

Auxiliary Input/Output Statements

You can specify character values at run time by substituting a general character expression
for a keyword value in the OPEN statement. The character value may contain trailing
spaces, but it must not contain either leading or embedded spaces. For example:
CHARACTER*7 QUAL

IF CexP) QUAL ='/DELETE'
OPEN CUNIT=l 1 STATUS='NEW',

DISP='SUBMIT'//OUAL>

Keyword specifications can appear in any order. In most cases, they are optional; default
values are provided in their absence. If the logical unit specifier is the first parameter in the
list, the UNIT keyword is optional.
The following examples illustrate various uses of the OPEN statement.
1. The following statement creates a new sequential formatted file on unit 1 with the
default file name FOROOl.DAT.
OPEN

<UNIT=1'

STATUS= 'NEW

I' ERR=100)

2. The following statement creates a 50-block direct access file for temporary storage.
The file is deleted at program termination.
OPEN
1

CUNIT=31 STATUS='SCRATCH' 1 ACCESS='DIRECT' 1
INITIALSIZE=501 RECL=G4)

3. The following statement creates a file on magnetic tape with a large block size for
efficient processing.
OPEN

CUN IT= I , FILE= 'MTAO:MYDATA.DAT',
STATUS='NEW' 1 ERR=141
RECORDTYPE='FIXED')

BLOCKSIZE=8192 1

RECL=10241

4. The following statement opens the file created in the previous example for input.
OPEN
1

(UN IT= I 1 FI LE=' MTAO: MYDATA, DAT' 1 READONL Y 1
STATUS= 'OLD
RECL= 1024' RECORDTYPE= 'Fl>(ED
BLOCKSIZE=8192)

5. The following statement uses the file name supplied by the user and the default file
specification supplied by the DEFAULTFILE keyword to define the file specification
for an existing file.
TYPE*'

'ENTER NAME OF DOCUMENT'

ACCEPT * ' DOC
OPEN CUNIT=l 1 FILE=DOC1
1

DEFAULTFILE='CARCH!l.1EJ.T)<T' 1

STATUS='OLD')

Sections 13.1 through 13.1.28 describe in detail the parameters represented by the various
keywords. As used in these sections, a numeric expression can be any integer or real
expression. The value of the expression is converted to integer data type before it is used in
the OPEN statement.

Auxiliary Input/Output Statements

13-5

13.1.1 ACCESS Keyword
The ACCESS parameter has the form:
ACCESS= ace

where:
ace
is a character expression having a value equal to 'DIRECT', 'SEQUENTIAL',
'KEYED', or 'APPEND'.
ACCESS specifies whether the file is to be opened for keyed, direct, or sequential access. If
you specify 'DIRECT', the file is accessed by record number. If you specify 'SEQUENTIAL', the file is accessed sequentially. If you specify 'KEYED', the file is accessed by a
specified key. 'APPEND ' implies sequential access and positioning after the last record of
the file. The default is 'SEQUENTIAL'.

13.1.2 ASSOCIATlEU ARIAliH.lE tteyword
The ASSOCIATEVARIABLE parameter has the form:
ASSOCIATEVARIABLE = asv

where:
asv

is an integer variable. It cannot be a dummy argument to the routine in which the
OPEN statement appears.
ASSOCIATEVARIABLE specifies the integer variable that is updated after each direct
access I/0 operation to reflect the record number of the next sequential record in the file.
This specifier is valid only for direct access mode; it is ignored for other access modes.

13.1.3 BLANK Keyword
The BLANK parameter has the form:
BLANK= blnk

where:
blnk

is a character expression having a value equal to either 'NULL' or 'ZERO'.
When BLANK specifies 'NULL', all blanks in a numeric input field are ignored (except if
the field is comprised of all blanks, in which case it is treated as zero). When BLANK
specifies 'ZERO', all blanks other than leading blanks are to be treated as zeros. The
default value is 'NULL'.
If the /NOF77 compiler command qualifier is specified, the default value is 'ZERO'.
13-6

Auxiliary Input/Output Statements

13.1.4 IIU.OmtS~ZlE tteyword
The BLOCKSIZE keyword specifies the physical I/0 transfer size for the file. It has the
form:
BLOCKSIZE = bks

where:
blcs

is a numeric expression.
For magnetic tape files, the value of bks specifies the physical record size in the range 18 to
32767 bytes. The default value is 2048 bytes.
For sequential disk files, the value of bks is rounded up to an integral number of 512-byte
blocks and used to specify RMS multiblock transfers. The number of blocks transferred can
be 1 to 127. The number of blocks transferred is determined by RMS defaults. Refer to the
description of the SET RMS_DEFAULT command in the Guide to Using DCL and
Command Procedures on VAX/VMS for more information on setting process and system
default multiblock counts if you do not specify a block size.
For relative files and indexed files, the value of bks is rounded up to an integral number of
512-byte blocks and used to specify the RMS bucket size in the range 1 to 32 blocks. The
default is the smallest value capable of holding a single record.

13.1.5 l:JUIFIF!ElllCOlBrJT tteyt"Jord
The BUFFERCOUNT parameter has the form:
BUFFERCOUNT = be

where:
be

is a numeric expression.
The range of values for be is from 1 to 127. The size of each buffer is determined by the
BLOCKSIZE keyword. Thus, if BUFFERCOUNT=3 and BLOCKSIZE=2048, the total
number of bytes allocated for buffers is 3*2048, or 6144.
BUFFERCOUNT specifies the number of buffers to be associated with the logical unit for
multibuffered I/O. The BLOCKSIZE keyword determines the size of each buffer. If you do
not specify BUFFERCOUNT, or if you specify zero, the system default is assumed. Refer to
the description of the SET RMS_DEFAULT command in the Guide to Using DCL and
Command Procedures on VAX/VMS for information on setting process and system default
buffer counts.

Auxiliary Input/Output Statements

13-7

13.1.6 CAliUllAGIECOr~TROL tteyword
The CARRIAGECONTROL parameter has the form:
CARRIAGECONTROL = cc

where:
cc

is a character expression having a value equal to 'FORTRAN', 'LIST', or 'NONE'.
The CARRIAGECONTROL parameter determines the type of carriage control processing
to be used when printing a file. The default for formatted files is 'FORTRAN'; for unformatted files, the default is 'NONE'. 'FORTRAN' specifies normal FORTRAN interpretation of the first character, 'LIST' specifies single spacing between records, and 'NONE'
specifies no implied carriage control.

13.1.7 DEIFAUlTIFH.IE tteyword
The DEFAULTFILE parameter has the form:
DEFAUL TFILE = ce

where:
ce

is a character expression which contains a default file name specification string.
The DEFAULTFILE keyword specifies a default file specification string. You can use this
keyword to supply a value to the RMS default file specification string for the missing
components of a file specification. If you do not specify the DEFAULTFILE keyword,
FORTRAN uses the default value 'FORnnn.DAT ', where nnn is the unit number with
leading zero(s).
The default file specification string is used primarily when accepting file specifications
interactively; file specifications known to a user program are normally completely specified
in the FILE keyword. You can specify defaults for one or more of the following file specification components:
o node
o

device

o directory
o filename

o filetype
o file version number

13-8

Auxiliary Input/Output Statements

When you specify any of the above components in the FILE=keyword, they override those
values specified in the DEFAULTFILE=keyword. Refer to the VAX Record Management
Services Reference Manual for more information.

13.1.8 DIS~OSIE [tavword
The DISPOSE (or DISP) parameter has the form:
DISPOSE = dis
DISP =dis

where:
dis

is a character expression having a value equal to 'KEEP', 'SAVE', 'DELETE',
'PRINT', 'SUBMIT', 'PRINT/DELETE', or 'SUBMIT/DELETE'.
The DISPOSE parameter determines the disposition of the file connected to the unit when
the unit is closed.
0

If you specify 'KEEP' or 'SAVE', the file is retained after the unit is closed; this is

the default value.
o If you specify
0

'DELETE', the file is deleted.

If you specify 'PRINT', the file is submitted to the system line printer spooler and is

not deleted; it is printed and then deleted if you specify 'PRINT/DELETE'.
0

If you specify 'SUBMIT', the file is submitted to the batch job queue and is not

deleted; it is submitted and then deleted if you specify 'SUBMIT/DELETE'.
A read-only file cannot be deleted. A scratch file cannot be saved, printed, or submitted.

13.1.9 ERR Keyword
The ERR parameter has the form:
ERR= s

where:

s
is the label of an executable statement.
The ERR parameter identifies the executable statement that is to receive control when an
error occurs. ERR applies only to the OPEN statement in which it is specified, and not to
subsequent I/0 operations on the unit. If an error occurs, no file is opened or created.

Auxiliary Input/Output Statements

13-9

13.1. ~ o rmTIH~DS DlrE meirword
The EXTENDSIZE parameter has the form:
EXTENDSIZE =es

where:

es
is a numeric expression.
The EXTENDSIZE parameter specifies the number of blocks by which to extend a disk
file when additional storage space is allocated. If you do not specify EXTENDSIZE or if
you specify zero, the system default for the device is used.
See Section 13.1.13 for a discussion about the relationship between the EXTENDSIZE
keyword and the INITIALSIZE keyword.

13.1.11 FILE Keyword
The FILE parameter has the form:
FILE= fin

where:
fin

is a character scalar reference, numeric scalar memory reference, or numeric array
name reference.
The FILE parameter specifies the name of the file to be connected to the unit. The name
can be any file specification accepted by the operating system. Section 1.5.1 describes
default file name conventions.

If the file name is stored in a numeric scalar or array, the name must consist of ASCII
characters terminated by an ASCII null character (zero byte). However, if it is stored in a
character scalar or array, it must not contain a zero bvte.

13.1.12 FORM Keyword
The FORM parameter has the form:
FORM= ft

where:
ft

is a character expression
'UNFORMATTED'.

13-10

having a

Auxiliary Input/Output Statements

value

equal to

'FORMATTED'

The FORM parameter specifies whether the file being opened is to be read or written using
formatted or unformatted READ or WRITE statements. For sequential access files,
'FORMATTED' is the default. For direct access and keyed access files,
'UNFORMATTED ' is the default.

13.1.13

mnuus1z1E ttevword

The INITIALSIZE parameter has the form:
INITIALSIZE = insz

where:
insz

is a numeric ~xpression.
If you do not specify INITIALSIZE, or if you specify zero, no initial allocation is made. The
system attempts to allocate contiguous space for INITIALSIZE. If not enough contiguous

space is available, noncontiguous space is allocated.
The INITIALSIZE parameter specifies the number of blocks in the initial storage allocation for a disk file. The EXTENDSIZE parameter specifies the number of blocks by which
a disk file is extended each time more space is needed for the file.
INITIALSIZE is effective only at the time the file is created. If EXTENDSIZE is specified
when the file is created, the value specified is the default value used to allocate additional
storage for the file. If you specify EXTENDSIZE when you open an existing file, the value
you specify supersedes any EXTENDSIZE value specified when the file was created, and
remains in effect until you close the file. Unless specifically overridden, the default
EXTENDSIZE value is in effect on subsequent openings of the file.

13.1.14 IOSTAT Keyword
The IOSTAT parameter has the form:
IOSTAT = ios

where:
ios

is an integer scalar memory reference.
The IOSTAT parameter is an I/0 status specifier. It causes ios to be defined as zero if no
error condition exists, or as a positive integer if an error condition exists. VAX FORTRAN
I/0 status values are described in Sections 18.1 and 18.3. IOSTAT applies only to the
OPEN statement in which it appears and not to subsequent I/O operations on the logical
unit that is opened; however, IOSTAT can be used in subsequent I/0 statements to perform a similar function (see Chapter 11).

Auxiliary Input/Output Statements

13-11

13.1.15 ttEV tteyword
The KEY parameter has the form:
KEY = (kspec[,kspec] ... )

where:
lcspec

has the form:
e1 :e2[:dt]

where:
e1

is the first byte position of the key.
e2

is the last byte position of the key.
dt

is the data type of the key: either INTEGER or CHARACTER.
The KEY parameter defines the access keys for records in an i~dexed file. The key starts at
position el in the record and has a length of e2-el+l. The values of el and e2 must be such
that:
1 .LE. (e1) .LE. (e2) .LE. record-length
1 .LE. (e2-e1+1) .LE. 255

If the key type is INTEGER, the key length must be either 2 or 4.

You must define at least one key for an indexed file. This mandatory key is called the
primary key of the file and usually has a unique value for each record (this is the default
condition). You can also define other keys, called alternate keys. RMS allows up to 254
alternate keys. The maximum allowed in an OPEN statement is, however, 85 and the use
of other OPEN keywords reduces this limit further. See the section on FOR$0PEN in the
VAX/VMS Run-Time Library Reference Manual for more information on OPEN statement limits. A file that requires more keys than the practical limit for the OPEN statement
must be created from another language or with FDL (File Definition Language). For information on FDL, see the VAX Record Management Services Reference Manual.
The default data type of a key is CHARACTER. The position of a key specification in the
list determines a key's key-of-reference number. This number is used in any subsequent
1/0 statement to specify the same key. The primary key is key-of-reference number 0, the
first alternate key is key-of-reference number 1, and so forth.
The key fields and key-of-reference numbers are permanent attributes of an indexed file
and are established when the file is created. The KEY parameter must be specified when a
file is created, but does not need to be specified when an existing file is opened. When an

13-12

Auxiliary Input/Output Statements

existing file is opened, key definitions and key-of-reference numbers are obtained from the
file itself. If the KEY parameter is specified for an existing file, it must agree with the
established attributes of the file.

13.1.15 MAlmlEC ttevword
The MAXREC parameter has the form:
MAXREC = mr

where:
mr

is a numeric expression.
The MAXREC parameter specifies the maximum number of records permitted in a direct
access file. The default is an unlimited number of records. This specifier applies only to
direct access files.

1a.1.11 rJAMIE m~vword
NAME is a nonstandard synonym for FILE. See Section 13.1.11.

13.1.18 rJOSu>ArJR1LOCtts mevword
The NOSPANBLOCKS parameter has the form:
NOSPANBLOCKS

The NOSPANBLOCKS parameter specifies that records are not to cross disk block boundaries. If any record exceeds the size of a physical block, an error occurs.

13.1.19 ORGJUJIZATIOrJ tCeyword
The ORGANIZATION parameter has the form:
ORGANIZATION= org

where:
org

is a character expression whose value is equal to 'SEQUENTIAL', 'RELATIVE', or
'INDEXED'.
The ORGANIZATION parameter specifies the internal organization of the file. The default
file organization is sequential. However, if you omit the ORGANIZATION keyword when
you open an existing file, the organization already specified in that file is used. If you
specify ORGANIZATION for an existing file, org must have the same value as that of the
existing file.

Auxiliary Input/Output Statements

13-13

13.1.20 ~IEJU»«Jlm. v tteyt"JOVd
The READONLY parameter has the form:
READONLY

The READONLY parameter specifies that an existing file can be read, but prohibits
writing to that file.
The FORTRAN 1/0 system's default file access privileges are read-write, which can cause
run-time 1/0 errors if the file protection does not permit write access. The READONLY
keyword has no effect on the protection specified for a file. Its main purpose is to allow a file
to be read simultaneously by two or more programs. For example, if you wish to open a file
for the purpose of reading the file but want to allow others to read the same file while you
have it open, specify the READONLY keyword. Refer to the VAX FORTRAN User's
Guide for information on file sharing.

13.1.21 RECL Keyword
The RECL parameter has the form:
RECL = rl

where:
rl

is a numeric expression indicating the length of logical records in the file.
The value of rl does not include space for control information, such as for two segment
control bytes (if present) or the bytes that RMS requires for maintaining record length and
deleted record control information. The specification is for record data only.
The value of rl is interpreted as either bytes or longwords, depending on whether the
records are formatted (bytes) or unformatted (longwords, that is, 4-byte units). Table 13-2
summarizes the maximum values that can be specified for rl, based on file organization
and record format.

Table 13-2: Record Size (RECL) Limits
Record Format

File Organization
Formatted
(bytes)

Unformatted
(longwords)

Sequential

32766

8191

Sequential and variable-length records on
ANSI magnetic tape

9999 1

2499 1

Relative and indexed

16380

4095

Limit imposed by 4-byte ASCII count field.

13-14

Auxiliary Input/Output Statements

The interpretation and effect of the logical record length varies under the following conditions:
0

If the file contains fixed-length records, RECL specifies the size of each record.

If the file contains variable-length records, RECL specifies the maximum length for

any record.
• If the records are formatted, the length is the number of bytes.
• If the records are unformatted, the length is the number of longwords.
• If you omit this specifier for existing files, the record length specified when the file was

created is assumed.
• If your program attempts to write, to an existing file, a record that is longer than the

logical record length, an error is signaled.
If you are opening an existing file that contains fixed-length records or that has relative

organization, and you specify a value for RECL that is different from the actual length of
the records in the file, an error occurs. If you omit RECL when opening an existing file, the
record length specified when the file was created is used.
You must specify RECL when you create files with fixed-length records or with relative or
indexed organization.

1a.1.22 mscornrns~zlE tt0ywoW""d
RECORDSIZE is a nonstandard synonym for RECL; refer to Section 13.1.21 for more
information.

13.1.23 ~lECOfUilTVUJ!E tt0yt11mrd
The RECORDTYPE parameter has the form:
RECORDTYPE = typ

where:
typ

is a character expression whose value is equal to 'FIXED', 'VARIABLE',
'SEGMENTED', 'STREAM', 'STREAM_CR', or 'STREAM_LF'.
The RECORDTYPE parameter specifies whether the file has fixed-length records, variable-length records, segmented records, or stream-type variable-length records. When you
create a file, the default record types are:
File Type

Default Record Type

Relative or indexed files

'FIXED'

Direct access sequential files

'FIXED'

Formatted sequential access files

'VARIABLE'

Unformatted sequential access files

'SEGMENTED

Auxiliary Input/Output Statements

13-15

A segmented record consists of one or more variable-length records. Use of segmented
records allows a FORTRAN logical record to span several RMS records. Only unformatted
sequential access files with sequential organization can use segmented records. You cannot
specify 'SEGMENTED' for any other file type.
If you do not specify the RECORDTYPE parameter when you are accessing an existing file,
the record type of the file is used. An exception to this rule is unformatted sequential access
files with sequential organization and variable-length records; these files have a default of
'SEGMENTED
I.

If you do specify the RECORDTYPE parameter when you are accessing an existing file, the
type that you specify must match the type of an existing file.

In fixed-length record files, if an output statement does not specify a full record, the record
is filled with spaces (for a formatted file) or zeros (for an unformatted file).
You cannot use an unformatted READ statement to access an unformatted sequential
organization file containing variable-length records, unless you specify the corresponding
RECORDTYPE value in your OPEN statement.
Files containing segmented records can be accessed only by unformatted sequential
FORTRAN I/O statements.

13.1.24 S~ARIED tteyword
The SHARED parameter has the form:
SHARED

The SHARED parameter specifies that the file can be opened for shared access by more
than one program executing simultaneously.
See the section on "file sharing" in the VAX FORTRAN User's Guide for additional
information on this keyword.

13.1.25 STATUS Keyword
The STATUS parameter has the form:
STATUS= sta

where:
sta

is a character expression whose value is equal to 'OLD', 'NEW', 'SCRATCH', or
'UNKNOWN'.
The STATUS parameter specifies the status of the file to be opened.
• If you specify 'OLD', the file must already exist.
• If you specify 'NEW', a new file is created.

13-16

Auxiliary Input/Output Statements

• If you specify 'SCRATCH', a new file is created and it is deleted when the file is

closed.
• If you specify 'UNKNOWN', the processor will first try 'OLD'; if the file is not

found, the processor will use 'NEW', thereby creating a new file.
The default is 'UNKNOWN'.
If the /NOF77 compiler command qualifier is specified, the default value is 'NEW'.

NOTE
The STATUS parameter is also used in CLOSE statements to specify the status
of a file after the file is closed; however, the values it uses are different from
those used in OPEN statements.

13.1.26 TVl?!E tteyword
TYPE is a nonstandard synonym for STATUS. See Section 13.1.25.

13.1.27 UNIT Keyword
The UNIT parameter has the form:
[UNIT=] u

where:
u

is a numeric expression.
The UNIT parameter specifies the logical unit to which a file is to be connected. The unit
specification must appear in the list. The UNIT keyword can be omitted only when the
unit specifier occupies the first position in the list.
The logical unit may already be connected to a file when an OPEN statement is executed.
If this file is not the same as the one to be opened, the OPEN statement executes as if a
CLOSE statement had executed just before it. If the file to be opened is already connected

to the unit or if the file specifier (FILE keyword) is not included in the OPEN statement,
only the blank specifier (BLANK keyword) can have a value different from the one currently in effect. The position of the file is unaffected.

13. ·i .20 usrrnmlJfErJ mayword
The US ERO PEN parameter has the· form:
USEROPEN = procedure-name

where:
procedure-name

is the symbolic name of the USEROPEN procedure.
Auxiliary Input/Output Statements

13-17

The procedure name must be declared EXTERNAL.
The USEROPEN parameter specifies a user-written external function that controls the
opening of the file. Knowledgeable users can employ additional features of the operating
system that are not directly available from FORTRAN, while retaining the convenience of
writing programs in FORTRAN. See the VAX FORTRAN User's Guide for more information on USEROPEN.

13.2 CLOSE Statement
The CLOSE statement disconnects a file from a unit. It has the form:
CLOSE

([UNIT=]U

.{~~PTi:E }= p [,ERR=s][,IOSTAT=ios])
DISP

where:
u

is a logical unit number.
p

is a character expression that determines the disposition of the file. Its values are
'KEEP', 'SAVE', 'DELETE', 'PRINT', 'SUBMIT', 'SUBMIT/DELETE', and
PRINT/DELETE'.
s
is the label of an executable statement.
ios

is an integer scalar memory reference.
The CLOSE statement parameters can occur in any order. The keyword UNIT is optional
only if the unit specifier is the first parameter in the list.
If you specify either 'SA VE' or 'KEEP', the file is retained after the unit is closed. If you
specify 'DELETE', the file is deleted. If you specify 'PRINT', the file is submitted to the
line printer spooler; it is printed and deleted if you specify 'PRINT/DELETE'. If you
specify 'SUBMIT', the file is submitted to the batch job queue; it is submitted and
deleted if you specify 'SUBMIT/DELETE'. For scratch files, the default is 'DELETE';
for all other files, the default is 'KEEP'. The disposition specified in a CLOSE statement
supersedes the disposition specified in the OPEN statement, except that a file opened as a
scratch file cannot be saved, printed, or submitted and a file opened for read-only access
cannot be deleted.

13-18

Auxiliary Input/Output Statements

For example:
CLOSE CUNIT=l 1 STATUS= 'PRINT')

This statement closes the file on unit 1 and submits the file for printing.
CLOSE CUNIT=J1 STATUS='DELETE', ERR=88)

This statement closes the file on unit J and deletes it.

13.3 INQUIRE Statement
The INQUIRE statement inquires about specified properties of a file or of a logical unit on
which a file might be opened. The INQUIRE statement has two forms, one for inquiring by
file and the other for inquiring by unit:
INQUIRE (FILE=fi[ ,DEFAULTFILE=dfi ... ],flist)
INQUIRE ([UNIT =]u,flist)

where:
fi

is a character expression, numeric scalar memory reference, or numeric array name
reference whose value specifies the name of the file. to be inquired about.
dfi

is a character expression specifying a default file name specification string.
flist

is a list of property specifiers in which any one specifier appears only once. The
specifiers are described in Sections 13.3.1 through 13.3.20.
u

is the number of the logical unit to be inquired about. The unit does not have to exist,
nor does it need to be connected to a file. If the unit is connected to a file, the inquiry
encompasses both the connection and the file.
FILE=fi and UNIT=u can appear anywhere in the property-specifier list; however, if the
UNIT keyword is omitted, the unit specifier (u) must be the first parameter in the list.
DEFAULTFILE=dfi can be used in addition to or in place of FILE=fi when used in
connection with an inquiry about a file. If a file is opened with both FILE and DEFAULTFILE keywords specified in the OPEN statement, then you can inquire about this file by
specifying both the FILE and DEFAULTFILE keywords in the INQUIRE statement.
An INQUIRE statement may be executed before, during, or after the connection of a file to
a unit; the values assigned by the statement are those that are current when the INQUIRE
statement is executed.

Auxiliary Input/Output Statements

13-19

13.3.1 ACCESS Specifier
The ACCESS specifier has the form:
ACCESS= ace

where:
ace
is a character scalar memory reference.
Ace is assigned the value SEQUENTIAL if the file is connected for sequential access,
DIRECT if the file is connected for direct access, and KEYED if the file is connected for
keyed access. If there is no connection, ace is UNKNOWN.

13.3.2 BLANK Specifier
The BLANK specifier has the form:
BLANK= blk

where:
blk

is a character scalar memory reference.
Blk is assigned the value NULL if null blank control is in effect for a file connected for
formatted I/0; it is assigned the value ZERO if zero blank control is in effect. If there is no
connection or if the connection is not for formatted 1/0, blk is assigned the value
UNKNOWN.

13.3.3 CIUUllAGIECDrJTROL Speciiier
The CARRIAGECONTROL specifier has the form:
CARRIAGECONTROL = cc

where:
cc
is a character scalar memory reference.
Cc is assigned the value FORTRAN if the file has the FORTRAN carriage control attrib. ute, LIST if the file has the implied carriage control attribute, NONE if the file has no
carriage control attribute, and UNKNOWN if no other value applies.

13-20

Auxiliary Input/Output Statements

13.3.4 DIRECT Specifier
The DIRECT specifier has the form:
DIRECT= dir

where:
dlr

is a character scalar memory reference.
Dir is assigned the value YES if DIRECT is an allowed access method for the file, NO if
DIRECT is not an allowed access method, and UNKNOWN if the processor is unable to
determine whether DIRECT is an allowed access method.

13.3.5 ERR Specifier
The ERR specifier has the form:
ERR= s

where:
s

is the label of an executable statement.
ERR is a control specifier rather than a property specifier. If an error occurs during execution of the INQUIRE statement, control is transferred to the statement whose label is s.

13.3.6 EXIST Specifier
The EXIST specifier has the form:
EXIST= ex

where:
ex

is a logical scalar memory reference.
Ex is assigned the value .TRUE. if the specified file or unit exists, and the value .FALSE. if
the specified file or unit does not exist.

Auxiliary Input/Output Statements

13-21

13.3.7 FORM Specifier
The FORM specifier has the form:
FORM= fm

where:
fm

is a character scalar memory reference.
Fm is assigned the value FORMATTED if the file is connected for formatted VO, and
UNFORMATTED if the file is connected for unformatted VO. If there is no connection, fm
is assigned the value UNKNOWN.

13.3.8 FORMATTED Specifier
The FORMATTED specifier has the form:
FORMATTED = fmd

where:
fmd

is a character scalar memory reference.
Fmd is assigned the value YES if formatted is an allowed form for the file, NO if formatted
is not an allowed form, and UNKNOWN if the processor is unable to determine whether
formatted is an allowed form.

13.3.9 IOSTAT Specifier
The IOSTAT specifier has the form:
IOSTAT = ios

where:
ios

is an integer scalar memory reference.
IOSTAT is a control specifier rather than a property specifier. Ios is assigned a processordependent positive integer value if an error occurs during execution of the INQUIRE
statement; it is assigned the value ZERO if there is no error condition.

13.3.10 CtlEVIED Speciiier
The KEYED specifier has the form:
KEYED= kyd

13-22

Auxiliary Input/Output Statements

where:
kyd

is a character scalar memory reference.
Kyd is assigned the value YES if KEYED is an allowed access method for the file (that is,
the file is indexed), NO if KEYED is not an allowed access method, and UNKNOWN ifthe
processor is unable to determine whether KEYED is an allowed access method.

13.3.11 NAME Specifier
The NAME specifier has the form:
NAME= nme

where:
nme

is a character scalar memory reference.
Nme is assigned the name of the file being inquired about. If the file does not have a name,
nme is not defined.
The value assigned to nme is not necessarily identical to the value specified with the FILE
keyword. For example, the value that the processor returns may be qualified by a directory
name or a version number. However, the value that is assigned is always valid for use with
the FILE keyword in an OPEN statement.
NOTE
FILE and NAME are synonyms when used with the OPEN statement, but not
when used with the INQUIRE statement.

13.3.12 NAMED Specifier
The NAMED specifier has the form:
NAMED= nmd

where:
nmd

is a logical scalar memory reference.
Nmd is assigned the value .TRUE. if the specified file has a name, and the value .FALSE.
if it does not have a name.

Auxiliary Input/Output Statements

13-23

13.3.13 NEXTREC Specifier
The NEXTREC specifier has the form:
NEXTREC = nr

where:
nr

is an integer scalar memory reference.
Nr is assigned an integer value which is one more than the number of the last record read or
written on the specified direct access file. If no records have been read or written, the value
of nr is one. If the file is not connected for direct access, or if the position is indeterminate
because of an error condition, nr is zero.

13.3.14 NUMBER Specifier
The NUMBER specifier has the form:
NUMBER= num

where:
num

is an integer scalar memory reference.
Num is assigned the number of the logical unit currently connected to the specified file. If.
there is no logical unit connected to the file, num is not defined.

13.3.15 OPENED Specifier
The OPENED specifier has the form:
OPENED= od

where:
od

is a logical scalar memory reference.
Od is assigned the value .TRUE. if the specified file is opened on a unit or if the specified
unit is opened; it is assigned the value .FALSE. if the file or unit is not open. ·

13.3.16 ORGArJIZATIOr~ Specifier
The ORGANIZATION specifier has the form:
ORGANIZATION= org

where:
org

is a character scalar memory reference.
13-24

Auxiliary Input/Output Statements

Org is assigned the value SEQUENTIAL if the file is a sequential file, RELATIVE if the
file is a relative file, and INDEXED if the file is an indexed file. If the processor is unable to
determine the organization, org is assigned the value UNKNOWN.

13.3.17 RECL Specifier
The RECL specifier has the form:
RECL =rel

where:
rel

is an integer scalar memory reference.
If the file (or unit) is opened, rel is the maximum record length allowed; if not opened, rel is
the longest record in the file. If a specified file does not exist, rel is zero. Rel is expressed in
bytes if the file is opened for formatted I/0, and in longwords if the file is unformatted.

The INQUIRE statement reports the record length either in longwords (if a file has been
previously opened for unformatted 1/0) or in bytes (in all other circumstances).

13.3.18 RIECODlDTVl?IE Speciiier
The RECORDTYPE specifier has the form:
RECORDTYPE = rtype

where:
rtype

is a character scalar memory reference.
Rtype is assigned the value FIXED if the file has fixed-length records, VARIABLE if the
file has variable-length records, and SEGMENTED if the file is connected for unformatted
sequential I/O using segmented records. If the file has stream-type records, rtype is assigned one of the following values: STREAM if the file's records are terminated with
carriage-return and line-feed, STREAM_CR if they are terminated only with carriagereturn, or STREAM_LF if they are terminated only with line-feed. If the processor cannot
determine the record type, rtype is assigned the value UNKNOWN.

13.3.19 SEQUENTIAL Specifier
The SEQUENTIAL specifier has the form:
SEQUENTIAL = seq

where:
seq

is a character scalar memory reference.

Auxiliary Input/Output Statements

13-25

Seq is assigned the value YES if SEQUENTIAL is an allowed access method for the
specified file, NO if SEQUENTIAL is not an allowed access method, and UNKNOWN if
the processor cannot determine whether SEQUENTIAL is an allowed access method.

13.3.20 UNFORMATTED Specifier
The UNFORMATTED specifier has the form:
UNFORMATTED = unf

where:
unf

is a character scalar memory reference.
Unf is assigned the value YES if unformatted is an allowed form for the file, NO if
unformatted is not an allowed form for the file, and UNKNOWN if the processor is unable
to determine whether unformatted is an allowed form for the file.

13.4 REWIND Statement
The REWIND statement repositions a sequential file currently open for sequential or
append access to the beginning of the file. It has the forms:
REWIND ([UNIT =]u[,ERR=s][,IOSTAT=ios])
REWIND u

where:
u

is a logical unit number.
s

is the label of the executable statement to which control is to be transferred if an error
occurs.
ios

is an integer scalar memory reference that is assigned a positive integer if an error
occurs, and zero if no error occurs.
The unit number must refer to a file on disk or magnetic tape.
For example:
REWIND 3

This statement repositions logical unit 3 to the beginning of the currently open file.
You must not issue a REWIND statement for a file that is open for direct or keyed access.

13-26

Auxiliary Input/Output Statements

13.5 BACKSPACE Statement
The BACKSPACE statement repositions a sequential file currently open for sequential
access to the beginning of the preceding record. When the next 1/0 statement for the unit is
executed, this preceding record is available for processing.
The BACKSPACE statement has the forms:
BACKSPACE ([UNIT =]u[,ERR=s][,IOSTAT=ios])
BACKSPACE u

where:
u

is a logical unit number.
s
is the label of the executable statement to which control is to be transferred if an error
occurs.
ios

is an integer scalar memory reference that is defined as a positive integer if an error
occurs, and zero if no error occurs.
The unit number must refer to an open file on disk or magnetic tape. For example:
BACKSPACE a
This statement repositions the open file on logical unit 4 to the beginning of the preceding
record.
You must not issue a BACKSPACE statement for a file that is open for direct, keyed, or
append access. Backspacing from record n is done by rewinding to the start of the file and
then performing n-1 successive reads to reach the previous record. For direct, keyed, and
append access, the current record count (n) is not available to the FORTRAN 1/0 system.

13.6 ENQFILE Statement
The ENDFILE statement writes an end-file record to the specified unit. It has the forms:
ENDFILE ([UNIT =]u[,ERR=s][,IOSTAT=ios])
ENDFILE u

Auxiliary Input/Output Statements

13-27

where:
u

is a logical unit number.
s

is the label of the executable statement to which control is to be transferred if an error
occurs.
ios

is an integer scalar memory reference that is defined as a positive integer if an error
occurs, and zero if no error occurs.
An end-file record can be written only to sequential organization files that are accessed as
formatted sequential or unformatted segmented sequential files.
For example:
ENDFILE 2

This statement writes an end-file record to logical unit 2.
You must not issue an ENDFILE statement for a file that is open for direct

access.

End-file records should not be written in files that are read by programs written in a
language other than FORTRAN because VAX RMS does not support the embedded endfile concept. An end-file record is a 1-byte record containing the hexadecimal code lA
(CTRL/Z).

13.7 IIlHEll.lETlE SRaiemenR
The DELETE statement deletes records from relative and indexed files. It has the form$:

Indexed File Access
DELETE ([UNIT =]u[,ERR=s][,IOSTAT=ios])

Relative File Access
DELETE ([UNIT =]u,REC=r[,ERR=s][,IOSTAT =ios])
DELETE (u 'r[,ERR=s][,IOSTAT =ios])

13-28

Auxiliary Input/Output Statements

where:
u

is the number of the logical unit containing the record to be deleted.
is the positional number of the record to be deleted.
s
is the label of an executable statement to which control is to be transferred if an error
condition occurs.
ios

is an integer scalar memory reference that is defined as a positive integer if an error
occurs, and zero if no error occurs.
The form of the DELETE statement for use with indexed files is a current-record delete.
This form of the statement deletes the current record, which is the last record to be
accessed by a READ statement on the specified logical unit.
The forms of the DELETE statement for use with relative files are direct access deletes.
These forms of the statement delete the record specified by the number r.
The DELETE statement logically removes the appropriate record from the specified file;
that is, it locates the record and marks it as a deleted record. It then frees the position
formerly occupied by the deleted record so that a new record can be written into that
position.
After a direct access delete, any associated variable is set to the next record number.
The following examples demonstrate the use of the DELETE statement:
1. The fifth record in the file connected to logical unit 10 is deleted from the file in the
following exam pie.
DELETE (101REC=5>

2. The current record is deleted from the file connected to logical unit 11 in the following example.
DELETE ( 11)

Auxiliary Input/Output Statements

13-29

The UNLOCK statement unlocks a record in a relative or indexed file locked by a previous
READ, without performing any other I/O operations. It has the forms:
UNLOCK ([unit=]u[,ERR=s][,IOSTAT=ios])
UNLOCK u

where:
u

is the number of a logical unit.
s
is the label of the executable statement to which control is to be transferred if an error
occurs.
ios

is an integer scalar memory reference that is defined as a positive integer if an error
occurs, and zero if no error occurs.
The UNLOCK statement frees a previously locked record on the specified logical unit. If no
record is locked, the operation has no effect.

13-30

Auxiliary Input/Output Statements

Chapter 14

Using Structures and Records
VAX FORTRAN structures and records allow you to easily group associated data together.
Like arrays, records can contain one or more data elements. Unlike arrays however, the
data elements in a record, called fields, can have different data types. Additionally, unlike
arrays in which each element has a numeric index with which to uniquely identify it, each
field of a record has a unique name.
This chapter provides an overview of how records can be used in VAX FORTRAN programs. Detailed information about the specifics of record use is split up among other
chapters in this manual. Topics addressed in preceding chapters are as follows:
• The way to reference records and how records appear in memory (Section 6.2.5)
• The use of records in assignment statements (Section 7.4)
• The format of the RECORD statement (Section 8.13)
• The format of structure declaration blocks, which define the fields or groups of fields
within a record (Section 8.15.1)
Aside from introducing terms relating to structured data items and their formation, the
record construct has affected the terminology used to describe data items in general. It is
important to understand the terminology changes relating to data items because they are
-in evidence throughout the manual. See Section 6.2.6 for a discussion of the terminology
used to collectively refer to data items.

14-1

14.1 Structures
In VAX FORTRAN, structures are used to describe the form of records. You canthink of
structures as templates for records, defining the form and size of records.

Structures are defined with blocks of statements originating with a STRUCTURE statement and ending with an END STRUCTURE statement. Structure declaration blocks can
contain the following statements:
• Statements that appear very much like data type declaration statements. These statements describe the fields contained within the structure.
• Statements that define substructures (nested structure declarations and RECORD
statements) and mapped common areas (union declarations). These constructs are not
discussed in this chapter; see Sections 8.15.2 and 8.15.3 for details.
I

• PARAMETER statements. A PARAMETER statement in a structure declaration
block has its normal effect of assigning a symbolic name to a constant.
The name of a structure is specified in the STRUCTURE statement. The RECORD statement uses this name to identify the structure that is to be made into a record (or structured
field) (see Section 14.2).
The following example defines the structure DATE. It contains three fields: DAY,
MONTH, and YEAR. Note that the field YEAR is initialized with 1984. Any records
defined to have the structure DATE will have their YEAR field initialized to 1984.
STRUCTURE /DATE/
LOGICAL*l DAY1 MONTH
INTEGER*2 YEAR /18Ba/
END STRUCTURE

The following example defines the structure PERSON, which might be used to hold information about an individual. It contains the fields NAME, SEX, and BIRTH_DATE. Note
that the fields NAME and BIRTH_DATE are themselves structured; that is, they are
substructures within the structure PERSON. NAME's structure declaration (unnamed)
contains the fields LAST_NAME, FIRST_NAME, and MIDDLE_INITIAL. BIRTH_
DATE has the structure of DATE, the structure defined in the preceding example.
STRUCTURE /PERSON/
STRUCTURE NAME
CHARACTER*20 LAST_NAME1 FIRST_NAME
CHARACTER*l MIDDLE_INITIAL
END STRUCTURE
LOGICAL*l
srn
RECORD /DATE/ BIRTH_DATE
END STRUCTURE

See Section 8.15 for detailed information about structure declarations and their syntactical
elements.

14-2

Using Structures and Records

14.2 Records
Records in FORTRAN are analogous to variables and arrays. Their "data type" is determined by the template, or structure, that is used to define them. The RECORD statement
is used to define record scalars and arrays, in much the same way that type declaration
statements are used. For example, the following RECORD statement, based on the structure PERSON shown in the preceding section, could be used.
RECORD /PERSON/ FATHER, MOTHER, CHILDRENC10)

The preceding statement creates twelve records with the structure PERSON. In all twelve
records, all fields are initially undefined, with the exception of BIRTH_DATE.YEAR,
which has been initialized to 1984 in the structure declaration DATE.
See Section 6.2.5 for information about how to reference records and fields and about how
they appear in memory. See Section 8.13 for detailed information about the syn~ax of
RECORD statements .

•

14.3 Uses of Records
When you have several data arrays, each containing a different, though related, type of
information, the use of records allows you to use the same index to refer to each array.
As an example, consider a FORTRAN program which maintains and manipulates a symbol
table. The symbol table consists of three arrays: the first contains the symbol names, the
second contains the symbol values, and the third contains a flag signaling whether the
symbol is defined. As an example, the declaration in FORTRAN-77 could be as follows:
PARAMETER IMAXSYM=lOOO>
CHARACTER*lG SYMBOL_NAMECMAXSYM>
INTEGER*ll
SYMBOL_VALUEIMAXSYM>
SYMBOL_FLAGIMAXSYM>
LOGICAL*l

Note that each, array is declared separately and that, although the data items are related,
they are declared (and later manipulated) separately. For example, to read or write such
related information from or to a file, you must specify each piece individually, such as in
the following WRITE statement:
WR I TE ( 10) SYMBOL_NAME (I) , SYMBOL_t,JALUE (I> , SYMBOL_FLAG (I)

With structures and records, however, the definition allows you to group the related information together, and refer to them as a whole in many cases. Instead, then, the symbol
table declaration could appear as follows:
STRUCTURE /SYM/
CHARACTER*lG
INTEGER*ll
LOGICAL*!
END STRUCTURE

NAME
t,JALUE
FLAG

RECORD /SYM/ SYMBOLIMAXSYM>

Using Structures and Records

14-3

With these definitions, there is only one array, the record array SYMBOL. Each element of
SYMBOL has the form, or structure, of SYM. This means that each element of SYMBOL
consists of the three fields NAME, VALUE, and FLAG. Note that the related information
about an individual symbol-it's name, value, and defined-flag-are now one element of a
record array. As a result, you can refer to a symbol table (that is, SYMBOL instead of
individual arrays such as SYMBOL_NAME), a single symbol I (for example, SYMBOL(!)
instead of SYMBOL_NAME(I)), or any of the fields in symbol I (for example, SYMBOL(l).NAME). Thus, the previous WRITE statement would be changed to:
WRITE

(10)

SYMBOLCII

This statement is equivalent to:
WR I TE C10 > SYMBOL.( I I , NAME, SYMBOL (I I , IJALUE , SYMBOL (I> , FLAG

In some cases, such as with arguments of system service calls, FORTRAN programs had to
use COMMON blocks to pass structured information to subroutines (see the
VAX FORTRAN User's Guide for information on data structure arguments). Routines
such as these expect the address of either a list, control block, or vector, and the COMMON statement constructs these arguments, with no empty spaces between adjacent
items, in order of declaration. The resulting COMMON block(s) can be used as records but
do not have the flexibility of records.
For example, a call to the SYS$GETJPI system service requires the address of a sequence
of items consisting of two words followed by two longwords. With records, this call can be
achieved with the following code:
STRUCTURE /GETJPI_ITEM/
INTEGER*2 W_LEN1 W_COOE
INTEGER*4 L_AODR1 L_LENADDR/O/
END STRUCTURE
RECORD /GETJPI_ITEM/GETJPIARGC51
GETJPIARGC41 .w_LEN = a
GETJPIARG<al .w_CODE
JPILCPUTIM
GETJPIARGC41 ,L_ADDR = %LOCCLCL_VALUESC4)1
CALL SYS$GET JPI C,, 1GET JPIARG,,, I

As this example illustrates, the primary advantage to using records is that they enable you
to group related data together in one conceptual whole.

14-4

Using Structures and Records

Chapter 15

Using Indexed Files
Traditionally, sequential and direct access have been the only file access modes available
to FORTRAN programs. To overcome some of the limitations of these access modes, VAX
FORTRAN supports a third access mode, called keyed access (see Section 11.2.3.4). Keyed
access allows you to retrieve records, at random or in sequence, based on key fields that are
established when you create a file with indexed organization.
You can access files with indexed organization using either sequential or keyed access, or a
combination of both.
1. Keyed access retrieves records randomly based on the particular key fields and key
values that you specify.
2. Sequential access retrieves records in an ascending sequence based on the values
within the particular key field that you specify.
The combination of k~yed and sequential access is commonly referred to as the Indexed
Sequential Access Method (ISAM). Once you have read a record by means of an indexed
read request, you can then use a sequential read request to retrieve records with ascending
key field values, beginning with the key field value in the record retrieved by the initial
read request.
Indexed organization is especially suitable for maintaining complex files in which you want
to select records based on one of several criteria. For example, a mail-order firm could use
an indexed organization file to store its customer list. Key fields could be a unique customer order number, the customer's zip code, and the item ordered. Reading sequentially
based on the zip code key would enable you to produce a mailing list sorted by zip code. A
similar operation based on customer order number or item number key would enable you to
list the records in customer order number or item number sequence.
The remainder of this chapter provides information of the following major topics:
• Creating an indexed file (Section 15.1)
• Writing records to an indexed file (Section 15.3)
• Reading records from an indexed file (Section 15.5)
• Deleting records from an indexed file (Section 15.4)
• Updating records in an indexed file (Section 15.4)

Information is also provided about the effects of read and write operations on positioning
your program to records within an indexed file (Section 15.6) and about how to build logic
into your programs to handle exception conditions that commonly occur (Section 15.7).

15.1 Creating an Indexed File
You can create a file with an indexed organization by using either the FORTRAN OPEN
statement or the RMS EDIT/FDL utility.
• Use the OPEN statement to specify the file optio_ns supported by FORTRAN.
• Use the EDIT/FDL utility to select features not directly supported by FORTRAN.
Any indexed file created with EDIT/FDL can be accessed by FORTRAN 1/0 statements.
When you create an indexed file, you define certain fields within each record as key fields.
One of these key fields, called the primary key, is identified as key number zero and must
be present in every record. Additional keys, called alternate keys, can also be defined; they
are numbered from 1 through a maximum of 254. An indexed file can have as many as 255
key fields defined. In practice, however, few applications require more than 3 or 4 key
fields.
The data types used for key fields must be either INTEGER*2, INTEGER*4, or
CHARACTER.
In designing an indexed file, you must decide the byte positions of the key fields. For
example, in creating an indexed file for use by a mail-order firm, you might define a file
record to consist of the following fields:
STRUCTURE /FILE-REC_STRUCT/
INTEGER*a ORDER-NUMBER
CHARACTER*ZO NAME
CHARACTER*ZO ADDRESS
CHARACTER*18 CITY
CHARACTER*Z STATE
CHARACTER*8 ZIP-CODE
INTEGER*2 ITEM_NUMBER
END STRUCTURE

Positions
Positions
Positions
Positions
Positions
Positions
Positions

1: a ,

f~ e >'

5:Za
Z5:aa
a5:63
6a:65
66 :7a,
75:761

f~ e >'

f: e >'

1
2

RECORD /FILE_REC_STRUCT/ FILE_REC

Given this record definition, you could use the following OPEN statement to create an
indexed file:
OPEN CUNIT=101 FILE='CUSTDMERS.DAT', STATUS='NEW',
DRGANIZATIDN='INDEXtD', ACCESS='KEYED',
2
RECDRDTYPE='VARIABLE', FDRM='UNFDRMATTED',
3
RECL=18t
a
KEY=Cl:a:INTEGERt 66:7a:CHARACTERt 75:7G:INTEGER>'
5
IDSTAT=IOSt ERR=8888)

15-2

Using Indexed Files

This OPEN statement establishes the attributes of the file, including the definition of a
primary key and two alternate keys. Note that the definitions of the integer keys do not
explicitly state INTEGER*4 and INTEGER*2. The data type sizes are determined by the
number of character positions allotted to the key fields, which in this case are 4 and 2
character positions, respectively.
If you specify the KEY keyword when opening an existing file, the key specification that
you give must match that of the file.

FORTRAN uses RMS default key attributes when creating an indexed file. These defaults
are as follows:
• The values in primary key fields cannot be changed when a record is rewritten and
cannot have duplicates.
• The values in alternate key fields can be changed and can have duplicates.
You can use the EDIT/FDL utility or a USEROPEN routine to override these defaults and
to specify other values not supported by VAX FORTRAN, such as null key field values,
null key names, and key data types other than integer and character.
Refer to VAX FORTRAN User's Guide for information on the use of the USEROPEN
-keyword in OPEN statements. The VAX Record Management Services Reference Manual
has more information on indexed file options.
Use of the EDIT/FDL utility is explained in detail in the VAX/VMS File Definition Language Facility Reference Manual.

15.2 Writing Indexed Files
You can write records to an indexed file with either formatted or unformatted indexed
WRITE statements. Each write operation inserts a new record into the file and updates the
key index(es) so that the new record can be retrieved in a sequential order based on the
values in the respective key fields.
For example, you could add a new record to the file for the mail-order firm (see Section
15.1) with the following statement:
WRITE (LJNIT=l01IOSTAT=IDS1ERR=8888) FILE-REC

The following two sections describe considerations that relate to write operations: (1) the
effects of writing records with duplicate values in key fields and (2) the method by which
you can prevent an alternate key field in a record from being indexed during a write
operation.

15.2.1 Duplicate Values in Key Fields
It is possible to write two or more records with the same value in a single key field. The
attributes specified for the file when it was created determine whether this duplication is
allowed. By default, FORTRAN creates files that allow duplicate alternate key field values
Using Indexed Files

15-3

and prohibit duplicate primary key field values (see Section 15.1). If duplicate key field
values are present in a file, the records with equal values are retrieved on a first-in/first-out
basis.
For example, assume that five records are written to an indexed file in this order (for
clarity, only key fields are shown):

ORDER_NUMBER

ZIP_CODE

ITEM__NUMBER

1023
942
903
1348
1263

70856
02163
14853
44901
33032

375
2736
375
1047
690

If the file is later opened and read sequentially by primary key (ORDER._NUMBER), the
order in which the records are retrieved is not affected by the duplicated value (375) in the
ITEM__NUMBER key field. In this case, the records would be retrieved in the following
order:

ORDER_NUMBER

ZIP_CODE

ITEM__NUMBER

903
942
1023
1263
1348

14853
02163
70856
33032
44901

375
2736
375
690
1047

However, if the read operation is based on the second alternate key (ITEM__NUMBER),
the order in which the records are retrieved is affected by the duplicate key field value. In
this case, the records would be retrieved in the following order:

ORDER_NUMBER

ZIP_CODE

ITEM__NUMBER

1023
903
1263
1348
942

70856
14853
33032
44901
02163

375
375
690
1047
2736

Notice that the records containing the same key field value (375) are retrieved in the order
in which they were written to the file.

15.2.2 Preventing the Indexing of Alternate Key Fields
When writing to an indexed file that contains variable-length records, you can prevent
entries from being added to the key index(es) for any alternate key field(s). This is done by
omitting the names of the alternate key field(s) from the WRITE statement. The omitted
alternate key field(s) must be at the end of the record; another key field cannot be specified
after the omitted key field.

15-4

Using Ind~xed Files

For example, assume that the last record (ORDER_NUMBER 1263) in the mail-order
example is written with the following statement:
WRITE CUNIT=101IOSTAT=IOS1ERR=9999) FILE-REC.ORDER_NUMBER1
FILE_REC.NAME1 FILE_REC.ADDRESS1 FILE_REC.CITY1
FILE_REC.STATE1 FILE_REC.ZIP_CODE

Because the field name FILE_REC.ITEM_NUMBER is omitted from the WRITE statement, an entry for that key field is not created in the index. As a result, an attempt to read
the file using the alternate key ITEM_NUMBER would not retrieve the last record and
would produce the following listing:

ORDER_NUMBER

ZIP_CODE

ITEM_NUMBER

1023
903
1348
942

70856
14853
44901
02163

375
375
1047
2736

You can omit only trailing alternate keys from a record; the primary key must always be
present.

15.3 Reading Indexed Files
You can read records in an indexed file with either sequential or indexed READ statements
(formatted or unformatted) under the keyed mode of access. By specifying
ACCESS= 'KEYED' in the OPEN statement, you enable both sequential and keyed access to the indexed file.
Indexed READ statements position the file pointers (see Section 15.6) at a particular
record, determined by the key field value, the key-of-reference, and the match criterion.
Once you retrieve a particular record by an indexed READ statement, you can then use
sequential access READ statements to retrieve records with increasing key field values.
The form of the external record's key field must match the form of the value you specify in
the KEY keyword. Thus, if the key field contains character data, you should specify the
KEY keyword value as a CHARACTER data type. If the key field contains binary data,
then the KEY keyword value should be of INTEGER data type.
Note that if you write a record to an indexed file with formatted 1/0, the data type is
converted from its internal representation to an external representation. As a result, the
key value must be specified in the external form when you read the data back with an
indexed read. Otherwise, a match will occur when you do not expect it.

Using Indexed Files

15-5

The following FORTRAN program segment prints the order number and zip code of each
record where the first five characters of the zip code are greater than or equal to '10000'
but less than '50000 ':
C
C

Read first record with ZIP_CODE Key sreater than or
eciual to '10000',
READ <UNIT=10tKEYGE='10000' tKEYID=l tlOSTAT=IOStERR=9999l
1
FILE_REC

C
C

While the zip code Previously read is within ranSet Print
the order nuMber and zip cadet then read the next record.
DD WHILE <FILE_REC.ZIP_CODE +LT+ '50000')
PRINT * t 'Order nur11ber' t FILE_REC.ORDER_NLJMBER t 'has ziP code' t
FILE_REC+ZIP_CODE
READ <UNIT=10tIOSTAT=IOStEND=200tERR=9999)
FILE_REC

C
C

200

END= branch will be taken if there are no More records
in the file.
END DO
CONTINUE

The error branch on the keyed READ in this example is taken if no record is found with a
zip code greater than or equal to '10000 '; an attempt to access a nonexistent record is an
error. If the sequential READ has accessed all records in the file, however, an end-of-file
status occurs, just as with other file organizations.
If you wish to detect a failure of the keyed READ, you can examine the I/0 status variable,
IOS, for the appropriate error number (see Table 18-1 for a list of the returned error codes).

15.4 Updating Records
The REWRITE statement updates existing records in an indexed file. You cannot replace
an existing record simply by writing it again; a WRITE statement would attempt to add a
new record.
An update operation is accomplished in two steps. First, you must read the record in order
to make it the current record. Next, you execute the REWRITE statement. For example, to
update the record containing ORDER_NUMBER 903 (see prior examples) so that the
NAME field becomes 'Theodore Zinck', you might use the following FORTRAN code
segment:
READ (LJNIT=10tKEY=903tKEYID=OtIOSTAT=IOStERR=9999) FILE_REC
FILE-REC.NAME = 'Theodore Zinck'
REWRITE (LJNIT=10tIOSTAT=IOStERR=9999l FILE_REC

When you rewrite a record, key fields may change. The attributes specified for the file when
it was created determine whether this type of change is permitted.

15-6

Using Indexed Files

15.5 Deleting Records
To delete records from an indexed file, you use the DELETE statement. The DELETE and
REWRITE statements are similar; a record must first be locked by a READ statement
before it can be operated on.
The following FORTRAN code segment deletes the second record in the file with ITEM_
NUMBER 375 (refer to previous examples):
READ (LJNIT=101KEY=3751KEYID=21IOSTAT=IDS1ERR=9999)
READ (LJNIT=101IOSTAT=IOS1ERR=9999) FILE_REC
IF (FILE_REC.ITEM_NUMBER ,EQ, 375) THEN
DELETE (LJNIT=101 IDSTAT=IDS1 ERR=9999)
ELSE
PRINT*' 'There is no second record.'
END IF

Deletion removes a record from all defined indexes in the file.

15.6 Current Record and Next Record Pointers
The RMS file system maintains two pointers into an open indexed file: the "next record"
pointer and the "current record" pointer.
0

The next record pointer indicates the record to be retrieved by a sequential read. When
you open an indexed file, the next record pointer indicates the record with the lowest
primary key field value. Subsequent sequential read operations cause the next record
pointer to be the one with the next higher value in the same key field. In case of
duplicate key field values, records are retrieved in the order in which they were written.

• The current record pointer indicates the record most recently retrieved by a READ
operation; it is the record that is locked from access by other programs sharing the file.
The current record is the one operated on by the REWRITE statement (see Section
11.6) and the DELETE statement (see Section 13.7). The current record is undefined
until a read operation is performed on the file. Any file operation other than a read
causes the current record pointer to become undefined. Also, an error results if a
rewrite or delete operation is performed when the current record pointer is undefined.

15.7 Exception Conditions
You can expect to encounter certain exception conditions when using indexed files. The two
most common of these conditions involve valid attempts to read locked records and invalid
attempts to create duplicate keys. Provisions for handling both of these situations should
be included in a well-written program.

Using Indexed Files

15-7

When an indexed file is shared by several users, any read operation may result in a
"specified record locked" error. One way to recover from this error condition is to ask if the
user would like to reattempt the read. If the user's response is positive, then the program
can go back to the READ statement, For example:
INCLUDE
100

($FOR I OSDEF)

READ <UNIT=lOtlOSTAT=IOS) DATA
IF <IDS ,EQ, FOR$IOS_SPERECLOC) THEN
TYPE*• 'That record is locked. Press RETURN'
TYPE*• 'to trY aiaint or CONTROL_Z to discontinue'
READ <UNIT=*tFMT=*tEND=800)
GO TO 100
ELSE IF (IDS .NE. 0) THEN
CALL ERROR (I OS)
END IF

You should avoid simply looping back to the READ statement without first providing some
type of delay (caused by a request to try again, or to discontinue, as in this example). If
your program reads a record but does not intend to modify the record, you should place an
UNLOCK statement immediately after the READ statement. This technique reduces the
time that a record is locked and permits other programs to access the record.
The second exception condition, creation of duplicate keys, occurs when your program tries
to create a record with a key field value that is already in use. When duplicate key field
values are not desirable, you might have your program prompt for a new key field value
whenever an attempt is made to create a duplicate. For example:
INCLUDE
200

($FOR I OSDEF)

WRITE IUNIT=lOtIOSTAT=IOS) KEY_VALt DATA
IF

IIOS ,EQ, FOR$IOS_INCKEYCHG) THEN
TYPE*• 'This KeY field value already exists. Please enter'
TYPE*• 'a different key field ualuet or Press CONTROL_Z'
TYPE*• 'to discontinue this operation.'
READ <UNIT=*tFMT=300tEND=888) KEY_VAL
GD TD 200
ELSE IF <IDS .NE, 0) THEN
CALL ERROR !IDS)
END IF

15-8

Using Indexed Files

Chapter 16

Using Character Data
VAX FORTRAN's character data type allows you to easily manipulate alphanumeric data.
You can use character data in the form of character variables, arrays, constants, and
expressions. A character operator ( //) is available to form character strings by concatenating character elements.

16.1 Character Substrings
You can select certain segments (substrings) from a character variable or character array
element by specifying the name of the variable or array element, followed by delimiter
values indicating the leftmost and/or rightmost characters in the substring. For example, if
the character variable NAME contained the string
ROBERT 6WILLIAM680Bi0.JACKSON

and you wished to extract the substring BOB, you would specify the following:
NAME< 16: 18)

If you omit the first value, you are indicating that the first character of the substring is the

first character in the variable. For example, if you specify
NAME<:18)

the resulting substring is
ROBERT6WILLIAM6BOB

If you omit the second value, you are specifying the rightmost character to be the last

character in the variable. For example:
NAMEC 16:)

encompasses
BOB6JACKSON

16-1

16.2 Building Character Strings
It is sometimes useful to create strings from two or more separate strings. This is done by
means of the concatenation operator, the double slash ( //).For example, you might wish to
create a variable called NAME, consisting of the values of the following variables:
FIRSTNAME
MIDDLENAME
NICKNAME
LASTNAME

To do so, define each as a character variable of a specified length. For example:
CHARACTER*a2 NAME
CHARACTER*12 FIRSTNAMEtMIDDLENAMEtLASTNAME
CHARACTER*B NICKNAME

Concatenation is accomplished as follows:
NAME = FIRSTNAME//MIDDLENAME//NICKNAME//LASTNAME
Thus, if the variables contained the values
FIRSTNAME = 'ROBERT'
MIDDLENAME = wI LLI AM
NICKNAME = 'BOB
LASTNAME = 'JACKSON'
I

which are stored individually as
ROBERTM!::,.M/::,.
WILLIAMMM/::,.
BOB/::,.M
JACKSONMM!::,.

then, when concatenated and stored in NAME, they become the string:
ROBERTMM!::,./::,.WILLIAMM1::,.MBOB1::,.MJACKSONM1::,.M

Applying the substring extraction facility described in Section 16.1, you can get the stored
nickname by specifying
NAME<25:30>

which picks up the 6-character substring BOB~ (including trailing blanks) in variable
NAME.

16.3 Character Constants
Character constants are strings of characters enclosed in apostrophes. You can assign a
character value to a character variable in much the same way you would assign a numeric
value to a real or integer variable. For example:
){YZ = 'ABC

16-2

Using Character Data

As a result of this statement, the characters ABC are stored in location XYZ. Note that if
XYZ's length is less than three bytes, the character string is truncated on the right. Thus, if
you specify
CHARACTER*2 NYZ
HYZ = 'ABC'

the result is AB. If, on the other hand, the variable is longer than the constant, it is padded
on the right with blanks. For example:
CHARACTER*G )-(YZ
)-(YZ = 'ABC

results in having
ABC~C.

stored in XYZ. The previous contents of XYZ are overwritten. Thus, if the previous contents of XYZ were CBSNBC, the result would still be ABC.6..6..6..
You can give character constants symbolic names by using the PARAMETER statement.
For example:
CHARACTER*(*) TITLE
PARAMETER (TITLE = 'THE METAMORPHOSIS')

The PARAMETER statement in the preceding example assigns the symbolic name TITLE
to the character constant THE METAMORPHOSIS.
You can use the symbolic name TITLE anywhere a character constant is allowed.
To include an apostrophe as part of the constant, specify two consecutive apostrophes. For
example:
CHARACTER*(*) TITLE
PARAMETER (TITLE = 'FINNEGAN' 'S WAKE')

results in the character constant FINNEGAN'S WAKE.
The value assigned to a character parameter can be any compile-time constant character
expression. Note in particular that the CHAR intrinsic function (see Section 16.7.1) with a
constant argument is a compile-time constant expression; therefore, you can assign nonprinting characters to parameter constants. For example:
CHARACTER*(*) CRLF
PARAMETER (CRLF=CHAR(13)//CHAR(10))

16.4 Declaring Character Data
To declare variables or arrays as character type, use the CHARACTER type declaration
statement, as shown in the following example:
CHARACTER* 10 TEAM ( 12) , PLAYER

Using Character Data

16-3

This statement defines a 12-element character array (TEAM), each element of which is 10
bytes long, and a character variable (PLAYER), which is also 10 bytes long.
You can specify different lengths for variables in a CHARACTER statement by including a
length value for specific variables. For example:
CHARACTER*G NAME1 AGE*21 DEPT

In this example, NAME and DEPT are defined as 6-byte variables, while AGE is defined
as a 2-byte variable.

16.5 Initializing Character Variables
Use the DATA statement to preset the value of a character variable. For example:
CHARACTER*lO NAME1 TEAMCS>
DATA NAME/' '/, TEAM/'SMITH' 1'JONES' 1
1
DOE
BROWN
GREEN I
I

Note that NAME contains 10 blanks, while each array element in TEAM contains the
corresponding character value, right-padded with blanks.
To initialize an array so that each of its elements contains the same value, use a DATA
statement of the following type:
CHARACTER*S TEAMC10)
DATA TEAM/lO*'WHITE'/

The result is a 10-element array in which each element contains WHITE.
You can also initialize character variables within the character declaration, as shown in the
following example:
CHARACTER* 10 METALS ( 3) I LEAD
I

I RDN

GOLD

16.6 Passed-Length Character Arguments
In writing subprograms that manipulate character data, you can get the subprogram to
accept actual character arguments of any length by specifying the length of the dummy
argument as passed-length. To indicate a passed-length dummy argument, use an asterisk
( * ) as follows:
SUBROUTINE REVERSEIS)
CHARACTER*(*) S

16-4

Using Character Data

The passed-length notation indicates that the length of the actual argument is used when
processing the dummy argument string. This length can change from one invocation of the
subprogram to the next. For example:
CHARACTER A*Z01 B*53

CALL REVERSE(A)
CALL REl,IERSE ( B)

In the first call to REVERSE, the length of S is 20; in the second call, its length is 53.
You can use the CHARACTER*(*) notation to define the length of parameter character
constants. The actual length is then the length of the character constant that is assigned to
the parameter name in a PARAMETER statement.
The FORTRAN function LEN can be used to determine the actual length of the string (see
Section 16.7.4).

16.7 Character Library Functions
VAX FORTRAN supports the following character functions:
•CHAR
•ICHAR
•INDEX
•LEN
• LGE, LGT, LLE, LLT
The following sections describe these functions.

16.7.1 CHAR Function
The CHAR function returns a 1-byte character value equivalent to the integer ASCII code
value passed as its argument. It has the form:
CHAR(i)

where:
is an integer expression equivalent to an ASCII code.

Using Character Data

16-5

16.7.2 ICHAR Function
The ICHAR function returns an integer ASCII code equivalent to the character expression
passed as its argument. It has the form:
ICHAR(c)

where:
c

is a character expression. If c is longer than one byte, the ASCII code equivalent to the
first byte is returned and the remaining bytes are ignored.

16.7.3 INDEX Function
The INDEX function is used to determine the starting position of a substring. It has the
form:
INDEX(c1 ,c2)

where:
c1

is a character expression that specifies the string to be searched for a match with the
value of c2.
c2

is a character expression representing the substring for which a match is desired.
If INDEX finds an instance of the specified substring (c2), it returns an integer value
corresponding to the starting location in the string (cl). For example, if the substring

sought is CAT, and the string that is searched contains DOGCATFISHCAT, the return
value of INDEX is 4.
If INDEX cannot find the specified substring, it returns the value 0.
If there are multiple occurrences of the substring, INDEX locates the first (leftmost) one.

Use of the INDEX function is illustrated in Figures 16-1 and 16-2.

16.7.4 LEN Function
The LEN function returns an integer value that indicates the length of a character expression. It has the form:
LEN(c)

where:
c

is a character expression.

16-6

Using Character Data

16. 7.5 LG~, LGT, LLE, LLT Functions
The lexical comparison functions LGE, LGT, LLE, and LLT are defined by the
FORTRAN-77 standard to make comparisons between two character expressions using the
ASCII collating sequence. The result is the logical value .TRUE. if the lexical relation is
true, and .FALSE. if the lexical relation is not true. The functions have the forms:
LGE(c1 ,c2)
LGT(c1 ,c2)
LLE(c1 ,c2)
LL T(c1 ,c2)

where:
c1,c2

are character expressions.
You may wish to include these functions in FORTRAN programs that can be used on
computers that do not use the ASCII character set. In VAX FORTRAN, the lexical comparison functions are equivalent to the .GE., .GT., .LE., .LT. relational operators. For
example:
IF (LLE(strinsl, strins2>> GO TD 100

is equivalent to
IF (strinsl .LE. strinS2) GO TO 100

16.8 Character Data Examples
An example of character data usage is shown in Figures 16-1 and 16-2. The example in
Figure 16-1 is a program that manipulates the letters of the alphabet. The results are
shown in Figure 16-2.

16.9 Character 1/0
The character data type simplifies the transmission of alphanumeric data. You can read
and write character strings of any length from 1 to 65535 characters. For example:
CHARACTER*24 TITLE

100

READ ( 12 t100 > TITLE
FORMAT (A)

Using Character Data

16-7

These statements cause 24 characters read from logical unit 12 to be stored in the 24-byte
character variable TITLE. Compare this with the code necessary if you used Hollerith data
stored in numeric variables or arrays:
INTEGER*a TITLECG>

100

READ <121100) TITLE
FORMAT CGAa>

Note that you must divide the data into lengths suitable for real or (in this case) integer
data and specify I/0 and FORMAT statements to match. In this example, a one-dimensional array comprising six 4-byte elements is filled with 24 characters from logical unit 12.
CHARACTER Ct ALPHABET*2G
DATA ALPHABET/'ABCDEFGHIJKLMNOPORSTUVWXYZ'/
80

WRITE CG 180)
FORMAT C' CHARACTER EXAMPLE PROGRAM OUTPUT'/)
DD I=l 126
WRITE CG1*) ALPHABET
ALPHABET= ALPHABETC2:)//ALPHABETC1:1>
END DO
CALL REVERSECALPHABET>
WRITE CG1*> ALPHABET
CALL REVERSECALPHABETC1:13))
WRITE CG1*) ALPHABET
CALL FIND_SUBSTRINGSC 'UVW', ALPHABET>
CALL FIND_SUBSTRINGSC 'A', 'DAJHDHAJDAHDJAaE CEUEBCUEIAWSAWQLO'>
WRITE ( G '*)
END

16-8

END OF CHARACTER E}<AMPLE PROGRAM

Using Character Data

SUBROUTINE REVERSECS)
CHARACTER T1 S*C*)
J = LENCS)
DD I=l ,J/2
T =SCI:!)
SCI:!) = SCJ:J)
SCJ:J) = T
j

= j

END DD
END
SUBROUTINE FIND_SUBSTRINGSCSUB1S)
CHARACTER*(*) SUB1 S
CHARACTER*132 MARKS
I

= 1

MARKS
10

J = INDEXCSCI:) 1SUB)
IF CJ .NE, 0) THEN
I = I + CJ-1)
MARKSCI:I)
I

= I+ 1

IF (I .LE. LEN CS)) GD TD 10
END IF
91

WRITE (6191) s, MARKS
FORMAT CZC/lX1A))
END

Figure 16-1: Character Data Program.Example

Using Character Data

16-9

CHARACTER E>{AMPLE PROGRAM OUTPUT
ABCDEFGHIJKLMNOPQRSTUVWXYZ
BCDEFG~IJKLMNOPQRSTUVWXYZA

CDEFGHIJKLMNOPQRSTUVWXYZAB
DEFGHIJKLMNOPQRSTUVWXYZABC
EFGHIJKLMNOPQRSTUVWXYZABCD
FGHIJKLMNOPQRSTUVWXYZABCDE
GHIJKLMNOPQRSTUVWXYZABCDEF
HIJKLMNOPQRSTUVWXYZABCDEFG
IJKLMNOPQRSTUVWXYZABCDEFGH
JKLMNOPQRSTUVWXYZABCDEFGHI
KLMNOPQRSTUVWXYZABCDEFGHIJ
LMNOPQRSTUVWXYZABCDEFGHIJK
MNOPQRSTUVWXYZABCDEFGHIJKL
NOPQRSTUVWXYZABCDEFGHIJKLM
OPQRSTUVWXYZABCDEFGHIJKLMN
PQRSTUVWXYZABCDEFGHIJKLMNO
QRSTUVWXYZABCDEFGHIJKLMNOP
RSTUVWXYZABCDEFGHIJKLMNOPQ
STUVWXYZABCDEFGHIJKLMNOPQR
TUVWXYZABCDEFGHIJKLMNOPQRS
UVWXYZABCDEFGHIJKLMNOPQRST
VWXYZABCDEFGHIJKLMNOPQRSTU
WXYZABCDEFGHIJKLMNOPQRSTUV
XYZABCDEFGHIJKLMNOPQRSTUVW
YZABCDEFGHIJKLMNOPQRSTUVWX
ZABCDEFGHIJKLMNOPQRSTUVWXY
ZYXWVUTSRQPONMLKJIHGFEDCBA
NOPQRSTUVWXYZMLKJIHGFEDCBA
NOPQRSTUVWXYZMLKJIHGFEDCBA
:1:1:

DAJHDHAJDAHDJA4E CEUEBCUEIAWSAWQLQ
END OF CHARACTER D(AMPLE PROGRAM
ZK-793-82

Figure 16-2: Output Generated by Example Program

16-10

Using Character Data

Chapter 17

Debugging VAX FORTRAN Programs
This chapter describes how to use VAX DEBUG (or, simply, the debugger).
The VAX/VMS Symbolic Debugger Reference Manual describes the debugger in detail.
Refer to that manual or access on-line HELP information from a debugging session for
detailed descriptions of the syntax of commands discussed in this chapter.
Topics covered by the individual sections are as follows:
• Section 17 .1 provides a general description of the de bugger.
• Section 17 .2 explains how to compile and link a program to be analyzed using the
debugger.
• Section 17.3 explains how to invoke and terminate the debugger.
• Section 17.4 describes debugger help, command entry options, and debugger command procedures and their use. It also provides a summary of debugger commands
and their syntax.
• Section 17 .5 describes how to start, stop, and control a program while you are running
it under the control of the debugger.
• Section 17 .6 describes what. you must know about how the debugger treats the symbolic names in your programs and explains how to designate program locations.
• Section 17. 7 explains how to examine variables and program locations and how to
modify their contents while you are debugging a program.
• Section 17 .8 explains how to control debugger screen displays.
• Section 17 .9 presents simple examples of debugging FORTRAN programs.

17-1

17 .1 Debugging Overview
Debugging, the process of locating and correcting errors, is one of the most difficult stages
in program development. You need to debug when one or more of the following situations
occur:
• Compile-time errors are signaled.
• Run-time errors are signaled.
• You determine, based on receiving incorrect output during a program's execution, that
a logic error exists.
The VAX FORTRAN compiler and run-time system display error and warning messages
when errors occur. You can use this information to determine where the error exists in your
program and then to correct it.
You must detect errors that produce incorrect output yourself. To help you find such errors,
VAXNMS provides a special program: VAX DEBUG. It enables you to control the execution of your program so that you can monitor specific locations, change the contents of
locations, check the sequence of program control, and otherwise locate and correct errors as
they occur. After you track down the mistakes, you can edit your source program and
repeat the compile-link-execute sequence with the corrected version.
The VAX Symbolic Debugger has many helpful features, among which are the following:
• It is interactive. You control your program and interact with the debugger from your
terminal.
• It understands FORTRAN variables and their data types. Thus, when you want to
look at or change the value of a variable, the debugger will display the value in a
manner appropriate to the data type or convert your ASCII text input to the data type
of the variable.
• It understands many other programming languages as well, such as PAS CAL and
PL/I. Thus, if your program consists of routines written in different languages, you can
change from one language to another during the course of a single debugging session.

17.2 Preparing a Program for Debugging-Compiling and
Linking
To execute a VAX FORTRAN program with the debugger, you should first compile the
program with the /DEBUG and /NOOPTIMIZE qualifiers on the FORTRAN command
and then link the program with the /DEBUG qualifier on the LINK command.
You should specify the /NOOPTIMIZE qualifier on the FORTRAN command because
several of the optimizations performed by the compiler can cause the program and the
debugger commands to behave in unexpected ways. Note: The VAX FORTRAN compiler,

17-2

Debugging VAX FORTRAN Programs

by default, optimizes the object code in order to make it run faster during execution. See
Chapter 1 in VAX FORTRAN User's Guide for detailed descriptions of the various optimizations performed by the compiler and how these affect debugging.
For a description of the effects of specifying the /DEBUG qualifier on FORTRAN, LINK,
and RUN commands, see Sections 3.2.3.4 and 4.3.
When you no longer need to use the debugger on your program, recompile the program with
the default qualifiers of /NODEBUG and /OPTIMIZE.

17 .3 Invoking and Terminating the Debugger
You can invoke, interrupt, and terminate the debugger in a variety of ways. This flexibility
can be an important tool during the debugging process. The various options are described
in the subsections that follow.

17 .3.1 Invoking the Debugger with the RUN Command
If your program has been compiled and linked with the /DEBUG qualifier, the RUN
command passes initial control to the debugger rather than commencing program execution.

The following example shows how the debugger identifies itself:
$

RUN CIRCLE
VAX DEBUG Version a.1-2

%DEBUG-I-INITIAL1 lansuase is FORTRAN, Module set to 'CIRCLE'
DBG>

The module name displayed in the debugger's message is the name of the main program
unit, which is associated with the executable image's entry point. In the example, the
debugger message indicates that the name of the main program unit is CIRCLE.
The DBG> prompt indicates that the debugger is ready to process your commands. You
respond to the prompt with any of the commands recognized by the debugger.
If your program was not linked with the /DEBUG qualifier, you can still have initial control
passed to the debugger by specifying /DEBUG on the RUN command; however, your
debugging options will be limited (see Section 4.3).

To avoid automatically invoking the debugger when you are running a program compiled
and linked with the /DEBUG qualifier, specify the /NODEBUG qualifier on your RUN
command. As described in the next section, even though you specify /NODEBUG, you can
still access the debugger during the execution of your program.

Debugging VAX FORTRAN Programs

17-3

17.3.2 Invoking the Debugger During Program Execution
You can interrupt an executing program at any time by entering <CTRL/Y>. You can then
invoke the debugger by entering the DEBUG command-even if you specified /NODEBUG
on the RUN command. This method of interrupting an executing program can be useful,
for example, if you think that the program is looping or if you see erroneous output.

17.3.3 Suspending the Debugger to Issue DCL Commands
At any point in a debugging session, you can use the debugger's SPAWN command to
create a subprocess that allows you to use DCL commands without terminating the debugging session.
If you specify the SP AWN command with a DCL command as a parameter, the spawned

subprocess executes the command and immediately returns control to the debugger. The
following example executes MAIL in the middle of a debugging session:
DBG> SPAWN MAIL
MAIL> READ

MAIL> E)OT
DBG>

If you specify the SPAWN command without a DCL command as a parameter, you can

enter any number of DCL commands before returning to your debugging session. To resume your debugging session, specify the LOGOUT command as shown in the following
example:
DBG> SPAWN
MAIL

MA IL> El-( IT
LOGOUT
Process USER_l lossed out at 28-JUL-1884 08:58:12:45
%DEBUG-I-RETURNED1 control returned to Process USER
DBG>

The debugger also has an ATTACH command. The debugger's ATTACH command works
the same way as the ATTACH command in DCL.

17-4

Debugging VAX FORTRAN Programs

17.3.4 Interrupting the Debugger
Entering <CTRL/Y> terminates any debugger command that is executing and puts you at
DCL command level. You can tµen return to the debugger with the DCL commands
CONTINUE or DEBUG. The CONTINUE command continues the debugging session as
though no interruption had occurred. The DEBUG command returns control to debugger
command level, allowing you to issue new debugger commands (useful for aborting an
infinite loop or a long operation associated with a debugger command).

17.3.5 Terminating a Debugger Session
The following message indicates that your program has executed normally:
%DEBUG-I-EXITSTATUS1is '%SYSTEM-S-NORMAL1norMal successful COMPietion'
DBG>

To terminate the debugging session, type <CTRL/Z> or EXIT:
DBG> rnIT
$

The dollar sign prompt indicates that you are at DCL command level.

17.4 The Debugger Environment
The debugger provides you with a subsystem for entering commands-much like MAIL
and EDT, for example. Many features that are available from DCL are also available in
this subsystem. This includes keypad definitions, HELP capability, command files, and so
forth. In some cases, DEBUG's syntax is different from DCL's syntax. This section explains
the DEBUG sub-environment.
The following topics are addressed in this section:
• Debugger HELP information
• Options relating to how you enter commands and command procedures
• Debugger commands (presented .in an alphabetical list that shows all of the optional
qualifiers and parameters)

17.4.1 Using Debugger HELP
To display the list of debugger commands on which information is available, type HELP.
To display information about a particular command, type HELP plus the command name.
For example, to display information about the use of the qualifier /ALL with the SET
MODULE command, specify:
DBG> HELP SET MODULE/ALL

Debugging VAX FORTRAN Programs

17-5

17 .4.2 Entering Commands
You can enter debugging commands in two ways: by typing out the commands on your
terminals' normal keyboard or by using keypad keys.

17 .4.2.1 Normal Keyboard Entry
To enter commands on the main keyboard, you type in the command and then press
<RET>. You can enter more than one command on a line by separating the commands
with semicolons ( ; ) . In addition, you can continue a command on a new line by ending the
line with a hyphen ( - ), and the debugger will then prompt for the remainder of the
command line with an underscore ( _).
Debugger commands, like DCL commands, can be abbreviated to unique characters. For
example, the command CANCEL EXCEPTION BREAK could be entered as CAN EX
BR. In addition, you can abbreviate a debugger command by using the DEFINE command
with its /COMMAND qualifier to equate the command to a shorter symbolic name. The
following example creates the symbol CEB to abbreviate the command CANCEL
EXCEPTION BREAK:
DBG> DEFINE/COMMAND CEB = 'CANCEL EXCEPTION BREAK'

To make your symbol definitions available at each debugging session, include them in a
debug initialization command file that is executed at the start of all debugging sessions
(see Section 17.4.5).

17 .4.2.2 Keypad Entry
You can also enter debugging commands by means of the keypad. Figure 17-1 shows the
default keypad definitions. You can redefine each of these keys with the DEFINE/KEY
command (see Section 17.4.3). The DCL and MAIL keypad entry rules work in a similar
way.
Each key can represent up to three debug commands. The first command is selected by
pressing the key by itself; the second by pressing the key in combination with the PFl
(GOLD) key; the third by pressing the key in combination with the PF4 (BLUE) key.
Each key also has a symbolic name associated with it. You can use this symbolic name to
define a key or key combination to represent debug commands of your own choosing .. In
Figure 17-1, the symbolic names are shown in at the top of the key.
To enter a debug command in keypad mode, you first press the desired key or key combination. Some commands, such as the GO and SET MODE commands, require no additional
parameters. When these keys are pressed, the command is executed immediately. Other
commands require you to enter a parameter. When those keys are pressed, you type the
parameter on the main keypad. The command is executed when you press either the
<RET> or <ENTER> key.

17-6

Debugging VAX FORTRAN Programs

PF1

PF3

PF2

PF4

Default

GOLD

HELP

SET MODE SCREEN

BLUE

GOLD

HELP

SET MODE NOSCR

BLUE

GOLD

HELP

DISP/GENERATE

BLUE

Default
GOLD

BLUE

KPB
SCROLL/UP

KP9

MINUS

SCROLL/TOP
SCROLL/UP •

DISP SRC, OUT

KPS

KP6

Default

SCROLL/LEFT

EX/SOU .0\ %PC

SCROLL/RIGHT

GOLD

SCROLL/LEFT:132

SHOW CALLS

BLUE

SCROLL/LEFT •

SHOW CALLS 3

SCROLL/RIGHT •

KP1

KP2

KP3

SCROLL/DOWN

SEL/SCROLL next

KP4

Default

DISP next AT FS

DISPLAY next

EXAMINE

GOLD

SCROLL/BOTTOM

SEL/OUTPUT next

BLUE

SCROLL/DOWN •

SEL/SOURCE next

D
0

ENTER
KPD

PERIOD

Default

STEP

Reset

GOLD

STEP/INTO

Reset

BLUE

STEP/OVER

Reset

ZK-1732-84

Figure 17-1: Default Keypad Definitions-VTlOO

17.4.3 User-Defined Keypad Command Keys
The following commands are used in examining and changing key definitions:
DEFINE/KEY

Creates a key definition, which associates a debug command of your own
choosing with a key or key combination.

DELETE/KEY

Deletes a key definition.

SHOW KEY

Displays the definition for a specified key.

Debugging VAX FORTRAN Programs

17-7

The debugger DEFINE/KEY command (similar to the DCL DEFINE/KEY command)
allows you to assign a debugger command to a keypad key. For example, to define the
keypad key 7 to enter and execute the SET MODULE/ALL command, specify:
DBG> DEFINE/KEY/TERMINATE KP7 'SET MODULE/ALL'

You must be in keypad mode to define, use, display, or delete a keypad key. To display the
current definition of a keypad key, specify:
DBG> SHOW KEY Kev

To delete a key's definition, specify:
DBG> DELETE/KEY Kev

You can put key definitions in a debugger initialization file so that the key is available
whenever the initialization file is executed (see Section 17.4.5).
Key Name

Key Designation

PFl
PF2
PF3
PF4
KPO, KPl, ... , KP9
PERIOD
COMMA
MINUS
ENTER
El
E2
E3
E4
E5
E6
HELP
DO
F6, F7, ... , F20

LK201, VTlOO, VT52 Red
LK201, VTlOO, VT52 Blue
LK201, VTlOO, VT52 Black
LK201, VTlOO
Keypad 0 - 9
Keypad period
Keypad comma
Keypad minus
Keypad enter
LK201 Find
LK201 Insert Here
LK201 Remove
LK201 Select
LK201 Prev Screen
LK201 Next Screen
LK201 Help
LK201 Do
LK201 Function keys

17.4.4 Using Debugger Command Procedures
Like DCL, the debugger has a capability for executing a sequence of commands contained
in a file. The syntax is the same as for DCL:
DBG> @filenari1e

You can execute a command procedure interactively, from within a DO command sequence, or from within another command procedure. Command procedures are especially
useful when you regularly perform a number of standard set-up debugger commands; see
Section 17.4.5 for information about initialization files.

17-8

Debugging VAX FORTRAN Programs

To display the commands in a command procedure (or DO command sequence) as they
execute, specify the VERIFY keyword of the SET OUTPUT command:
DBG> SET OUTPUT VERIFY

If you want the debugger to accept input commands automatically from a file whenever

you invoke the debugger, assign the logical name DBG$INPUT to point to the file before
invoking the debugger. For example:
$TYPE E}-(IT.COM
$ ASSIGN EXIT.COM DBG$INPUT
$ RUN/DEBUG PROG
DBG> EXIT
$

In the preceding example, the debugger accepts its input from the file EXIT.COM, thus
causing it to exit immediately.

17 .4.5 Initializing a Debugging Session
The logical name DBG$INIT can be used to specify a command file that is to be executed
whenever you start a debugging session. This capability is analogous to the LOGIN.COM
file that is always executed at the start of a terminal session.
The following commands are examples of commands that are commonly used in initialization files:
SET OUTPUT LOG1VERIFY
SET LOG filenar11e
SET MODULE/ALL
SET MODE SCREEN
SET STEP SILENT

Note that in addition to establishing a "generic" initialization command procedure that
would be invoked whenever you access the debugger, you may also want to establish special
initialization command procedures for use with individual programs that require repeated
debugging because of their complexity or size.

17.4.6 Recording Debug Sessions in Log Files
A debugger log file maintains a history of a debugging session. Each debugger command
and display that occurs during a debugging session is stored in the log file.
The DBG> prompt is not recorded and the displays are commented out with exclamation
points in order to allow the use of log files as command procedures. Thus, if a lengthy
debugging session is interrupted for some reason, you can execute the log file as you would
any other debugger command procedure and it will restore your debugging session to the
point at which it was previously terminated.

Debugging VAX FORTRAN Programs

17-9

To create a log file, specify the following debugger commands:
• SET LOG filename-specifies the name of the log file.
• SET OUTPUT LOG-directs the debugger to begin to send output to a log file (as well
as to the terminal).
For example:
DBG> SET LOG HIST.LOG
DBG> SET OUTPUT LOG

The default file specification of a log file is DEBUG.LOG.
To use a log file as a command procedure, invoke it as follows:
DBG> SET OUTPUT VERIFY
DBG> @HIST.LOG
%DEBUG-I-VERIFYICF1 enterins indirect COMMand filB
SET BREAK /CALL/TEMPORARY

%DEBUG-I-VERIFYICF1 exitins indirect coMMand file
DBG>

'HIST.LOG'

17.4. 7 Debugger Command Syntax and Summary
Debugger commands have the format:
cmd [keyword] [/qualifier] [param ... ] !comment

cmd

A command verb (for example, CANCEL, SET, SHOW) that indicates the general
function to be performed.
keyword

Gives the specific function to be performed by the command verb (for example,
CANCEL MODULE, SET SCOPE, SHOW LANGUAGE).
/qualifier

Modifies the effect of the command. Qualifiers change the defaults that the debugger
uses to process commands. For example, when you deposit a value, the debugger uses
decimal radix by default. You can override the default by specifying either /HEXADECIMAL or /OCTAL.

17-10

Debugging VAX ;FORTRAN Programs

param

Qualifies the function in some way, such as specifying a range oflocations to be acted
upon by the command.
comment

Any text message. The debugger ignores all text after the exclamation mark.
Separate the command, keyword, and operand fields by one or more spaces. Multiple
commands can be specified on one line by using a semicolon (;) as a command separator.
The debugger prompts for commands with the symbol DBG>.
Table 17-1 summarizes the debugger commands.

Table 17-1: Summary of Debug Commands
@filespec
ALLOCATE n-bytes
ATTACH process-name
CALL routine [(arg [,arg ... ])]
CANCEL ALL

CANCEL BREAK

CANCEL DISPLAY

/BRANCH
/CALL
/EXCEPTION
/INSTRUCTION [=opcode]
/LINE
/MODIFY

/ALL
}
{ breakpt [, breakpt ... ]

/ALL
}
{ display-name

CANCEL EXCEPTION BREAK
CANCEL MODE
CANCEL MODULE

/ALL
}
{ module-name

CANCEL RADIX [ /OVERRIDE l
CANCEL SCOPE
CANCEL SOURCE [ /MODULE=module-name l

CANCEL TRACE

/BRANCH
/CALL
/EXCEPTION
/INSTRUCTION [=opcode]
/LINE
/MODIFY

/ALL
}
{ tracept [, tracept ... ]

Debugging VAX FORTRAN Programs

17-11

Table 17-1 (Cont.): Summary of Debug Commands
CANCEL TYPE/OVERRIDE
CANCEL WATCH

{

CANCEL WINDOW

/ALL
}
watchpt [,watchpt . 1 .]
{

/ALL
}
window-name [,window-name ... ]

DECLARE name [:kind] [,name [:kind]]

[r~~J::DJ

DEFINE

symbol = expression [,symbol = expression ... ]

/GLOBAL

DEFINE/KEY

/[NOJECHO
/[NO]IF_STATE
/[NOJLOCK_STATE
/[NOJLOG
/[NOJSET_STATE
/[NOJTERMINATE

DELETE/KEY

[~~~LOG J

keyname expression

keyname

/[NOJSTATE

DEPOSIT

/ASCII:n
/ASCIC
/ASCIW
/ASCIZ
/BYTE
/D_FLOAT
/FLOAT
/G_FLOAT
/H_FLOAT
/INSTRUCTION
/LONG
/OCTA WORD
/QUADWORD
/WORD

DISPLAY

/CLEAR
/GENERATE
/HIDE
/MARK_CHANGE
/REFRESH
/REMOVE
/SIZE:n

17-12

{ addr-expresn = expression }

[display-name [AT window-name] [kind]] , ...

Debugging VAX FORTRAN Programs

Table 17-1 (Cont.): Summary of Debug Commands

EVALUATE

EXAMINE

/ADDRESS
/BINARY
/CONDITIQN_VALUE
/DECIMAL
/HEXADECIMAL
/OCTAL
/ASCII:n
/AS CIC
/AS CID
/ASCIW
/ASCIZ
/BINARY
/BYTE
/CONDITION_VALUE
/D_FLOAT
/DECIMAL
/FLOAT
/G_FLOAT
/H_FLOAT
/HEXADECIMAL
/INSTRUCTION
/LONG
/OCTAL
/OCTA WORD
/QUADWORD
/SOURCE
/[NOJSYMBOL
/WORD

expression [,expression ... ]

addr-expresn [,addr-expresn ...

EXIT
EXITLOOP [n-levelJ
FOR name =expression TO expression [BY expression] DO (debug-cmds)
GO
HELP [topic]
IF language-expression THEN (debug-cmds) [ELSE (debug-cmds)J
REPEAT language-expression DO (debug-cmds)
SAVE old-display AS new-display

SCROLL

/BOTTOM
/DOWN
/LEFT
/RIGHT
;TOP
/UP

[display-name]

Debugging VAX FORTRAN Programs

17-13

Table 17-1 (Cont.): Summary of Debug Commands

SELECT

/ALL
]
/NEXT
/IDENTIFIER
[
/STRING

[range) string

/OUTPUT]
/SCROLL
/SOURCE

display-name

[

/AFTER:n
/BRANCH
/CALL
/EXCEPTION
/INSTRUCTION [=opcode)
SET BREAK

SET DISPLAY

addr-expresn [, addr-expresn ... )
[WHEN (condition-expresn)J
[DO (debug-cmds)J

/LINE
/MODIFY
/[NOJSOURCE
/RETURN
/[NOJSILENT
/TEMPORARY

[

/MARK_CHANGE]
/REMOVE
/SIZE:n

[display-name [AT window] [kind]) , ...

SET EXCEPTION BREAK
SET LANGUAGE language
SET LOG filespec

SET MARGIN

right-margin
left-margin:right-margin
[ left-margin:
:right-margin

SET MAx_soURCE_FILES n-files
SET MODE mode [,mode ... J
SET MODULE [/ALLOCATE J {
/ALL
}
module-name [,module-name ... ]

[NOJLOG
[NOJSCREEN-1..0G
SET OUTPUT [NOJTERMINAL
[
[NOJVERIFY

17-14

Debugging VAX FORTRAN Programs

Table 17-1 (Cont.): Summary of Debug Commands
/INPUT
/OUTPUT
/OVERRIDE

SET RADIX
[

BINARY
]
DECIMAL
DEFAULT
[ HEXADECIMAL
OCTAL

SET SCOPE [ /MODULE 1 location [,location ... J

SET SEARCH

ALL
]
NEXT
IDENTIFIER
[
STRING

SET SOURCE

[ /MODULE=module-name 1 filespec

SET STEP

BRANCH
CALL
EXCEPTION
INSTRUCTION[=opcodel
INTO
LINE
OVER
RETURN
[NOJSILENT
[NOJSOURCE
[NOJSYSTEM

SET TRACE

/AFTER:n
/BRANCH
/CALL
/EXCEPTION
/INSTRUCTION [=opcode]
/LINE
/MODIFY
/[NOJSOURCE
/RETURN
/[NOJSILENT
/TEMPORARY

SET TYPE [ /OVERRIDE 1

ASCII
AS CID
ASCII:n
ASCIZ

addr-expresn [,addr-expresn ... ]

BYTE
D_FLOAT
DATE_TIME
FLOAT

G_FLOAT
H_FLOAT
INSTRUCTION
LONG

OCTAWORD}
PACKED:n
QUADWORD
WORD

Debugging VAX FORTRAN Programs

17-15

Table 17-1 (Cont.): Summary of Debug Commands
SET TERMINAL/WIDTH:n
/AFTER:n
]
/SILENT
SET WATCH /SOURCE
[
/TEMPORARY

addr-expresn , ... [WHEN (condition)]

SET WINDOW name AT (line, line)
SHOW BREAK
SHOW CALLS [n-callsl
SHOW DISPLAY

SHOW KEY

[~~~~TORY
J
/STATE=statname

/ALL
}
{ key-name [,key-name ... ]

SHOW LANGUAGE
SHOW LOG
SHOW MARGINS
SHOW MA:x__soURCE_FILES
SHOW MODE
SHOW MODULE
SHOW OUTPUT
SHOW SCOPE
SHOW SEARCH
SHOW SOURCE
SHOW STEP
/ADDRESS]
SHOW SYMBOL
/DIRECT
symbol , ... [IN scope , ... ]
[
/TYPE
SHOW TRACE
SHOW TYPE [ /OVERRIDE l
SHOW WATCH
SHOW WINDOW
SPAWN
/NOWAIT
dcl-command

STEP

17-16

/BRANCH
/CALL
/EXCEPTION
/INSTRUCTION [=opcode]
/INTO
/LINE
/OVER
/RETURN
/SILENT
/[NOJSOURCE
/[NOJSYSTEM

Debugging VAX FORTRAN Programs

[ n-units l

Table 17-1 (Cont.): Summary of Debug Commands
SYMBOLIZE addr-expression
TYPE [module\Jline[:line] , ...

UNDEFINE

[j~t~BALJ

symbol
/KEY
WHILE language-expression DO (debug-cmds)

17.5 Controlling Program Execution
After you have invoked the debugger (see Section 17 .3), you must decide how you wish to
control the execution of your program. The debugger provides several commands, with a
wide range of options, for you to select from.
Using these commands, you can suspend execution of your program at points that are
interesting to you, and you can then examine variables at those points.
The following sections, Sections 17 .5.1 and 17 .5.2, contain information on the following
topics concerning execution control:
• Starting program execution (GO, STEP, and CALL commands)
• Suspending or tracing program execution (SET BREAK, SET TRACE, and SET
WATCH commands)

17 .5.1 Starting Program Execution
The command with which you start program execution determines when the debugger
regains control and prompts you for other debugger commands that may aid in isolating
the error in your program.
The GO, STEP, and CALL commands execute varying numbers of source lines before
returning control to the debugger. The SHOW CALLS command displays the current
hierarchy of routine calls.
Table 17-1 contains complete specifications for each of these debugger commands.

17 .5.1.1 GO Command
The GO command starts execution at the current line, continuing it either to the conclusion of the program (as in the following example), to an error, or to the next breakpoint or
watch point (see Section 17 .5.2):
DBG> GO
%DEBUG-I-EXITSTATUS1is '%SYSTEM-S-NORMAL1norMal successful COMPietion'
DBG>

Debugging VAX FORTRAN Programs

17-17

An optional parameter of the GO command allows you to specify an address at which to
start program execution. However, this &lters the normal flow of the. program and is likely
to produce meaningless results.

17.5.1.2 STEP Command
By default, the STEP command executes one source statement. To execute more than one
statement, specify the number of statements to be executed as a parameter of the STEP
command. The following command executes the next two source statements:
DBG> STEP 2
stepped to MAIN\%LINE 5

CALL SUB2(J)

If you are debugging in screen mode (see Section 17 .8), the information displayed by the
STEP command is extraneous since the SRC display shows the source code and your
current position. Use the SET STEP SILENT command to prevent the STEP command
from displaying any text.
If the STEP command encounters a subprogram invocation, the following keywords determine whether the subprogram executes as a single step:

• OVER-indicates that the debugger executes subprograms as a single STEP command.
• INTO-indicates that the debugger steps through subprograms line by line.
To display the current default keywords in effect for the STEP command, enter the SHOW
STEP command. The following SHOW STEP command displays the default keywords for
the STEP command:
DBG> SHOW STEP
STEP TYPE: NOSYSTEMt SOURCEt OVER ROUTINE CALLSt BY LINE

By default, the debugger executes all subprograms as a single step. To set the STEP
characteristics so that the debugger steps through user subprograms, but not system subprograms, specify:
DBG> SET STEP NOSYSTEMt SOURCEt INTO, LINE

The LINE keyword in the previous example (same as BY LINE in the SHOW STEP
display) indicates that a STEP command executes source line by source line. Alternatively,
you can use the following keywords to specify that a STEP command executes all lines up
to an exception or a particular type of machine code instruction (the BRANCH, CALL, and
INSTRUCTION keywords are useful only if you are familiar with machine code):
• BRANCH-step to the next machine code branch instruction.
• CALL-step to the next machine code call instruction.
• EXCEPTION-step to the next exception (error).

17-18

Debugging VAX FORTRAN Programs

• INSTRUCTION-step to the next machine code instruction.
• LINE-step to the next source code statement.
• RETURN-step to the end of the currently executing subprogram.
To use one of the previously listed keywords to affect a single STEP command, name the
keyword as a qualifier of the STEP command (for example, STEP/INSTRUCTION). To
use one of the previously listed keywords as the default for the STEP command, use the
keyword as a parameter of the SET STEP command (for example, SET STEP INSTRUCTION).

17.5.1.3 CALL Command
The CALL command invokes a subprogram (passing it specified arguments), executes the
subprogram, and displays the function value returned (none for a subroutine).
Typically, you use the CALL command to invoke a subprogram that you have written in
order to display data structures or other information required for debugging.
When passing arguments to a subprogram invoked by the CALL command, you can use the
following keywords to specify the passing mechanism:
• %DES CR-pass by descriptor. Unlike FORTRAN, you must use %DES CR explicitly
when specifying CHARACTER type arguments.
• %REF-pass by reference. Unlike FORTRAN, you must use %REF explicitly when
specifying expression arguments that do not refer to specific locations. For example, to
pass A*B, you must specify %REF (A*B).
• %VAL-pass by value.
For example, the subprogram INC_DUMP is a subroutine that requires two arguments,
both passed by reference. To invoke INC_DUMP, specify:
DBG> CALL INC_DUMP IPERSDNS_HOUSE1 ADULTS_HOUSE)
value

returned

is 0

17.5.1.4 SHOW CALLS Command
The SHOW CALLS command produces a traceback of calls and is particularly useful when
you have returned to the debugger following a <CTRL/Y> interrupt or a program exception. For each call frame (beginning with the most recent call), the debugger displays one
line of information, including the name of the routine, the name of the module containing
the routine, and the line number of the call. For example:
DBG> SHOW CALLS
r11odule narrie

SUB1
*MAIN

routine nar11e

SUB1
MAIN

line

re 1

oooooooc
00000011

abs

oooooazc
oooooa11

Debugging VAX FORTRAN Programs

17-19

The name of the routine and the name of the module containing the routine are always the
same for FORTRAN subroutines. (Note: This is not the case with other languages.)
The value of the program counter (PC) in the calling subroutine at the time that control
passed to the called subroutine is also displayed. The is expressed both as a virtual address
relative to the virtual address of the subroutine's name and as an absolute address.
The asterisk ( * ) indicates which modules are set (SET MODULE command).

17.5.2 Suspending or Tracing Program Execution
You can suspend program execution at specified locations in your program by setting
breakpoints and watchpoints with the SET BREAK and SET WATCH commands. In
addition, you can follow program execution without suspending execution by setting tracepoints with the SET TRACE command.
An optional WHEN clause allows you to conditionally activate a breakpoint, tracepoint, or
watchpoint. An optional DO clause allows you to specify one or more debugger commands
to be executed when a breakpoint, tracepoint, or watchpoint is activated. SHOW and
CANCEL commands display and cancel the breakpoints, tracepoints, and watchpoints
that you have set.

NOTE
You cannot set breakpoints, tracepoints, and watchpoints at the same location:
the most recently issued command overrides any other breakpoint, tracepoint, or
watchpoint at that location.
Table 17-1 contains complete specifications for each of these debugger commands.

17 .5.2.1 Breakpoints and Tracepoints
You can set a breakpoint at a particular program location, on an exception, or on a
particular type of instruction. When your program encounters a breakpoint, the debugger
suspends program execution, displays the address of the breakpoint and the source line at
that address, executes the DO command sequence (if specified), and prompts for a command (unless the DO command sequence causes an alternative action).
A tracepoint is exactly like a breakpoint, except that instead of prompting for a command,
the debugger executes an implicit GO command to continue program execution.

17-20

Debugging VAX FORTRAN Programs

The options associated with the SET BREAK and SET WATCH commands are described
in the following list:
• To set a breakpoint or tracepoint at a particular program location, specify that location as the parameter of the SET BREAK or SET TRACE command. The following
example sets a breakpoint that causes the debugger to suspend execution just before
line 3 in subroutine SUBl:
DBG> SET MODULE/All
DBG> SET BREAK SUB1\%LINE 3
DBG> GO
breaK at SUB1\%LINE 3
3:

= M +1

A breakpoint usually suspends execution at the first byte of the specified location so
that the instruction beginning at that location does not execute. However, if you set a
breakpoint at a subroutine, the breakpoint is actually set at the memory address two
bytes greater than the address of the subroutine name itself (the entry point), thereby
causing the subroutine to be called before the debugger takes control and issues the
message: "routine break at routine NAME."
• To set a breakpoint or tracepoint on an exception or on a particular type of instruction,
use the following qualifiers of the SET BREAK and SET TRACE commands (note
that these qualifiers are the same as those used on the STEP and SET STEP commands):
- /BRANCH-break on the next machine code branch instruction.
- /CALL-break on the next machine code call instruction.
- /EXCEPTION-break on the next exception (error). The debugger reports the
exception and the line at which it occurred, after which you can execute or inhibit a
user-declared condition handler. You cannot use the STEP command to step into a
condition handler, but you can set a breakpoint or tracepoint within the handler.
(The SET BREAK/EXCEPTION command is the same as the SET EXCEPTION
BREAK command.)
- /INSTRUCTION-break on the next machine code instruction.
- /LINE-break on the next source code statement.
- /RETURN-break on the end of the currently executing subprogram.

Debugging VAX FORTRAN Programs

17-21

• To have a breakpoint or tracepoint execute a list of commands when it is activated,
use a DO command sequence.
DBG> SET BREAK SUB1 DO <EXAMINE Ml

The preceding command specifies that the EXAMINE M command is to be executed
each time that the breakpoint at subroutine SUBl is encountered.
• To activate a tracepoint or breakpoint exactly once, specify the /TEMPORARY qualifier. For example:
DBG> SET BREAK/TEMPORARY %LINE 8
DBG > GO
break at CIRCLE\%LINE 8
8:
AREA = PI*RADIUS**2

• To activate a tracepoint or breakpoint after a certain number of iterations, specify the
/AFTER qualifier. For example, to activate a tracepoint on the second execution of
line 3 in program CIRCLE, specify:
DBG> SET TRACE/AFTER:2 %LINE 3 DO <IF I ,EQ, 2 THEN <GO) ELSE <EXAMINE Ill
DBG> GO
trace at CIRCLE\%LINE 3
3: a
TYPE 5
trace at CIRCLE\XLINE 3
3: a
TYPE 5
CIRCLE\ I:
3
%DEBUG-I-EXITSTATUS1 is '%SYSTEM-S-NORMAL1 norMal successful COMPietion'

The tracepoint is activated at each successive execution of that line (unless you specify
/TEMPORARY).
• To conditionally execute a breakpoint or tracepoint, use the optional WHEN clause.
Each time the debugger encounters the breakpoint or tracepoint, it evaluates the
expression in the WHEN clause: if the expression is true, the breakpoint or tracepoint
is activated; if it is false, the breakpoint or tracepoi~t is ignored. For example, in the
following command, the DO command sequence executes only if the expression
RADIUS .LT. 10 is true:
DBG > SET TRACE 'X.LI NE 8 WHEN <RAD I US • LT. 10) DO <DEPOSIT RAD I US = 0)

The SHOW BREAK and SHOW TRACE commands display the breakpoints and
tracepoints currently set in the program. You can cancel any of the currently set breakpoints and tracepoints by means of the CANCEL BREAK or CANCEL TRACE commands. For example:
DBG> CANCEL BREAK %LINE 8

This command cancels the breakpoint at line 9. To cancel all breakpoints, enter the
following:
DBG> CANCEL BREAK/ALL

The commands to cancel tracepoints have the same syntax as the preceding examples.
17-22

Debugging VAX FORTRAN Programs

17.5.2.2 Watchpoints
Specify a watchpoint to display a particular program location each time that the contents
of that location are modified. When your program modifies a value in the specified location, the debugger performs the following operations:
• Suspends program execution.
• Displays the address of the location, the old and new values of the location, and the
source line that modified the location.
• Executes the DO command sequence (if specified).
• Prompts for a command (unless the DO command sequence causes an alternative
action).
To set a watchpoint on a location, specify that location as the parameter of the SET
WATCH command. The following example sets a watchpoint on the location I in the
program unit MAIN and starts execution:
DBG> SET MODULE/ALL
DBG> SET WATCH I
DBG> GD
watch of MAIN\I at SU51\%LINE 3
3:

M = M+ 1

old t.ialue: 1
ne1A1 1.1alue: 2
break at SU51\%LINE t'.I
t'.I:
RETURN

DBG>

The I AFTER and /TEMPORARY qualifiers and the DO and WHEN commands can be
used with the SET WATCH command in the same way that they are used with the SET
BREAK and SET TRACE commands. See Section 17.5.2.1 for examples of the /AFTER
and /TEMPORARY qualifiers, as well as the DO and WHEN clauses.
The SHOW and CANCEL commands work the same way with watchpoints as they do with
breakpoints and tracepoints (see Section 17 .5.2.1).

17.5.3 Displaying Source Lines
Debugger commands allow you to display source lines under a variety of circumstances.
The STEP/SOURCE and SET MODE SCREEN commands display source lines as they
execute; the TYPE and SEARCH commands display source lines independently. All commands that display source lines require the following:
1. The source file must have been compiled with the /DEBUG and /NOOPTIMIZE
qualifiers.

Debugging VAX FORTRAN Programs

17-23

2. The source file must reside in the same directory in which it was compiled. If not,
you must use the SET SOURCE command to establish the file's new directory. For
example:
DBG> SET SOURCE CdirectorY1H tdirecton·2J. ..

Note that by specifying a directory list, you can tell the debugger which directories it
should search (in the order specified) to find the files.
3. When necessary, you must specify the appropriate scope or, alternatively, the appropriate pathname.
The STEP/SOURCE command displays the currently executing source lines; see Section
17.5.1.2 for information about the STEP command.
The SET MODE SCREEN command generates the SRC display by default; SRC shows
the currently executing source line, the lines preceding it, and the lines following it; see
Section 17.8 for information on debugger screen displays.
The TYPE and SEARCH commands display source lines independent of their execution:
• TYPE-displays a specified range of source lines. For example, to display lines 1
through 5 of module SUBl, type:
DBG> SET MODULE/ALL
DBG> TYPE SUB1\1:5
rriodule SUB1
1:
SUBROUTINE SUB1CM>
2:
INTEGER M1N/5/1 L/31/
3:
M= M+ 1
ll:
RETURN
"5:
END

In SCREEN mode, the source lines appear in the source display (SRC, by default); in
NOSCREEN mode, the source lines appear with other debugger output.
• SEARCH-displays the source lines containing the specified string. For example, to
display all lines containing the string M in the module named SUBl, specify:
DBG> SEARCH/ALL SUB1 M
rriodule SUB1
1:
SUBROUTINE SUB1<M>
2:
INTEGER M1N/5/, L/31/
3:
M= M+ 1

The SEARCH display appears with other debugger output.

17-24

Debugging VAX FORTRAN Programs

17.5.4 Using the Debugger's Logical Control Commands
You can control the execution of debugger commands by using the following logical control
commands:
• IF THEN ELSE-a conditional construct that executes a THEN clause of one or
more debugger commands if a specified logical expression is true. If the expression is
false, the command either terminates or executes an optional ELSE clause of one or
more debugger commands. The format of an IF construct is:
.IF expression THEN (command[; ... ]) [ELSE(command[; ... ])]

In the following example, if the expression in the IF clause is false, the ELSE clause
executes:
DBG> IF I .GT. 100 THEN (EXAMINE X> ELSE (GO>

• WHILE-an iterative construct that executes a DO command sequence while a specified logical expression is true; if the expression is false, the command terminates. The
format of a WHILE construct is:
WHILE expression DO(command[; ... ])

The following example causes the debugger to step line by line while I is less than 5:
DBG> WHILE I .LT. 5 DO(STEP/LINE>

• FOR-an iterative construct that executes a DO command sequence through a range
of values. FOR control = init TO term [BY inc] DO(command[; ... ])
The control variable is initialized to the value of init and compared to term. If control
is less than term, the commands in the DO command sequence execute and control is
incremented by one (or the value of inc). If control is less than term, the command
terminates. For example, the following FOR command displays the value of three
variables 3 times:
DBG> FDR I = 1 TO 3 DO(EXAMINE RADIUS1AREA>

Logical control constructs are especially useful in command procedures and DO command
sequences (see Section 17.4.4 for information about using debugger command procedures).

17.6 Using Symbolic Names and Accessing Program Locations
During a debugging session you can reference the following items:
1. Locally defined symbolic names, such as names of variables

2. Globally defined symbolic names, such as names of subroutines
3. Virtual memory locations, such as an address returned by a system-defined routine

Debugging VAX FORTRAN Programs

17-25

4. Debugger symbols for VAX registers:
'X,RO 'X,AP
'X,FP
'X.SP
'X.PC
'X.PSL

'X,R 11

General resisters 0 throush
Arsu1r1ent Pointer
Fra1r1e Pointer
Stad\ pointer
Prosrar11 counter
Processor status lonsword

5. User-defined debugger symbols, as described in Section 17.6.4
Access to symbols described by items 1 and 2 in the preceding list depends on whether you
specify /DEBUG when you compile and link your program. Also, note that some of these
symbols may disappear as a result of optimizations performed at compile time. Thus, in
addition to /DEBUG, you should specify /NOOPTIMIZE when you compile a program that
you intend to run using the debugger (see Section 17.2).
Much of the information in this section is needed only when you are debugging multiunit
programs and you must exercise control over the debugger symbol table (see Section 17.6.1)
or resolve "not unique" debugger messages (see Section 17 .6.3). Information in this section
is not necessary if you are debugging a single unit program and are just examining and
manipulating values in variables. This section describes how to access "lower level" constructs (such as absolute addresses, registers, or instructions) that are seldom needed.

17.6.1 Making Symbolic Names Accessible-SET MODULE
The MODULE commands (SET, SHOW, and CANCEL) enable you to control the contents of the debugger's symbol table when the program you want to debug consists of
multiple program units. These commands perform the following functions:
• SET MODULE places the symbols defined in the specified program unit or units in
the symbol table. By default, the debugger initializes the symbol table to include all
global symbols and the local symbols of the first program unit specified in the LINK
command.
• SHOW MODULE displays the names of all program units whose symbols are potentially available. "Yes" means the symbols for that module are in the symbol table;
"No" means they are not.
• CANCEL MODULE removes the specified program unit's symbols from the symbol
table.
For example, to make the symbols in the program unit SUB2 available while operating in
SUBl (see sample program MAIN in Section 17 .9.2) specify:
DBG> SET MODULE SUB2

If your program is not too large, it is useful to make the symbols of all modules available at
the outset of the debugging session. (Performance will suffer noticeably if your program is
too large for all of its modules to be set.) To set all modules, specify the /ALL qualifier with
the SET MODULE command:
DBG> SET MODULE/ALL

17-26

Debugging VAX FORTRAN Programs

Depending upon the size of your program, most or all of the symbols in its modules will be
set. To display the names of modules whose symbols are available, use the debugger
command SHOW MODULE. The following example demonstrates the effect of the SET
MODULE/ALL command. At the outset of a debugging session on a program named
MAIN, only the symbols of the first linked module (the main program unit named MAIN)
are available:
DBG> SHOW MODULE
111odule na111e

S}'111bols

lansuase

size

MAIN
SUB!
SUB2
SHARE$DEBUG
SHARE$DBGSSISHR
SHARE$LIBRTL
SHARE$FORRTL
SHARE$LBRSHR
SHARE$MTHRTL
SHARE$PLIRTL
SHARE$SCRSHR
SHARE$SMGSHR

Yes
no
no
no
no
no
no
no
no
no
no
no

FORTRAN
FORTRAN
FORTRAN
I 111 as e
I fll as e

660

total r11odules:

aao
t'.168
0
0
0
0
0

I 111 as e

I 111ase
I 111 as e
I 111 as e
I 111 as e
I 111 as e

0
0
0
0

I 111 as e

re111ainins size:

5t'.11t'.IO,

Entering the SET MODULE/ALL command makes the symbols in all of the modules
available:
DBG> SET MODULE/ALL
DBG> SHOW MODULE
111odule na111e

S}'1T1bols

lansuase

size

MAIN
SUB1
SUB2
SHARE$DEBUG
SHARE$DBGSSISHR
SHARE$LIBRTL
SHARE$FORRTL
SHARE$LBRSHR
SHARE$MTHRTL
SHARE$PLIRTL
SHARE$SCRSHR
SHARE$SMGSHR

}'es
Yes
}'es
no
no
no
no
no
no
no
no
no

FORTRAN
FORTRAN
FORTRAN
I 111 as e
I fll as e
I 111 as e
I 111 as e
I 111 as e
I 111ase
I 111ase
I 111 as e
I fll as e

660

total 1T1odules:

aao

t'.168
0
0
0
0
0
0
(l

0
0

re111ainins size: 53336.

Note that the SHOW MODULE command displays the remaining size of the debugger's
storage area. You can increase this storage area by using the ALLOCATE command or the
I ALLOCATE qualifier of the SET MODULE command.
In addition to using the debugger SET MODULE command, you may also need to use the
debugger SET SCOPE command to reference symbols during the debugging session; see
Section 17.6.3.2.
Debugging VAX FORTRAN Programs

17-27

17.6.2 Referencing Locations in a Program
As illustrated in previous sections, the debugger allows you to specify addresses as symbolic
names in debugger commands. For example, to examine a variable you simply refer to it by
its name; you do not need to concern yourself with its actual memory location. This form of
symbolic expression applies to data addresses, such as variables and array elements, and to
program addresses, such as program labels and program unit names.
When you are debugging more than one program unit, you should be aware of the concept
of scope because it affects how the debugger searches for symbols (see Section 17 .6.3). The
following sections describe how to specify data and program addresses in debugger commands.

17 .6.2.1 Specifying Data Addresses
You can specify data addresses symbolically using the same syntax as in your FORTRAN
program. For example:
DBG> DEPOSIT ISSUE=100
DBG> El{AMINE PURCH( I tJ+1)

The first command deposits a value of 100 in the program variable ISSUE, and the second
command examines an element of array PURCH.
You can reference array elements with constants and variable expressions. If you reference
a variable or array element that is not defined in the symbol table, or if you attempt to
reference out of the array bounds defined at compile time, the debugger issues a warning.

· 17.6.2.2 Current, Previous, and Next Locations
The debugger provides a quick method for referencing any of three relative data addresses,
or locations:
.

• The current location (the location most recently referenced by an EXAMINE or
DEPOSIT command)
• The previous location (the location at the next lower address from the current location)
• The next location (the location at the next higher address from the current location)

To specify the current location, type a period ( . ) . For example:
DBG> DEPOSIT .=100

This command puts a value of 100 in the current location.
To specify the previous location, type an up-arrow or a circumflex ( " ) . For example:
DBG> E}(AMINE

17-28

Debugging VAX FORTRAN Programs

This command displays the the contents of the previous location.
To specify the next higher location, simply omit the address value entirely. For example:
DBG > E)<AM I NE

This command displays the next location's contents.

17.6.2.3 Specifying Program Addresses
You can specify program addresses by program unit name, line number, statement label, or
(nonsymbolic) virtual address. To specify a program unit by name, give the command
followed by the name of the program unit. For example, the command
DBG> SET BREAK SUBl

sets a breakpoint at the entry to program unit SUBl.
To specify a line number, use the %LINE prefix, as shown here:
DBG> SET BREAK %LINE G

This command sets a breakpoint at line 6, corresponding to the compiler-generated line
number shown in the listing. Note that the debugger does not recognize all line numbers. In
particular, it does not recognize those line numbers associated with nonexecutable statements. If you specify such a line number, the debugger responds with a message indicating
that no such line exists.
You can also set a break at a line number within a particular program unit. For example, to
stop execution at line 11 in SUB2, you could set a breakpoint as follows:
DBG> SET BREAK SUB2\%LINE 11

To specify a statement label, use the %LABEL prefix. For example:
DBG> SET BREAK %LABEL 7

This command sets a breakpoint at statement label 7.
To specify a virtual address, issue the command without a prefix. For example:
DBG> SET BREAK 700

You can also enter virtual addresses in symbolic form. To do so, you must have previously
defined them symbolically with the DEFINE command (see Section 17 .6.4).

17.6.3 Making Symbolic References Unique-Prefixes and Scope
If the program you are debugging consists of more than one program unit, you must be sure
that your symbolic references are unambiguous. Most of the time, you can let the debugger
define scope for you. At certain times, however, you must give the debugger additional
information in order to enable it to resolve symbolic references. For example, assume that
you are debugging two program units; both units use the variable I, and both occurrences
are defined in the symbol table. Unless you explicitly specify scope, the debugger may be
unable to determine which variable I you want.

Debugging VAX FORTRAN Programs

17-29

When you begin a debugging session, the debugger automatically defines the first program
unit linked (normally the main program unit) as the default scope. However, this default
scope is dynamic; that is, as you debug your program, the default scope (PC scope) is
always the subroutine you are currently executing. The debugger default scope rules are as
follows:
• If the symbol name is unique within the debugger symbol table, the debugger can
reference its definition.
• If the symbol is not unique within the symbol table, but is used within the current
scope, the debugger uses the definition for the symbol as defined by the current scope.
• If the symbol is not defined within the symbol table, the debugger issues a message
indicating that the symbol is "not in the symbol table." In this case, you might have
misspelled the symbol, forgotten to use the SET MODULE command to include the
symbols of a particular module, or forgotten the /DEBUG qualifier when you compiled
or linked the program.
If the symbol is not unique within the program and is not used within the current scope, the
debugger issues a message indicating that the symbol "is not unique." In this case, you
must specify a pathname or use the SET SCOPE command, as shown in the following
sections, to resolve the ambiguity for the debugger. (If necessary, use the SHOW SYMBOL
command to list the modules that define the symbol.)

17 .6.3.1 Pathname Prefix
You can make a symbol unique by specifying a string of symbolic names connected by
backslashes that fully identify the symbol. The string, or pathname, can include the symbolic name of the subroutine, block, labeled section, and/or the number of the line that
contains it. The pathname can be incomplete, so long as it makes the symbol unique.
Usually one pathname prefix is sufficient to make the symbol unique. For example, while
executing within subroutine SUB2, the following command examines the variable M in
subroutine SUBl:
DBG> EXAMINE SUB1\M

Examples of other pathnames are:
DBG> EXAMINE %LINE 2\M
DBG> EXAMINE SUB1\%LINE 3\M
DBG> EXAMINE O\M

Subroutines in pathnames can be specified numerically (as shown in the preceding example), where the currently executing subroutine is 0, the subroutine that calls the currently
executing subroutine is 1, the subroutine that calls the subroutine that calls the currently
executing subroutine is 2, and so on.

17-30

Debugging VAX FORTRAN Programs

17.6.3.2 SET SCOPE Command
You can use the SET SCOPE command to specify one or more program regions to be used
by default in the interpretation of symbols. For example, to make the subroutine SUBl the
default scope, specify:
DBG> SET SCOPE SUB1

Subsequent references to symbols without pathnames use the pathname string "SUBl \"as
the default pathname prefix.
DBG > El<AM I NE M
SUBl\M:

You can also use a list of subroutines or pathnames as a parameter of the SET SCOPE
command to set the order in which the debugger searches. for the symbol referenced. For
example, the following command makes the debugger search first the subroutine SUBl and
then search the subroutine SUB2 for whatever symbol is being referenced.
DBG> SET SCOPE SUB1 tSUB2
DBG> SHOW SCOPE
scope: SUB1 t SUB2

17.6.4 Defining Addresses Symbolically
You can assign a symbolic name to a program location, value, or character string with the
debugger command DEFINE. You might, for instance, define a symbol to represent a
frequently referenced location that is hard to remember. The following example assigns the
symbolic name M2 to the integer variable M in the subroutine SUB2 and then references
the variable by its assigned name:
DBG> DEFINE M2 = SUB2\M
DBG > El<AM I NE M2
SUB2\M: G

The symbol definition lasts for the duration of the debugging session or until you cancel it
with the UNDEFINE command.

17.6.5 Displaying Symbol Information-SHOW SYMBOL
To display information about the symbols in your program, use the SHOW SYMBOL
command. For example, to display the address and type of all symbols named M, enter:
DBG> SHOW SYMBOL/ADDRESS/TYPE M
data SUB2\M
address: 00000250
atomic tYPet lonSword inteSert size:
data SUBl\M
address: .C.%AP+a>
atomic tYPet lonSword inteSert size:

a bytes
a bytes

Debugging VAX FORTRAN Programs

17-31

To display information about symbols you have defined during the debugging session, use
the SHOW SYMBOL/DEFINED command:
DBG> SHOW SYMBOL/DEFINED M2
defined M2
bound to: SUB2\M
was defined /address

By default, the SHOW SYMBOL command returns information about global symbols and
symbols in those subroutines that have been set (either by default or with the SET
MODULE command). The IN clause allows you to restrict the SHOW SYMBOL command
to one or more subroutines. You can use the wildcard character (an asterisk) with the
SHOW SYMBOL command to match any number of characters in the symbol's name. The
following command displays information about all symbols within the scope of the subroutine SUB2 (any specified scope must be in a module that is set in order for the SHOW
SYMBOL command to work properly):
DBG> SHOW SYMBOL * IN SUB2
routine SUB2
data SUB2\N
data SUB2\M
data SUB2\K
data SUB2\L

To display the address specification of all symbols beginning with the characters XYZ,
specify:
DBG> SHOW SYMBOL/ADDRESS XYZ*

17.7 Examining and Manipulating Data
You use the EXAMINE and EVALUATE commands and the DEPOSIT command to,
respectively, examine and manipulate data as your program executes. If the locations
referenced by the following commands are not in your default scope, you must set the
module, as described in Section 17 .6.1, and specify a scope or pathname, as described in
Section 17 .6.3. (For all examples in this section, it is assumed that the module and scope
are set properly.)
Table 17-2 summarizes the command qualifiers of particular significance in FORTRAN
debugging for the EXAMINE, EVALUATE, and DEPOSIT commands.

17-32

Debugging VAX FORTRAN Programs

Table 17-2: Debugger Command Qualifiers
Qualifier

Function

Commands

/ADDRESS

Indicates that an address value is
desired

EVALUATE

/HEXADECIMAL
/OCTAL

Override the default radix (decimal)

EVALUATE
EXAMINE
DEPOSIT

/BYTE
/WORD
/ASCII
/LONG
/FLOAT
/D_FLOAT
/G_FLOAT
/H_FLOAT

Override the EXAMINE display
type

EXAMINE

17.7.1 Hints about the Use of Expressions
When using the EXAMINE, EVALUATE, and DEPOSIT commands, be aware of the
difference between an address expression and a language expression:
• Address expression-an address expression specifies a program location. If the location is that of a symbol defined by the source program, it has a language-dependent
data type associated with it; otherwise, no data type is associated with it. An address
expression may consist of a single operand or multiple operands combined with the
debugger operators (see Table 17-3); it is evaluated as follows:
1. Parenthesized parts of the expression
2. Operators by rank low to high (see Table 17-3)
3. Operators of the same rank from left to right
The result of an address expression is a 32-bit longword integer that represents a
program location. In Table 17-1, arguments named "address-expression" should be
specified as address expressions.
• Language expression-a language expression specifies a value; the value is associated with a data type. A language expression can consist of a single operand or
multiple operands combined with operators; the expression is evaluated according to

Debugging VAX FORTRAN Programs

17-33

the rules of precedence for the source language. (Section D.1 lists the legal FORTRAN
operators and FORTRAN's rules of precedence.) The result of a language expression
must be a value that is valid for the current source language. In Table 17-1, arguments
named "expression" accept language ex~ressions.
For example, assume that you have a symbol named NUMBER and that it has a value of 3
and is located at address 1600. The EXAMINE command, which expects an address
expression, interprets (NUMBER+ 1) as 1601. The EVALUATE command, which expects
a language expression, interprets (NUMBER + 1) as 4.
Table 17-3: Debugger Operators
Operator

Rank

Description

. or@

Unary operators specify the contents of the operand.

+or -

Unary operators specifying the positive or negative value of
the operand.

*or I

Binary operators specifying the multiplication or division of
the operands.

+or -

Binary operators specifying the addition or subtraciton of the
operands.

Array element references and record field references are also supported in address and
language expressions.

17.7.2 Displaying Values-EXAMINE
The EXAMINE command displays the contents of a specified program location. For example, to display the contents of the variable M in the routine SUB2, specify:
DBG > E>{AM I NE M

SUB2\M: G

To display array elements, specify the elements individually (1:1, 2:2, and so forth), in a
range (1:10), or with a wildcard (*).The following command displays three elements of the
array ARRMN:
EXAMINE ARRMNC12:1a>
MA-IN\ARRMN
c 12>:
1a.soooo
(13>:
1a.soooo
(la>:
1a.soooo

DBG>

17-34

Debugging VAX FORTRAN Programs

17.7.3 Calculating Values-EVALUATE
The EVALUATE command displays the value of a specified language expression. For
example, to add the value in ARRMN(12) and the value in ARRMN(l 7), where both
symbols are defined in the program unit MAIN, specify:
DBG> EVALUATE ARRMN(12) + ARRMN(17)
28.00000

You can also perform arithmetic calculations with the EVALUATE command that may or
may not be related to your program, in effect using the debugger as a calculator.

17.7.4 Assigning Values-DEPOSIT
The DEPOSIT command assigns a language expression to a program location. For example, to assign the value 9 to the array element ARRMN(19) in program unit MAIN, specify:
DBG> DEPOSIT ARRMN(18) = 8,
DBG> EXAMINE ARRMN(18)
MAIN\ARRMN(18): 8.000000

17.7.5 Specifying Data Type
Typically, when you examine a program location, you want to use the data type that your
program has associated with that location. For example, if you have defined STATUS as a
variable of data type INTEGER, when you examine STATUS in the debugger, you probably want to examine it as an integer value. By default, the debugger uses the program
assigned data types when it displays program locations.
However, if necessary, you can specify a data type for a program location other than the
data type your program has associated with it:
• SET TYPE/OVERRIDE command-sets the default data type for debugger commands that interpret and display program data. For example, if you set the default
data type to be BYTE, any variable that you examine (regardless of how you declared
it in your program) will be displayed as a BYTE value. In the following example, the
program unit MAIN declared PI as a REAL*4 value.
DBG> EXAMINE PI
CIRCLE\PI:
3.141583
DBG> SET TYPE/OVERRIDE BYTE
DBG> D(AMINE PI
CIRCLE\PI:
73

Debugging VAX FORTRAN Programs

17-35

• Data type qualifiers on EXAMINE command-indicates that the modified command
should display or evaluate the referenced location using the data type specified by the
qualifier. A type qualifier overrides the default type specified with the SET
TYPE/OVERRIDE command. In the following example, the default type for the debugging session is set to BYTE. The EXAMINE command uses the /FLOAT qualifier
(FORTRAN data type REAL*4) to examine the variable PI.
DBG> SET TYPE/OVERRIDE BYTE
DBG > E)-(AM I NE PI
CIRCLE\PI:
73
DBG> EXAMINE/FLOAT PI
CIRCLE\ PI:
3.1£11593

The following table displays debugger data types and their FORTRAN equivalents. The
SHOW TYPE command displays the default FORTRAN data type and the SHOW
TYPE/OVERRIDE displays the current type setting of the /OVERRIDE qualifier.
Debugger

FORTRAN

BYTE

LOGICAL*l

WORD

INTEGER*2, LOGICAL*2

LONG

INTEGER*4, LOGICAL*4

FLOAT

REAL*8

D_FLOAT

REAL*8

G_FLOAT

REAL*B

H_FLOAT

REAL*B

ASCil[:nJ

CHARACTER*n

In addition to the familiar data types, the debugger provides an INSTRUCTION data
type, which interprets values as VAX machine code instructions. The INSTRUCTION
data type is a powerful debugging tool for those programmers who are familiar with machine code instructions.

17.7.6 Specifying Radix
To specify a radix other than the decimal default, use either the SET MODE command or
include a radix qualifier (for example, OCTAL or HEX) with individual debugger commands.

17-36

Debugging VAX FORTRAN Programs

• SET MODE command-sets the default radix and symbolic mode for debugger commands that display and interpret data. The default for FORTRAN is decimal radix
and symbolic mode (displaying symbolic rather than numeric addresses). For example, the following commands display the contents of RO in hexadecimal and then in
octal as the default radix mode:
DBG> SET MODE HEX
DBG > EJ<AM I NE RO
CIRCLE\%RO:
00004410
DBG> SET MODE OCTAL
DBG> EXAMINE RO
CIRCLE\%RO:
00000042020

• Radix qualifier on EXAMINE command-controls the radix of values interpreted by
individual commands (and whether those commands display symbolic or numeric
addresses). A qualifier that specifies radix overrides the default radix set by the SET
MODE command, as is shown in the following example:
DBG> EXAMINE AREA
CIRCLE\AREA:
201,0618
DBG> EXAMINE/HEX AREA
CIRCLE\AREA:
OFDB4448

To display the current type and mode settings, use the SHOW TYPE and SHOW MODE
commands. For example, the following commands display the FORTRAN default type and
mode:
DBG> SHOW TYPE
tYPe:

Ions inteser

DBG> SHOW MODE
Mode:
SYMbolic' noscreen1 keypad
input radix:
deciMal
output radix: deciMal

17.7. 7 Using Numeric Data Types in Expressions
You can use arrays and records and any of the following types of values in expressions in all
appropriate debugger commands:
LOGICAL*l
LOGICAL*2
LOGICAL*4
INTEGER*2
INTEGER*4
REAL*4
REAL*8
REAL*16
COMPLEX*8
COMPLEX*16
CHARACTER

Debugging VAX FORTRAN Programs

17-37

You can use the EXAMINE and DEPOSIT commands with any of the VAX FORTRAN
data types. Furthermore, if you attempt to deposit a numeric value into a variable or array
element that does not have a matching data type, the value is converted to the data type of
the variable or array element.
To deposit a complex value, you must use two DEPOSIT commands:
DEPOSIT x =real part
DEPOSIT/FLOAT x = imaginary part

For example:
DBG> DEPOSIT CPLX=3,a
DBG> DEPOSIT/FLOAT CPLX=-a,7

When you examine a complex variable or array element, the data is displayed as a complex
constant, as (real part, imaginary part).
When you deposit a real number, you must specify a decimal point. To distinguish
REAL*4, REAL*8, and REAL*l6 numbers, use E, D, and Q, respectively. For example:
Number

Data Type

24.1
24.lEO
24.lDO
24.lQO
241EO

REAL*4 (default)
REAL*4
REAL*8
REAL*l6
Invalid (no decimal point)

17 .8 Using Screen Displays
Screen mode debugging allows you to keep various types of debugging information on the
screen by dividing the screen into sections and displaying a different type of information in
each section. The sections of the screen are called windows and the contents of the windows
are called displays. In screen mode, the debugger defines a number of default windows and
maintains three default displays:
• A display of source lines (SRC)
• A display of debugger output (OUT)
• A display of register contents (REG)
The bottom lines on the screen are reserved for debugger commands. (These lines also
receive program output, unless the program specifies otherwise.)

17-38

Debugging VAX FORTRAN Programs

17 .8.1 Invoking and Terminating Screen Mode
To use screen mode debugging, press the PF3 key or enter the SET MODE SCREEN
command. Two displays appear on the screen by default:
• SRC, the default source display, appears in window Hl (the top half of your screen).
The SRC display, by default, points to the next executable source line and shows the
four lines preceding and following it. The entire source program is available through
scrolling, as long as the conditions for normal source display are met (see Section
17.8.3.2 for a list of these conditions).
• OUT, the default output display, appears in window H2 (the bottom half of your
screen). The OUT display, by default, shows debugger output, such as responses to
SHOW and EXAMINE commands. (The 100 most recent lines of debugger output are
available through scrolling.)
The display name and characteristics are placed on the title line of the window.
The following screen appears when you execute a STEP command followed by a SET
MODE SCREEN command when debugging program unit MAIN:
-SRC: Module MAIN-source-scroll---------1:
PROGRAM MAIN
INTEGER I/1/, J/11/, K/21/
2:
REAL ARRMNC10:20)/11*14.5/
3:
CALL SUB1CI>
-> a:
5:
CALL SUB2CJ>
G:
END
-OUT-outPUt-----------------------------stepped to MAIN
4:
CALL SUB1CI>

DBG>SET MODE SCREEN
DBG>STEP
DBG>

Note: The arrow at the left side of the SRC display indicates the next statement to be
executed.
The debugger makes the third display, REG, available but not visible by default; the REG
display shows the current contents of machine registers.

Debugging VAX FORTRAN Programs

17-39

To see existing screen displays (including those not currently displayed on the screen),
specify the SHOW DISPLAY command. The information is displayed in the OUT display
area.
-SRC: module MAIN-source-scroll----------------------> 1:
PROGRAM MAIN
INTEGER 1/1/, J/11/, K/21/
2:
3:
REAL ARRMNC10:20l/11*14.5/
CALL SU51(1)
a:
CALL SU52(J)
5:
G:
END
-OUT-outPUt------------------------------------------disPlaY SRC at Hl, size = 50
kirtd = SOURCE <EXAMINE/SOURCE ,o
disPlaY REG at R21 size
5, removedt kind =REGISTER
disPlaY OUT at H21 size = 1001 kind =NORMAL

DBG>SET MODE SCREEN
DBG>SHOW DISPLAY
DBG>

When debugger output from a single command exceeds the dimensions of the OUT display
(the output from the SHOW WINDOW command, for example), the beginning of the
display is not visible. To view the entire display, you can scroll the display (see Section
17 .8.3.1), place the display into window FS (full screen) or another large screen region (see
Section 17.8.3.2) or terminate screen mode (SET MODE NOSCREEN) before entering the
command. ·(A subsequent SET MODE SCREEN command restores the screen displays.)

17.8.2 Defining Windows
The debugger provides a number of default windows that allow you to treat the entire
screen as a single window (FS) or divide the screen into halves (Hl,H2), into thirds
(Tl,T2,T3), or into quarters (Ql,Q2,Q3,Q4). In addition, the debugger defines a number of
windows that combine the fractional screens; for example, window Q12 refers to the top two
quarters of the screen (same as Hl) and window T23 refers to the bottom two thirds of the
screen. Most of the debugger windows hold any type of display; however, three windows
(Rl,R2,R3), each one third of the screen, are reserved for register displays.
A window is defined by its top line and the number of lines that it can hold. For example,
the window Hl is defined as Hl (1,9) and H2 as H2 (11,9). You can use the SET WINDOW
command to define your own windows; however, with all of the default windows, your own
definitions are usually superfluous.
Use the SHOW WINDOW command to display the name and dimensions of all windows
currently defined. Use the CANCEL WINDOW command to delete one or more windows.

17-40

Debugging VAX FORTRAN Programs

17.8.3 Manipulating Displays
You can manipulate screen displays in several ways, including showing them on the screen,
scrolling forward or backward through them, and removing them from the screen.
You can use the following pseudo-display names to reference displays in debugger commands:
The current (most recently viewed) display
%CURD ISP
The next display in the list
%NEXTDISP
%NEXTOUTPUT The next output display
%NEXTSCROLL The next scrolling display
%NEXTSOURCE The next source display

17.8.3.1 Scrolling Screen Displays
The SCROLL command allows you to show different parts of a display on the screen. The
SELECT/SCROLL command determines which display is affected by the SCROLL command. For example, to establish the SRC display as the default scrolling display, specify:
DBG> SELECT/SCROLL SRC

The SRC display remains the default parameter of the SCROLL command until you
specify another SELECT/SCROLL command. Using key 3 on the keypad, you can step
through the scrolling displays until you get the display that you want.
·
To display the previous 5 lines of source code, you could specify:
DBG> SCROLL/UP:5

Typically, however, you scroll a display using the keypad keys:
• Up-key 8 scrolls towards the beginning of the display by entering the SCROLL/UP
command. To scroll to the top of the display, press PFl followed by key 8.
• Down-key 2 scrolls towards the end of the display by entering the SCROLL/DOWN
command. To scroll to the bottom of the display, press PFl followed by key 2.
• Left-key 4 scrolls towards the left of the display by entering the SCROLL/LEFT
command.
• Right-key 6 scrolls toward the right of the display by entering the SCROLL/RIGHT
command.
Keypad key 5 refreshes the current source display (SRC, by default), causing the next
source line to be executed (marked with an arrow at the left of the source display) to appear
in the middle of the display.

17.8.3.2 Creating Screen Displays
In addition to the default displays, you can define other source, output, and register
displays. To create a display, use the SET DISPLAY command:
SET DISPLAY display-name [AT window] [type]

Debugging VAX FORTRAN Programs

17-41

You must specify a display name; optionally, you can specify the window into which the
display is mapped and the type of display to create. The following display types are
available:
• DO (command-list)-display contains the results of the debugger commands specified
in the command list. The command list is executed each time the debugger regains
control. If you specify more than one command, separate the commands using semicolons.
• NORMAL-display contains all debugger output, but only if the display is selected for
output with the SELECT/OUTPUT command. By default, the OUT display is selected for output.
• REGISTER-display contains the VAX registers and their contents; the display is
updated each time the debugger regains control. The REG display is type REGISTER.
• SOURCE-display contains the program source statements, but only if the display is
selected for source display with the SELECT/SOURCE command.
• SOURCE (command-list)-display contains the results of the debugger commands
specified in the command list, but only if the display is selected for source display with
the SELECT/SOURCE command. The command list, which should consist of a single
TYPE or EXAMINE/SOURCE command, is executed each time the debugger regains
control. The SRC display is type SOURCE with a command list of
EXAMINE/SOURCE .O\%PC (examine the source line in the current module at the
location that is in the program counter). By default, the SRC display is selected for
source display.
The following example defines a display XYZ to be shown in window T2 on the screen.
Each time the debugger regains control, it executes the DO command list (here the
EXAMINE command) and lists the results in display XYZ:
-SRC: Module CIRCLE-source-scroll----------------- > 1:
PROGRAM CIRCLE
2:
DD I= 1,311
3: LI
TYPE 5
FORMAT (' enter radius value ')
LI: 5
ACCEPT 10,RADIUS
5:
G: 10
FORMAT IFG,2l
-XYZ---------------------------------------------CIRCLE\AREA:
0.0000000
CIRCLE\RADIUS: 0.0000000

-OUT-output---------------------------------------

DBG>SET DISPLAY XYZ AT T2 DO !EXAMINE AREA,RADIUSl
DBG>SET BREAK %LINE 8
DBG>

17-42

Debugging VAX FORTRAN Programs

17.8.3.3 Accessing Displays
To control the display of different screen displays, you can use keypad keys or the
DISPLAY command. Typically, the keypad keys (key 9 and key minus) are used for this
operation:
• Key 9 performs the DISPLAY %NEXTDISP command; it displays the next display on
the debugger's current list. Repeated use of this key causes the debugger to step
through the displays in the display· list.
•Key minus(-) performs the DISPLAY %NEXTDISP AT FS and SELECT/SCROLL
%CURDISP commands. It displays the next display in the display list on the full
screen, covering any other displays that are currently visible. It also establishes this
new display as the current scrolling display. Repeated use of this key allows you to step
through you displays, displaying each one at window FS (the full screen).

17.8.3.4 Removing Screen Displays
You can use the CANCEL DISPLAY command to delete displays that you previously set.

17.9 Sample Debugging Sessions
This section contains two FORTRAN programs and the listings (with comments) of sample
debugging sessions that control the execution and analyze the effects of the programs. The
second debugging session (Section 17.9.2) is particularly important because it shows how to
access symbols in a multi-unit program.

17.9.1 Debugging a FORTRAN Program Unit
Figure 17-2 illustrates a program that requires debugging. The program was compiled and
linked without diagnostic messages from either the compiler or the linker. (Appendix E
summarizes compiler diagnostic messages.) However, the program produces erroneous results because of a missing asterisk in the exponentiation operator (RADIUS*2 should be
RADIUS**2). This error is so obvious that you hardly need the services of the debugger to
find it. However, for purposes of illustration, this example deals with the error as though it
were not obvious.
0001
0002
0003

oooa
0005
0006
0007
0008
0008
0010
0011
0012
0013

Figure 17-2:

PROGRAM CIRCLE
DO I= l13tl
TYPE 5
FORMAT (' enter radius value ')
ACCEPT 10 1RADIUS
FORMAT CFG,2>
PI = 3, la15827
AREA = PI*RADIUS*2
TYPE 151 AREA
FORMAT (' area of circle equals '1F10.3)
END DO
STOP
END

Sampl~ FORTRAN Program

Debugging VAX FORTRAN Programs

17-43

The key to debugging is to find out what happens at critical points in your program. To do
this, you need a way to stop execution at these points and look at the contents of program
variables to see if they contain the correct values. Points at which execution is stopped are
called breakpoints. The SET BREAK command lets you specify where you want to stop
the program. You can specify a breakpoint at the beginning of a routine or at a specific line.
To look at the contents of a location, use the EXAMINE command. To resume execution,
use either the GO or STEP command. The DEBUG commands relevant to FORTRAN are
discussed in subsequent sections of this chapter.
Figure 17-3 is an example of typical terminal dialog for a debugging session. The circled
numbers are keyed to notes that follow the figure and explain the dialog.
S FORTRAN/LIS1/NOOPTIMIZE/DEBUG
S LINK/DEBUG CIRCLE
S RUN CIRCLE

CIRCLE

VAX DEBUG Version 4.1-2
%DEBUG-I-INITIAL1 lansuase is FORTRAN, Module set to 'CIRCLE' 0
DBG> SET BREAK %LINE 8
0
DBG> GO
0
enter radius value

za.

breaK at CIRCLE\%LINE 8
8:
AREA = PI*RADIUS*2
DBG > E)<AM I NE PI
CIRCLE\PI:
3+141593
DBG> EXAMINE RADIUS
CIRCLE\RADIUS: 2a.oooooo
DBG> EXAMINE AREA
CIRCLE\AREA:
0+0000000
DBG> GO
area of circle equals
150.796
enter radiu~ value
3.

breaK at CIRCLE\%LINE 8
8:
AREA = PI*RADIUS*2
DBG> CANCEL BREAK %LINE 8
DBG> GO
area of circle equals
18+850
enter radius value
13.
area of circle equals
81+681
%DEBUG-I-EXITSTATUS, is '%SYSTEM-S-NDRMAL1 norMal successful COMPietion'
DBG> E)<IT
4D
$

Figure 17-3: Sample Debugging Session

17-44

Debugging VAX FORTRAN Programs

Invoke the FORTRAN compiler, specifying the qualifiers shown. You should include
the /NOOPTIMIZE qualifier when you use symbolic debugging.

Link your program using the /DEBUG qualifier to include a symbol table for the
debugger.

In response to the RUN command, the debugger displays its identification, indicating
that your program will be executed under the debugger's control. Following the identification message, the debugger displays an initial message, identifying the language and
module settings it has assumed. The debugger derives these mode settings from the first
module specified in the LINK command. If this message does not appear, or if the
settings assumed are not appropriate, use the SET LANGUAGE and SET MODULE
commands.
Set a breakpoint at an appropriate point in the program. This point should be one at
which you are able to examine key variables. Note: Breakpoints suspend execution just
before the point specified.

Begin program execution. The debugger displays the point at which execution starts.

The debugger annou11ces that it has suspended execution at the specified breakpoint.

Examine the variable PI to make sure that the correct value is stored there. The
debugger displays the contents of PI, showing that its scope is in module CIRCLE.

Examine the variable RADIUS. The debugger shows that the specified value has been
properly stored.

Examine the variable AREA.

CID

Resume execution. The debugger displays a message indicating the point of program
resumption.

Cancel the breakpoint at line 8 so that subsequent calculations will not be interrupted.

Successful completion of the program is indicated by this message. However, as you can
see, the results are incorrect.

Exit from the debugger.

By examining the variables Pl, RADIUS, and AREA as the program is executing, you can
determine that the correct values are being stored. It follows, then, that the error is probably in the expression of the formula for computing the area. To correct.the problem, you
must edit and recompile the source program, with the exponentiation operator properly
specified in the formula expression.

Debugging VAX FORTRAN Programs

17-45

17.9.2 Debugging a FORTRAN Program with Subprograms
This section shows how you can use some of the debugging commands and concepts discussed in the preceding sections, and gives the responses you might expect from the debugger. Figure 17-4 illustrates a program with three program units:
0001
0002
0003

oooa
0005
0006
0001
0002
0003

oooa
0005
0001
0002
0003

oooa
0005

PROGRAM MAIN
INTEGER 1/1/, J/11/, K/21/
REAL ARRMNC10:20l/11*1a.5/
CALL SUB1Cil
CALL SUB2CJ)
END
SUBROUTINE SUB1CMl
INTEGER M1N/5/ t L/31/

M= M+ 1
RETURN
END
SUBROUTINE SUB2CNl
INTEGER M/G/, N 1K/a1/, L/51/

N = N + 1
RETURN
END

Figure 17-4: Sample FORTRAN Program with Subprograms

Figure 17-5 is the sample debugging session. It illustrates in particular how to specify
addresses to the debugger when several program units are involved in the session and when
a symbol is not unique in the symbol table. The circled numbers are keyed to explanatory
notes following the session.
VAX DEBUG Version a.1-2
%DEBUG-I-INITIAL, lansuase is FORTRANt Module set to 'MAIN' 0
DBG> EXAMINE ARRMNC1)
e
%DEBUG-I-SUBOUTBND1 subscriPt 1 is out of bounds; value is 1, bounds are
10:20
%DEBUG-W-NOACCESSR1 no read access to virtual address 000001DC
DBG> EXAMINE ARRMNC1Bl:ARRMNCK-Il
0
MAIN\ARRMNC18): 1a.50000
MAIN\ARRMNC18): 1a.50000
MAIN\ARRMNC20): 1a.50000
DBG> E>{AMINE L
0
%DEBUG-W-NOSYMBOL1 SYMbol 'L' is not in the SYMbol table
DBG> SHOW MODULE
0

17-46

Debugging VAX FORTRAN Programs

111odule na111e

S>'111bols

lansuase

size

MAIN
SUB1
SUB2
SHARE$DEBUG
SHARE$DBGSSISHR
SHARE$LIBRTL
SHARE$FORRTL
SHARE$LBRSHR
SHARE$MTHRTL
SHARE$PLIRTL
SHARE$SCRSHR
SHARE$SMGSHR

>'es
no
no
no
no
no
no
no
no
no
no
no

FORTRAN
FORTRAN
FORTRAN
I ri1a s e
I 111 as e
I 111 as e
I 111 a se
I 111 as e
I 111 as e
I 111 as e
I 111 as e
I 111a s e

660

aao

ass
(l
(l
(l
(l
(l
(l
(l
(l
(l

total Modules: 12,
re111ainins size: 536Gt'.l,
DBG> SET MODULE/ALL
0
f)
DBG> rnAMINE L
%DEBUG-W-NOUNIQUE1 SYMbol 'LI is not uni~ue
DBG> EXAMINE SUB1\L
Q
SUB1\L: 31
DBG> SET SCOPE SUB1
DBG > E}<AM I NE N
SUBl\N: 5
DBG> EXAMINE M
~
%DEBUG-W-SYMNOTACT1 SYMbol SUB1\M not active or not in active scope
DBG> SET BREAK %LINE 3
~
DBG> SHOW BREAK
breakpoint at SUB1\%LINE 3
DBG> GO
break at SUB1\%LINE 3
3:

= M + 1

DBG> rnAMINE
MAIN\!: 1
DBG> STEP
stepped to SUB1\%LINE a
a:
RETURN
DBG> rnAMINE ,
MAIN\!: 2
DBG > E>( IT
$

Figure 17-5: Sample Multiunit Debugging Session
0

The debugger indicates that the language is FORTRAN and the module is set to
program unit MAIN (that is, symbols contained in MAIN have been placed in the
symbol table).

Attempt to examine an out-of-bounds array element. The debugger issues a warning.

Examine contents of array elements 18 through 20 (expression K-I). The debugger
prints their values.

Debugging VAX FORTRAN Programs

17-47

Attempt to examine the variable L. However, the debugger announces that this symbol
is not in the symbol table.

Use SHOW MODULE to see which program units have symbols in the symbol table.

Place all symbols in the symbol table.

Examine variable L again. The debugger indicates that this symbol is duplicated in the
symbol table.

Explicitly specify variable Lin program unit SUBl. The debugger successfully displays
the contents of L.

Examine the variable N after issuing the SET SCOPE command. Program unit SUBl
is now the scope and N is examined.

4D>

Attempt to examine a dummy argument. This produces an informational message from
the debugger, warning that the symbol Mis not within the PC scope. Because it is only
correct to examine a dummy argument within the routine declaring it, the value displayed for M is unpredictable.

Set a breakpoint at program address %LINE 3 and begin program ececution (GO). The
debugger identifies the starting point and breakpoint. Execution stops at line 3 in
SUBl.

Examine variable I located in program unit MAIN. (This symbol is unique in the
symbol table and so is examined successfully even though the scope is set to SUBl.)

Step to line 4 (RETURN) in SUBl check the value of the current location. Notice that
the previous EXAMINE command established the variable I in routine MAIN as the
current location.

17-48

Debugging VAX FORTRAN Programs

Chapter 18

Error Processing
During execution, your program may encounter errors or exception conditions. These conditions can result from errors that occur during 1/0 operations, from invalid input data,
from argument errors in calls to the mathematical library, from arithmetic errors, or from
system-detected errors. The Run-Time Library provides default processing for error conditions, generates appropriate messages, and takes action to recover from errors whenever
possible. You can, however, explicitly supplement or override default actions by using:
• The error (ERR) and end-of-file (END) specifiers in 1/0 statements to transfer control
to error-handling code within the program.
• The 1/0 status specifier (!OSTAT) in 1/0 statements to identify FORTRAN-specific
errors based on the value of IOSTAT.
• The VAX condition-handling facility (including user-written condition handlers) to
tailor error processing to the special requirements of your applications. Note: Information about user-written condition handlers is provided in the VAX FORTRAN User's
Guide.
These error-processing methods are complementary; you can use them within the same
program. However, before attempting to write a condition handler, you should be familiar
with the VAX condition-handling facility and with the condition-handling description in
the VAX/VMS Run-Time Library Reference Manual and the VAX FORTRAN User's
Guide.
This chapter describes how the Run-Time Library processes errors. It also provides information about using 1/0 specifiers for explicit error processing and control, and shows how
these methods affect the default error processing of the Run-Time Library.

18.1 Run-Time Library Default Error Processing
The Run-Time Library contains condition handlers that process a number of errors that
may occur during FORTRAN program execution. A default action is defined for each
FORTRAN-specific error recognized by the Run-Time Library. The default actions described throughout this chapter occur unless overridden by explicit error-processing methods.

18-1

How the Run-Time Library actually processes errors depends upon several factors: how
severe the error is, whether an 1/0 error-handling specifier or a condition handler was used,
and whether the error permits continuation.
Table 18-1 lists the FORTRAN-specific errors processed by the Run-Time Library. For
each error, the table shows the message text, the symbolic condition name, the FORTRANspecific error code, and the severity code. (Note: Refer to Table E-4 for more detailed
descriptions of errors processed by the Run-Time Library.)
The condition symbols shown in the left column are the status codes signaled by the
FORTRAN RTL 1/0 support routines. You can define these symbolic values in your program by including the module $FORDEF from the system-supplied default library FORSYSDEF. TLB.
The error numbers shown in the second column are the standard Digital FORTRAN errors
numbers that are compatible with other versions of Digital FORTRAN. These are the error
values returned to IOSTAT variables when an 1/0 error is detected. They are also used to
index the error table maintained by the ERRSET and ERRTST subroutines. See Appendix
B in the VAX FORTRAN User's Guide for descriptions of the ERRSET and ERRTST
subroutines.
The codes in the third column indicate the severity of the error conditions. All FORTRANspecific errors have severity codes of either error (E) or severe error (F). As shown in the
table, most FORTRAN-specific errors are severe. If no explicit recovery action is specified
for a severe error, program execution terminates by default.
The letter C in the "Severity" column of the table means that you can continue execution
immediately after the error, if a user-written condition handler specifies that execution
should continue. If there is no letter C in the "Severity" column, you cannot continue
execution immediately after the error. If you attempt to do so, program execution terminates.
When errors occur for which no recovery method is specified, the program exits; that is, an
error message is printed and execution of the program terminates. To prevent program
termination, you must include an appropriate 1/0 error-handling specifier (see Sections
18.2 and 18.3) or a condition handler that performs an unwind (see Chapter 6 in the VAX
FORTRAN User's Guide).

18-2

Error Processing

Table 18-1: Summary of FORTRAN Run-Time Errors
FORTRAN
Condition Symbol

Error
Number

Severity

Message Text

FOR$_NOTFORSPE

not a FORTRAN-specific error

FOR$_SYNERRNAM

syntax error in NAMELIST input

FOR$_TOOMANVAL

too many values for NAMELIST variable

FOR$-1NVREFVAR

invalid reference to variable in NAMELIST input

FOR$-REWERR

REWIND error

FOR$_DUPFILSPE

duplicate file specifications

FOR$-1NPRECTOO

input record too long

FOR$--13ACERR

BACKSPACE error

FOR$_ENDDURREA

end-of-file during read

FOR$-RECNUMOUT

record number outside range

FOR$_0PEDEFREQ

OPEN or DEFINE FILE required

FOR$_TOOMANREC

too many records in I/O statement

FOR$_CLOERR

CLOSE error

FOR$_FILNOTFOU

file not found

FOR$_0PEFAI

open failure

FOR$_MIXFILACC

mixed file access modes

FOR$-1NVLOGUNI

invalid logical unit number

FOR$_ENDFILERR

ENDFILE error

FOR$_UNIALROPE

unit already open

FOR$_SEGRECFOR

segmented record format error

FOR$_ATTACCNON

attempt to access non-existent record

FOR$-1NCRECLEN

inconsistent record length

FOR$_ERRDURWRI

error during write

FOR$_ERRDURREA

error during read

FOR$-RECIO_OPE

recursive I/O operation

FOR$-1NSVIRMEM

insufficient virtual memory

FOR$_NO_SUCDEV

no such device

FOR$_FILNAMSPE

file name specification error

Error Processing

18-3

Table 18-1 (Cont.): Summary of FORTRAN Run-Time Errors
FORTRAN
Condition Symbol

Error
Number

Severity

Mes~age Text

FOR$-1NCRECTYP

inconsistent record type

FOR$_KEYVALERR

keyword value error in OPEN statement

FOR$-1NCOPECLO

i~consistent OPEN/CLOSE parameters

FOR$_WRIREAFIL

write to READONLY file

FOR$-1NVARGFOR

invalid argument to FORTRAN RunTime Library

FOR$-1NVKEYSPE

invalid key specification

FOR$_1NCKEYCHG

inconsistent key change or duplicate key

FOR$-1NCFILORG

inconsistent file organization

FOR$_SPERECLOC

specified record locked

FOR$_NO_CURREC

no current record

FOR$_REWRITERR

REWRITE error

FOR$_DELERR

DELETE error

FOR$_UNLERR

UNLOCK error

FOR$_FINERR

FIND error

FOR$-1...ISIO_SYN

F,C

list-directed I/0 syntax error

FOR$-1NFFORLOO

infinite format loop

FOR$_FORVARMIS

F,C

format/variable-type mismatch

FOR$_SYNERRFOR

syntax error in format

FOR$_0UTCONERR

E,C

output conversion error

FOR$-1NPCONERR

F,C

input conversion error

FOR$_0UTSTAOVE

output statement overflows record

FOR$-1NPSTAREQ

input statement requires too much data

FOR$_VFEVALERR

F,C

variable format expression value error

SS$-1NTOVF

F,C

arithmetic trap, integer overflow

SS$-1NTDIV

F,C

arithmetic trap, integer zero divide

SS$_FLTOVF

F,C

arithmetic trap, floating overflow

SS$_FLTOVF_F

F,C

arithmetic fault, floating overflow

SS$_FLTDIV

F,C

arithmetic trap, zero divide

18-4

Error Processing

Table 18-1 (Cont.): Summary of FORTRAN Run-Time Errors
FORTRAN
Condition Symbol

Error
Number

Severity

Message Text

SS$__FLTDIV_F

F,C

arithmetic fault, zero divide

SS$__FLTUND

F,C

arithmetic trap, floating underflow

SS$__FLTUND_F

F,C

arithmetic fault, floating overflow

SS$_SUBRNG

F,C

subscript out of range

MTH$_WRONUMARG

wrong number of arguments

MTH$-1NVARG MAT

invalid argument to math library

MTH$_UNDEXP

F,C

undefined exponentiation

MTH$_LOGZERNEG

F,C

logarithm of zero or negative value

MTH$_SQUROONEG

F,C

square root of negative value

MTH$-8IGLOSMAT

F,C

significance lost in math library

MTH$__FLOOVEMAT

F,C

floating overflow in math library

MTH$__FLOUNDMAT

F,C

floating underflow in math library

FOR$_ADJARRDIM

F,C

adjustable array dimension error

Notes
1. The ERR transfer is taken after completion of the I/0 statement for continuable errors
numbered 59, 61, 63, 64, and 68; the resulting file status and record position are the
same as though no error had occurred. However, other I/0 errors take the ERR transfer
as soon as the error is detected; thus, file status and record position are undefined.

2. If no ERR address has been defined for error 63, the program continues after the error
message is printed. The entire overflowed field is filled with asterisks to indicate the
error in the output record.
3. Function return values for errors numbered 82, 83, 84, 87, 88, and 89 can be modified by
means of user-written condition handlers. See the VAX FORTRAN User's Guide and
the VAX/VMS Run-Time Library Reference Manual for information about user-written condition handlers.
4. Error number 1 (FOR$_NOTFORSPE) indicates that an error was detected that was
not a :FORTRAN-specific error; that is, it was not reportable through any other message in the table. If you call ERRS NS, an error of this kind returns a value of 1. Use the
fifth argument of the call to ERRS NS (condval) to obtain the unique system condition
value that identifies the error. Refer to Appendix D.4.3 for more information.

Error Processing

18-5

Notes (Cont.)
5. If error number 93 (FOR$_ADJARRDIM) occurs and a user-written condition handler
causes execution to continue, any reference to the array in question will cause an access
violation.
Refer to Table E-4 for more detailed descriptions of errors processed by the Run-Time
Library.

18.2 Using the ERR and END Specifiers
When a severe error occurs during program execution, the Run-Time Library default action
is to print an error message and terminate the program. You can use the ERR and END
specifiers in I/0 statements to override this default by transferring control to a specified
point in the program. No error message is printed, and execution continues at the desigriated statement. For example, assume that a program contains this WRITE statement:
WRITE

cs,50,ERR=aOOl

If an error occurs during execution of this statement, the Run-Time Library transfers
control to the statement at label 400. Similarly, you can use the END specifier to handle an
end-of-file condition that might otherwise be treated as an error. For example:
READ

c1z,70,END=550)

You can also specify ERR as a keyword in an OPEN, CLOSE, or INQUIRE statement. For
example:
OPEN

CUNIT=lOt FILE='FILNAM', STATUS='OLD', ERR=999l

If an error is detected during execution of this OPEN statement, control transfers to
statement 999.

18.3 Using the IOSTAT Specifier
You can use the IOSTAT specifier to continue program execution after an I/0 error and to
return information about I/O operations. It can supplement or replace the END and ERR
transfers. Execution of an VO statement containing the IOSTAT specifier suppresses printing of an error message and causes the specified integer scalar memory reference to become
defined as one of the following:
• A value of -1 if an end-of-file condition occurs
• A value of 0 if neither an error condition nor an end-of-file condition occurs
• A positive integer value if an error condition occurs (this value is one of the
FORTRAN-specific error numbers listed in Table 18-1)

18-6

Error Processing

Following execution of the 1/0 statement and assignment of an IOSTAT value, control
transfers to the END or ERR statement label, if any. If there is no control transfer, normal
execution continues.
You can include SYS$LIBRARY:FORSYSDEF.TLB($FORIOSDEF) in your program to
obtain symbolic definitions for the values of IOSTAT. The symbolic names in this file have
a form similar to the FORTRAN condition symbols:

Condition symbol

IOSTAT value

FOR$_error

FOR$IOS_error

Note that the values of the IOSTAT symbols are not the same as the values of the condition symbols described in Table 18-1.
The following example uses the IOSTAT specifier and the FORIOSDEF module to detect
and process an OPEN error.
CHARACTER*aO FILN
INCLUDE '($FORIOSDEF>
ACCEPT*' FILN
OPEN CUNIT=11 FILE=FILN1 STATUS='OLD', IOSTAT=IERR1 ERR=100)
I

(process the inPut file>

100

IF CIERR .EQ. FOR$10S_FILNOTFOU) THEN
TYPE*' 'File:', FILN1 'Does not exist1 enter new filenaMe'
ELSE IF CIERR .EQ. FOR$IOS_FILNAMSPE> THEN
TYPE*' 'File:'1 FILN1 'Was bad1 enter ne1A1 filenaflie'
ELSE
TYPE*' 'Unrecoverable error1 code ='' !ERR
STOP
END IF
GO TO 10
END

Error Processing

18-7

b!~~]!EHnl[~Dlt £

b\rrilrruaUa®uu©J~ rL®rrTI~[H®WJ® lE~®uuu®~uu~
For the purpose of facilitating compatibility with other versions of FORTRAN, VAX
FORTRAN includes the statements ENCODE, DECODE, DEFINE FILE, and FIND, and
it offers alternative syntax for the PARAMETER statement and octal constants. These
language elements are particularly useful in transporting older FORTRAN programs to
VAX, but should be avoided in new FORTRAN programs for use on VAX systems and in
new programs for which portability to other FORTRAN-77 implementations is important.
The ANSI FORTRAN-77 interpretation of the EXTERNAL statement is incompatible
with the previous standard and with previous DIGITAL implementations of FORTRAN.
Section A.6 describes the interpretation of the EXTERNAL statement that applies when
the /NOF77 compiler command qualifier is used.

The ENCODE and DECODE statements transfer data between variables or arrays in
internal storage and translate that data from internal to character form, and vice versa,
according to format specifiers. Similar results can be accomplished using internal files with
formatted sequential WRITE and READ statements.
The ENCODE and DECODE statements have the forms:
ENCODE (c,f,b[,IOSTAT =ios][,ERR=s]) [list]
DECODE (c,f,b[,IOSTAT =ios][,ERR=s]) [list]

where:
c
is an integer expression. In the ENCODE statement, c is the number of characters
(bytes) to be translated to character form. In the DECODE statement, c is the
number of characters to be translated to internal form.
is a format identifier. If more than one record is specified, an error occurs.

A-1

is a scalar reference or array name reference. In the ENCODE statement, b receives
the characters after translation to external form. In the DECODE statement, b contains the characters to be translated to internal form.
ios

is an integer scalar memory reference that is defined as a positive integer if an error
occurs, and as a zero if no error occurs.
s
is the label of an executable statement.
list

is an I/0 list. In the ENCODE statement, the 1/0 list contains the data to be translated to character form. In the DECODE statement, the list receives the data after
translation to internal form.

Considerations/Restrictions
o The ENCODE statement translates the list elements to character form according to

the format specifier, and stores the characters in b, as does a WRITE statement. If
fewer than c characters are transmitted, the remaining character positions are filled
with spaces.
o The DECODE statement translates the character data in b to internal (binary) form

according to the format specifier, and stores the elements in the list, as does a READ
statement.
0

If b is an array, its elements are processed in the order of subscript progression.

The number of characters that the ENCODE or DECODE statement can process
depends on the data type of b. For example, an INTEGER*2 array can contain two
characters per element, so that the maximum number of characters is twice the number of elements in that array. A character variable or character array element can
contain characters equal in number to its length. A character array can contain characters equal in number to the length of each element multiplied by the number of
elements.

The interaction between the format specifier and the I/0 list is the same as for a
formatted I/0 statement.

E>rnmples
An example of the ENCODE and DECODE statements follows:

100

A-2

DIMENSION K(3)
CHARACTER*12 A,B
DATA A/'123456789012'/
DECODE ( 12 t100 , A) K
FORMAT (3!4l
ENCODE (12t100,Bl K(3)1 K(2l1

Additional Language Elements

K(ll

The DECODE statement translates the 12 characters in A to integer form (specified by
statement 100) and stores them in array K, as follows:
K(1) = 1234
K(2) = 5678
K(3) = 9012

The ENCODE statement translates the values K(3), K(2), and K(l) to character form and
stores the characters in the character variable B as follows:
B = '901256781234'

The DEFINE FILE statement establishes the size and structure of relative organization
files and associates them with a logical unit number. The OPEN statement performs the
same function, and its use is preferred.
The DEFINE FILE statement has the form:
DEFINE FILE u (m,n,U,asv)[,u(m,n,U,asv)] ...

where:
u

is an integer constant or variable that specifies the logical unit number.
m

is an integer constant or variable that specifies the number of records in the file.
n

is an integer constant or variable that specifies the length of each record in 16-bit
words (2 bytes).

u
specifies that the file is unformatted (binary); this is the only acceptable entry in this
position.
asv

is an integer variable, called the associated variable of the file. At the end of each
direct access I/0 operation, the record number of the next higher numbered record in
the file is assigned to v; asv must not be a dummy argument.
The DEFINE FILE statement specifies that a file containing m fixed-length records, each
composed of n 16-bit words, exists (or is to exist) on the specified logical unit. The records
in the file are numbered sequentially from 1 through m.
A DEFINE FILE statement must be executed before the first direct access I/O statement
referring to the specified file, even though the DEFINE FILE statement does not itself open
the file. The file is actually opened when the first direct access I/0 statement for the unit is
Additional Language Elements

A-3

executed. If this I/O statement is a WRITE, a new relative organization file is created. If it
is a READ or FIND, an existing file is opened-unless, of course, the specified file does not
exist, in which case an error occurs.
The DEFINE FILE statement also establishes the integer variable asv as the associated
variable of a file. At the end of each direct access 1/0 operation, the FORTRAN I/O system
places in asv the record number of the record immediately following the one just read or
written. Because the associated variable always points to the next sequential record in the
file (unless the associated variable is redefined by an assignment, input, or FIND statement), direct access I/0 statements can perform sequential processing on the file. They do
this by using the associated variable of the file as the record number specifier.
For example:
DEFINE FILE 3 c1000,as,u1NREC)

This statement specifies that logical unit 3 is to be connected to a file of 1000 fixed-length
records; each record is forty-eight 16-bit words long. The records are numbered sequentially
from 1 through 1000 and are unformatted. After each direct access I/0 operation on this
file, the integer variable NREC will contain the record number of the record immediately
following the record just processed.

A FIND statement is similar to a direct access READ statement with no I/O. list and can
result in the opening of an existing file. The FIND statement positions a relative organization file to a particular record and sets the associated variable of the file to that record
number. No data transfer takes place. See the description of the OPEN statement's ASSOCIATEVARIABLE keyword or the DEFINE FILE statement for information about associate variables.
The FIND statement has the forms:
FIND (u 'r[,ERR=s][,IOSTAT =ios])
FIND ([UNIT =]u,REC=r[,ERR=s][,IOSTAT =ios])

where:
u

is a logical unit number.
is the direct access record number.
s
is the label of the executable statement to which control is to be transferred if no error
occurs.

A-4

Additional Language Elements

ios

is an integer variable or integer array element that is defined as a positive integer if an
error occurs, and as a zero if no error occurs.
The unit number must refer to a relative organization file.
The record number cannot be less than one or greater than the number of records defined
for the file.
For example:
FIND

Cl'l)

This statement positions logical unit 1 to the first record of the file; the file's associated
variable is set to one.
FIND

(l'.j I IND)-()

This statement positions the file to the record identified by the content of INDX; the file's
associated variable is set to the value of INDX.

The PARAMETER statement has two forms. Both forms of the PARAMETER statement
assign a symbolic name to a constant. The PARAMETER statement discussed here differs
from the PARAMETER statement discussed in Section 8.11 in the following ways: its list is
not bounded with parentheses, and the form of the constant, rather than implicit or
explicit typing of the symbolic name, determines the data type of the variable.
The PARAMETER statement has the form:
PARAMETER P=C [,p=c] ...

where:
p

is a symbolic name.
c
is a constant, the symbolic name of a constant, or a compile-time constant expression.
Each symbolic name (p) becomes a constant and is defined as the value of the constant or
constant expression (c). Once a symbolic name is defined as a constant, it can appear in
any position in which a constant is allowed. The effect is the same as if the constant were
written there instead of the symbolic name.
The symbolic name of a constant cannot appear as part of another constant, but it can
appear as a real or imaginary part of a complex constant.
Compile-time constant expressions are defined in Section 8.11.

Additional Language Elements

A-5

You can use a symbolic name in a PARAMETER statement only to identify the symbolic
name's corresponding constant in that program unit. Such a name can be defined only once
in PARAMETER statements within the same program unit.
The symbolic name of a constant assumes the data type of its corresponding constant
expression. The initial letter of the constant's name does not affect its data type. You
cannot specify the data type of a parameter constant in a type declaration statement.
For example:
PARAMETER
PARAMETER
PARAMETER

PI=3,1Q158271 DPI=3.1Q1582G53588783238DO
PIDV2=Pl/21 DPIDV2=DPI/2
FLAG=,TRLJE,, LONGNAME='A STRING OF 25 CHARACTERS'

Octal forms of integer constants are provided for compatibility with PDP-11 FORTRAN.
The octal form of an integer constant is:
"nn

where:
nn

is a string of digits in the range 0 to 7.
Examples of valid and invalid octal integer constants are:

Valid

Invalid (with explanation)

"107
"177777
"17777"

"108
"1377.

(contains a digit outside the allowed range)
(contains a decimal point)
(contains a trailing quotation mark)

Note that these octal forms are not the same as the typeless octal constants discussed in
Section 6.2.1.4. Integer constants in octal form have integer data type and are treated as
integers.

The /NOF77 interpretation of the EXTERNAL statement combines the function of the
INTRINSIC statement with that of the EXTERNAL statement discussed in Section 8.7. It
is available only if the /NOF77 compiler command qualifier is present.
The /NOF77 EXTERNAL statement allows the programmer to use subprograms as arguments to other subprograms. The subprograms to be used as arguments can be either usersupplied procedures or FORTRAN library functions.

A-6

Additional Language Elements

The /NOF77 EXTERNAL statement has the form:
EXTERNAL [•]v[,[•]v) ...

where:
v

is the symbolic name of a subprogram or the name of a dummy argument associated
with the symbolic name of a subprogram.
specifies that a user-supplied function is to be used instead of a FORTRAN library
function having the same name. See Section 10.3 for information on FORTRAN
library functions (intrinsic functions).
The /NOF77 EXTERNAL statement declares that each symbolic name in its list is an
external procedure name. Such a name can then be used as an actual argument to a
subprogram, which in turn can use the corresponding dummy argument in a function
reference or CALL statement.
Note however, that a complete function reference used as an argument represents a value,
not a subprogram name, for example, SQRT(B) in CALL SUBR(A, SQRT(B), C). It is not,
therefore, defined in an EXTERNAL statement (as would be the incomplete reference
SQRT).
An example of the /NOF77 EXTERNAL statement follows:
Main Program

Subprograms

EXTERNAL SIN. COS, *TAN. SINDEG

SUBROUTINE TRIGCX.F.Yl
Y = F<l:<l
RETURN
END

CALL TRIGCANGLE.SIN.SINEl
CALL TRIGCANGLE.COS.COSINEl
CALL TRIGCANGLE.TAN.TANGNTl

FUN CT I ON TAN<}( l
TAN = SINCXl/COSCXl
RETURN
END

CALL TRIGCANGLED.SINDEG.SINEl
FUNCITON SINDEG<Xl
SINDEG
SINCXlX*3.1a158/80l
RETURN
END

Additional Language Elements

A-7

The CALL statements pass the name of a function to the subroutine TRIG. The function
reference F(X) subsequently invokes the function in the second statement of TRIG. Depending on which CALL statement invoked TRIG, the second statement is equivalent to
one of the following:
Y = SIN(X)
Y = COS(X)
Y = TAN(X)
Y = SINDEG(X)
The functions SIN and COS are examples of trigonometric functions supplied in the
FORTRAN library. The function TAN is also supplied in the library. But the asterisk in
the EXTERNAL statement specifies that the user-supplied function be used, instead of
the library function. The function SINDEG is also a user-supplied function. Because no
library function has the same name, no asterisk is required.

A-8

Additional Language Elements

Appendix B

Character Sets
8.1 FORTRAN Character Set
The FORTRAN character set consists of the following:
• All upper- and lowercase letters (A through Z, a through z)
• The numerals 0 through 9
• The following special characters:

Character
6. or TAB

*
I

Name

Character

Space or tab
Equal sign
Plus sign
Minus sign
Asterisk
Slash
Left parenthesis
Right parenthesis
Comma
Period

<
>
%

Name
Apostrophe
Quotation mark
Dollar sign
Underscore
Exclamation point
Colon
Left angle bracket
Right angle bracket
Percent sign
Ampersand

Other printing characters can appear in a FORTRAN statement only as part of a Hollerith
or character constant. Any printing character can appear in a comment. Printing characters are characters whose ASCII codes are in the range 20 through 7D. See Table B-1.

B-1

B.2 ASCII Character Set
Table B-1 represents the ASCII character set. At the top of the table are hexadecimal
digits (0 to 7), and to the left of the table are hexadecimal digits (0 to F). To determine the
hexadecimal value of an ASCII character, use the hexadecimal digit that corresponds to
the row in the "units" position, and use the hexadecimal digit that corresponds to the
column in the "16's" position. For example, the value of the character representing the
equal sign is 3D.
Table B-1: ASCII Character Set

Row

1
2
3
4
5
6
7
8

A
B

D
E

F
NUL
SOH
STX
ETX
EOT
ENQ
ACK
BEL
BS
HT
LF
VT
FF
CR

so
SI
SP

B-2

Column
4

1
2
3
4
5
6
7

A
B

Q
R

a
b

w
x

d
e
f
g
h

[

D
E
F
G
H
I
J
K
L
M
N

k
1
m
n

NUL
SOH
STX
ETX
EOT
ENQ
ACK
BEL
BS
HT
LF
VT
FF
CR

DLE
DCl
DC2
DC3
DC4
NAK
SYN
ETB
CAN
EM
SUB
ESC
FS
GS
RS

so
SI

$
%
&

<
I

Null
Start of Heading
Start of Text
End of Text
End of Transmission
Enquiry
Acknowledge
Bell
Backspace
Horizontal Tabulation
Line Feed
Vertical Tab
Form Feed
Carriage Return
Shift Out
Shift In
Space

Character Sets

DLE
DCl
DC2
DC3
DC4
NAK
SYN
ETB
CAN
EM
SUB
ESC
FS
GS
RS

DEL

s
u

\
1

7
p
q
r
s
t
u
v
w
x
y
z

DEL

Data Link Escape
Device Control 1
Device Control2
Device Control 3
Device Control 4
Negative Acknowledge
Synchronous Idle
End of Transmission Block
Cancel
End of Medium
Substitute
Escape
File Separator
Group Separator
Record Separator
Unit Separator
Delete

Radix-50 is a special character data representation in which up to 3 characters can be
encoded and packed into 16 bits. The Radix-50 character set is a subset of the ASCII
character set and is provided for compatibility with PDP-11 FORTRAN.
The Radix-50 characters and their corresponding code values are:
Character
Space
A-Z
$
(Unassigned)
0-9

ASCII Octal
Equivalent

Radix-50 Value
(Octal)

40
101 - 132
44
56

0
1 - 32
33
34
35
36 - 47

60 - 71

Radix-50 values are stored, up to three characters per word, by packing them into single
numeric values according to the formula:
((i * 50 + j) * 50 + k)

where:
i, j, and I<

represent the code values of three Radix-50 characters.
Thus, the maximum Radix-50 value is:
47*50*50 + 47*50 + 47 = 174777

A Radix-50 constant has the form:
nRc 1c 2 ... cn

where:
n

is an unsigned, nonzero integer constant that states the number of characters to
follow.
c
is a character from the Radix-50 character set.
The maximum number of characters is 12. The character count must include any spaces
that appear in the character string (the space character is a valid Radix-50 character). You
can use Radix-50 constants only in DATA statements.

Character Sets

B-3

Examples of valid and invalid Radix-50 constants are:

Valid

Invalid (with explanation)

4RABCD
6R.0.T0.0..0..0.

4RDKO:

(colon is not a Radix-50 character)

When a Radix-50 constant is assigned to a numeric variable or array element, the number
of bytes that can be assigned depends on the data type of the component (refer to Table
6-1). If the Radix-50 constant contains fewer bytes than the length of the component,
ASCII null characters (zero bytes) are appended on the right. If the constant contains more
bytes than the length of the component, the rightmost characters are not used.

B-4

Character Sets

Appendix C

FORTRAN Data Representation
This appendix describes the data types supported by VAX FORTRAN and illustrates how
they are stored in memory. The symbol :A in any illustration specifies the address of the
byte containing bit 0, the starting address of the data element represented.

C.1 LOGICAL•1 (BYTE) Representation
7

BINARY NUMBER

ZK-797-82

LOGICAL*l (or BYTE) values are in the range -128 to 127.

C.2 INTEGER•2 Representation
15 14

~;_'~'--------B-1N_A_R_v

__N_u_M_s_E_R___________I :A
ZK-798-82

SIGN= O(+), 1(-)

Integers are stored in a twos complement representation. INTEGER*2 values are in the
range -32768 to 32767, and are stored in two contiguous bytes aligned on an arbitrary byte
boundary. For example:
+22 = 0016(hex)
-7 = FFF9(hex)

C-1

C.3 INTEGER•4 Representation
31 30

~'~_ ._,

____________
s1_N_A_R_v_N_u_M_s_E_R_ _ _ _ _ _ _ _ _ _ _ _____.I :A
ZK-799-82

SIGN= O(+), 1(-)

INTEGER*4 values are stored in twos complement representation and lie in the range
-2147483648 to 2147483647. Each value is stored in four contiguous bytes, aligned on an
arbitrary byte boundary. Note that if the value is in the range of an INTEGER*2 value,
that is, -32768 to 32767, then the first word can be referenced as an INTEGER*2 value.

C.4 Floating-Point Representations
The exponent for the REAL*4 and REAL*8 (D_floating) formats is stored in binary excess
128 notation. Binary exponents from -127 to 127 are represented by the binary equivalents
of 1 through 255.
The exponent for the REAL*8 (G_floating) format is stored in binary excess 1024 notation. The exponent for the REAL*16 format is stored in binary excess 16384 notation. In
REAL*8 (G_floating) format, binary exponents from -1023 to 1023 are represented by the
binary equivalents of 1through2047. In REAL*16 format, binary exponents from -16383 to
16383 are represented by the binary equivalents of 1 through 32767.
For each floating-point format, fractions are represented in sign-magnitude notation, with
the binary radix point to the left of the most significant bit. Fractions are assumed to be
normalized, and therefore the most significant bit is not stored (this is called "hidden bit
normalization"). This bit is assumed to be 1 unless the exponent is 0. If the exponent
equals 0, then the value represented is either zero (refer to the section entitled "Representation of 0.0" in VAX FORTRAN User's Guide) or is a reserved operand (refer to the
section entitled "Reserved Operand Faults" in VAX FORTRAN User's Guide).

C.4.1 REAL •4 (F_floating)
REAL*4 (F_floating) data is four contiguous bytes starting on an arbitrary byte boundary.
Bits are labeled from the right, 0 through 31.

C-2

FORTRAN Data Representation

15 14

I
G
N

FRACTION

EXPONENT

:A+2

FRACTION
31

16
ZK-800-82

SIGN= O(+), 1(-)

The form of REAL*4 (F_floating) data is sign magnitude, with bit 15 the sign bit, bits 14:7
an excess 128 binary exponent, and bits 6:0 and 31:16 a normalized 24-bit fraction with the
redundant most significant fraction bit not represented. The value of F_floating data is in
the approximate range: 0.29*10**-38 through l.7*10**38. The precision is approximately
one part in 2**23, that is, typically seven decimal digits.

C.4.2 REAL •8 (D_f loating)
REAL*8 (D_floating) data is eight contiguous bytes starting on an arbitrary byte boundary. Bits are labeled from the right, 0 through 63.
15 14

s
I

EXPONENT

FRACTION

:A+2

FRACTION

:A+4.

FRACTION

:A+6

48
ZK-801-82

SIGN= O(+), 1(-)

The form of REAL*8 (D_floating) data is identical to an F_floating real number, except
for an additional 32 low-significance fraction bits. The exponent conventions and approximate range of values are the same as those for F_floating. The precision is approximately
one part in 2**55, that is, typically 16 decimal digits.

FORTRAN Data Representation

C-3

C.4.3 REAL •8 (G_f loating)
REAL*8 (G_floating) data is eight contiguous bytes starting on an arbitrary byte boundary. The bits are labeled from the right, 0 through 63.
15 14

s
I

EXPONENT

FRACTION

:A+2

FRACTION

:A+4

FRACTION

:A+6

48
ZK-804-82

SIGN= O(+), 1(-)

The form of REAL*8 (G_floating) data is sign magnitude, with bit 15 the sign bit, bits
14:4 an excess 1024 binary exponent, and bits 3:0 and 63:16 a normalized 53-bit fraction
with the redundant most significant fraction bit not represented. The value of a Q_
floating data is in the approximate range 0.56*l0**-308 through 0.9*l0**308. The precision
of G_floating data is approximately one part in 2**52, that is, typically 15 decimal digits.

C.4.4 REAL•16 (H_floating)
REAL*16 (H_floating) data is 16 contiguous bytes starting on an arbitrary byte boundary.
The bits are labeled from the right, 0 through 127.

C-4

FORTRAN Data Representation

15 14

s
I

EXPONENT

FRACTION

:A+2

FRACTION

:A+4

FRACTION

:A+6

FRACTION

:A+8

FRACTION

:A+10

FRACTION

:A+12

FRACTION

:A+14

127

112
ZK-805-82

SIGN = O(+), 1(-)

The form of a REAL*16 (H_floating) data is sign magnitude with bit 15 the sign bit, bits
14:0 an excess 16384 binary exponent, and bits 127:16 a normalized 113-bit fraction with
the redundant most significant fraction bit not represented. The value of H_floating data
is in the approximate range 0.84*10**-4932 through 0.59*10**4932. The precision of H_
floating data is approximately one part in 2**112, that is, typically 33 decimal digits.

FORTRAN Data Representation

C-5

C.4.5 COMPLEX•B (F_floating)
COMPLEX*8 data is eight contiguous bytes aligned on an arbitrary byte boundary. The
low-order four bytes contain REAL*4 data that represents the real part of the complex
number. The high-order four bytes contain REAL*4 data that represents the imaginary
part of the complex number.
76

15 14

s
REAL PART

I
G
N

EXPONENT

FRACTION

:A+2

s
IMAGINARY PART

I
G
N

EXPONENT

FRACTION

:A+4

FRACTION

:A+6

48
ZK-806-82

SIGN= O(+), 1(-)

C.4.6 COMPLEX•16 (D_floating)
COMPLEX*l6 (D_floating) data is 16 contiguous bytes aligned on an arbitrary byte
boundary. The low-order eight bytes contain REAL*8 (D_floating) data that represents
the real part of the complex data. The high-order eight bytes contain REAL*8 (D_floating) data that represents the imaginary part of the complex data.

C-6

FORTRAN Data Representation

15 14

I
G
N

EXPONENT

FRACTION

:A+2

FRACTION

:A+4

FRACTION

:A+6

REAL PART

I
G
N

EXPONENT

:A+S

FRACTION

:A+10

FRACTION

:A+12

FRACTION

:A+14

IMAGINARY PART

127

112
ZK-807-82

SIGN= O(+), 1(-)

C.4. 7 COMPLEX•16 (G_floating)
COMPLEX*16 (G_f1oating) data is 16 contiguous bytes aligned on an arbitrary byte
boundary. The low-order eight bytes contain REAL*8 (G_f1oating) data that represents
the real part of the complex data. The high-order eight bytes contain REAL*8 (G_f1oating) data that represents the imaginary part of the complex data.

FORTRAN Data Representation

C-7

15 14

I
G
N

EXPONENT

FRACTION

:A+2

FRACTION

:A+4

FRACTION

:A+6

REAL PART

I
G
N

EXPONENT

:A+8

FRACTION

:A+10

FRACTION

:A+12

FRACTION

:A+14

IMAGINARY PART

127

112
ZK-808-82

C.5 Logical Representation
Logical values are stored in two or four contiguous bytes, starting on an arbitrary byte
boundary. The low-order bit (bit 0) determines the value. If bit 0 is set, the value is
.TRUE .. If bit 0 is clear, the value is .FALSE ..

C-8

FORTRAN Data Representation

LOGICAL•2
15
TRUE:

1 0

'--~~~~~u-N_D_E_F_1N_E_D_B_1_T_s~~~---"l~1-JI
15

FALSE:

UNDEFINED BITS

ZK-802-82

Insert FA-8

LOGICAL•4
15
TRUE:

1 0
UNDEFINED BITS

UNDEFINED BITS

:A+2

15
FALSE:

UNDEFINED BITS

UNDEFINED BITS
31

:A+2
16
ZK-803-82

FORTRAN Data Representation

C-9

C.6 Character Representation
A character string is a contiguous sequence of bytes in memory.

CHAR 1

•
•
•
CHAR L

:A+L-1

ZK-809-82

A character string is specified by two attributes: the address A of the first byte of the string,
and the length L of the string in bytes. The length L of a string is in the range 1 through
65535.

C. 7 Hollerith Representation
Hollerith constants are stored internally, one character per byte.

1 Byte
7

0
CHAR 1

2 Bytes
15

87
CHAR 2

C-10

FORTRAN Data Representation

0
CHAR 1

4 Bytes
31

24 23
CHAR 4

16 15
CHAR 3

CHAR 2

0
CHAR 1

8 Bytes
87

CHAR 2

CHAR 1

CHAR 4

CHAR 3

:A+2

CHAR 6

CHAR 5

:A+4

CHAR 8

CHAR 7

:A+6

56 55

48
ZK-810-82

FORTRAN Data Representation

C-11

Appendix D

FORTRAN Language Summary
D.1 Expression Operators
This section lists the expression operators in each data type in order of descending precedence:

Table D-1: Expression Operators
Data Type

Operator

Operation

Operates Upon

Arithmetic

**
*,/

Exponentiation

Arithmetic or logical expressions

+,-

Addition, subtraction, unary
plus and minus

Character

Concatenation

Character expressions

Relational

.GT.
.GE.

Greater than
Greater than or equal to

Arithmetic, logical, or character
expressions (all relational operators
have equal precedence)

.LT.

Less than

.LE .

Less than or equal to

.EQ.

Equal to

.NE.

Not equal to

Multiplication, division

D-1

Table D-1 (Cont.): Expression Operators
Data Type

Operator

Operation

Operates Upon

Logical

.NOT.

.NOT.A is true only if A is
false

Logical or integer expressions

.AND.

A.AND .B is true only if A
and B are both true

.OR.

A.OR.B is true if either A or
B or both are true

.EQV.

A.EQV .B is true only if A and
B are both true or A and B
are both false

.NEQV.

A.NEQV .B is true only if A is
true and B is false or B is true
and A is false

.XOR.

Same as .NEQV.

.EQV., .NEQV., and .XOR. have
equal priority

D.2 Statements
This section summarizes the statements available in the VAX FORTRAN language, including the general form of each statement. The statements are listed alphabetically for
ease of reference. The "Manual Section" column indicates the section of this manual that
describes each statement in detail.

Table D-2: VAX FORTRAN Statements

Statement Form

Description

Manual
Section

See READ.

11.7

ASSIGN s TO v

7.4

is the label of an executable statement or a FORMAT
statement.

is an integer variable name.

Associates the statement label s with the integer variable v for later
use as a format specifier or in an assigned GO TO statement.

D-2

FORTRAN Language Summary

Table D-2 (Cont.): VAX FORTRAN Statements

Statement Form

Manual
Section

Description

7.1-7.3

Assignment Statement
v=e
v

is a scalar memory reference or an aggregate reference.

is an expression or an aggregate.

The assignment statement assigns the value of the arithmetic, logical,
or character expression on the right of the equal sign to the corresponding numeric, logical, or character scalar memory reference on
the left. If aggregates are involved, the aggregate reference and the
aggregate must have matching structures.
13.5

BACKSPACE ( [UNIT=Ju[,ERR=sl [,IOSTAT=iosJ)
BACKSPACE u

is a logical unit specifier.

is the label of an executable statement.

ios

is an I/O status specifier.

The BACKSPACE statement backspaces the currently open file on
logical unit u by one record.
BLOCK DATA [namJ

nam

8.1

is a symbolic name.

The BLOCK DATA statement specifies the subprogram that follows
as a BLOCK DATA subprogram.
CALL sub[([a][,[a]] ... )]

9.1, 10.2.3

sub

is a subprogram name or entry point name.

is an expression, an array name, a procedure name, or
an alternate return specifier. An alternate return
specifier is *S or &s, where s is the label of an executable statement.

The CALL statement calls the subroutine subprogram with the name
specified by s, passing the actual arguments (a) to replace the dummy
arguments in the subroutine definition.

FORTRAN Language Summary

D-3

Table D-2 (Cont.): VAX FORTRAN Statements

Statement Form

Manual
Section

Description

CLOSE ([UNIT=]u[,p] [,ERR=sl [,IOSTAT=ios])

13.2

is one of the following parameters:

STATUS}
f DISPOSE =
DISP

'SAVE'
'KEEP'
'DELETE'
'PRINT'
'SUBMIT'
'PRINT/DELETE'
'SUBMIT/DELETE'

is a logical unit specifier.

is the label of an executable statement.

ios

is an 1/0 status specifier.

The CLOSE statement closes the specified file.
COMMON [/[cb]/]nlist[[,] /[cb]/nlist] ...
ch

is a common block name.

nlist

is a list of one or more variable names, array names,
array declarators, or records separated by commas.

8.2

The COMMON statement reserves one or more blocks of storage
space to contain the variables associated with a specified block name.

9.2

CONTINUE
The CONTINUE statement transfers control to the next executable
statement.
DATA nlist/clist/[[,l nlist/clist/] ...

D-4

nlist

is a list of one or more variable names, array names,
array element names, character substring names, or
implied-DO lists, separated by commas. Subscript
expressions and substring ·expressions must be constant.

clist

is a list of one or more constants separated by commas, each optionally preceded by j, where j is a nonzero, unsigned integer constant.

FORTRAN Language Summary

8.4

Table D-2 (Cont.): VAX FORTRAN Statements

Statement Form

Manual
Section

Description

The DATA statement initially stores elements of clist in the corresponding elements of nlist.

A.l

DECODE (c,f,bf,ERR=sH,IOSTAT=ios]) [list]
c

is an integer expression representing the number of
characters to be translated to internal form.

is a format identifier.

is a scalar reference or array name reference that contains the characters to be translated to internal form.

is the label of an executable statement.

ios

is an integer scalar memory reference that is defined
as a positive integer if an error occurs or as a zero if no
error occurs.

list

is an I/0 list.

The DECODE statement reads c characters from buffer b and assigns
values to the elements in the list converted according to format specification f.

A.2

DEFINE FILE u(m,n,U,v)[,u(m,n,U,v)l ...
u

is a logical unit specifier.

specifies the number of records in the file.

specifies the length of each record in 16-bit words.

specifies unformatted.

is an integer variable name.

The DEFINE FILE statement defines the record structure of a direct
access file where u is the logical unit number, m is the number of
fixed-length records in the file, n is the length in 16-bit words of a
single record, U is a fixed argument, and vis the associated variable.

FORTRAN Language Summary

· D-5

Table D-2 (Cont.): VAX FORTRAN Statements

Statement Form

Description

DELETE ([UNIT=]u[,REC=r][,ERR=s][,IOSTAT=ios])
DELETE (u 'r[,ERR=sH,IOSTAT=ios])
u

is a logical unit specifier.

is a record specifier.

is the label of an executable statement.

ios

is an l/0 status specifier.

Manual
Section

13.7

The DELETE statement deletes records from relative or indexed
files, where u is the logical unit connected to the file, r is the number
of the record in a relative file, ios is an l/0 status specifier, ands is the
label of the statement to which control is to be transferred if an error
occurs.
DICTIONARY 'cdd-path[/[N01LIST1'

cdd-path

is the full or relative pathname of a CDD object.

[NO]LIST

directs the compiler to include or not include the generated FORTRAN source code in the listing.

3.5.3

The DICTIONARY statement extracts a data definition from the
VAX Common Data Dictionary, t~anslates it to FORTRAN source
code, and includes it in a FORTRAN source program.
DIMENSION a(d)[,a(d)] ...

a(d)

is an array declarator.

is an array name.

dl:du

are the lower (optional) and upper bounds of the array.

The DIMENSION statement specifies storage space requirements for
arrays.

D-6

FORTRAN Language Summary

8.5

Table D-2 (Cont.): VAX FORTRAN Statements

Statement Form

Manual
Section

Description

DO [s[,]] v=el,e2[,e3]

9.3

is the label of an executable statement. VAX
FORTRAN allows the statement label to be omitted.

is a variable name.

is a numeric expression that specifies the initial value
of v.

is a numeric expression that specifies the terminal
value of the control variable.

is a numeric expression that specifies the value by
which to increment the control variable.

The DO statement executes the DO loop by performing the following
steps:
1. Evaluates cnt = INT((e2-el+e3)/e3).

2. Sets v = el.
3. If cnt is less than or equal to zero, does not execute the loop.
4. If cnt is greater than zero, then:
a. Executes the statements in the body of the loop.
b. Evaluates v = v + e3.
c. Decrements the loop count (cnt = cnt-1). If cnt is greater than
zero, repeats the loop.
DO [s[,]] WHILE (e)

9.3.2

is the label of an executable statement. VAX
FORTRAN allows the statement label to be omitted.

is a logical expression.

The DO WHILE statement is similar to the DO statement, but executes as long as the logical expression contained in the statement
continues to be true, instead of for a specified number of iterations.

FORTRAN Language Summary

D-7

Table D-2 (Cont.): VAX FORTRAN Statements

Statement Form

Description

ELSE

Manual
Section
9.7.3

The ELSE statement defines a block of statements to be executed if
logical expressions in previous IF THEN and ELSE IF THEN statements have values of false. See IF THEN.
ELSE IF (e) THEN
e

9.7.3
is a logical expression.

The ELSE IF THEN statement defines a block of statements to be
executed if logical expressions in previous IF THEN and ELSE IF
THEN statements have values of false, and the logical expression e
has a value of true. See IF THEN.
ENCODE (c,f,b[,ERR=sH,IOSTAT=iosl) [list]
c

is an integer expression representing the number of
characters (bytes) to be translated to character form.

is a format identifier.

is a scalar reference or array name reference.

is a label of an executable statement.

ios

is an integer scalar memory reference that is defined
as a positive integer if an error occurs or as a zero if no
error occurs.

list

is an I/O list.

A.1

The ENCODE statement writes c characters into buffer b, which
contains the values of the elements of the list, converted according to
format specification f.
END

9.5
The END statement marks the end of a program unit.

END DO
The END DO statement marks the end of the body of a DO loop, and
may be used in place of a labeled statement.

D-8

FORTRAN Language Summary

9.4

Table D-2 (Cont.): VAX FORTRAN Statements

Statement Form

Manual
Section

Description

END IF

9.7.3

The END IF statement marks the end of a block IF construct.
END MAP

8.15.3

The END MAP statement marks the end of a field declaration or a
series of field declarations.
END STRUCTURE

8.15.1

The END STRUCTURE statement marks the end of a structure
declaration.
END UNION

8.15.3

The END UNION statement marks the end of a union declaration.
ENDFILE (fUNIT=luf,ERR=sH,IOSTAT=ios])
ENDFILE u

13.6

is a logical unit specifier.

is a label of an executable statement.

ios

is an I/0 status specifier.

The ENDFILE statement writes an end-of-file record on logical unit

u.
ENTRY nam[([p[,p] ... ])]

10.2.4

nam

is a subprogram name.

is a dummy argument or an alternate return specifier
( *).

The ENTRY statement defines an alternate entry point within a
subroutine or function subprogram.

FORTRAN Language Summary

D-9

Table D-2 (Cont.): VAX FORTRAN Statements

Statement Form

Description

EQUIVALENCE (nlist) [,(nlist)] ...

nlist

Manual
Section

8.6

is a list of two or more variable names, array names,
array element names, or character substring names
separated by commas. Subscript expressions and
substring expressions must be compile-time constant
expressions. Records and record fields cannot be
specified in EQUIVALENCE statements.

The EQUIVALENCE statement assigns the same storage location to
each of the names in nlist.
EXTERNAL v[,v] ...
EXTERNAL *v[,*v] ...
v

is a subprogram name.

is used only if /NOF77 is specified.

8.7, A.6
8.7

The EXTERN AL statement defines the names specified as user-defined subprograms.
FIND ([UNIT= ]u,REC=r[,ERR=sl [,IOSTAT=ios])
FIND (u 'r[,ERR=sH,IOSTAT=ios])
u

is a logical unit specifier.

is a direct access record number.

u'r

is a logical unit specifier, not prefaced by UNIT=.

is a label of an executable statement.

ios

is an 1/0 status specifier.

A.3

The FIND statement positions the file on logical unit u to record r
and sets the associated variable to record number r.
FORMAT (field-specification[, ... ])
The FORMAT statement describes the format in which one or more
records are to be transmitted; a statement label must be present.

D-10

FORTRAN Language Summary

12.1-12.8

Table D-2 (Cont.): VAX FORTRAN Statements

Statement Form

Manual
Section

Description

[typl FUNCTION nam[*m][([p[,p] ... ])]
typ

is a data type specifier.

nam

is a function name.

is a data type length spedfier.

is a dummy argument.

10.2.2

The FUNCTION statement begins a function subprogram, indicating
the program name and any dummy argument names (p). An optional
type specification can be included.
GO TO s
s

9.6.1
is a label of an executable statement.

This GO TO statement transfers control to statement numbers.
GO TO (slist)[,l e

9.6.2

slist

is a list of one or more statement labels separated by
commas.

is an integer expression.

This GO TO statement transfers control to the statement specified by
the value of e (if e=l, control transfers to the first statement label; if
e=2, control transfers to the second statement label, and so forth). If e
is less than one or greater than the number of statement labels present, no transfer takes place.
GO TO v[[,](slist)l

9.6.3

is an integer variable name.

slist

is a list of one or more statement labels separated by
commas.

This GO TO statement transfers control to the statement most recently associated with v by an ASSIGN statement.

FORTRAN Language Summacy

D-11

Table D-2 (Cont.): VAX FORTRAN Statements

Statement Form

Description

IF (e) sl,s2,s3

Manual
Section

9.7.1

is an expression.

sl,s2,s3

are labels of executable statements.

This IF statement transfers control to statement sl, s2, or s3 depending on the value of e (if e is less than zero, control transfers to sl; if e
equals zero, control transfers to s2; if e is greater than zero, control
transfers to s3).
IF (e) st

9.7.2

is an expression.

is any executable statement except a DO, END DO,
END, block IF, or logical IF.

This IF statement executes the statement if the logical expression has
a value of true.
IF (el) THEN

9.7.3

block
ELSE IF (e2) THEN
block
ELSE
block
END IF

el,e2

are logical expressions.

block

is a series of zero or more FORTRAN statements.

This IF statement defines blocks of statements and conditionally executes them. If the logical expression in the IF THEN statement has a
value of true, the first block is executed and control transfers to the
first executable statement after the END IF statement.

If the logical expression has a value of false, the process is repeated for
the next ELSE IF THEN statement. If all logical expressions have
values of false, the ELSE block is executed. If there is no ELSE block,
control transfers to the next executable statement following END IF.
D-12

FORTRAN Language Summary

Table D-2 (Cont.): VAX FORTRAN Statements

Statement Form

Manual
Section

Description

8.8

IMPLICIT typ(a[,aJ ... )[,typ(a[,aJ ... )J ...
IMPLICIT NONE
typ

is a data type specifier.

is either a single letter, or two letters in alphabetical
order, separated by a hyphen (that is, X-Y).

NONE

inhibits the implicit declaration of variables in the
module.

The IMPLICIT statement implicitly declares the data types of variables within program units. The element a represents a single (or a
range of) letter(s) whose presence as the initial letter of a variable
specifies the variable to be of that data type.
IMPLICIT NONE and IMPLICIT must not be used in the same
program unit.
INCLUDE 'file-spec[/[NOJLISTJ'
INCLUDE '[file-spec](module-name) [/[NOJLISTJ'
file-spec

3.5.1

is a character constant that specifies the file to be
included.

module-name is the name of a text module located in a text library.
/[NOJLIST

indicates that the statements in the specified file are
to be in the source listing.

The INCLUDE statement includes the source statements in the compilation from the file or module specified.

13.3

INQUIRE(par[,par] ... )
par

is a keyword specification having the form:
key= value

where:
key

is a keyword as described below.

value

depends on the keyword.

FORTRAN Language Summary

D-13

Table D-2 (Cont.): VAX FORTRAN Statements

Statement Form

Manual
Section

Description

Keyword

Values
inputs

FILE
UNIT
DEFAULTFILE

fin
e

fin

outputs
ACCESS
BLANK
CARRIAGECONTROL
DIRECT
ERR
EXIST
FORM
FORMATTED
IOSTAT
KEYED
NAME
NAMED
NEXTREC
NUMBER
OPENED
ORGANIZATION
RECL
RECORDTYPE
SEQUENTIAL
UNFORMATTED

cv
CV

s
Iv
CV
CV

v
CV
CV

v
v
~

cv
v
CV
CV
CV

is a numeric expression identifying a logical unit.

fin

is a character expression identifying a file.

is an integer scalar memory reference.

is a logical scalar memory reference.

is a character scalar memory reference.

is a statement label.
The INQUIRE statement furnishes information on
specified characteristics of a file or of a logical unit on
which a file might be opened.

D-14

FORTRAN Language Summary

Table D-2 (Cont.): VAX FORTRAN Statements

Statement Form

Manual
Section

Description

INTRINSIC v[,v]...
v

8.9
is an intrinsic function name.

The INTRINSIC statement identifies symbolic names as representing
intrinsic functions and allows those names to be used as actual arguments.
Map Declaration (see Union Declaration)
NAMELIST /group-name/ namelist[[,] /group-name/ namelist]. ..
group-name

is a symbolic name.

namelist

is a list of variables or array names, separated by
commas, that is associated with the preceding groupname.

8.10

The NAMELIST statement defines a list of variables or array names
and associates that list of names with a unique group-name for use in
namelist-directed I/O statements.
OPEN (par[,par]. .. )
par

13.1

is a keyword specification in one of the following
forms:
key
key= value

key

is a keyword, as described below.

value

depends on the keyword.
Keyword

Values

ACCESS

'SEQUENTIAL'
'DIRECT'
'KEYED'
'APPEND'
v

ASSOCIATEVARIABLE
BLOCKSIZE
BLANK

BUFFERCOUNT

'NULL'
'ZERO'

FORTRAN Language Summary

D-15

Table D-2 (Cont.): VAX FORTRAN Statements

Statement Form

Keyword
CARRIAGECONTROL
DEFAULTFILE
DISP
DISPOSE

ERR
EXTEND SIZE
FILE
FORM
INITIAL SIZE
IOSTAT
KEY
MAXREC
NAME
NOSPANBLOCKS
ORGANIZATION
READONLY
RECL
RECORDSIZE
RECORDTYPE
SHARED
STATUS

. D-16

Manual
Section

Description

FORTRAN Language Summary

Values (Cont.)
'FORTRAN'
'LIST'
'NONE'
c

(same as DISPOSE)
'KEEP' or 'SAVE'
'PRINT'
'DELETE'
'SUBMIT'
'SUBMIT/DELETE'
'PRINT/DELETE'
s
e
c
'FORMATTED'
'UNFORMATTED'
v

'OLD'
'NEW'
'SCRATCH'
'UNKNOWN'

Table D-2 (Cont.): VAX FORTRAN Statements

Statement Form

Manual
Section

Description
Keyword
TYPE
UNIT
USEROPEN

Values (Cont.)
(same as STATUS)
e
p

is a character scalar reference, numeric scalar memory reference, or numeric array name reference.

is a numeric expression.

is a program unit name.

is a statement label.

is an integer scalar memory reference.

key spec

is (el :e2 [:type]).

where:

is the beginning byte of the key field.

is the ending byte of the key field.

type

is either INTEGER or CHARACTER.

The OPEN statement opens a file on the specified logical unit according to the parameters specified by the keywords.

3.5.2

OPTIONS qualifier[,qualifier ... ]
qualifier
is one of the following:
/NO CHECK
/CHECK=

{t~~JOVERFLOW, [NOJBOUNDS, [NOJUNDERFLOW)}

NONE
/[NOJEXTENDSOURCE
/[NOJF77
/[NOJGFLOATING
/[NOJI4

The OPTIONS statement overrides the command line qualifiers for a
single program unit.

FORTRAN Language Summary

D-17

Table D-2 (Cont.): VAX FORTRAN Statements

Statement Form

Description

PARAMETER (p=c[,p=c] ... )
p

is a symbolic name.

is a constant, the name of a constant, or compile-time
constant expression.

Manual
Section
8.11, A.4

The PARAMETER statement defines a symbolic name for a constant.

9.8

PAUSE [disp]
disp

is a decimal digit string containing 1 to 5 digits or a
character constant.

The PAUSE statement displays a message on the screen and temporarily suspends program execution in order to permit you to take some
action. You can respond by typing CONTINUE, EXIT, or DEBUG.
PRINT

See WRITE.

PROGRAM nam
nam

11.8
8.12

is a program name.

The PROGRAM statement specifies a name for the main program.
READ Statement-Formatted Sequential Access
READ ([UNIT=]u,[FMT=]f[,ERR=sH,IOSTAT=ios][,END=s]) [list]

11.4.1.1

READ f[,list]

11.4.1.1

ACCEPT f[,list]

11.7

D-18

is a logical unit specifier.

is the nonkeyword form of a format specifier.

is a label of an executable statement.

ios

is an l/0 status specifier.

list

is an I/O list.

FORTRAN Language Summary

Table D-2 (Cont.): VAX FORTRAN Statements

Statement Form

Manual
Section

Description

This READ statement reads one or more logical records from unit u
and assigns values to the elements in the list. The records are converted according to the format specifier (f).
READ Statement-List-Directed Sequential Access
READ ([UNIT= lu, [FMT=l *[,ERR=sH,IOSTAT=ios][,END=s]) [list]

11.4.1.2

READ *[,list]

11.4.1.2

ACCEPT *[,list]

11.7

is a logical unit specifier.

denotes list-directed formatting.

is a label of an executable statement.

ios

is an I/0 status specifier.

list

is an I/O list.

This READ statement reads one or more logical records from unit u
and assigns values to the elements in the list. The records are converted according to the data type of the list element.
READ Statement-Namelist-Directed Sequential Access
READ ([UNIT= Ju, [NML=]nl[,ERR=s] [,IOSTAT=ios] [,END=s])

11.4.1.3

READ nl

11.4.1.3

ACCEPT n

11.7

is a logical unit specifier.

is a namelist group-name.

is the nonkeyword form of a namelist group-name
specifier.

is a label of an executable statement.

ios

is an I/O status specifier.

This READ statement reads one or more logical records from unit u
and assigns values to specified namelist entities. The records are converted according to the data type of the namelist entities.
FORTRAN Language Summary

D-19

Table D-2 (Cont.): VAX FORTRAN Statements

Statement Form

Description

Manual
Section

READ Statement-Unformatted Sequential Access
READ ([UNIT=]u[,ERR=s][,IOSTAT=ios][,END=sl) [list]
u

is a logical unit specifier.

is a label of an executable statement.

ios

is an 1/0 status specifier.

list

is an 1/0 list.

11.4.1.1

This READ statement reads one unformatted record from unit u and
assigns values to the elements in the list.

READ Statement-Formatted Direct Access
READ ( [UNIT]=u, [FMT=lf,REC=r[,ERR=sl [,IOSTAT=iosl) [list]

11.4.2.1

READ (u 'r,[FMT=lf[,ERR=sH,IOSTAT=iosl) [list]

11.4.2.1

is a logical unit specifier.

is a record specifier.

u'r

is a logical unit specifier, not prefaced by UNIT=.

is a format specifier.

is a label of an executable statement.

ios

is an I/O status specifier.

list

is an I/0 list.

This READ statement reads record r from unit u and assigns values
to the elements in the list. The record is converted according to f.

READ Statement-Unformatted Direct Access
READ ([UNIT=lu,REC=r[,ERR=sH,IOSTAT=iosl) [list]

11.4.2.2

READ (u 'r[,ERR=sH,IOSTAT=ios]) [list]

11.4.2.2

D-20

is a logical unit specifier.

is a record specifier.

u'r

is a logical unit specifier, not prefaced by UNIT=.

FORTRAN Language Summary

Table D-2 (Cont.): VAX FORTRAN Statements

Statement Form

Manual
Section

Description

is a label of an executable statement.

ios

is an I/0 status specifier.

list

is an I/0 list.

This READ statement reads record r from unit u and assigns values
to the elements in the list.
READ Statement-Formatted Indexed
READ ([UNIT=]u,[FMT=lf,keyspec[,KEYID=kn][,ERR=s] [,IOSTAT=ios]) [list] 11.4.3.1
READ Statement-Unformatted Indexed
READ ([UNIT=lu,keyspec[,KEYID=kn][,ERR=sl [,IOSTAT=ios]) [list]
is a logical unit specifier.
u
f

is a format specifier.

key spec

is a key specifier (see Section 7.2.1.6).

is a key-of-reference specifier.

is the label of an executable statement.

ios

is an I/0 status specifier.

list

is an I/0 list.

11.4.3.2

This READ statement reads one or more logical records specified by
key value, and assigns values to the elements in the list.
READ Statement-Formatted Internal
READ ([UNIT= le, [FMT=lf[,ERR=s] [,IOSTAT=ios] [,END=s]) [list]

11.4.4

READ Statement-List-Directed Internal
READ ( [UNIT=]c, [FMT=l* [,ERR=s] [,IOSTAT=ios] [,END=sl) [list]

is an internal file specifier.

denotes list-directed formatting.

is a format specifier.

is a label of an executable statement.

ios

is an I/0 status specifier.

list

is an I/O list.

11.4.4

FORTRAN Language Summary

D-21

Table D-2 (Cont.): VAX FORTRAN Statements

Statement Form

Description

Manual
Section

This READ statement reads into elements in the list one or more
internal records containing character strings, converting in accordance with the format specification.
RECORD structure-name/ record-namelist
[,/structure-name/record-namelist]

8.13

[,/structure-name/record-namelist]
structure-name is the name of a previously declared structure.
record-namelist is one or more variable names and/or array names.
The RECORD statement creates a record for each variable specified
or an array of records for each array specified. The structure declaration identified by structure-name defines the form of these records.
RETURN [il
i

9.9
is an integer value that indicates which alternate return is to be taken.

The RETURN statement returns control to the calling program from
the current subprogram.
REWIND ([UNIT=]U[,ERR=s] [,IOSTAT=iosl)
REWIND u
u

is a logical unit specifier.

is a label of an executable statement.

ios

is an I/O status specifier.

13.4

The REWIND statement repositions logical unit u to the beginning of
the currently opened file.
REWRITE Statement-Formatted Indexed
REWRITE ([UNIT=lu, [FMT=Jf[,ERR=sH,IOSTAT=iosl) [list]

D-22

FORTRAN Language Summary

11.6.1

Table D-2 (Cont.): VAX FORTRAN Statements

Statement Form

Manual
Section

Description

REWRITE Statement-Unformatted Indexed

REWRITE ([UNIT=Ju[,ERR=sH,IOSTAT=ios]) [list]
u

is a logical unit specifier.

is a format specifier.

is a label of an executable statement.

ios

is an I/O status specifier.

list

is an I/0 list.

11.6.2

The REWRITE statement transfers data from internal storage to the
current record in an indexed file.
SA VE [a[,aJ ... J
a

8.14

is the name of a variable, an array, or a named common block enclosed in slashes.

The SA VE statement retains the definition status of an entity after
the execution of a RETURN or END statement in a subprogram.
Statement Function

10.2.1

f([p[,p] ... ]) = e
f

is a statement function name.

is a dummy argument.

is an expression.

A statement function creates a user-defined function having the variables p as dummy arguments. When referred to, the expression is
evaluated using the actual arguments in the function call.
STOP [dispJ
disp

9.10

is a decimal digit string containing 1 to 5 digits or a
character constant.

The STOP statement terminates program execution and prints the
display, if one is specified.

FORTRAN Language Summary

D-23

Table D-2 (Cont.): VAX FORTRAN Statements

Statement Form

Description

Manual
Section

Structure Declaration Block
STRUCTURE [/structure-name/] [field-namelist]
field-declaration
[field-declaration]

[field-declaration]
END STRUCTURE
structure-name
is the name that is used in RECORD statements to
refer to a structure.
field-namelist are unique field names. (Used only in nested structure declarations.)
field-declaration
is any declaration or combination of declarations of
substructures, unions, or typed data.

A structure declaration block defines the field names, types of data
within fields, and the order and alignment of fields within a record.
Unlike type declaration statements, structure declarations do not create variables. Structured variables (called records) are created when
you use a RECORD statement containing the name of a previously
declared structure.
SUBROUTINE nam[([p[,pJ ... l)]
nam

is a subroutine name.

is a dummy argument or an alternate return specifier

10.2.3

( ).

The SUBROUTINE statement begins a subroutine subprogram, indicating the program name and any dummy argument names (p).
TYPE

D-24

See WRITE.

FORTRAN Language Summary

11.8

Table D-2 (Cont.): VAX FORTRAN Statements

Statement Form

Manual
Section

Description

Type Declarations-Character and Numeric
Type Declaration (Character)

8.3.2

CHARACTER[*len[,JJ v[*len] [/clist/1[,v[*len] [/clist/J...

len

specifies the length of the character data elements.

is a variable name, array name, function or function
entry name, or an array declarator. The name can
optionally be followed by a data type length specifier
(*n). For character entities, the length specifier can
be *len or ( * ) .
is an initial value or values to be assigned to the
immediately preceding variable or array element.

clist

The character type declaration assigns the specified data type to the
symbolic names (v).
Type Declaration (Numeric)

5.3.1

typ v [/clist/][, v [/clist/J...

typ

is any data type specifiers except CHARACTER, that
is, BYTE, LOGICAL, LOGICAL*l, LOGICAL*2,
LOGICAL*4, INTEGER, INTEGER*2,
REAL, REAL*4, REAL*S,
REAL*16, DOUBLE PRECISION, COMPLEX,
COMPLEX*8, COMPLEX*16, DOUBLE COMPLEX.

is a variable name, array name, function or function
entry name, or an array declarator. The name can
optionally be followed by a data type length specifier
(*n).

clist

is an initial value or values to be assigned to the
immediately preceding variable or array element.
The Numeric Type Declaration assigns the specified
data type to the symbolic names (v).

FORTRAN Language Summary

D-25

Table D-2 (Cont.): VAX FORTRAN Statements

Statement Form

Description

Union Declaration

Manual
Section
8.15.3

UNION
map-declaration
map-declaration
[ma p-declara ti on]

[ma p-declara ti on]
END UNION
where map-declaration is:
MAP
field-declaration
[field-declaration]

[field-declaration]
END MAP

field-declaration
is any declaration or combination of declarations of
substructures, unions, or typed data.
Unions define a data area that can be shared by fields or groups of
fields at run time.
UNLOCK ([UNIT=Ju[,ERR=s][,IOSTAT=iosl)

13.8

UNLOCK u

13.8

is a logical unit specifier.

is a label of an executable statement.

ios

is an 1/0 status specifier.

The UNLOCK statement removes the access protection from the file
connected to logical unit u.

D-26

FORTRAN Language Summary

Table D-2 (Cont.): VAX FORTRAN Statements

Statement Form

Manual
Section

Description

VIRTUAL a(d)[,a(d)] ...

8.5

a(d)

is an array declarator.

is an array name.

are the lower (optional) and upper bounds of the array in the form [dl:]du.

The VIRTUAL statement has the same effect as the
DIMENSION statement and is included for compatibility with
PDP-11 FORTRAN.
8.16

VOLATILE nlist
nlist

is a list of one or more variable names, array names,
or common block names separated by commas.

The VOLATILE statement prevents all optimizations for the items
specified in the namelist.

WRITE Statement-Formatted Sequential Access
WRITE ([UNIT= Ju, [FMT= Jf[,ERR=sH,IOSTAT=ios]) [list]

11.5.1.1

PRINT f[,list]

11.8

TYPE f[,list]

11.8

is a logical unit specifier.

is a format specifier.

is a label of an executable statement.

ios

is an 1/0 status specifier.

list

is an I/O list.

This WRITE statement writes one or more logical records to unit u
containing the values of the elements in the list. The records are
converted according to f.

FORTRAN Language Summary

D-27

Table D-2 (Cont.): VAX FORTRAN Statements

Statement Form

Description

Manual
Section

WRITE Statement-List-Directed Sequential Access
WRITE ([UNIT=Ju, [FMT=]* [,ERR=sH,IOSTAT=ios]) [list]

11.5.1.2

PRINT f[,listJ

11.8

TYPE f[,listJ

11.8

is a logical unit specifier.

denotes list-directed formatting.

is a label of an executable statement.

ios

is an I/O status specifier.

list

is an 1/0 list.

This WRITE statement writes one or more logical records to unit u
containing the values of the elements in the list. The records are
converted according to the data type of the list element.

WRITE ( [UNIT=Ju, [NML=Jnl[,ERR=s] [,IOSTAT=ios])

11.5.1.3

PRINT n

11.8

TYPE n

11.8

is a logical unit specifier.

is a nonkeyword form of a namelist group-name specifier.

is a namelist group-name.

is a label of an executable statement.

ios

is an I/0 status specifier.

This WRITE statement writes one or more logical records to unit u
containing the values of the namelist entities. The records are converted according to the data type of the namelist entities.

D-28

FORTRAN Language Summary

Table D-2 (Cont.): VAX FORTRAN Statements
Statement Form

Manual
Section

Description

WRITE Statement-Unformatted Sequential Access
11.5.1.4

WRITE ( [UNIT=Ju [,ERR=s][,IOSTAT=iosl) [list]
u

is a logical unit specifier.

is a label of an executable statement label.

ios

is an I/O status specifier.

list

is an I/0 list.

This WRITE statement writes one unformatted record to unit u containing the values of the elements in the list.

WRITE Statement-Formatted Direct Access
WRITE ([UNIT= Ju, [FMT=Jf,REC=r[,ERR=sJ [,IOSTAT=ios]) [list]

11.5.2.1

WRITE (u 'r,f[,ERR=sH,IOSTAT=ios]) [list]

11.5.2.1

is a logical unit specifier.

is a record specifier.

u'r

is a logical unit specifier, not prefaced by UNIT=.

is a format specifier.

is a label of an executable statement.

ios

is an I/O status specifier.

list

is an I/0 list.

This WRITE statement writes the values of the elements of the list to
record r on unit u. The record is converted according to f.

WRITE Statement-Unformatted Direct Access
WRITE ([UNIT=Ju,REC=r[,ERR=s][,IOSTAT=ios]) [list]

11.5.2.2

WRITE (u 'r[,ERR=sJ[,IOSTAT=ios]) [list]

11.5.2.2

is a logical unit specifier.

is a record specifier.

u'r

is a logical unit specifier, not prefaced by UNIT=.

FORTRAN Language Summary

D-29

Table D-2 (Cont.): VAX FORTRAN Statements

Statement Form

Description

is a label of an executable statement.

ios

is an I/O status specifier.

list

is an I/O list.

Manual
Section

This WRITE statement writes record r to unit u containing the values
of the elements in the list.

WRITE Statement-Formatted Internal
WRITE ([UNIT=]c,[FMT=lfl,ERR=sH,IOSTAT=ios]) [list]

11.5.4

WRITE Statement-List-Directed Internal
WRITE ([UNIT=lc,[FMT=l*[,ERR=sl[,IOSTAT=iosl) [list]

is an internal file specifier.

denotes list-directed formatting.

is a format specifier.

is the label of an executable statement.

ios

is an 1/0 status specifier.

list

is an 1/0 list.

11.5.4

This WRITE statement writes elements in the list to the internal file
specified by the unit, converting the elements to character strings in
accordance with the format specification.

D.3 Library Functions
Table D-3 lists the VAX FORTRAN intrinsic functions. Superscripts in the table refer to
the notes that follow the table. Refer to Section 10.3 for more information about intrinsic
functions. For descriptions of the intrinsic function algorithms, refer to the VAX/VMS
Run-Time Library Routines Reference Manual.

D-30

FORTRAN Language Summary

Table D-3: Generic and Intrinsic Functions
Functions

Number of Generic
Arguments Name

Specific
Name

Type of
Argument

Type of
Result

Square Root 1
a112

SQRT

SQRT
DSQRT
QSQRT
CSQRT
CD SQRT

REAL*4
REAL*8
REAL*16
COMPLEX*8
COMPLEX*16

Natural Logarithm 2
logea

LOG

ALOG
DLOG
QLOG
CLOG
CD LOG

REAL*4
REAL*8
REAL*16
COMPLEX*8
COMPLEX*16

Common Logarithm 2
log 10 a

LOGlO

ALOGlO
DLOGlO
QLOGlO

REAL*4
REAL*8
REAL*16

Exponential
ea

EXP

EXP
DEXP
QEXP
CEXP
CD EXP

REAL*4
REAL*8
REAL*16
COMPLEX*8
COMPLEX*16

REAL*4
REAL*8
REAL*16
COMPLEX*8.
COMPLEX*16

Sine3
Sina

SIN

SIN
DSIN
QSIN
CSIN
CD SIN

REAL*4
REAL*8
REAL*16
COMPLEX*8
COMPLEX*16

SIND

SIND
DSIND
QSIND

REAL*4
REAL*S
REAL*16

cos
CDC OS

REAL*4
REAL*8
REAL*16
COMPLEX*8
COMPLEX*16

Sine 3 (degree)
Sina
Cosine 3
Cos a

cos

DCOS
QCOS

ccos

Cosine (degree)
Cos a

COSD

COSD
DCOSD
QCOSD

REAL*4
REAL*S
REAL*16

REAL*4
REAL*8
REAL*16

Tangent3
Tana

TAN

TAN
DTAN
QTAN

REAL*4
REAL*S
REAL*16

REAL*4
REAL*8
REAL*16

Tangent3 (degree)
Tana

TAND

TAND
DTAND
QTAND

REAL*4
REAL*S
REAL*16

Arc Sine 4 •5
Arc Sin a

ASIN

ASIN
DASIN
QA SIN

REAL*4
REAL*8
REAL*16

FORTRAN Language Summary

D-31

Table D-3 (Cont.): Generic and Intrinsic Functions
Functions

Number of Generic
Arguments Name

Specific
Name

Type of
Argument

Type of
Result

Arc Sine (degree)
Arc Sin a

AS IND

ASIND
DAS IND
QASIND

REAL*4
REAL*8
REAL*16

Arc Cosine4 •5
Arc Cos a

ACOS

ACOS
DACOS
QA COS

REAL*4
REAL*8
REAL*16

Arc Cosine (degree)
Arc Cos a

ACOSD

ACOSD
DACOSD
QACOSD

REAL*4
REAL*8
REAL*16

Arc Tangent5
Arc Tana

ATAN

ATAN
DATAN
QATAN

REAL*4
REAL*S
REAL*16

REAL*4
REAL*8
REAL*16

Arc Tangent 5 •7 (degree)
Arc Tana

AT AND

AT AND
DATAND
QATAND

REAL*4
REAL*8
REAL*16

Arc Tangent5 •6
Arc Tan a 1/a2

ATAN2

ATAN2
DATAN2
QATAN2

REAL*4
REAL*8
REAL*16

Arc Tangent 5 •7 (degree)
Arc Tan a 1/a2

ATAN2D ATAN2D
DATAN2D
QATAN2D

REAL*4
REAL*8
REAL*16

Hyperbolic Sine
Sinha

SINH

SINH
DSINH
QSINH

REAL*4
REAL*8
REAL*16

Hyperbolic Cosine
Cosha

COSH

COSH
DCOSH
QCOSH

REAL*4
REAL*8
REAL*16

Hyperbolic Tangent
Tanh a

TANH

TANH
DTANH
QTANH

REAL*4
REAL*8
REAL*16

Absolute Value 8
lal

ABS

IIABS
JIABS
ABS
DABS
QABS
CABS
CD ABS
IIABS
JIABS

INTEGER*2
INTEGER*4
REAL*4
REAL*8
REAL*16
COMPLEX*8
COMPLEX*16
INTEGER*2
INTEGER*4

INTEGER*2
INTEGER*4
REAL*4
REAL*8
REAL*16
REAL*4
REAL*8
INTEGER*2
INTEGER*4

IINT
JINT
II DINT
JIDINT
IIQINT

REAL*4
REAL*4
REAL*8
REAL*8
REAL*16

INTEGER*2
INTEGER*4
INTEGER*2
INTEGER*4
INTEGER*2

IABS
Truncation9 •12
lal

D-32

FORTRAN Language Summary

INT

Table D-3 (Cont.): Generic and Intrinsic Functions
Functions

Specific
Name

Type of
Argument

Type of
Result

JIQINT

II DINT
JIDINT
IIQINT
JIQINT

REAL*16
COMPLEX*8
COMPLEX*8
COMPLEX*16
COMPLEX*16
REAL*S
REAL*S
REAL*16
REAL*16

INTEGER*4
INTEGER*2
INTEGER*4
INTEGER*2
INTEGER*4
INTEGER*2
INTEGER*4
INTEGER*2
INTEGER*4

AINT

AINT
DINT
QINT

REAL*4
REAL*S
REAL*16

NINT

IN INT
JNINT
IIDNNT
JIDNNT
IIQNNT
JIQNNT
IIDNNT
JIDNNT
IIQNNT
JIQNNT

REAL*4
REAL*4
REAL*8
REAL*S
REAL*16
REAL*16
REAL*8
REAL*8
REAL*16

INTEGER*2
INTEGER*4
INTEGER*2
INTEGER*4
INTEGER*2
INTEGER*4
INTEGER*2
INTEGER*4
INTEGER*2

AN INT

ANINT
DNINT
QNINT

REAL*4
REAL*8
REAL*16

REAL*4
REAL*S
REAL*16

ZEXT

IZEXT

LOGICAL*l
LOGICAL*2
INTEGER*2
LOGICAL*l
LOGICAL*2
LOGICAL*4
INTEGER*2
INTEGER*4

INTEGER*2

INTEGER*2
INTEGER*4
REAL*4
REAL*8
REAL*16
COMPLEX*8
COMPLEX*16

REAL*4
REAL*4
REAL*4
REAL*4
REAL*4
REAL*4
REAL*4

INTEGER*2
INTEGER*4
REAL*4
REAL*S
REAL*16
COMPLEX*8
COMPLEX*16

REAL*8
REAL*S
REAL*8
REAL*8
REAL*S
REAL*S
REAL*8

Number of Generic
Arguments Name

ID INT
IQINT

Nearest Integer9 •12
[a+ .5*sign(a)]

IDNINT
IQNINT

Zero-Extend Functions

JZEXT

Conversion to 10 REAL*4

REAL

FLOAT!
FLOATJ
SNGL
SNGLQ

Conversion to 10 REAL*8

DBLE
DBLE
DBLEQ

INTEGER*4

FORTRAN Language Summary

D-33

Table D-3 (Cont.): Generic and Intrinsic Functions
Functions

Number of Generic
Arguments Name

Conversion to REAL*16

Specific
Name

QEXT
QEXT
QEXTD

Type of
Argument

Type of
Result

INTEGER*2
INTEGER*4
REAL*4
REAL*8
REAL*16
COMPLEX*8
COMPLEX*16

REAL*16
REAL:1:l6
REAL*16
REAL*16
REAL*16
REAL:1:l6
REAL*16

Fix 10 •12
(REAL*4-to-integer conversion)

IFIX

IIFIX
JIFIX

REAL*4
REAL*4

INTEGER*2
INTEGER*4

Float10
(lnteger-to-REAL*4 conversion)
REAL*8 Float 10

FLOAT

FLOAT!
FLOATJ

INTEGER*2
INTEGER*4

REAL*4
REAL*4

DFLOAT DFLOTI
DFLOTJ

INTEGER*2
INTEGER*4

REAL*8
REAL:1:8

QFLOAT

INTEGER*2
INTEGER*4
INTEGER*2
INTEGER*4
REAL*4
REAL*8
REAL*16
COMPLEX*8
COMPLEX*16

REAL*16
REAL*16

INTEGER*2
INTEGER1:4
REAL*4
REAL*8
REAL:1:l6
COMPLEX*8
COMPLEX:1:l6

COMPLEX*16
COMPLEX*16
COMPLEX:1:l6
COMPLEX:d6
COMPLEX*16
COMPLEX*16
COMPLEX:1:l6

(lnteger-to-REAL*8 conversion)

Conversion to COMPLEX*8,
or
COMPLEX*8 from Two Arguments

Conversion to COMPLEX*16,
or
COMPLEX:1:16 from Two Arguments

1,213
1,2
1,2
1,2
1,2
1
1
1,2 13
1,2
1,2
1,2
1,2
1
1

CMPLX

DCMPLX

COMPLEX*8
COMPLEX*8
COMPLEX*8
COMPLEX*8
COMPLEX*8
COMPLEX*8
COMPLEX:1:8

Real Part of Complex

REAL
DRE AL

COMPLEX*8
COMPLEX:1:l6

REAL*4
REAL*S

Imaginary Part of Complex

AIMAG
DIMAG

COMPLEX*8
COMPLEX*16

REAL*4
REAL*8

Complex from Two Arguments

(See Conversion to COMPLEX*8 and
Conversion toCOMPLEX*16)

Complex Conjugate
(ifa=(X,Y)
CONJG (a)= (X,-Y))

REAL*8 product of REAL*4's
ai*a2

D-34

FORTRAN Language Summary

CONJG

CONJG
DCONJG

COMPLEX*8
COMPLEX*16

DPROD

REAL*4

REAL*8

Table D-3 (Cont.): Generic and Intrinsic Functions
Functions
Maximum 12

Number of Generic
Arguments Name
n

MAX

max(a i.a2, ... an)
(returns the maximum
value from among the
argument list; there must
be at least two arguments)

MAXO
MAXl
AMAXO

Minimum 12
min(ai.a2, ... an)

(returns the minimum value
among the argument list;
there must be at least two
arguments)

MIN

MINO
MINl
AMINO

Positive Difference
a 1-(min(ai.a 2))

(returns the first argument
minus the minimum of the
two arguments)
Remainder
a1-a2*[a1/a2l

DIM

!DIM

Type of
Result

IMAXO
JMAXO
AMAXl
DMAXl
QMAXl
IMAXO
JMAXO

INTEGER1:2
INTEGER*4
REAL*4
REAL*8
REAL*16
INTEGER1:2
INTEGER*4

INTEGER::2
INTEGER*4
REAL*4
REAL*B
REAL*16
INTEGER1:2
INTEGER*4

IMAXl
JMAXl
AIMAXO
AJMAXO

REAL*4
REAL*4
INTEGERr.2
INTEGER*4

INTEGER1:2
INTEGER*4
REAL*4
REAL*4

!MINO
JMINO
AMINI
DMINl
QMINl
IMINO
JMINO
IMINl
JMINl
AIMINO
AJMINO

INTEGER*2
INTEGER*4
REAL*4
REAL*8
REAL*16
INTEGER*2
INTEGER*4
REAL*4
REAL*4
INTEGERr.2
INTEGER*4

INTEGERr-2
INTEGER*4
REAL*4
REAL*8
REAL*16
INTEGER*2
INTEGER*4
INTEGER*2
INTEGER*4
REAL*4
REAL*4

II DIM
JIDIM
DIM
DDIM
QDIM
II DIM
JIDIM

INTEGER*2
INTEGER*4
REAL*4
REAL*8
REAL*16
INTEGER1:2
INTEGER*4

INTEGERr-2
INTEGER*4
REAL*4
REAL*8
REAL*16
INTEGER*2
INTEGER*4

MOD

IMOD
JMOD
AMOD
DMOD
QMOD

INTEGER*2
INTEGER*4
REAL*4
REAL*8
REAL*16

SIGN

IISIGN
JISIGN
SIGN
DSIGN
QSIGN
IISIGN
JISIGN

INTEGERr-2
INTEGER*4
REAL*4
REAL*8
REAL*16
INTEGER*2
INTEGER*4

INTEGER*2
INTEGER*4
REAL*4
REAL*B
REAL*16
INTEGER*2
INTEGER*4

IIAND
JIAND

INTEGER*2
INTEGER*4

!SIGN
Bitwise AND
(performs a logical AND on
corresponding bits)

Type of
Argument

(returns the remainder
when the first argument
is divided by the second)
Transfer of Sign
la 11 Sign a 2

Specific
Name

!AND

FORTRAN Language Summary

D-35

Table D-3 (Cont.): Generic and Intrinsic Functions
Functions

Number of Generic
Arguments Name

Specific
Name

Type of
Argument

Type of
Result

Bitwise OR
(performs an inclusive OR
on corresponding bits)

IOR

IIOR
JIOR

INTEGER*2
INTEGER*4

Bitwise Exclusive OR
(performs an exclusive OR
on corresponding bits)

IEOR

IIEOR
JIEOR

INTEGER*2
INTEGER*4

Bitwise Complement
(complements each bit)

NOT

INOT
JNOT

INTEGER*2
INTEGER*4

Bitwise Shift
(a 1 logically shifted left
a 2 bits)

ISHFT

IISHFT
JISHFT

INTEGER*2
INTEGER*4

Bit Extraction
(extracts bits a 2 through
a 2 + a 3 -1 from a 1); see also
MVBITS system subroutine

IBITS

IIBITS
JIB ITS

INTEGER*2
INTEGER*4

Bit Set
(returns the value of a 1
with bit a 2 of a 1 set
to 1)

IBSET

IIBSET
JIB SET

INTEGER*2
INTEGER*4

Bit Test
(returns .TRUE. ifbit
a 2 of argument a 1 equals 1)

BTEST

BITE ST
BJ TEST

INTEGER*2
INTEGER*4

LOGICAL*2
LOGICAL*4

Bit Clear
(returns the value of a 1
with bit a 2 of a 1 set to 0)

IBCLR

IIBCLR
JIBCLR

INTEGER*2
INTEGER*4

Bitwise Circular Shift 14
(circularly shifts rightmost
a 3 bits of argument a 1 by a 2
places)

ISHFTC

IISHFTC
JISHFTC

INTEGER*2
INTEGER*4

Length 12
(returns length of the
character expression)

LEN

CHARACTER

INTEGER*4

Index (Ci,C 2 ) 12
(returns the position of the
substring c2 in the character
expression c1)

INDEX

CHARACTER

INTEGER*4

Character12
(returns a character that has
the ASCII value specified
by the argument)

CHAR

LOGICAL*1
INTEGER*2
INTEGER*4

CHARACTER

D-36

FORTRAN Language Summary

Table D-3 (Cont.): Generic and Intrinsic Functions
Functions

Number of Generic
Arguments Name

Specific
Name

Type of
Argument

Type of
Result

ASCII Value 11
(returns the ASCII value of
the argument; the argument
must be a character expression that has a length of 1)

ICHAR

CHARACTER

INTEGER*4

Character relationals
(ASCII collating sequence)

2
2
2
2

LLT
LLE
LGT
LGE

CHARACTER
CHARACTER
CHARACTER
CHARACTER

LOGICAL*4
LOGICAL*4
LOGICAL*4
LOGICAL*4

Notes
1. The argument of SQRT, DSQRT, or QSQRT must be greater than or equal to zero. The result of
CSQRT or CDSQRT is the principal value, with the real part greater than or equal to zero. When
the real part is zero, the result is the principal value, with the imaginary part greater than or
equal to zero.

2. The argument of ALOG, DLOG, QSQRT, ALOGlO, DLOGlO, QLOGlO, ATAND, ATAN2D,
ASIND, DASIND, ACOSD, DACOSD, or QACOSD must be greater than zero. The argument of
CLOG or CDLOG must not be (0.,0.).
3. The argument of SIN, DSIN, QSIN, COS, DCOS, QCOS, TAN, DTAN, or QTAN must be in
radians. The argument is treated modulo 2*pi. The argument of SIND, COSD, or TAND must be
in degrees. The argument is treated modulo 360.
4. The absolute value of the argument of ASIN, DASIN, QASIN, ACOS, DACOS, QACOS, ASIND,
DASIND, QASIND, ACOSD, DACOSD, or QACOSD must be less than or equal to 1.
5. The result of ASIN, DASIN, QASIN, ACOS, DACOS, QACOS, ATAN, DATAN, QATAN, ATAN2, DATAN2, or QATAN2 is in radians. The result of ASIND, DASIND, QASIND, ACOSD,
DACOSD, QACOSD, ATAND, DATAND, QATAND, ATAN2D, DATAN2D, or QATAN2D is in
degrees.
6. If the value of the first argument of ATAN2, DATAN2, or QATAN2 is positive, the result is
positive. When the value of the first argument is zero, the result is zero if the second argument is
positive and pi if the second argument is negative. If the value of the first argument is negative,
the result is negative. If the value of the second argument is zero, the absolute value of the result
is pi/2. Both arguments must not have the value zero. The range of the result for ATAN2,
DATAN2, and QATAN2 is: -pi < result < pi.
7. If the value of the first argument of ATAN2D, DATAN2D, or QATAN2D is positive, the result is
positive. When the value of the first argument is zero, the result will be zero if the second
argument is positive and 180 degrees if the second argument is negative. If the value of the first
argument is negative, the result is negative. If the value of the second argument is zero, the
absolute value of the result is 90 degrees. Both arguments must not have the value zero. The
range of the result for ATAN2, DTAN2D, QATAN2D is: -180 degrees < result < 180 degrees.

FORTRAN Language Summary

D-37

Notes (Cont.)
8. The absolute value of a complex number, (X,Y), is the real value:
( X2+ y2 )112

9. [x] is defined as the largest integer whose magnitude does not exceed the magnitude of x and
whose sign is the same as that of x. For example [5.7] equals 5. and [-5.7] equals -5.
10. Functions that cause conversion of one data type to another type provide the same effect as the
implied conversion in assignment statements. The following functions return the value of the
argument without conversion: the function REAL with a real argument, the function DBLE with
a double precision argument, the function INT with an integer argument, and the function QEXT
with a REAL*16 argument.
11. See Chapter 6 for additional information on character functions.
12. The functions INT, IDINT, IQINT, NINT, IDNINT, IQNINT, IFIX, MAXl, MINI, and ZEXT
return INTEGER*4 values if the /14 command qualifier is in effect, INTEGER*2 values if the
/NOI4 qualifier is in effect.
13. When CMPLX and DCMPLX have only one argument, this argument is converted into the real
part of a complex value, and zero is assigned to the imaginary part. (When there are two arguments (not complex), a complex value is produced by converting the first argument into the real
part of the value and converting the second argument into the imaginary part.)
14. Bits in a 1 beyond the value specified by a 3 are unaffected.

The VAX FORTRAN system provides subroutines that you call in the same manner as a
user-written subroutine. These subroutines are described in this section.
The subroutines supplied are:
DATE

Returns a 9-byte string containing the ASCII representation of the current
date.

IDATE

Returns three integer values representing the current month, day, and year.

ERRS NS

Returns information about the most recently detected error condition.

EXIT

Terminates the execution of a program and returns control to the operating
system.

SECNDS

Provides system time of day, or elapsed time, as a floating-point value in
seconds.

TIME

Returns an 8-byte string containing the ASCII representation of the current
time in hours, minutes, and seconds.

D-38

FORTRAN Language Summary

RAN

Returns the next number from a sequence of pseudo random numbers of
uniform distribution over the range 0 to 1.

MVBITS

Transfers a bit field from one storage location to another.

References to integer arguments in the following subroutine descriptions refer to arguments
of either INTEGER*4 data type or INTEGER*2 data type. However, the arguments must
be either all INTEGER*4 or all INTEGER*2. In general, INTEGER*4 variables or array
elements may be used as input values to these subroutines if their value is within the
INTEGER*2 range.

IDJ.lJ. ~ IID~ilE Sulbrouiima
The DATE subroutine obtains the current date as set within the system. The call to DATE
has the form:
CALL DATE(buf)

where:
buf

. is a 9-byte variable, array, array element, or character substring. The date is returned
as a 9-byte ASCII character string of the form:
dd-mmm-yy

where:
dd

is the 2-digit date.
mmm

is the 3-letter month specification.
yy

is the last two digits of the year.

fl].4.2 m£YIE Sul!Jrouiine
The ID ATE subroutine returns three integer values representing the current month, day,
and year. The call to !DATE has the form:
CALL IDATE(i,j,k)

If the current date were October 9, 1984, the values of the integer variables upon return
would be:
i = 10
j=9
k = 84

FORTRAN Language Summary

D-39

D.4.3 rrnnsr~s Subrouiine
The ERRSNS subroutine returns information about the most recent error that has occurred during program execution. The call to ERRSNS has the form:
CALL ERRSNS(fnum,rmssts,rmsstv,iunit,condval)

where:
fnum

is an integer variable or array element in which the most recent FORTRAN error
number is stored. VAX FORTRAN error numbers are listed in Table 18-1.
A zero is returned if no error has occurred since the last call to ERRS NS, or if no error
has occurred since the start of execution.
rmssts

if the last error was an RMS I/0 error, is an integer variable or array element in which
the RMS completion status code (STS) is stored.
rmsstv

if the last error was an RMS I/O error, is an integer variable or array element in which
the RMS status value (STV) is stored. This status value provides additional status
information.
Iunit

if the last error was an I/O error, is an integer variable or array element in which the
logical unit number is stored.
condval

is an integer variable or array element in which the actual VAX condition value is
stored.
Any of the arguments can be null. If the arguments are ofINTEGER*2 type, only the loworder 16 bits of information are returned. The saved error information is set to zero after
each call to ERRSNS.

HD.4l.LiJ IEmT Subrouiine
The EXIT subroutine causes program termination, closes all files, and returns control to
the operating system. A call to EXIT has the form:
CALL EXIT[(exit-status)]

where:
exit-status

is an optional integer argument you can use to specify the image exit-status value.

D-40

FORTRAN Language Summary

[JJ.LJ.5 SIEmJ[J)S Su~uouiine
The SECNDS function subprogram returns the system time in seconds as a single-precision, floating-point value, minus the value of its single-precision, floating-point argument.
The call to SECNDS has the form:
y = SECNDS(x)

where:
y

is set equal to the time in seconds since midnight, minus the user-supplied value of x.
The SECNDS function can be used to perform elapsed-time computations. For example:
C

START OF TIMED SEQUENCE
Tl = SECNDSCO.Ol

CODE TD BE TIMED
DELTA = SECNDSCTll

where DELTA will give the elapsed time.
The value of SECNDS is accurate to 0.01 second, which is the resolution of the system
clock.

NOTE
1. The time is computed from midnight. SECNDS also produces correct results
for time intervals that span midnight.

2. The 24 bits of precision provides accuracy to the resolution of the system
clock for about one day. However, loss of significance can occur if you attempt to compute very small elapsed times late in the day. More precise
timing information can be obtained using Run-Time Library procedures:
LIB$1NIT_TIMER
LIB$SHOW_TIMER
LIB$STAT_TIMER

D.4.6 TDM!E Subrouiine
The TIME subroutine returns the current system time as an ASCII string. The call to
TIME has the form:
CALL TIME(buf)

where buf is an 8-byte variable, array, array element, or character substring.
The TIME call returns the time as an 8-byte ASCII character string of the form:
hh:mm:ss

FORTRAN Language Summary

D-41

where:
hh

is the 2-digit hour indication.

mm
is the 2-digit minute indication.
SS

is the 2-digit second indication.
For example:
10:ll5:23

A 24-hour clock is used.

HD.4. 7 ll:UUJ SubrouRine
The RAN function is a general random number generator of the multiplicative congruential
type. The result is a floating-point number that is uniformly distributed in the range
between 0.0 inclusive and 1.0 exclusive. The call to RAN has the form:
y = RAN(i)

where:
y

is set equal to the value associated, by the function, with the argument i. The argument i must be an INTEGER*4 variable or INTEGER*4 array element.
The argument should initially be set to a large, odd integer value. The RAN function stores
a value in the argument that it later uses to calculate the next random number.
There are no restrictions on the seed, although it should be initialized with different values
on separate runs in order to obtain different random numbers. The seed is updated automatically, and RAN uses the following algorithm to update the seed passed as the parameter:
SEED

= 69069 * SEED + 1

<MOD 2**32)

The value of SEED is a 32-bit number whose high-order 24 bits are converted to floating
point and returned as the result.

IDl.4.0 rVjUOITS Subrouiine
The MVBITS subroutine transfers a bit field from one storage location (source) to a field in
a second storage location (destination). The call to MVBITS has the form:
CALL MVBITS(m,i,len,n,j)

D-42

FORTRAN Language Summary

where:
m

is an integer variable or array element that represents the source location, that is, the
location from which a bit field is transferred.
is an integer expression that identifies the first bit position in the field transferred
from m.
len

is an integer expression that identifies the length of the field transferred from m.
n

is an integer variable or array element that represents the destination location, that
is, the location to which a bit field is transferred.
is an integer expression that identifies the bit in which the transferred bit field begins.
The MVBITS subroutine transfers len bits from positions i through i+len-1 of the source
location (m) to positions j through j+len-1 of the destination location (n). Other bits of the
destination location and all of the bits of the source location remain unchanged. The values
of i+len must be less than 32, and j+len must be less thah or equal to 32.

VAX FORTRAN provides intrinsic functions for manipulation of the bits in the binary
patterns that represent integer data types. For more information, refer to Table D-3.

D.5.1 ~m Posmon
Integer data types are represented internally in binary twos complement notation. Bit
positions in the binary representation are numbered from right (least significant bit) to left
(most significant bit); the rightmost bit position is numbered 0. A bit in a binary pattern
has a value of 0 or 1.

D.5.2 ma IFunciion Argumenis
The intrinsic functions IAND, IOR, IEOR, and NOT operate on all of the bits of their
argument or arguments. Bit 0 of the result is the result of applying the specified logical
operation to bit 0 of the argument or arguments. Bit 1 of the result is the result of applying
the specified logical operation to bit 1 of the argument or arguments, and so on for all of the
bits of the result.

FORTRAN Language Summary

D-43

The shift functions ISHFT and ISHFTC shift binary patterns. A positive shift count
indicates a left shift, while a negative shift count indicates a right shift. ISHFT specifies a
logical shift; bits shifted out of one end are lost and zeros are shifted in at the other end.
ISHFTC performs a circular shift; bits shifted out at one end are shifted back in at the
other end.
The functions IBSET, IBCLR, BTEST, and IBITS and the subroutine MVBITS operate on
bit fields. A bit field is a contiguous group of bits within a binary pattern. Bit fields are
specified by a starting bit position and a length. A bit field must be entirely contained in its
source operand.
For example, the integer 47 is represented by the binary pattern:
0 ... 0101111

bit position:

n... 6543210
where: n is the number of bit positions in the numeric storage unit

You can refer to the bit field contained in bits 3 through 6 by specifying a starting position
of 3 and a length of 4.
Negative integers are represented in twos complement notation. The binary pattern for -47
is:
1...1010001

bit position:

n ... 6543210
where: n is the number. of bit positions in the numeric storage unit

In particular, note that the value of bit position n is 1 for a negative number and 0 for a
non-negative number and that all of the high-order bits of the pattern from the last
significant bit of the value up to bit n are the same as bit n.
IBITS and MVBITS operate on general bit fields. Both the starting position of a bit field
and its length are arguments to these intrinsics. IBSET, IBCLR, and BTEST operate on 1bit fields. They do not require a length argument.
For optimum selection of performance and memory requirements, FORTRAN provides two
integer data types: INTEGER*2 requires two bytes of storage, while INTEGER*4 requires
four bytes. The bit manipulation functions each have a generic form which operates on
either of the two integer types and a specific form for each type. When you use the intrinsic
functions which refer to bit positions or which shift binary patterns within a storage unit,
you must be careful that you do not create a value that is outside the range of integers
representable by the data type. For example:
I NTEGER*2 I , J
I
1
J
17
ISHFT(l1J)

D-44

FORTRAN Language Summary

The variables I and J have INTEGER*2 data type. Therefore, the generic function ISHFT
maps to the specific function IISHFT, which returns an INTEGER*2 result. INTEGER*2
results must be in the range -32768 to 32767, but the value 1, shifted left 17 positions, yields
the binary pattern 1 followed by 17 zeros, which represents the integer 131072. Note that
this would be valid if either I or J or both were INTEGER*4 because in both cases ISHFT
would map to the specific function JISHFT, which returns an INTEGER*4 value.
If ISHFT is called with constant arguments, it returns an INTEGER*4 value.

FORTRAN Language Summary

D-45

Appendix E

Diagnostic Messages
Diagnostic messages related to a VAX FORTRAN program can come from the compiler,
the linker, or the VAX run-time system. The compiler detects syntax errors in the source
program, such as unmatched parentheses, invalid characters, misspelled keywords, and
missing or invalid parameters. The run-time system reports errors that occur during execution.
This chapter lists and describes the messages issued by the compiler and the run-time
system. It also provides a summary of the DICTIONARY messages that may accompany
Common Data Dictionary messages. Linker messages are summarized in the VAX/VMS
Linker Reference Manual.

E.1 Diagnostic Messages from the Compiler
A diagnostic message issued by the compiler describes the detected error, and in some cases
contains an indication of the action taken by the compiler in response to the error.
Besides reporting errors detected in source program syntax, the compiler issues messages
indicating errors that involve the compiler itself, such as I/0 errors.

E.1.1 Source Program Diagnostic Messages
There are four classes of source program diagnostic messages. In order of greatest to least
severity, these classes are:

Code

Description

Fatal; must be corrected before the program can be compiled. No object file is
produced if an F-class error is detected during compilation.

Error; should be corrected. An object file is produced despite the E-class error, but
the output or program result may be incorrect.

E-1

Code

Description

Warning; should be investigated by checking the statements to which W-class
diagnostic messages apply. Warnings are issued for statements that use acceptable,
but nonstandard, syntax and for statements corrected by the compiler. An object
file is produced, but the program results may be incorrect. Note that W-class
messages are produced unless the /NOWARNINGS qualifier is specified in the
FORTRAN command.

Information; not an error message and does not call for corrective action. However,
the I-class message informs you that either a correct VAX FORTRAN statement
may have unexpected results or you have used a VAX extension to FORTRAN-77.

Typing mistakes are a likely cause of syntax errors: they can cause the compiler to generate
misleading diagnostic messages. Beware especially of the following:
• Missing comma or parenthesis in a complicated expression or FORMAT statement.
• Misspelled variable names. The compiler may not detect this error, so execution can
be affected.
• Inadvertent line continuation mark. This can cause a diagnostic message for the preceding line.
.
• Extension of the statement line past column 72. Unless /EXTEND_SOURCE is
specified, this can cause diagnostic messages because the statement is terminated
early.
• Confusion between the digit 0 and the uppercase letter 0. This can result in variable
names that appear identical to you but not to the compiler.
Another source of diagnostic messages is the inclusion of invalid ASCII characters in the
source program. With the exception of the tab, space, and form-feed characters, nonprinting ASCII control characters are not valid in a FORTRAN source program. As the source
program is scanned, such invalid characters are replaced by a question mark(?). However,
because the question mark cannot occur in a FORTRAN statement, a syntax error usually
results.
Because a diagnostic message indicates only the immediate cause, you should always check
the entire source statement carefully.
The following examples show how source program diagnostic messages are displayed in
interactive mode at your terminal. Figure E-1 shows how these messages appear in listings.

E-2

Diagnostic Messages

%FORT-W-FMTEXTCOM, Extra comma in format list
CFORMAT (13,)J in module MORTGAGE at line 13
%FORT-F-UNDSTALABt Undefined statement label
CGGJ in module MORTGAGE at line 18
%FORT-F-ENDNOOBJ, DB1:CSMITHJMOR.FOR;1 completed
with 2 dia~nostics - obJect deleted
Pro~ram to calculate monthly mort~a~e payments
0001
c
0002
0003
PROGRAM MORTGAGE
0004
0005
TYPE 10
FORMAT (' ENTER AMOUNT OF MORTGAGE ')
0006
10
ACCEPT 20, I PlJ
0007
0008
20
FORMAT CIGl
0008
TYPE 30
0010
FORMAT (' ENTER LENGTH OF MORTGAGE IN MONTHS ')
0011
30
ACCEPT 40, I MON
0012
FORMAT <13,)
0013
40
0014
%FORT-W-FMTEXTCOMt Extra comma in format list
CFORMAT CI3,)J in module MORTGAGE at line 13

0015
TYPE 50
FORMAT (' ENTER ANNUAL INTEREST RATE ')
0016
50
0017
ACCEPT GOt VINT
0018
GO
FORMAT <FG.4>
0018
GO TO GG
!Get monthly rate
0020
YI = YINT/12
65
0021
!MON = -IMON
0022
FIPV = IPlJ * YI
0023
YI = YI + 1
0024
FIMON = YI**IMON
0025
FIMON = 1 - FIMON
0026
FMNTHLY = FIPV/FIMON
0027
TYPE 70t FMNTHLY
0028
FORMAT (I MONTHLY PAYMENT EQUALS
tF7.3 )
0028
70
0030
STOP
END
0031
%FORT-F-UNDSTALAB, Undefined statement label
CGGJ in module MORTGAGE at line 18
I

Figure E-1: Sample Diagnostic Messages (Listing Format)

Diagnostic Messages

E-3

Table E-1 is an alphabetical list of FORTRAN diagnostic error messages. For each message, the table gives a mnemonic, an error code level, the text of the message, and an
explanation of the message.
Table E-1: Source Program Diagnostic Messages
Mnemonic

Error
Code

Text/Meaning

ADJARRBOU

Adjustable array bounds must be dummy arguments or in common
Variables specified in dimension declarator expressions must either
be subprogram dummy arguments or appear in common.

ADJ ARRUSE

Adjustable array used in invalid context
A reference was made to an adjustable array in a context where
such a reference is not allowed.

ADJLENUSE

Passed-length character name used in invalid context
A reference was made to a passed-length character array or variable in a context where such reference is not allowed.

ALTRETLAB

Alternate return label used in invalid context

An alternate return argument was used in a function reference.
ALTRETO MI

Alternate return omitted in SUBROUTINE or ENTRY statement
An asterisk is missing in the argument list of a subroutine for which
an alternate return is specified. Examples:
1.

SUBROUTINE ><YZCAtB>

RETURN 1

ENTRY ABC CQ tR >

RETURN I

E-4

Diagnostic Messages

Table E-1 (Cont.): Source Program Diagnostic Messages
Mnemonic

Error
Code

Text/Meaning

ALTRETSPE

Alternate return specifier invalid in FUNCTION subprogram
The argument list of a FUNCTION declaration contains an asterisk, or a RETURN statement in a function subprogram specifies an
alternate return. Examples:
1.

INTEGER FUNCTION TCB ( ARG 1

FUNCTION I MA}{

* 1}0

RETURN I +J
END

ARIVALREQ

Character expression where arithmetic value required

An expression that must be arithmetic (INTEGER, REAL, LOGICAL, or COMPLEX) was of type CHARACTER.
AS SARRUSE

Assumed size array name used in invalid context

An assumed size array name was used where the size of the array
was also required, for example, in an 1/0 list.
ASSDOVAR

Assignment to DO variable within loop
The control variable of a DO loop has been altered within the range
of the DO statement.

BAD END

END [STRUCTUREIUNIONIMAPJ must match top.
A STRUCTURE, UNION, or MAP statement did not have a corresponding END STRUCTURE, END UNION, or END MAP statement, respectively.

BAD FIELD

Field name not defined for this structure.
A field name not defined in a structure was used in a qualified
reference.

BADRECFEF

Aggregate reference where scalar reference required

An aggregate reference was used, where a scalar reference was required.
CDDBITSIZ

CDD field specifies a bit size or alignment. Size or address rounded
up to byte alignment.
CDD's bit datatype and bit alignment are not supported by FORTRAN.

Diagnostic Messages

E-5

Table E-1 (Cont.): Source Program Diagnostic Messages
Mnemonic

Error
Code

Text/Meaning

CDDERROR

CDD description extraction condition
The FORTRAN compiler is in the process of extracting a data
definition from the Common Data Dictionary. See the accompanying messages for more information.

CDDNOTSTR

CDD record is not a structure
CDD record description was not structured. VAX FORTRAN requires structure definitions (elementary field descriptions in
CDDL).

CDDRECDIM

CDD record is dimensioned
VAX FORTRAN does not support dimensioned structures, for example, arrays of structures.

CDDSCALED

CDD description specifies a scaled data type
VAX FORTRAN does not support scaled data types. The data
described by the CDD specifies a scaled component.

CDDTOOBIG

Attributes for some member of CDD record description exceed implementation's limit for member complexity
Some member of the CDD record description has too many attributes and has created a program that is too large. Change the Common Data Dictionary description to make the field description
smaller.

CDDTOODEEP

Attributes for CDD record description exceed implementation's
limit for record complexity
The COD record description contains structures that are nested too
deeply. Modify the CDD description to reduce the level of nesting
in the record description.

CHANAMINC

Character name incorrectly initialized with numeric value
Character data with a length greater than one was initialized with
a numeric value in a data statement. Example:
CHARACTER*ll A
DATA A/ 1ll/

CHASBSLIM

Character substring limits out of order
The first character position of a substring expression is greater than
the last character position. Example:
CC5:3)

E-6

Diagnostic Messages

Table E-1.(Cont.): Source Program Diagnostic Messages
Mnemonic

Error
Code

Text/Meaning

CHAVALREQ

Arithmetic expression where character value required

An expression that must be of type CHARACTER was of another
data type.
COLMAJOR

CDD description specifies that it is not a column major array
FORTRAN only supports column-major arrays. Change the CDD
description to specify a column-major array.

CONSIZEXC

Constant size exceeds variable size in data initialization
A constant used for data initialization is larger than its corresponding variable.

DBGOPT

The NOOPTIMIZE qualifier is recommended with the DEBUG
qualifier.
Optimizations performed by the compiler can cause several differ. ent kinds of unexpected behavior when using VAX DEBUG. See
Chapter 1 of VAX FORTRAN User's Guide for more information.

DEFSTAUNK

Default STATUS= 'UNKNOWN' used in OPEN statement
The OPEN statement default STATUS='UNKNOWN' may
cause an old file to be inadvertently modified.

DEPEND ITEM

CDD description contains Depends Item attribute (ignored).
FORTRAN does not support the CDD Depends Item attribute. No
action is required.

DICTABORT

DICTIONARY processing of CDD record description aborted
The FORTRAN compiler is unable to process the CDD record description. See the accompanying messages for further information.

ENTDUMVAR

ENTRY dummy variable previously used in executable statement
The dummy arguments of an ENTRY statement must not have
been used previously in an executable statement in the same program unit.

EQVEXPCOM

EQUIVALEN CE statement incorrectly expands a common block
A common block cannot be extended beyond its beginning by an
EQUIVALEN CE statement.

EXCCHATRU

Non-blank characters truncated in string constant
A character or Hollerith constant was converted to a data type
which was not large enough to contain all the significant characters.
Diagnostic Messages

E-7

Table E-1 (Cont.): Source Program Diagnostic Messages
Mnemonic

Error
Code

Text/Meaning

EXCDIGTRU

Non-zero digits truncated in hex or octal constant

An octal or hexadecimal constant was converted to a data type
which was not large enough to contain all the significant digits.
EXCNAMDAT

Number of names exceeds number of values in data initialization
The number of constants specified in a DATA statement must
match the number of variables or array elements to be initialized.
The remaining variables andr array elements are not initialized.

EXCVALDAT

Number of values exceeds number of names in data initialization
The number of variables or array elements to be initialized must
match the number of constants specified in data initialization. The
remaining constant values are ignored.

EXPSTAOVE

Compiler expression stack overflow

An expression is too complex or there are too many actual arguments in a subprogram reference. A maximum of 255 actual arguments can be compiled. You can subdivide a complex expression or
reduce the number of arguments.
EXTCHAFOL

Extra characters following a valid statement
Superfluous text was found at the end of a syntactically correct
statement. Check for typing or syntax errors.

EXTMIXCOM

Extension to FORTRAN-77: Mixed numeric and character elements in common
Numeric and character variable and array elements cannot be
equivalenced to each other.

EXTMIXEQV

Extension to FORTRAN-77: Mixed numeric and character elements in EQUIVALEN CE
A common block must not contain both numeric and character
data.

EXTRECUSE

Extension to FORTRAN-77: Nonstandard use of field reference.
A record reference (for example, record-name.field-name) was used
in a program compiled with the /STANDARD=lSYNTAX_ALLl
qualifier in the FORTRAN command.

EXT_COM

Extension to FORTRAN-77: nonstardard comment
FORTRAN-77 allows only the characters 11 C11 and "*" to begin a
comment line; "D", "d", and 11 !11 are extensions to FORTRAN-77.

E-8

Diagnostic' Messages

Table E-1 (Cont.): Source Program Diagnostic Messages
Mnemonic

Error
Code

Text/Meaning

EXT_CONST

Extension to FORTRAN-77: nonstandard constant
The following constant forms are extensions to FORTRAN-77:
• Hollerith

nH .....

• Typeless

'xxxx 'X or 'oooo 'O

• Octal

• Hexadecimal

Zxxxx

• Radix-50

nR .....

0000 or Ooooo

• Complex with
PARAMETER components

EXT_FMT

• COMPLEX*l6

(www.xxxDn, yyy.zzzDn)

• REAL*l6

yyy.zzzQn

Extension to FORTRAN-77: nonstandard FORMAT statement
item
The following format
FORTRAN-77:

EXT_KEY

field

descriptors

are

extensions

• $,0,Z

All forms

• A,L,l,F,E,G,D

Default field width forms

• p

Without scale factor

Extension to FORTRAN-77: nonstandard keyword
A nonstandard keyword was used.

EXT-LEX

Extension to FORTRAN-77: nonstandard lexical item
One of the following nonstandard lexical items was used:

• An alternate return specifier with an ampersand(&) in a CALL
statement
• The apostrophe ( ') form of record specifier in a direct access 1/0
statement
• A variable format expression
EXT_NAME

Extension to FORTRAN-77: nonstandard name
A name longer than six characters or one that contained a dollar
sign ( $ ) or an underscore ( _) was used.

Diagnostic Messages

E-9

Table E-1 (Cont.): Source Program Diagnostic Messages
Mnemonic

Error
Code

Text/Meaning

EXT_OPER

Extension to FORTRAN-77: nonstandard operator
The operators .XOR., %VAL, %REF, %DESCR, and %LOC are
extensions to FORTRAN-77. The standard form of .XOR. is
.NEQV. The% operators are extensions provided to allow access to
non-FORTRAN parts of the VAX-11 environment.

EXT_SOURC

Extension to FORTRAN-77: tab indentation or lowercase source
The use of tab indentation or lowercase letters in source code is an
extension to FORTRAN-77.

EXT_STMT

Extension to FORTRAN-77: nonstandard statement type
A nonstandard statement type was used.

EXT_SYN

Extension to FORTRAN-77: nonstandard syntax
One of the following syntax extensions was specified:
• PARAMETER name= value
No parentheses
• type name/value/
Data initialization in type declaration
• DATA (ch(exp:exp),v=e2)/values/
Substring initialization with implied-DO in DATA statement
• CALL name(arg2,,arg3)
Null actual argument
• READ ( ... ),iolist
Comma between I/0 control and element lists
• PARAMETER (name2=ABS(namel))
Function use in PARAMETER
• el ** -e2
Two consecutive operators

E-10

Diagnostic Messages

Table E-1 (Cont.): Source Program Diagnostic Messages
Mnemonic

Error
Code

Text/Meaning

EXT_TYPE

Extension to FORTRAN-77; nonstandard data type specification
The following DATA type specifications are extensions to
FORTRAN-77. The FORTRAN-77 equivalent is given where
available. This message is issued when these types are used in the
IMPLICIT statement or in a numeric type statement.

Extension
BYTE
LOGICAL*l
LOGICAL*2
LOGICAL*4
INTEGER*2
INTEGER*4
REAL*4
REAL*B
REAL*l6
COMPLEX*B
COMPLEX*l6
DOUBLE COMPLEX
FLDNAME

Standard

LOGICAL (with /NOI4
specified only)
LOGICAL
INTEGER (with /NOI4
specified only)
INTEGER
REAL
DOUBLE PRECISION
COMPLEX

Structure field is missing a field name.
Unnamed fields are not allowed. The effect of an unnamed field
can be achieved by using the pseudo-name %FILL in place of a
field name in a typed data declaration.

FMTEXTCOM

Extra comma in format list
Example: FORMAT (I4,)

FMTEXTNUM

Extra number in format list
Example: FORMAT (I4,3)

FMTINVCHA

Format item contains meaningless character

An invalid character or a syntax error was detected in a FORMAT
statement.
FMTINVCON

Constant in format item out of range
A numeric value in a FORMAT statement exceeds the allowable
range. Refer to Chapter 12 for information about range limits.

FMTMISNUM

Missing number in format list
Example: FORMAT (F6.)

Diagnostic Messages

E-11

Table E-1 (Cont.): Source Program Diagnostic Messages
Mnemonic

Error
Code

Text/Meaning

FMTMISSEP

Missing separator between format items
A required separator character has been omitted between fields in a
FORMAT statement.

FMTNEST

Format groups nested too deeply
Format groups cannot be nested beyond eight levels.

FMTPAREN

Unbalanced parentheses in format list
The number of right parentheses does not match the number of left
parentheses.

FMTSIGN

Format item cannot be signed
A signed constant is valid only with the P format code.

HOLCOURED

Count of Hollerith or Radix-50 constant too large, reduced
The value specified by the integer preceding the H or R is greater
than the number of characters remaining in the source statement.

IDOINVOP

Invalid operation in implied-DO list

An invalid operation was attempted in an implied-DO list in a
DATA statement, for.· example, a function reference in the subscript or substring expression of an array or character substring
reference. Example:
DATA CACSIN<REAL<I>)) t I=1 t10) /101./

IDOINVPAR

Invalid DO parameters in implied-DO list

An invalid control parameter was detected in an implied-DO list in
a DATA statement, for example, an increment of zero.
IDOINVREF

Invalid reference to name in implied-DO list
A control parameter expression in an implied-DO list in a DATA
statement contains a name which is not the name of a control
variable of any implied-DO list which has the name in its scope.
Example:
DATA CACJ),J=1t10>tCBCI>t I=JtK> /1001,/

Both J and Kin the second implied-DO list are invalid names.

E-12

Diagnostic Messages

Table E-1 (Cont.): Source Program Diagnostic Messages
Mnemonic

Error
Code

Text/Meaning

IDOSYNERR

Syntax error in implied-DO list in data initialization
Improper syntax was detected in an implied-DO list in data initialization, for instance, improperly nested parentheses.

IMPDECLAR

Use of implicit with declaration warnings.

An IMPLICIT statement was used in a program compiled with the
/WARNINGS=DECLARATIONS qualifier in the FORTRAN command.
IMPMULTYP

Letter mentioned twice in IMPLICIT statement, last type used
A letter has been given an implicit data type more than once. The
last data type given is used.

IMPNONE

Untyped name, Il\USt be explicitly typed
The displayed name has not been defined· in any data type declaration statement, and IMPLICIT NONE statement has been specified. Check that the name was not accidentally created by an undetected syntax error. Example:
DO 10 I = 1 .10

The apparent DO statement is really an assignment to the accidentally created variable DOlOI.
IMPSYNERR

Syntax error in IMPLICIT statement
Improper syntax was used in an IMPLICIT statement. Refer to
Section 8.8 for the syntax rules.

INCDONEST

DO or IF statement incorrectly nested
One of the following conditions was found:
• A statement label specified in a DO statement has been used
previously. Example:
10

I=I+1

J =J + 1
DO 10 K = 1 , 10

Diagnostic Messages

E-13

Table E-1 (Cont.): Source Program Diagnostic Messages
Mnemonic
INCDONEST
(Cont.)

Error
Code
F

Text/Meaning
• A DO loop contains an incomplete DO loop or IF block. Examples:
1.

DD 10 I=1110
J =J + 1
DD20K=1t10

J = J + K
10

CONTINUE

The start of the incomplete IF block can be a block IF, ELSE IF,
or ELSE statement.
2.

DD 10 I=1 t10
J = J + I
IF (J .GT. 20) THEN
J
ELSE

=J - 1

J =J + 1
10

INCFILNES

CONTINUE
END IF

INCLUDE files and/or DICTIONARY statements nested too
deeply
Up to 10 levels of nested INCLUDE files and/or DICTIONARY
statements are permitted.

INCFUNTYP

Inconsistent function data types
The function name and entry points in a function subprogram
must be consistent within one of three groups of data types:
Group 1: All numeric types except REAL*l6,
COMPLEX*16
Group 2: REAL*l6, COMPLEX*l6
Group 3: Character
Example:
CHARACTER* 15 FUNCTION I
REAL*a G
ENTRY G

INCLABUSE

Inconsistent usage of statement label
Labels of executable statements have been confused with labels of
FORMAT statements or with labels of nonexecutable statements.
Example:
GO TD 10
10

E-14

Diagnostic Messages

FDRMAT(I5>

Table E-1 (Cont.): Source Program Diagnostic Messages
Mnemonic

Error
Code

Text/Meaning

INCLENMOD

Incorrect length modifier in declaration

An unacceptable length has been specified in a data type declaration (see Section 8.4). For example:
INTEGER PI PES*B

INCMODNAM

Module name not found in library
The module name specified in an INCLUDE statement could not
be located in the specified library. Check the name of the module
and library.

INCOPEFAI

Open failure on INCLUDE file
The specified file could not be opened, possibly due to an incorrect
file specification, nonexistent file, unmounted volume, or a protection violation.

INCSTAFUN

Inconsistent statement function reference
The actual argument(s) in a statement function reference do not
agree in either order, number, or data type with the formal arguments declared.

INCSYNERR

Syntax error in INCLUDE file specification
The file-name string is not acceptable (invalid syntax, invalid
qualifier, undefined device, and so on).

INQUNIT

Missing or invalid use of UNIT or FILE specifier in INQUIRE
statement.

An INQUIRE statement must have a UNIT specifier or a FILE
specifier, but may not have both.
INTFUNARG

Arguments incompatible with intrinsic function, assumed EXTERNAL
A function reference was made, using an intrinsic function name,
but the argument list does not agree in order, number, or type with
the intrinsic function requirements. The function is assumed to be
supplied by you as an EXTERNAL function.

INTVALREQ

Non-integer expression where integer value required

An expression that must be of type INTEGER was another data
type.
~
INVACTARG

Invalid use of intrinsic function name as actual argument
A generic intrinsic function name was used as an actual argument.

Diagnostic Messages

E-15

Table E-1 (Cont.): Source Program Diagnostic Messages
Mnemonic

Error
Code

Text/Meaning

INVASSVAR

Invalid ASSOCIATEVARIABLE specification

An AS SOCIATEVARIABLE specification in an OPEN or DEFINE
FILE statement was a dummy argument or an array element.
INVCHAUSE

Invalid character used in constant

An invalid character was detected in a constant. Valid characters
are:
Hexadecimal: 0 - 9, A - F, a - f
Octal:
0- 7
Radix-50:
A - Z, 0 - 9, $, period, or space
For Radix-50, a space is substituted for the invalid character. For
hexadecimal and octal, the entire constant is set to zero.
INV CONST

Arithmetic error while evaluating constant or constant expression
The specified value of a constant is too large or too small to be
represented.

INVCONSTR

Invalid control structure using ELSE IF, ELSE, or END IF
The order of ELSE IF, ELSE, or END IF statements is incorrect.
ELSE IF, ELSE, and END IF statements cannot stand alone.
ELSE IF and ELSE must be preceded by either a block IF statement or an ELSE IF statement. END IF must be preceded by
either a block IF, ELSE IF, or ELSE statement. Examples:
1.

DO 10 I=1110

J =J + I
ELSE IF (J .LE. K> THEN

Error: ELSE IF preceded by a DO statement.
2.

IF < J • LT. K) THEN
J = I + J
ELSE
J =I - J
ELSE IF (J .EQ. K> THEN
END IF

Error: ELSE IF preceded by an ELSE statement.
INVDOTERM

Statement cannot terminate a DO loop
The terminal statement of a DO loop cannot be a GO TO, arithmetic IF, RETURN, block IF, ELSE, ELSE IF, END IF, DO, or END
statement.

E-16

Diagnostic Messages

Table E-1 (Cont.): Source Program Diagnostic Messages
Mnemonic

Error
Code

Text/Meaning

INVENDKEY

Invalid END= keyword, ignored
The END keyword was used illegally in a WRITE, REWRITE,
direct access READ, or keyed access READ statement.

IN VENTRY

ENTRY within DO loop or IF block, statement ignored

An ENTRY statement is not allowed within the range of a DO loop
or IF block.
INVEQVCOM

Invalid equivalence of two variables in common
Variables in common cannot be equivalenced to each other.

INVFUNUSE

Invalid use of function name in CALL statement
A CALL statement referred to a subprogram name that was used as
a CHARACTER, REAL*16, or COMPLEX*l6 function. Example:
IMPLICIT CHARACTER*lO<C>
CSCAL = CFUNC <H)
CALL CFUNC <){ >

INVINIVAR

Invalid initialization of variable not in common

An attempt was made, in a BLOCK DATA subprogram, to initialize a variable that is not in a common block.
INVINTFUN

Name used in INTRINSIC statement is not an intrinsic function
A function name which appeared in the INTRINSIC statement is
not an intrinsic function.

INVIOSPEC

Invalid I/0 specification for this type of I/0 statement
A syntax error was found in the portion of an I/0 statement that
precedes the I/0 list. Examples:

INVKEYOPE

TYPE <B>, J

WR !TE 100, J

Incorrect keyword in OPEN, CLOSE, or INQUIRE statement

An OPEN, CLOSE, or INQUIRE statement contains a keyword
which is not valid for that statement.

Diagnostic Messages

E-17

Table E-1 (Cont.): Source Program Diagnostic Messages
Mnemonic

Error
Code

Text/Meaning

INVLEFSID

Left side of assignment must be variable or array element
The symbolic name to which the value of an expression is assigned
must be a variable, array element, or character substring referenee.

INVLEXEME

Variable name, constant, or expression invalid in this context
An entity has been used incorrectly; for example, the name of a
subprogram was used where an arithmetic expression is required.

INVLOGIF

Statement cannot appear in logical IF statement
A logical IF statement must not contain a DO statement or another
logical IF, IF THEN, ELSE IF, ELSE, END IF, or END statement.

INVNMLELE

Invalid NAMELIST element
Dummy argument or element other than variable or array name
appeared in NAMELIST declaration.

INVNUMSUB

Number of subscripts does not match array declaration
More or fewer dimensions than were declared for the array are
referenced.

INVPERARG

Invalid argument to %VAL, %REF, %DES CR, or %LOC
- The argument specified for one of the built-in functions is not
valid. Examples:
1. %VAL (3.5DO) - Argument cannot be REAL*8, REAL*l6,
character, or complex.
2.

INVPERUSE

%LOC (X+ Y) - Argument must not be an expression.

%VAL, %REF, or %DESCR used in invalid context
The argument list built-in functions (%VAL, %REF, %DESCR)
cannot be used outside an actual argument list. Example:
X = i..REF<Y>

INVQUAL

Invalid qualifier or qualifier value in OPTIONS statement
An invalid qualifier or qualifier value was specified in the OPTIONS statement. The qualifier is ignored.

E-18

Diagnostic Messages

Table E-1 (Cont.): Source Program Diagnostic Messages
Mnemonic

Error
Code

Text/Meaning

INVRECUSE

Invalid use of record or array name
A statement in the program violated one of the following rules:
• An aggregate cannot be assigned to a nonaggregate or to an
aggregate with a structure that isn't the same.
• An array name reference cannot be qualified.
• Aggregate references cannot be used in 1/0 lists of formatted 1/0
statements.

INVREPCOU

Invalid repeat count in data initialization, count ignored
The repeat count in a data initialization was not an unsigned,
nonzero integer constant. The count is ignored.

INVSBSREF

Substring reference used in invalid context
A substring reference to a variable or array that is not of type
CHARACTER has been detected. Example:
REAL }{(10)

Y = XCJ:Kl

INVSTALAB

Invalid statement label ignored

An improperly formed statement label (namely, a label containing
letters) has been detected in columns 1 to 5 of an initial line. The
statement label is ignored.
INVSUBREF

Subscripted reference to non-array variable
A variable that is not defined as an array cannot appear with
subscripts.

INVTYPUSE

Name previously used with conflicting data type
A data type was assigned to a name that had already been used in a
context that required a different data type.

IODUPKEY

Duplicated keyword in 1/0 statement
Each keyword subparameter in an 1/0 statement or auxiliary 1/0
statement can be specified only once.

Diagnostic Messages

E-19

Table E-1 (Cont.): Source Program Diagnostic Messages
Mnemonic

Error
Code

Text/Meaning

IOINVFMT

Format specifier in error
The format specifier in an I/0 statement is invalid. It must be one
of the following:
• The label of a FORMAT statement.
• An asterisk ( * ). (List-directed I/0.)

• A run-time format specifier: variable, array element, or character substring reference.
• An integer variable that has been assigned a FORMAT label by
an ASSIGN statement.
IOINVKEY

Invalid keyword for this type of I/0 statement
An I/0 statement contains a keyword which cannot be used with
that type of I/0 statement.

IOINVLIST

Invalid I/0 list element for input statement
An input statement I/O list contains an invalid element, such as an
expression or a constant.

IOSYNERR

Syntax error in I/0 list
Improper syntax was detected in an I/0 list.

LABASSIGN

Label in ASSIGN statement exceeds INTEGER*2 range
A label whose value is assigned to an INTEGER*2 variable by an
ASSIGN statement must not be separated by more than 32K bytes
from the beginning of the code for the program unit.

LENCHAFUN

Length specified must match CHARACTER FUNCTION declaration
The length specifications for all ENTRY names in a character
function _subprogram must be the same. Example:
CHARACTER* 15 FUNCTION F
CHARACTER*20 G
ENTRY G

LOGVALREQ

Non-logical expression where logical value required
An expression that must be of type LOGICAL was of another data
type.

E-20

Diagnostic Messages

Table E-1 (Cont.): Source Program Diagnostic Messages
'Mnemonic

Error
Code

Text/Meaning

LOWBOUGRE

Lower bound greater than upper bound in array declaration
The upper bound of a dimension declarator must be equal to or
greater than the lower bound.

MINDIGITS

CDD description specifies precision less than allowed for data type.
Minimum precision has been supplied.
:some Common Data Dictionary data types specify a number of
digits which is incompatible with FORTRAN data types. The
FORTRAN compiler has expanded the data type to conform to a
FORTRAN data type. No action required.

MIN OCCURS

CDD description contains Minimum Occurs attribute (ignored).
FORTRAN does not support the Common Data Dictionary Minimum Occurs attribute. No action required.

MISSAPOS

Missing apostrophe in character constant
A character constant must be enclosed by apostrophes.

MISS CONST

Missing constant
A required constant was not found.

MIS SD EL

Missing operator or delimiter symbol
Two terms of an expression are not separated by an operator, or a
punctuation mark (such as a comma) has been omitted; Examples:
1. CIRCUM = 3, 14 DIAM
2. IF (I 10t20t30

MIS SEND

Missing END statement, END is assumed

An END statement was missing at the end of the last input file,
and it has been inserted.
MISS EXPO

Missing exponent after E, D, or Q
A floating-point constant was specified in E, D, or Q notation, but
the exponent was omitted.

MISS KEY

Missing keyword
A required keyword, :such as TO, was omitted from a statement
such as ASSIGN 10 TO I.

MISS LABEL

Missing statement label
A required statement laqel reference was omitted.

Diagnostic Messages

E-21

Table E-1 (Cont.): Source Program Diagnostic Messages
Mnemonic

Error
Code

Text/Meaning

MlSSNAME

Missing variable or subprogram name
A required variable name or subprogram name was not found.

MlSSUNlT

Unit specifier keyword missing in l/O statement
An 1/0 statement must include a unit specifier subparameter.

MlSSVAR

Missing variable or constant
An expression, or a term of an expression, has been omitted. Examples:

1. WRITE ( >
2. DI ST = *TI ME

MULDECNAM

Multiple declaration of name
A name appears in two or more inconsistent declaration statements.

MULDECTYP

Multiple declaration of data type for variable, first type used
A variable appears in more than one data type declaration statement. The first type declaration is used.

MULDEFLAB

Multiple definition of statement label, second ignored
The same label appears on more than one statement. The first
occurrence of the label is used.

MULFLDNAM

Multiply defined field name
Each field name within the same level of a given structure declaration must be unique.

MULSTRNAM

Multiply defined STRUCTURE name
A STRUCTURE name must be unique among STRUCTURE
names.

NAMTOOLON

Name longer than 31 characters
A symbolic name has been truncated to 31 characters.

NMLIOLIST

l/0 list not permitted with namelist l/O
An 1/0 statement with a namelist specifier incorrectly contained an

l/0 list.

E-22

Diagnostic Messages

Table E-1 (Cont.): Source Program Diagnostic Messages
Mnemonic

Error
Code

NODFLOAT

Text/Meaning
CDD description specifies the D_Floating data type. The data
cannot be represented when compiling /G_FLOAT.
D_floating datatype was specified when compiling with /G_
FLOATING qualifier. Ignore the warning message or recompile the
program using the /NOG_FLOATING qualifier.

NOGFLOAT

CDD description specifies G_Floating data type. The data cannot
be represented when compiling /NOG_FLOAT.
G_floating datatype was specified when compiling with /NOG_
FLOATING qualifier. Ignore the warning message or recompile the
program using the /G_FLOAT qualifier.

NOHFLOAT

CDD description specifies H_Floating data type. The data cannot
be represented when compiling /NOG_FLOAT.
H_floating datatype was specified when compiling with /NOG_
FLOATING qualifier. Ignore the warning message or recompile the
program using the /G_FLOATING qualifier.

NONCONSUB

Non-constant subscript where constant required
Subscript and substring expressions used in DATA and EQUIVALENCE statements must be constants.

NOPATH

No path to this statement
Program control cannot reach this statement. The statement is
deleted. Example:
10

I=I+l
GO TO 10
STOP

OPEDOLOOP

Unclosed DO loop or IF block
The terminal statement of a DO loop or the END IF statement of
an IF block was not found. Example:
D020I=lt10

}·{ = y
END

OPENOTPER

Operation not permissible on these data types

An invalid operation was specified, such as an .AND. of two real
variables.

Diagnostic Messages

E-23

Table E-1 (Cont.): Source Program Diagnostic Messages
Error
Mnemonic

Code

Text/Meaning

PROSTOREQ

Program storage requirements exceed addressable memory
The storage space allocated to the variables and arrays of the program unit exceeds the addressing range of the machine.

REDCONMAR

Redundant continuation. mark ignored
A continuation mark was detected where an initial line is required.
The continuation mark is ignored.

REFERENCE

CDD description contains Reference attribute (ignored).
The Reference attribute is not supported by FORTRAN. No action
required.

SOURCETYPE

CDD description contains Source Type attribute (ignored).
FORTRAN does not support the Common Data Dictionary Source
Type attribute. No action required.

STAENDSTR

Statement not allowed within structure; structure definition closed
A statement not allowed in a structure declaration block was encountered. The compiler assumes that you omitted one or more
END STRUCTURE statements.

STAINVSTR

Statement not allowed within structure definition; statement ignored
A statement not allowed in a structure declaration block was encountered. Structure declaration blocks can only include the following statements: typed data declaration statements, RECORD
statements, UNION/END UNION statements, MAP/END MAP
statements, and STRUCTURE/END STRUCTURE statements.

STANOTVAL

Statement not valid in this program unit, statement ignored
A program unit contains a statement that is not allowed; for example, a BLOCK DATA subprogram contains an executable statement.

STAOUTORD

Statement out of order, statement ignored
The order of statements was not as specified in Section 5.2.2.1. The
statement found to be out of order is ignored.

STATOOCOM

Statement too complex
A statement is too complex to be compiled. It must be subdivided
into two or more statements.

E-24

Diagnostic Messages

Table E-1 (Cont.): Source Program Diagnostic Messages
Mnemonic

Error
Code

Text/Meaning

STRCONTRU

String constant truncated to maximum length
A character or Hollerith constant can contain up to 2000 characters. A Radix-50 constant can contain up to 12 characters.

STRDEPTH

STRUCTUREs/UNIONs/MAPs nested too deeply
The combined nesting level limit for structures, unions, and maps
is 20 levels.

STRNAME

Outer level structure is missing a structure name
An outer level STRUCTURE statement must have a structure

name in order for a RECORD statement to be able to reference the
structure declaration.
STRNOTDEF

Structure name in RECORD statement not defined
Either a RECORD statement did not contain a structure name
enclosed within slashes or the structure name contained in a RECORD statement was not defined in a structure declara:tion.

SUBEXPVAL

Subscript or substring expression value out of bounds
An array element beyond the specified dimensions, or a character
substring outside the specified bounds, was referenced.

TAGVARIAB

CDD description contains Tag Variable attrib_ute (ignored).
FORTRAN does not support the Common Data Dictionary Tag
Variable attribute. No action required.

TOOMAN COM

Too many named common blocks
Reduce the number of named common blocks.

TOOMANCON

Too many continuation lines, remainder ignored
Up to 99 continuation lines are permitted, as determined by the
/CONTINUATIONS=n qualifier (default, 19).

TOO MAND IM

More than 7 dimensions specified, remainder ignored
An array can be defined as having up to seven dimensions.

TOOMANYDO

DO and IF statements nested too deeply
DO loops and block IF statements cannot be nested beyond 20
levels.

Diagnostic Messages

E-25

Table E-1 (Cont.): Source Program Diagnostic Messages
Mnemonic

Error
Code

Text/Meaning

UNDARR

Undimensioned array or statement function definition out of order
Either a statement function definition was found among executable
statements or an assignment statement involving an undimensioned array was found.

UNDSTALAB

Undefined statement label
Reference has been made to a statement label that is not defined in
the program unit.

UNSUPPTYPE

CDD description specifies an unsupported data type.
The Common Data Dictionary description for a structure item has
attempted to use a data type that is not supported by FORTRAN.
The FORTRAN compiler makes the data type accessible by declaring it as an inner structure containing a single CHARACTER
%FILL field with an appropriate length. Change the data type to
one that is supported by FORTRAN or use the FORTRAN built-in
functions to manipulate the contents of the field.

VARINCEQV

Variable inconsistently equivalenced to itself
EQUIVALEN CE statements specify inconsistent relationships between variables or array elements. Example:
EQLJJl.JALENCE (A( 1 >, A(2) >

ZERLENSTR

Zero-length string
The length specified for a character, Hollerith, hexadecimal, octal,
or Radix-50 constant must not be zero.

E.1.2 Compiler-Fatal Diagnostic Messages
Conditions can be encountered of such severity that compilation must be terminated at
once. These conditions are caused by hardware errors, software errors, and errors that
require changing the FORTRAN command. Printed messages have the form:
FORT-F-error name, error message

E-26

Diagnostic Messages

The first line of the message contains the appropriate file specification or keyword involved
in the error. The operating system supplies more specific information about the error
whenever possible. For example, a file read error might produce the following error message:
%FORT-F-READERR1 error readinf _OBAO:[SMITHJMAIN,FOR;3
-RMS-W-RTB1 512 bYte record too bif for user's buffer
-FORT-F-ABORT1 abort

Table E-2 lists the diagnostic messages that report the occurrence of such compiler-fatal
errors. Because the exact content of the message depends upon the individual problem,
only the first line of the message is provided here. Also, "file-spec" represents placement of
the actual file specification in the message, and "keyword-value" represents the specific
keyword value.

Table E-2: Compiler-Fatal Diagnostic Messages
1/0 Errors

FORT-F-OPENIN, error opening "file-spec" as input
FORT-F-NOSOUFILE, no source file specified
FORT-F-OPENOUT, error opening "file-spec" as output
FORT-F-READERR, error reading "file-spec"
FORT-F-WRITEERR, error writing "file-spec"
FORT-F-CLOSEIN, error closing "file-spec" as input
FORT-F-CLOSEOUT, error closing "file-spec" as output
Command Qualifier Messages

FORT-F-VALERR, specified value is out of legal range
FORT-F-BADVALUE, "keyword-value" is an invalid keyword value
FORT-F-SUBNOTALL, subqualifier not allowed with negated qualifier
Compiler Internal Logic Error

FORT-F-BUGCHECK, internal consistency failure

If you receive the compiler internal logic error, FORT-F-BUGCHECK, you should report
both the error and the circumstance in which it occurred to DIGITAL by means of a
Software Performance Report (SPR).

E.1.3 Compiler Limits
There are limits to the size and complexity of a single VAX FORTRAN program unit.
There are also limits on the complexity of FORTRAN statements. Table E-3 describes
some of these limits.

Diagnostic Messages

E-27

Table E-3: Compiler Limits
Language Element

Limit

Structure nesting

DO, and block IF statement nesting (combined)

Actual number of arguments per CALL or function reference

255

Named common blocks

250

Format group nesting

Labels in computed or assigned GO TO list

500.

Parentheses nesting in expressions

INCLUDE file nesting

Continuation, lines

FORTRAN source line length

132 characters

Symbolic name length

31 characters

Constants
Character, Hollerith
Radix-50

2000 characters
12 characters

Array dimensions
Number of names in a NAMELIST group

7
250

The amount of data storage, the size of arrays, and the total size of executable programs are
limited only by the amount of process virtual address space available, as determined at
VAXNMS system generation.

E.2 Run-Time Diagnostic Messages
Errors that occur during execution of your FORTRAN program are.reported by diagnostic
messages from the Run-Time Library. These messages may result from hardware conditions, file system errors, errors detected by RMS, errors that occur during transfer of data
between the. program and an internal record, computations that cause overflow or underflow, incorrect calls to the Run-Time Library, problems in array descriptions, and conditions detected by the operating system. Refer to the VAX/VMS Run-Time Library
Routines Reference Manual for more information.

E.2.1 Run-Time Library Diagnostic Message Presentation
Run-Time Library diagnostic messages are usually sent either to your terminal (interactive
mode) or to the log file (batch mode).
E-28

Diagnostic Messages

E.2.2 Run-Time Library Diagnostic Messages
Descriptions of Run-Time Library diagnostic messages can be found in Table E-4.
Table E-4 lists each Run-Time diagnostic message in alphabetical order according to its
unique 6- to 9-character ·name. For organizational purposes, the message prefixes FOR$,
SS$, and MTH$ are not shown in this table. (Note: Refer to Table 18-1 for a presentation
of the messages in order of their error numbers.)
Table E-4: Run-Time Diagnostic Messages
Condition
Symbol

Err
No

Sev

Message Text

ADJARRDIM

F,C

adjustable array dimension error
Upon entry to a subprogram, -the evaluation of dimensioning information detected an array in which:
• An upper-dimension bound was less than a lowerdimension bound.

• The dimensions imply an array that exceeds the
addressable memory.
ATTACCNON

attempt to access non-existent record
· One of the following conditions occurred:
• An attempt was made to READ, FIND, or DELETE a nonexistent record .from a relative organization file using direct access.

• An attempt was made to access beyond the end of
the file with ·a direct access READ or FIND to a
sequential organization file.
• An attempt was made to read a nonexistent record
from an indexed organization file with a keyed access READ statement.

BACERR

BACKSPACE error
One of the following conditions occurred:
• The file was not a sequential organization file.
• The file was not opened for sequential access. (A
unit opened .for append access may not be backspaced until a REWIND statement is executed for
that unit.)
• RMS detected an error condition during execution
of a BACKSPACE statement.

Diagnostic Messages

E-29

Table E-4 (Cont.): Run-Time Diagnostic Messages
Condition
Symbol

Err
No

Sev

Message Text

CLO ERR

CLOSE error

An error condition was detected by RMS during execution of a CLOSE statement.
DELERR

DELETE error
One of the following conditions occurred:
• On a direct access DELETE, the file did not have
relative organization.
• On a current record DELETE, the file did not
have relative or indexed organization, or the file
was opened for direct access.
• RMS detected an error condition during execution
of a DELETE statement.

DUPFILSPE

duplicate file specifications
Multiple attempts were made to specify file attributes without an intervening close operation. One of
the following conditions occurred:
• A DEFINE FILE was followed by DEFINE FILE.
• A DEFINE FILE was followed by an OPEN statement.
• A CALL ASSIGN or CALL FDBSET was followed
by an OPEN statement.

ENDDURREA

end-of-file during read
One of the following conditions occurred:

• An RMS end-of-file condition was encountered
during execution of a READ statement that did
not contain an END, ERR, or IOSTAT specification.
• An end-of-file record written by the ENDFILE
statement was encountered during execution of a
READ statement that did not contain an END,
ERR, or IOSTAT specification.
• An attempt was made to read past the end of an
internal file character string or array during execution of a READ statement that did not contain an
END, ERR, or IOSTAT specification.

E-30

Diagnostic Messages

Table E-4 (Cont.): Run-Time Diagnostic Messages
Condition
Symbol

Err
No

Sev

Message Text

ENDFILERR

ENDFILE error
One of the following conditions occurred:

• The file was not a sequential organization file with
variable-length records.

• The file was not opened for sequential or append
access.

• An unformatted file did not contain segmented records.

• RMS detected an error during execution of an
ENDFILE statement.
ERRDURREA

error during read
RMS detected an error condition during execution of
a READ statement.

ERRDURWRI

error during write
RMS detected an error condition during execution of
a WRITE statement.

FILNAMSPE

file name specification error
A file-name specification given to OPEN, INQUIRE, ·
or CALL ASSIGN was not acceptable to RMS.

FILNOTFOU

file not found
A file with the specified name could not be found
during an open operation.

FINE RR

FIND error
RMS detected an error condition during execution of
a FIND statement.

FLOOVEMAT

F,C

floating overflow in math library
A floating overflow condition was detected during execution of a math library procedure. The result returned was the reserved operand, -0.

FLOUNDMAT

F,C

floating underflow in math library
A floating underflow condition was detected during
execution of a math library procedure. The result returned was zero.

Diagnostic Messages

E-31

Table E-4 (Cont.): Run-Time Diagnostic Messages.
Condition
Symbol

Err
No

Sev

Message Text

FLTDIV

F,C

arithmetic trap, zero divide
During a floating-point or decimal arithmetic operation, an attempt was. made to divide by 0.0. If floating, the result of the operation was set to the reserved
operand, -0. If decimal, the result of the operation is
unpredictable.

FLTDIV_F

F,C

arithmetic fault, zero divide
During a floating-point arithmetic operation, an attempt was made to divide by zero.

FLTOVF

F,C

arithmetic trap, floating overflow
During an arithmetic operation a floating-point value
exceeded the largest representable value for that data
type. The result of the operation was set to the reserved operand, -0.

FLTOVF_F

F,C

arithmetic fault, floating overflow
During an arithmetic operation, a floating-point
value exceeded the largest representable value for
that data type.

FLTUND

F,C

arithmetic trap, floating underflow
During an arithmetic operation a floating-point value
became less than the smallest representable value for
that data type and was replaced with a value of zero.

FLTUND_F

F,C

arithmetic fault, floating overflow
During an arithmetic operation a floating-point value
became less than the smallest representable value for
that data type.

FORVARMIS

F,C

format/variable-type mismatch
An attempt was made either to read or write a real
variable with an integer· field descriptor (I or L), or to
read or write an integer or logical variable with a real
field descriptor (D, E, F, or G). If execution continued, the following actions occurred:
• If I or L, convert as if INTEGER*4.
• If D, E, F, or G, convert as if REAL*4.

E-32

Diagnostic Messages

Table E-4 (Cont.): Run-Time Diagnostic Messages
Condition
Symbol

Err
No

Sev

Message Text

INCFILORG

inconsistent file organization
One of the following conditions occurred:
• The file organization specified in an OPEN statement did not match the organization of the existing file.
• The file organization of the existing file was inconsistent with the specified access mode; that is, direct access was specified with an indexed organization file, or keyed access was specified with a sequential or relative organization file.

INCKEYCHG

inconsistent key change or duplicate key
A WRITE or REWRITE to an indexed organization
file caused a key field to change or be duplicated.
This condition was not allowed by the attributes of
the file, as established when the file was created.

INCOPECLO

inconsistent OPEN/CLOSE parameters
Specifications in an OPEN or CLOSE statement
were inconsistent. Some invalid combinations are:
• READONLY with STATUS= 'NEW'
STATUS= 'SCRATCH'

• ACCESS=' APPEND' with READ ONLY,
STATUS='NEW', or STATUS='SCRATCH'
• DISPOSE= 'SAVE', 'PRINT', or 'SUBMIT'
with STATUS= 'SCRATCH'
• DISPOSE= 'DELETE' with READONLY
INCRECLEN

inconsistent record length
One of the following conditions occurred:

• An attempt was made to create a new relative,
indexed, or direct access file without specifying a
record length.
• An existing file was opened in which the record
length did not match the record size given in an
OPEN or DEFINE FILE statement.

Diagnostic Messages

E-33

Table E-4 (Cont.): Run-Time Diagnostic Messages
Condition
Symbol

Err
No

Sev

Message Text

INCRECTYP

inconsistent record type
The RECORDTYPE value in an OPEN statement
did not match the record type attribute of the existing file that was opened.

INFFORLOO

infinite format loop
The format associated with an I/0 statement that
included an I/0 list had no field descriptors to use in
transferring those values.

INPCONERR

F,C

input conversion error
During a formatted input operation, an invalid character was detected in an input field, or the input
value overflowed the range representable in the input
variable. The value of the variable was set to zero.

INPRECTOO

input record too long
A record was read that exceeded the explicit or the
default record length specified at OPEN (or by the
default OPEN). To read the file, use an OPEN statement with a RECL value of the appropriate size.

INPSTAREQ

input statement requires too much data

An unformatted READ statement attempted to read
more data than existed in the record· being read.
INSVIRMEM

insufficient virtual memory
The FORTRAN Run-Time Library attempted.to exceed its virtual page limit while dynamically allocating space.

INTDIV

F,C

arithmetic trap, integer zero divide
During an integer arithmetic operation, an attempt
was made to divide by zero. The result of the operation was set to the dividend, which is equivalent to
division by one.

INTO VF

F,C

arithmetic trap, integer overflow
During an arithmetic operation, an integer value exceeded byte, word, or longword range. The result of
the operation was the correct low-order part.

E-34

Diagnostic Messages

Table E-4 (Cont.): Run-Time Diagnostic Messages
Condition
Symbol

Err
No

Sev

Message Text

INVARGFOR

invalid argument to FORTRAN Run-Time Library
One of the following conditions occurred:
• An invalid argument was given to a PDP-11 FORTRAN compatibility subroutine such as
ERRSET.
• The FORTRAN compiler passed an invalid coded
argument to the Run-Time Library. This can occur if the compiler is newer than the Run-Time
Library in use.

INVARGMAT

invalid argument to math library
One of the mathematical procedures detected an invalid argument value.

INVKEYSPE

invalid key specification
A key specification in an OPEN statement or in a
keyed access READ statement was invalid. For example, the key length may have been zero or greater
than 255 bytes, or the key length may not conform to
the key specification of the existing file.

INVLOGUNI

invalid logical unit number
A logical unit number greater than 99 or less than
zero was used in an I/O statement.

INVREFVAR

invalid reference to variable in NAMELIST input
The variable in error is shown as "varname" in the
message text. One of the following conditions occurred:
• The variable was not a member of the namelist
group.
• An attempt was made to subscript the scalar vari-

able.
• A subscript of the array variable was out-ofbounds.
• There were too many or too few subscripts for the
variable.

Diagnostic Messages

E-35

Table E-4 (Cont.): Run-Time Diagnostic Messages
Condition
Symbol

Err
No

Sev

Message Text

INVREFVAR
(Cont.)

• An attempt was made to specify a substring of a
noncharacter· variable or array name.
• A substring specifier of the character variable is
out-of-bounds.
• A subscript or substring specifier of the variable
was not an· integer constant.

• An attempt was made. to substring the unsubscripted. array variable.
KEYVALERR

keyword value error· in OPEN statement

An OPEN or CLOSE. statement keyword requiring a
value had an. improper value.
LISIO:....__SYN

F,C

list-directed I/0 syntax error
The data in a list-directed input record had an invalid format, or the type of the constant was incompatible with the corresponding variable. The value of
the variable was unchanged.

LOGZERNEG

F,C

logarithm of zero or negative value

An attempt was made to take the logarithm of zero or
of a negative number. The result returned was the
reserved operand, -0.
MIXFILACC

mixed file access modes
One of the following conditions occurred:
• An attempt was made to use both formatted and
unformatted operations on the same unit.

• An attempt was made to use an invalid combination of access modes on a unit, such as direct and
sequential. The only valid combination is sequential and keyed on a unit opened with
ACCESS= 'KEYED'.
• An attempt was made. to execute a FORTRAN I/0
statement on a logical unit that was opened by a
language· other than FORTRAN.
NO_CURREC

no current record
A REWRITE or current record DELETE was attempted when no current record was defined.

E-36

Diagnostic Messages

Table E-4 (Cont.): Run-Time Diagnostic Messages
Condition
Symbol

Err
No

Sev

Message Text

NO_SUCDEV

no such device
A file-name specification included an invalid or unknown device name when an open operation was attempted.

NOTFORSPE

not a FORTRAN-specific error

An error occurred in the user program or in the RunTime Library that was not a FORTRAN-specific error.
OPEDEFREQ

OPEN or DEFINE FILE required for keyed or direct
access
One of the following conditions occurred:·
• A direct access READ, WRITE, FIND, or DELETE statement was attempted for a file when no
DEFINE FILE or OPEN statement with
ACCESS= 'DIRECT' was performed for that file.
• A keyed access READ statement was attempted
for a file when no OPEN statement with
ACCESS= 'KEYED' was performed for that file.

OPEFAI

open failure

An error was detected by RMS while attempting to
open a file in an OPEN, INQUIRE, or other I/0 statement. This message is used when the error condition
is not one of the more common conditions for which
specific error messages are provided.
OUTCONERR

E,C

output conversion error
During a formatted output operation, the value of a
particular number could not be output in: the specified field length without loss of significant digits. The
field is filled with asterisks.

OUTSTAOVE

output statement overflows record

An output statement attempted to transfer more data
than would fit in the maximum record size.

Diagnostic Messages

E-37;

Table E-4 (Cont.): Run-Time Diagnostic Messages
Condition
Symbol

Err
No

Sev

Message Text

RECIO_OPE

recursive I/0 operation
While processing an I/0 statement for a logical unit,
another I/0 operation on the same logical unit was
attempted. One of the following conditions may have
occurred:
• A function subprogram that performs I/0 to the
same logical unit was referenced in an expression
in an I/0 list or variable format expression.
• An I/0 statement was executed at AST level for
the same logical unit.
• An exception handler (or a procedure it called)
executed an I/0 statement in response to a signal
from an I/0 statement for the same logical unit.

RECNUMOUT

record number outside range
A direct access READ, WRITE, or FIND statement
specified a record number outside the range specified
when the file was created.

REWERR

REWIND error
One of the following conditions occurred:
• The file was not a sequential organization file.
• The file was not opened for sequential or append
access.
• RMS detected an error condition during execution
of a REWIND statement.

REWRITERR

REWRITE error
RMS detected an error condition during execution of
a REWRITE statement.

SEGRECFOR

segmented record format error
An invalid segmented record control data word was
detected in an unformatted sequential file. The file
was
probably
either
created
with
RECORDTYPE= 'FIXED' or 'VARIABLE' in effect, or was written by a language other than FORTRAN.

E-38

Diagnostic Messages

Table E-4 (Cont.): Run-Time Diagnostic Messages
Condition
Symbol

Err
No

Sev

Message Text

SIGLOSMAT

F,C

significance lost in math library
The magnitude of an argument or the magnitude of
the ratio of the arguments to a math library function
was so large that all significance in the result was
lost. The result returned was the reserved operand,
-0.

SPERECLOC

specified record locked
A READ or direct access WRITE, FIND, or DELETE
was attempted on a record which was locked by another user.

SQUROONEG

F,C

square root of negative value
An argument required the evaluation of the square
root of a negative value. The result returned was the
reserved operand, -0.

SUBRNG

F,C

trap, subscript out of range
An array reference was detected outside the declared
array bounds.

SYNERRFOR

syntax error in format
A syntax error was encountered while the Run-Time
Library was processing a format stored in an array or
character variable.

SYNERRNAM

syntax error in NAMELIST input "text"
The syntax of input to a namelist-directed READ
statement was incorrect. The part of the record in
which the error was detected is shown as "text" in the
message text.

TOOMANREC

too many records in I/0 statement
One of the following conditions occurred:

• An attempt was made to read or write more than
one record with an ENCODE or DECODE statement.

• An attempt was made to write more records than
existed.

Diagnostic Messages

E-39

Table E-4 (Cont.): Run-Time Diagnostic Messages
Condition
Symbol

Err
No

Sev

Message Text

TOOMANVAL

too many values for NAMELIST variable "varname"
An attempt was made to assign too many values to a
variable during a namelist-directed READ statement. The name of the variable is shown as "varname" in the message text.

UNDEXP

F,C

undefined exponentiation
An exponentiation was attempted which is
mathematically undefined, as for example, O.**O.
The result returned was the reserved operand, -0 for
floating-point operations, and zero for integer operations.

UNIALROPE

unit already open
A DEFINE FILE statement specified a logical unit
that was already opened.

UN LE RR

UNLOCK error
RMS detected an error condition during execution of
an UNLOCK statement.

VFEVALERR

F,C

variable format expression value error
The value of a variable format expression was not
within the range acceptable for its intended use; for
example, a field width was less than or equal to zero.
A value of one was assumed, except for a P edit descriptor, for which a value of zero was assumed.

WRONUMARG

wrong number of arguments
An improper number of arguments was used to call a
math library procedure.

WRIREAFIL

write to READO NLY file
A write operation was attempted to a file that was
declared READO NLY by the currently active OPEN.

E-40

Diagnostic Messages

E.3 DICTIONARY Error Messages
When an error occurs while using the Common Data Dictionary (CDD) (that is, while
compiling a DICTIONARY statement), error messages will be generated from one or more
of the following sources:
1. The FORTRAN compiler, which generates error messages that begin with %FORT.
These messages appear in Section E.1.
2. The Common Data Dictionary, which generates error messages that begin with
%CDD. These messages appear in Appendix D of the VAX Common Data Dictionary Utilities Reference Manual. CDDL error messages appear in Appendix C of the
VAX Common Data Dictionary Data Definition Language Reference Manual.
3. The CRX, which generates error messages that begin with %CRX. These messages
are listed in this section.
Most CRX messages are related to errors that cannot be corrected by the user. As indicated, submit an SPR to CDD or to the product that created the record description when
you receive one of these messages.
The informational messages are related to problems that do not inhibit the production of
an object file. They indicate, however, that your results may not be as you had anticipated.
Table E-5: CRX Error Messages
CRX Error

Message

User Action

%CRX-E-BADBASE

Field description specifies base
other than 2 or 10.

Correct the description to
be base 2 or 10.

%CRX-E-BADCORLEV

Record description specifies unsupported core level.

Submit an SPR to CDD or
to the product that created the description.

%CRX-E-BADDIGITS

Field description specifies improper
record format.

Correct the field description to specify the proper
number of digits.

%CRX-E-BADFORMAT

Record description specifies improper record format.

Submit an SPR to CDD or
to the product that created the description.

%CRX-E-BADLENGTH

Field description specifies improper
length.

Submit an SPR to CDD or
to the product that created the description.

%CRX-E-BADOCCURS

Dimension description improperly
specifies Minimum Occurs.

Submit an SPR to CDD or
to the product that created the description.

Diagnostic Messages

E-41

Table E-5 (Cont.): CRX Error Messages
CRX Error

Message

User Action

%CRX-E-BADOFFSET

Field description specifies improper
offset.

Submit an SPR to CDD or
to the product that created the description.

%CRX-E-BADOVERLAY

Field description specifies overlay
for nonoverlay field.

Submit an SPR to CDD or
to the product that created the description.

%CRX-E-BADPRTCL

Pathname does not designate a
node with record protocol.

Correct the pathname.

%CRX-E-BADREFER

Field description specifies reference
for nonpointer field.

Submit an SPR to CDD or
to the product that created the description.

%CRX-E-BADSCALE

Field description specifies scale
greater than precision.

Correct the precision or
scale specified in the field
description.

%CRX-E-BADSTRIDE

Dimension description specifies improper stride.

Submit an SPR to CDD or
to the product that created the description.

%CRX-E-BADTAGVAR

Field description specifies tag for
nonoverlay field.

Submit an SPR to CDD or
to the product that created the description.

%CRX-I-INITVAL

Initial value in field description
being ignored.

No action.

%CRX-I-LITERALS

Literal definitions in record description being ignored.

No action.

%CRX-E-MEMBADTYP

Field description specifies data
type for field with members.

Submit an SPR to CDD or
to the product that created the description.

%CRX-I-NOCONTIN

Improper continuation after a noncontinuable condition.

Submit
SPR.

%CRX-E-NOCORATT

Record description does not specify
core level.

Submit an SPR to CDD or
to the product that created the description.

%CRX-E-NOFORMAT

Record description does not specify
record format.

Submit an SPR to CDD or
to the product that created the description.

E-42

Diagnostic Messages

FORTRAN

Table E-5 (Cont.): CRX Error Messages
CRX Error

Message

User Action

%CRX-E-NOLENGTH

Field description does not specify
length.

Submit an SPR to CDD or
to the product that created the description.

%CRX-E-NOLOWER

Dimension description does not
specify lower bound.

Submit an SPR to CDD or
to the product that created the description.

%CRX-E-NOOFFSET

Field description does not specify
offset.

Submit an SPR to CDD or
to the product that created the description.

%CRX-E-NOOVERLAY

Field description does not specify
overlay for overlay field.

Submit an SPR to CDD or
to the product that created the description.

%CRX-E-NOSTRIDE

Dimension description does not
specify stride.

Submit an SPR to CDD or
to the product that created the description.

%CRX-E-NOTCOMPUT

Field definition specifies numeric
attributes for nonnumeric data.

Submit an SPR to CDD or
to the product that created the description.

%CRX-E-NOUPPER

Dimension description does not
specify upper bound.

Submit an SPR to CDD or
to the product that created the description.

%CRX-I-REFERENCE

Reference in overlay description
being ignored.

No action.

%CRX-I-TAGVALUES

Tag values in overlay description
being ignored.

No action.

%CRX-E-UNALIGNED

Field description specifies improper
field alignment.

Correct the field description to specify the proper
alignment.

%CRX-I-UNKFACIL

Unknown facility specified for record description extraction.

Submit
SPR.

FORTRAN

Diagnostic Messages

E-43

Index

! (exclamation point)
comment indicator, 5-10
" (double quotation marks)
octal notation for integer constants, A-1,
A-6
$ (dollar sign)
delimiter for namelist record, 11-30
edit descriptor, 12-24 to 12-25
* (asterisk)
comment line indicator, 5-10
format specifier
in list-directed IIO, 11-16, 11-18
multiplication operator, 6-33
to 6-34, 6-40, 17-34
upper bound of array, 6-18
** (double asterisk)
exponentiation operator, 6-33 to 6-34, 6-40
+ (plus)
addition or unary plus operator, 6-33 to
6-34, 6-40, 17-34
- (minus)
subtraction or unary minus operator, 6-33
to 6-34, 6-40, 17-34
{period)
current location indicator (Debug), 17-28
operand contents specifier (De bug), 17-34
I (slash)
division operator, 6-33 to 6-34, 6-40, 17-34
record terminators
in FORMAT statements, 12-1
II (double slash)
concatenation operator, 6-37, 6-40, 16-2
: (colon)
edit descriptor, 12-25
? (question mark)
namelist prompt, 11-32

@(AT sign)
execute procedure (DCL) 1-27 to 1-28
operand contents specifier (Debug), 17-34
(circumflex)
previous location indicator (Debug), 17-28

A
A field descriptor, 12-18 to 12-20
ACCEPT statement, 11-52
ACCESS
INQUIRE statement specifier, 13-19,
13-20
OPEN statement keyword, 13-3, 13-6
Access keys
for indexed files
specified in OPEN statement, 13-12 to
13-13
Access modes
direct, 11-15
OPEN statement keywords, 13-2
keyed, 11-15
sequential, 11-14 to 11-15
Access, shared
SHARED keyword
on OPEN statement, 13-4, 13-16
Actual and dummy arguments
see arguments, actual and dummy
Addition operator ( +), 6-33 to 6-34, 6-40
Address correlation table
effect of /DEBUG, 3-8
Addresses
specifying program addresses (Debug),
17-29
virtual memory locations
defining symbolically (Debug), 17-31

Index-1

Adjustable arrays, 6-21, 10-3 to 10-4
Aggregate assignment statement, 7-5 to 7-6
Aggregate field reference
see record and field references
Aggregate reference
definition and examples, 6-31 to 6-32
Allocation
file storage allocation
OPEN statement keywords, 13-2
Allocation listing, memory
linker output, 4-2, 4-4 to 4-5
ALLOCATE command (Debug), 17-27
Alphanumeric data
using character data type to
manipulate, 16-1 to 16-10
I/0 example, 16-7 to 16-10
see also character data type
Alternate key fields
definition, 15-2
discussion of use, 15-2 to 15-5
Alternate return arguments, 10-6
to 10-7
.AND.
see logical operators
ANSI standards
flagging extensions
SYNTAX parameter (/SHOW), 3-14
VAX FORTRAN extensions, v, 5-1
see also FORTRAN-66, FORTRAN-77
'APPEND'
OPEN statement keyword value, 13-3
to 13-6
APPEND command (DCL), 1-22 to 1-23
Arguments, actual and dummy
general description, 10-2 to 10-8
overview, 10-2
adjustable arrays, 10-3 to 10-4
alternate return arguments, 10-6 to 10-7
assumed-size arrays, 10-4 to 10-5
character arrays, 10-5 to 10-6
defaults for arguments passing,
10-7 to 10-8
Hollerith and character constants, 10-6
passed-length character arguments,
10-5 to 10-6, 16-4 to 16-5
associating variables with, 6-16
bit function arguments, D-43 to D-45
use of aggregate field references, 6-29
use of built-in functions

Index-2

Arguments, actual and dummy, (Cont.)
argument list functions (%VAL,
%REF, %DESCR), 10-7 to 10-8
%LOC function, 10-8
use of external procedure names,
8-16 to 8-17
use of intrinsic function names, 8-18
Argument list built-in functions
%VAL, %REF, %DESCR, 10-7 to 10-8
use with Debug, 17-19
Arithmetic assignment statement, 7-1 to 7-3
Arithmetic expressions, 6-33 to 6-37
compile-time arithmetic expressions
use in PARAMETER statements, 8-21,
8-22
use in relational expressions, 6-38, 6-39
Arithmetic IF statement, 9-13
Arithmetic operators
in expressions, 6-33 to 6-34, D-1
Arithmetic overflow
check options at compilation, 3-6
Arrays
definition of, 6-17
general description, 6-17
adjustable, 6-21, 10-3 to 10-4
array names, references to
in FORTRAN statements, 6-21
assigning values to
with DATA statements, 8-4 t~ 8-6
assumed-size, 6-21, 10-4 to 10-5
character substrings
see character substrings
contrasted with records, 6-23
data typing of, 6-21
declarators, 6-18 to 6-19
dimensions
see dimensions, DIMENSION statement
dummy, 10-4 to 10-5
elements, 6-19 to 6-20
terminology used to describe,
6-31 to 6-32
making arrays equivalent, 8-11 to 8-16
initializing character arrays, 8-4
to 8-6, 16-4
subscripts, 6-19
unsubscripted arrays
statements used in, 6-21
use in structure declaration blocks,
6-24

Arrays, (Cont.)
terminology used to describe,
6-31 to 6-32
Array name reference
definition and examples, 6-31 to 6-32
Array references
check options at compilation, 3-6
ASCII character set, B-2
ASCII control characters
assigning to character data entities
with DATA statements, 8-5, 8-6
ASSIGN command (DCL), 1-18, 1-34, 11-9
ASSIGN statement, 7-6 to 7-7
Assigned GO TO statement
general description, 9-12
statement label references, establishing,
7-6
see also ASSIGN statement
Assignment operations (DCL)
assigning character values to symbols,
1-29
assigning numeric values to symbols,
1-29 to 1-31
Assignment statements
aggregate, 7-5 to 7-6
arithmetic, 7-1 to 7-3
character, 7-4 to 7-5
logical, 7-3 to 7-4
ASSOCIATEVARIABLE
OPEN statement keyword, 13-3, 13-6
Assumed-size arrays, 6-21, 10-4 to 10-5
Asterisk (*)
comment line indicator, 5-10
format specifier
in list-directed I/0, 11-16,
11-18
multiplications operator, 6-33 to
6-34, 6-40, 17-34
upper bound of array, 6-18
AT sign(@)
execute procedure (DCL), 1-27 to 1-28
operand contents specifier (Debug), 17-34
ATTACH command (Debug), 17-4

B
BACKSPACE statement
general description, 13-27
see also REWIND statement

Bit field transfers
MVBITS subroutine, D-42 to D-43
Bit functions
general information about, D-43
to D-45
BLANK
INQUIRE statement specifier, 13-19,
13-20
OPEN statement keyword, 13-3, 13-6
Blank characters
see space characters
Blank common blocks, 8-3
Blank control editing
BN and BZ edit descriptors, 12-5
Blank lines
treated as comment lines, 5-10
Blocks
OPEN keywords affecting, 13-2
Block data program unit, 8-2
BLOCK DATA statement, 8-2 to 8-3
Block data subprograms
forcing linker to search libraries,
8-17
Block IF constructs, 9-14 to 9-20
BLOCK SIZE
OPEN statement keyword, 13-3, 13-7
BN
edit descriptor, 12-5
Breakpoints
setting in debug sessions, 17-20 to 17-23
BUFFERCOUNT
OPEN statement keyword, 13-7
Built-in functions
argument list functions
%VAL, %REF, %DESCR, 10-7 to 10-8
%LOC function, 10-8
BYTE data type
relationship to LOGICAL*!, 8-7
see also LOGICAL
BZ
edit descriptor, 12-5

c
C comment indicator, 5-10
Calendar dates
subroutines for calculating
DATE and IDATE, D-39
CALL command (Debug), 17-19

Index-3

CALL statement, 9-2
use with ENTRY statement, 10-18, 10-19
use with EXTERNAL statement, 8-17
use with INTRINSIC statement, 8-18,
8-19
use with RETURN statement, 9-21, 9-22
use with SUBROUTINE statement, 10-14,
10-15, 10-16
CANCEL commands (Debug)
CANCEL BREAK, 17-22
CANCEL DISPLAY, 17-43
CANCEL MODULE, 17-26
CANCEL TRACE, 17-22
CANCEL WATCH, 17-23
CANCEL WINDOW, 17-40
CARRIAGECONTROL
INQUIRE statement keyword, 13-19,
13-20
OPEN statement keyword, 13-3, 13-8
Carriage control editing, 12-24 to 12-25
Carriage control characters, 12-25 to 12-26
CDD, 3-19 to 3-23
CDD records
creating CDD records, 3-22
Gfloating/Dfloating caution, 3-23
including in source listing, 3-13, 3-20,
3-27
see also DICTIONARY statement,
/DICTIONARY qualifier
CDD$TOP, 3-27
CDDL, 3-19, 3-20
data types supported, 3-22, 3-23
CDDV, 3-20
Cells
in relative organization files,
11-10, 11-11
Change mode editing (EDT)
see character mode editing
CHAR function, 10-25, 16-5
CHARACTER
constants
as actual arguments, 10-6
general description, 6-13
general discussion of use,
16-1 to 16-10
1/0 examples, 16-7 to 16-10
data type
definition, 6-1
representation in memory, C-10

Index-4

CHARACTER, data type, (Cont.)
storage requirement, 6-3
see also arrays, constants, data
types, variables
CHARACTER*n
see CHARACTER
Character, continuation, 5-11
Characters
flagging lowercase in output
(/STANDARD), 3-14
in character and Hollerith constants,
5-7
supported by VAX FORTRAN, 5-6
see also character sets
Character arguments
passed length, 6-17, 10-5 to 10-6,
16-4 to 16-5
Character assignment statement, 7-4 to 7-5
Character editing (A,H), 12-18 to 12-21
character constants, 12-20, 12-21
Character expressions, 6-37
compile-time character expressions
use in PARAMETER statements,
8-21, 8-22
operators, 6-37, D-1
use in relational expressions, 6-38,
6-39
Character comparison library functions
LEN, INDEX, !CHAR, CHAR, 10-24
to 10-26, 16-5 to 16-6
see also lexical comparison functions
CHARACTER FUNCTION statement,
10-12
Character mode editing (EDT), 2-1, 2-6 to
2-12
deleting text, 2-10 to 2-11
inserting text, 2-10
moving text, 2-11 to 2-12
positioning cursor, 2-7 to 2-10
undeleting text, 2-10 to 2-11
Character operators, 6-37, D-1
Character scalar memory reference
see scalar memory reference
Character sets
ASCII, B-2
assigning ASCII characters to
data entities, 8-5, 8-6
FORTRAN, B-1
Radix-50, B-3 to B-4

Character statement
see character type declaration statement
Character substrings
definition, 6-4
concatenating, 16-2
establishing equivalence among, 8-13 to
8-16
use in variables and arrays, 6-22 to 6-23
terminology used to describe, 6-31 to 6-32
Character type declaration statement
general description, 8-8 to 8-9
Character variables
initializing, 6-4
/CHECK qualifier, 3-6
Circumflex ( )
previous location indicator (De bug), 17-28
CLOSE statement
general description, 13-18 to 13-19
Coding form, 5-8
Coding requirements
see source code
Colon (:)
edit descriptor, 12-25
Column(s)
one
comment indicator, 5-10
one through five
statement label field, 5-10
six
continuation indicator, 5-11
seven through 72 (optionally, to 132)
statement field, 5-2, 5-11
73 - 80
sequence number field, 5-11
Command procedures
see DCL command procedures,
debugger command procedures
Command qualifiers
rules for specifying, 1-3
Comment line indicators
D in column 1, 3-9, 5-10
general description, 5-5
Common blocks
COMMON and EQUIVALENCE
interaction, 8-16
establishing order of contents, 8-3 to 8-4
initializing values in, 8-2 to 8-3
Common block names
use in COMMON statement, 8-3

Common Data Dictionary
see CDD
COMMON statement
general description, 8-3 to 8-4
interaction with EQUIVALENCE, 8-16
establishing arrays with, 6-17
establishing variables with, 6-16
use of unsubscripted arrays with, 6-21
Compatibility
additional language elements for,
A-1 to A-8
Compilation options
options affecting output
contents of source listing file
(/SHOW), 3-13
debugging information (/DEBUG,
/OPTIMIZE), 3-8, 3-12, 17-2, 17-3
messages (/STANDARD and
/WARNINGS), 3-14 to 3-15
object code listing (/MACHINECODE),
3-12
object file name (/OBJECT), 3-12
source listing (/LIST), 3-11
options affecting processing
checking overflow, bounds, underflow
(/CHECK), 3-6
continuation line limits
(/CONTINUATION), 3-7
D in column 1 (/DLINES), 3-9
FDML preprocessing (/DML), 3-9
FORTRAN-77 or FORTRAN-66 (/F77),
3-10
Gfloating vs. Dfloating (/GFLOATING),
3-10
INTEGER and LOGICAL defaults (/14),
3-11
optimization (/OPTIMIZE), 3-12
source line length (/EXTENDSOURCE),
3-9
text library files (/LIBRARY), 3-11, 3-18
overriding options on FORTRAN
command
OPTIONS statement, 3-24, 3-26
Compilation summary listing, 3-35
Compiler
coding restrictions/limits
summary of, E-27 to E-28
default file names, 11-7
diagnostic messages issued by

Index-5

Compiler, (Cont.)
compiler-fatal diagnostic messages,
E-26 to E-27
source program diagnostic messages,
E-1 to E-26
functions, 3-1 to 3-2
input to linker, 3-1 to 3-2
Compiler output listing
see output listing
Compile-time constant expression
arithmetic, character, and logical, 8-21
Completion status values
returning to command procs, 4-8
Complex data editing, 12-15 to 12-16
COMPLEX
see COMPLEX*8
COMPLEX*8
constants, 6-9 to 6-10
data type
definition, 6-1
representation in memory, C-6
storage requirement, 6-3
see also arrays, constants, data
types, variables
COMPLEX*l6
constants, 6-10
data type
Gfloating vs. Dfloating, 3-10, 6-3
representation in memory, C-6 to C-8
storage requirement, 6-3
see also arrays, constants, data types,
variables
Computed GOTO statement, 9-11
Concatenation operator (//), 6-37, 6-40, 16-2
Condition handlers, 18-1, 18-2
Condition symbols, FORTRAN
summary of, 18-3 to 18-5
Connections, logical
to logical 1/0 units
explicitly by means of OPEN, 13-17
implicitly by system default, 11-7 to
11-8
Constants
definition of, 6-4
assigning symbolic names
by means of PARAMETER statement,
8-21 to 8-22
character, 6-13

Index-6

Constants, (Cont.)
complex, 6-9 to 6-10
hexadecimal, 6-11 to 6-12
Hollerith, 6-14
integer, 6-5
logical, 6-13
octal, 6-11 to 6-12
Radix-50, B-3
real 6-5 to 6-9
terminology used to describe, 6-31 to 6-32
Continuation character, 5-11
Continuation lines
DCL commands, 1-7
FORTRAN source code
debug source statements, use in, 5-10
indicator in source code, 5-11
source program limits, how to modify,
3-7
statement labels, affect on, 5-10
/CONTINUATION qualifier, 3-7
CONTINUE command (DCL), 4-7, 17-5
CONTINUE statement, 9-3
Control statements, FORTRAN, 9-1 to 9-23
see also CALL, RETURN
Conversion
of data types
in arithmetic assignment statements, 7-3
in DATA statements, 8-5 to 8-6
with FORMAT statements, 12-1
COPY command (DCL), 1-22
CREATE /DIRECTORY command (DCL),
1-15 to 1-16
Cross-reference information
compiling
/CROSSREFERENCE qualifier, 3-7
/SHOW qualifier (SINGLE parameter),
3-13
general description, 3-23
linking
/CROSSREFERENCE qualifier, 4-2
<CTRL/C> and <CTRLIY>
interrupting interactive program execution,
4-7 to 4-8
use of <CTRL/y> during debug session,
17-4 to 17-5
<CTRL/z>
terminating a debug session, 17-5
Cursor positioning (EDT), 2-7 to 2-10

D
D debugging statement indicator
use in column 1, 3-9, 5-10
field descriptor, 12-13
in complex data editing, 12-15
Data
as stored in memory
by VAX FORTRAN, C-1 to C-11
editing
with FORMAT statements, 12-1
examining and manipulating (Debug),
17-32 to 17-38
passing to programs, 1-33
retaining after END or RETURN, 8-24
to 8-25
see also data items, data types
Data items
definition, 6-4
printing warnings if unused, 3-15
terminology used to describe, 6-31 to 6-32
see also arrays, character substrings,
constants, records, variables
Data Manipulation Language, 3-9
DATA statement
general description, 8-4 to 8-6
use of unsubscripted arrays with, 6-21, 8-5
use to define arrays and elements, 6-17
Data transfer
see I/0
Data types
conversion rules
for arithmetic assignment statements,
7-3
for DATA statements, 8-5 to 8-6
declaration within structures, 8-28 to 8-30
default data types
of undeclared symbolic names, 8-17
definition of different types, 6-1 to 6-2
expressions
establishing data types of, 6-35 to 6-37
FORTRAN-to-CDD mapping, 3-22 to 3-23
INTEGER and LOGICAL
setting default lengths, 3-11
length specifiers, 6-2
method of specifying
arrays, 6-21
constants, 6-4 to 6-15
variables, 6-15, 6-16 to 6-17

Data types, method of specifying, (Cont.)
rank in arithmetic expressions, 6. . . 35
specifying during debug sessions, 17-35
to 17-36
see also BYTE, CHARACTER,
INTEGER,
LOGICAL, REAL
Data type declaration statement
general descriptions
· ,. character type declarations, 8-8 to 8-9
numeric type declarations, 8-7 to 8-8
use of unsubscripted arrays with, 6-21
use to establish arrays, 6-17
use to establish variables, 6-15,
6-16 to 6-17
DATE subroutine, D-39
Dates, calendar
subroutines for calculating
DATE and IDATE, D-39
DBG$INIT, 17-9
DBG$INPUT, 17-9
DCL commands
continuation indicator, 1-7
issuing during debug sessions, 17-4
rules and options, 1-7 to 1-9
DCL command 'procedures, 1-27 to 1-38
controlling execution 1-35 to 1-36
creation of symbols, 1-28 to 1-32
error handling, 1-36 to 1-37
executing, 1-28, 1-37 to 1-38
login command file, 1-38
passing data to programs, 1-34 to 1-35
passing parameters, 1-32 to 1-33
DEASSIGN command (DCL), 1-20
DEBUG command (DCL), 17-4, 17-5
Debugger
command summary, 17-11to17-17
command entry in keypad mode
keypad command layout, 17-7
controlling program execution, 17-17
to 17-23
using logical control commands, 17-25
defining special function keys, 17-6,
17-7 to 17-8
displaying source lines, 17-23 to 17-24
examining and manipulating data, 17-32
to 17-38
debugger operators, 17-34
examples sessions, 17-43 to 17-48

Index-7

Debugger, (Cont.)
invoking, interrupting, terminating
sessions, 17-4 to 17-5
referencing symbolic names and programs
locations, 17-25 to 17-32
use of prefixes and scope, 17-29 to 17-31
using screen displays, 17-38 to 17-43
see also /DEBUG qualifier
Debugger command procedures, 17-8 to
17-9, 17-10
Debugger symbol table (DST), 17-26
Debugging statements
in source code, 3-9, 5-10
/DEBUG qualifier
FORTRAN command, 3-8
LINK command, 4-2, 4-3
overview/summary, 4-9 to 4-11
RUN command, 4-7
Declarators, array, 6-18
DECODE statement, A-1 to A-3
Defaults
argument passing defaults, 10-7 to 10-8
data type defaults
of undeclared symbolic names, 8-17
field descriptors vs. 1/0 list elements,
12-21
logical 1/0 unit names, 11-7 to 11-8
predefined system logical names, 1-19
DEFAULTFILE
INQUIRE statement keyword, 13-19
OPEN statement keyword, 13-3, 13-18
DEFINE command (DCL), 1-18
DEFINE commands (Debug)
DEFINE, 17-31
DEFINE/KEY, 17-7 to 17-8
DEFINE FILE statement, A-1, A-3 to A-4
'DELETE'
file description, 13-18
DELETE command (DCL), 1-23
DELETE statement
general description, 13-28 to 13-29
DELETE/KEY command (Debug), 17-7,
17-8
Deleting files
DELETE command (DCL), 1-23
PURGE command (DCL), 1-23 to 1-24
DEPOSIT command (Debug), 17-28, 17-32,
17-33, 17-35, 17-38
depositing complex values, 17-38

Index-8

%DESCR built-in function, 10-7 to 10-8
use with Debug, 17-9
Descriptors
see field and edit descriptors
Devices
default, 1-13
defining logical names for, 1-18
identifying in file specs, 1-11
Dfloating implementations
effect of /GFLOATING qualifier, 3-10
CDD caution, 3-23
representation in memory, C-2
COMPLEX*16, C-6 to C-7
REAL*8, C-3
with COMPLEX*16 data type, 6-10
with REAL*8 data type, 6-3, 6-7 to 6-8
Diagnostic messages
see messages
Dictionary.Management Utility, 3-20
DICTIONARY parameter (/SHOW), 3-13
DICTIONARY statement
general discussion, 3-20 to 3-21
Dimensions
array declarators, 6-18
array limits, 6-17
see also DIMENSION statement
DIMENSION statement
general description, 8-9 to 8-10
use to establish arrays, 6-17
'DIRECT'
OPEN statement keyword value, 13-3,
13-6
DIRECT
INQUIRE statement specifier, 13-19,
13-21
Direct access mode, 11-15
OPEN statement keywords, 13-2
see also relative organization files
Direct access FIND statements, A-1, A-4 to
A-5
Direct access READ statements, 11-35 to
11-36
Direct access WRITE statements, 11-46 to
11-47
Directories
changing a file's directory, 1-22
default, 1-13
description, 1-14 to 1-17
defining logical names for, 1-17 to 1-18

Directories, (Cont.)
displaying files in, 1-24
specifying in file specs, 1-11
DIRECTORY command (DCL), 1-24
/PROTECTION qualifier, 1-26
DISP .
CLOSE statement keyword, 13-18
DISPLAY command (Debug), 17-43
Display screens (Debug), 17-39 to 17-43
Displaying file contents
TYPE and PRINT commands (DCL), 1-26
to 1-27
TYPE and <RET> commands (EDT),
2-17 to 2-18
DISPOSE
CLOSE statement keyword, 13-18
OPEN statement keyword, 13-3, 13-9
Division operator (/), 6-33 to 6-34, 6-40
/DLINES qualifier, 3-9, 5-10
/DML qualifier, 3-9
DMU, 3-20, 3-21
Dollar sign ($)
delimiter for namelist record, 11-30
edit descriptor, 12-24 to 12-25
DO loops
see DO statements
DO statements, 9-3 to 9-10
DOUBLE COMPLEX
see COMPLEX*16 data type
DOUBLE PRECISION
see REAL*8 data type
DST (debugger symbol table), 17-26
Dummy and actual arguments
see subprogram arguments

E
E field descriptor, 12-11 to 12-12
in complex data editing, 12-15
Edit and field descriptors
summary, 12-30
see also FORMAT statements
EDIT /EDT command (DCL), 2-3 to 2-4
Edi tor, text
see EDT text editor
EDTINI.EDT file, 2-25 to 2-26
EDT text editor, 2-1 to 2-26
changing editing modes, 2-5

EDT text editor, (Cont.)
character mode editing
see character mode editing
command summary (line editing), 2-12 to
2-14
editing modes
see character mode editing, line mode
editing
EDTINI.EDT file, 2-25 to 2-26
HELP facilities, 2-2 to 2-3
invoking EDT, 2-3 to 2-4
keypad editing
see character mode editing
range specifications (line editing), 2-14 to
2-17
setting up tabs, 2-23 to 2-24
startup command files, 2-25 to 2-26
terminating EDT, 2-4 to 2-5
ELSE statement
block IF constructs, 9-14 to 9-20
ELSE IF THEN statement
block IF constructs, 9-14 to 9-20
ENCODE statement, A-1 to A-3
END statement
affect on program execution, 4-7
general description, 9-10
effecting a return from subprograms, 9-10
when not to use, 4-8
with BLOCK DATA statement, 8-2
with FUNCTION statement, 10-11
with SUBROUTINE statement, 10-14
see also END DO, ENDFILE, ENDIF,
END MAP, END STRUCTURE, END
UNION
END DO statement, 9-9 to 9-10
ENDFILE statement, 13-27 to 13-28
END IF statement
block IF constructs, 9-14 to 9-20
END MAP statement
see MAP statement, map declaration
End-of-file condition
reporting with IOSTAT value, 11-21
transferring control with END specifier,
11-21 to 11-22
End-of-file record
ENDFILE statement, 13-27 to 13-28
END specifier
in I/0 statements, 11-21 to 11-22, 18-1,
18-6

Index-9

END STRUCTURE statement
see STRUCTURE statement, structure declaration block
END UNION statement
see UNION statement, union declaration
Entry names
rules. applying to, 10-16, 10-17
ENTRY statement, 10-16 to 10-19
use with CALL statement, 9-2
use with FUNCTION statement, 10-11
use with SUBROUTINE statement, 10-15
.EQ.
see relational operators
EQUIVALEN CE statement
associating variables with, 6-16
contrasted with union declaration, 8-32
general description, 8-10 to 8-16
interaction with COMMON, 8-16
use of unsubscripted arrays with, 6-16
.EQV.
see logical operators
ERR
1/0 statement specifier, 11-21 to 11-22,
18-1, 18-6
BACKSPACE statement keyword, 13-27
CLOSE statement keyword, 13-18
DELETE statement keyword, 13-28, 13-29
END FILE statement keyword, 13-27, 13-28
INQUIRE statement specifier, 13-19, 13-21
OPEN statement keyword, 13-3, 13-9
REWIND statement keyword, 13-26
UNLOCK statement keyword, 13-30
Error handling
condition handlers, 18-1, 18-2
DCL command proc errors, 1-36 to 1-37
processing performed by RTL, 18-1 to 18-7
subroutine for obtaining error info
ERRSNS subroutine, D-40
summary of FORTRAN run-time errors,
18-3 to 18-5
user controls in 1/0 statements
ERR, END, and IOSTAT specifiers,
11-21 to'll-22, 18-1
Error codes
$STATUS and $SEVERITY symbols, 1-36
Error condition
reporting with IOSTAT specifier, 11-21
transferring control with END specifier,
11-21, 11-22

Index-10

Error messages
see messages
Error-related command qualifiers
summary, 4-9
Error traceback mechanism
see traceback mechanism
ERRSET subroutine
error table maintained by, 18-2
ERRSNS subroutine, D-40
ERRTST subroutine
error table maintained by, 18-2
EVALUATE command (Debug), 17-32,
17-33, 17-34
EXAMINE command (Debug), 17-28, 17-32,
17-33, 17-34, 17-38
data type qualifiers, 17-35 to 17-36
radix qualifier, 17-37
Exception condition
common when using indexed files, 15-7 to
15-8
Exclamation point (!)
comment indicator, 5-10
/EXECUTABLE
LINK command option, 4-2, 4-3 to 4-4
Executable statements
definition and list of, 5-2
Execution, program, 4-6 to 4-11
controlling during debug session, 17-17 to
17-23
interrupting
<CTRL/C> and <CTRL/Y>, 4-7 to 4-8
temporarily suspending (PAUSE), 9-20 to
9-21
terminating
EXIT, D-40
STOP, 9-23
EXIST
INQUIRE statement specifier, 13-19, 13-21
EXIT command (DCL), 1-35 to 1-36
EXIT system subroutine, 4-8, D-40
Explicit formatting
1/0 statement specifier, 11-17 to 11-18
Exponents
in REAL*4 constants, 6-6
in REAL*8 constants, 6-7
in REAL* 16 constants, 6-8
Exponentiation operator ( ** ), 6-33 to 6-34, 6-4
Expressions
definition of, 6-32

Expressions, (Cont.)
arithmetic, 6-33 to 6-37
data type .ranking, 6-35
operator precedence, 6-33 to 6-34
rules governing typing of, 6-35 to 6-37
character, 6-37
compile-time constant expressions
arithmetic, character, and logical, 8-21
expression operators
summary of, D-1 to D-2
logical, 6-39 to 6-40
operator precedence, 6-40
relational, 6-38 to 6-39
terminology used to describe, 6-31
Expressions, variable FORMAT, 12-4 to 12-5
Extended ranges, DO LOOP, 9-7
EXTEND SIZE
OPEN statement keyword, 13-3, 13-10
EXTENDSOURCE qualifier, 3-9
affect on sequence number field, 5-11
External field separators, 12-27
External procedures
invoking by means of CALL, 9-2
External procedure names
duplicating intrinsic function names, 8-17
use as arguments, 8-16 to 8-17
EXTERNAL statement, 8-16 to 8-17
/NOF77 implementation, A-6 to A-8

F
F field descriptor, 12-10 to 12-11
in complex data editing, 12-15
.FALSE.
see logical constants
FDML, 3-9
Ffloating data
representation in memory, C-2
COMPLEX*8, C-6
REAL*4, C-2 to C-3
Fields
definition in structure declarations, 8-26,
8-27 to 8-33
in FORTRAN source code, 5-7 to 5-11
I/0 fields
see FORMAT statements
in records
see records (structured data items)

Field and edit descriptors
summary, 12-30
see references to individual descriptors
see also FORMAT statements
Field declaration
see structure declaration blocks
Field descriptors, default
for I/0 list elements, 12-21
Field reference
see record and field references
Field separators, external, 12-27
FILE
INQUIRE statement keyword, 13-19
OPEN statement keyword, 13-4, 13-10
Files
assigning to logical units
summary, 11-9 to 11-10
changing directories/devices, 1-22
combining files at compilation, 3-24 to 3-25
copying to another node, 1-10 to 1-11
creating source files (EDT), 2-7
deleting, 1-23 to 1-24
deleting records from
DELETE statement, 12-28 to 12-29
displaying contents
TYPE and PRINT commands (DCL),
1-26 to 1-27
TYPE and <RET> commands (EDT),
2-17 to 2-18
displaying file status info, 1-24
disposition
CLOSE statement keywords, 13-18
INCLUDE files, 3-24 to 3-25
processing options
OPEN statement keywords, 13-2
properties, inquiring about
INQUIRE statement, 13-19 to 13-26
protecting, 1-25 to 1-26
record description options, I/0
OPEN statement keywords, 13-2
repositioning
BACKSPACE statement, 13-27
REWIND statement, 13-26
searching file contents, 1-26
search lists, use of, 1-21
status options
OPEN statement keywords, 13-2
see also internal files, source files,

Index-11

Files, (Cont.)
object files, text library
files, listing files
File-handling commands
DCL commands, 1-21to1-27
FORTRAN statements
BACKSPACE statement, 13-27
CLOSE statement, 13-18 to 13-19
INQUIRE statement,· 13-19 to 13-26
OPEN statement, 13-1 to 13-18
REWIND statement, 13-26
File name
defining logical names for, 1-17 to 1-18,
11-5 to 11-6
displaying, 1-24
specifying in file specs, 1-11
File organizations
overview (sequential, relative, indexed),
11-10 to 11-11
see also indexed organization files, relative
organization files, sequential
organization files
File sharing .
SHARED keyword (OPEN statement),
13-4, 13-16
File specifications
defaults, 1-13
OPEN statement keywords, 11-8 to 11-9,
13-2
field descriptions, 1-10 to 1-13
use of wildcards, 1-14
File status
CLOSE statement keywords, 13-18
OPEN statement keywords
DISPOSE, 13-3, 13-9
STATUS or TYPE, 13-4, 13-16 to 13-17
File storage allocation
OPEN statement keywords, 13-2
File type
default, 1-13
specifying in file specs, 1-11
File version number
specifying in file specs, 1-11 to 1-12
%FILL, 6-24
FIND statement, A-1, A-4 to A-5
Fixed format
see formats
Fixed-length records
format, 11-11

Index-12

Fixed-length records, (Cont.)
RECORDTYPE keyword (OPEN
statement), 13-4, 13-15 to 13-16
Floating-point representation in memory,
C-2 to C-8
FMT format specifier
in I/0 statements, 11-17 to 11-18
FOR command (Debug), 17-25
FOR$
prefix for condition symbols
for FORTRAN run-time errors, 18-3 to
18-4
FORM
INQUIRE statement specifier, 13-19, 13-22
OPEN statement keyword, 13-3, 13-10 to
13-11
Formats
I/0 formatting
see FMT format specifier
passed length, 6-3
run-time, 12-27 to 12-28
Formats, coding
fixed format, 5-7 to 5-8
tab format, 5-9 to 5-10
Format specification separators, 12-26
Format specifier, FMT
see FMT format specifier
FORMAT statements
description of use, 12-1
arithmetic expressions in, 12-4 to 12-5
external field separators, 12-27
field and edit descriptors
summary of, 12-30
counts, repeat, 12-3
blank control editing, (BN,BZ), 12-5
character editing (A,H), 12-18 to 12-21
character constants, 12-20, 12-21
integer editing (I,0,Z), 12-6 to 12-9
logical editing (L), 12-18
miscellaneous editing operations (Q,$,:),
12-24 to 12-25
positional editing (X,T,TL,TR), 12-22 to
12-23
real editing (F,E,D,G), 12-10 to 12-16
scale factor editing (P), 12-16 to 12-17
sign control editing (SP,SS,S), 12-6
format expressions, variable, 12-4 to 12-5
format specification separators, 12-26
I/O lists, interaction with, 12-28 to 12-19

FORMAT statements, (Cont.)
run-time formats, 12-27 to 12-28
summary information about
field and edit descriptors, 12-30
general rules, 12-31
input rules, 12-32
output rules, 12-32
syntax, 12-1 to 12-2
FORMATTED
INQUIRE statement specifier, 13-19, 13-22
Formatted I/O statements
ACCEPT statement, 11-52
establishing statement label references, 7-6
general description, 11-3
PRINT statement, 11-53
READ statements
direct access, 11-35, 11-37 ·
indexed, 11-37, 11-38
internal, 11-39, 11-40
sequential, 11-26, 11-27
REWRITE statement, 11-50, 11-51
TYPE statement, 11-53
WRITE statements
direct access, 11-46, 11-47
indexed, 11-47, 11-48
internal, 11-49, 11-50
sequential, 11-41, 11-42 to 11-43
FORSYSDEF.TLB, 3-19
condition symbol values, 18-2
FORT$LIBRARY, 3-18 to 3-19
FORTRAN character set, B-1
FORTRAN command (DCL), 3-2 to 3-15
/CHECK, 3-6
/CONTINUATIONS, 3-7
/CROSSREFERENCE, 3-7
/DEBUG, 3-8, 4-9, 4-10
/DLINES, 3-9, 5-10
/DML, 3-9
/EXTENDSOURCE, 3-10
affect on sequence number field, 5-11
/F77, 3-10
/GFLOATING, 3-10
/I4, 3-11
/LIBRARY, 3-11
/LIST, 3-3, 3-4, 3-11
/MACHINECODE, 3-12
/OBJECT, 3-3, 3-4, 3-12
/OPTIMIZE, 3-12
/SHOW, 3-13.

FORTRAN command (DCL), (Cont.)
/STANDARD, 3-14
/WARNINGS, 3-15
format, 3-2
library search order, 3-18
overriding options on FORTRAN command
OPTIONS statement, 3-24, 3-26 to
3-27
qualifier summary, 3-5
specifying files in, 3-3 to 3-4
FORTRAN compiler
coding restrictions/limits
summary of, E-27 to E-28
default file names, 11-7
diagnostic messages issued by
compiler-fatal diagnostic messages,
E-26 to E-27
source program diagnostic messages,
E-1 to E-26
functions, 3-1 to 3-2
input to linker, 3-1 to 3-2
FORTRAN condition symbols
for run-time errors, 18-3 to 18-5
FORTRAN Data Manipulation Language,
3-9
FORTRAN data representation in memory,
C-1 to C-11
FORTRAN logical names
defaults and use, 11-6 to 11-7
FORTRAN logical unit numbers, 11-7to11-8
FORTRAN statements
assignment statements, 7-1 to 7-7
coding restrictions/limits
summary of, E-27 to E-28
control statements, 9-1 to 9-23
see also CALL, RETURN
executable/nonexecutable, 5-2
general description, 5-2, 5-11
I/0 statements, 11-1 to 11-53
I/0 statements, auxiliary, 13-1 to 13-30
language summary (alphabetic), D-2 to
D-30
maximum line length, 3-9
ordering requirements, 5-2 to 5-3
specification statements, 8-1 to 8-34
supplemental statements
supported to maintain non-VAX
FORTRAN compatibility, A-1 to
A-8

Index-13

FORTRAN-66
/NOF77 qualifier, 3-10
FORTRAN-77
/F77 qualifier, 3-10
/STANDARD qualifier, 3-14
VAX FORTRAN extensions, v, 5-1
/FULL qualifier
LINK command option, 4-2, 4-4 to 4-5
Functions, built-in
argument list functions
%VAL, %REF, %DESCH, 10-7 to 10-8
%LOC function, 10-8
Function names
see subprograms
Function references
general description, 10-13 to 10-13
types of references to intrinsic functions
specific and generic, 10-19 to 10-24
FUNCTION statement, CHARACTER, 10-12
FUNCTION statement, 10-11to10-14
Function subprograms, statement
see subprograms
/F77 qualifier, 3-10

G
G field descriptor, 12-13 to 12-15
in complex data editing, 12-15
.GE.
see relational operators
Generic references
to intrinsic function names, 10-20 to 10-24
Gfloating implementations
CDD caution, 3-23
/GFLOATING qualifier, 3-10
representations in memory
COMPLEX*l6, C-7 to C-8
REAL*8, C-4
with COMPLEX*16 data type, 6-10
with REAL*8 data type, 6-3, 6-7 to 6-8
/GFLOATING qualifier, 3-10
Global symbols
assignment operations, 1-8 to 1-9, 1-29
GO command (Debug), 17-17 to 17-18
GOTO command (DCL), 1-35
GOTO statements
general descriptions
assigned GOTO, 9-12
computed GOTO, 9-11
unconditional GOTO, 9-10 to 9-11
Index-14

GROUP file access, 1-25
GROUP logical name table, 1-18 to 1-19
Group repeat counts
in FORMAT statements, 12-3
.GT.
see relational operators

H
field descriptor, 12-20
Hexadecimal constants, 6-11 to 6-12
HELP command, 1-9 to 1-10
Hfloating data
representation in memory, C-2
REAL*16, C-4 to C-5
Hollerith
data type
definition, 6-1
constants, 6-4
as actual arguments, 10-6
representation in memory, C-10 to C-11

I field descriptor, 12-6 to 12-7
ICHAR function, 10-25, 16-6
IDATE subroutine, D-39
IF statements
general descriptions
arithmetic IF, 9-13
block IF, 9-14 to 9-20
logical IF, 9-13 to 9-14
IF...THEN command (DCL), 1-35
IF THEN statement
block IF constructs, 9-14 to 9-20
IF THEN ELSE command (Debug), 17-25
IMPLICIT statement
data typing variables with, 6-5, 6-16
effect of /WARNINGS option, 3-15, 8-18
general description, 8-17 to 8-18
Implied-DO list
1/0 list parameter
in DATA statements, 8-4, 8-5
in 1/0 statements, 11-24 to 11-26
Implied-DO variable
in DATA statements, 8-5
INCLUDE files
including in output listing
/SHOW qualifier, 3-13

/INCLUDE qualifier (LINK), 4-3, 4-5
INCLUDE statement, 3-15, 3-16
statement definition, 3-24 to 3-25
Indefinite DO statement, pretested
DO WHILE, 9-9
Indexed DO statement, 9-3 to 9-8
Indexed files
see indexed organization files
INDEX function, 10-25, 10-26, 16-6
Indexed I/0 statements
READ statements, 11-37 to 11-39
WRITE statements, 11-47 to 11-49
Indexed organization files
access keys
specifier in OPEN statement, 13-12,
13-13
creating, 15-2 to 15-3
deleting records from, 15-7
DELETE statement, 13-28 to 13-29
exception conditions, 15-7 to 15-8
freeing locked records
UNLOCK statement, 13-30
general description, 11-11
reading operations, 15-5 to 15-6
record pointers
next and last, 15-7
rewrite operations, 11-51
sequential access, 15-1
updating records in, 15-6
writing operations, 15-3 to 15-5
see also keyed access
Indexed sequential access method (ISAM),
15-1
INITIAL SIZE
OPEN statement keyword, 13-4, 13-11
Input/output
see I/0
INQUIRE command (DCL), 1-35
INQUIRE statement
general description, 13-19 to 13-26
Integer
constants, 6-5
in COMPLEX*8 constants, 6-9
in COMPLEX*l6 constants, 6-10
in REAL*4 constants, 6-6, 6-7
in REAL*8 constants, 6-7, 6-8
in REAL*l6 constants, 6-8, 6-9
octal notation, A-1, A-6
setting default length, 3-11

Integer, (Cont.)
data type
default type of undeclared symbolic
names, 8-17
definition, 6-1
representation in memory, C-1, C-2
storage requirements, 6-2
see also arrays, constants, data types,
variables
INTEGER
see integer
INTEGER*n
see integer
Integer editing (I,0,Z), 12-6 to 12-9
Interactive program execution
continuing, 4-7
interrupting, 4-7, 4-8
Internal files, 11-11
Internal file specifier
control list parameter
in 1/0 statements, 11-17
Internal I/0 statements, 11-11
ENCODE and DECODE statements, A-1
to A-3
READ statements, 11-39 to 11-41
WRITE statements, 11-49 to 11-50
Interprocess communication, 11-3
Interrupting program execution
<CTRL/c> and <CTRL/y>, 4-7 to 4-8
Intrinsic functions, system-supplied
algorithms used in, D-30
complete list of, D-30 to D-38
character comparison functions, 10-24 to
10-26
description of types, 10-1
external procedures of same name, 8-17
lexical comparison functions, 10-26 to
10-27
references, generic, 10-20 to 10-21,
10-22 to 10-24
references, specific, 10-19 to 10-20,
10-22 to 10-24
use of names as arguments, 8-18
Intrinsic function references
specific and generic, 10-19 to 10-24
INTRINSIC statement
general description, 8-18 to 8-19
I/0
character I/O, 16-7 to 16-10

Index-15

I/0, (Cont.)
controlling l/0 in command procs, 1-34 to
1-35
internal I/0, 11-11
I/0 records, 11-12 to 11-14
l/0, internal
see internal I/0
l/O records
general description, 11-3
see also records (1/0)
IOSTAT
specifier in l/0 statements, 11-21,
18-1, 18-6 to 18-7
BACKSPACE statement keyword, 13-27
CLOSE statement keyword, 13-18
DELETE statement keyword, 13-28, 13-29
ENDFILE statement keyword, 13-27, 13-28
INQUIRE statement specifier, 13-19, 13-22
OPEN statement keyword, 13-4, 13-11
REWIND statement keyword, 13-26
UNLOCK statement keyword, 13-30
I/O statements
forms of, 11-3 to 11-4
list of, 11-16
OPEN statement interdependencies
file organization, 11-10
file specification, 11-8 to 11-9
logical unit specifier, 11-17
specifiers
see l/0 statement components
types of access modes, 11-2
use of unsubscripted arrays with, 6-21
see also, I/0 statement components,
ACCEPT, FORMAT, OPEN, PRINT,
READ,
REWRITE, TYPE, WRITE
I/0 statement components
control list parameters, 11-16,
rules for specifying, 11-22 to 11-23
format specifier, 11-17 to 11-18
internal file specifier, 11-17
I/O status specifier, 11-21
key-field-value specifier, 11-19 to 11-20
key-of-reference specifier, 11-20 to 11-21
logical unit specifier, 11-17
namelist specifier, 11-18
record specifier, 11-19
transfer-of-control specifier, 11-21 to
11-22

Index-16

I/0 list parameter, 11-23
implied-DO lists, 11-24 to 11-26
interaction with format controls, 12-28
to 12-29
simple list elements, 11-23 to 11-24
I/O status specifier
control list parameter
in l/0 statements, 11-21
I/0 units
see logical I/0 units
ISAM, 15-1
Iterative I/0
implied-DO list, 11-24 to 11-26
iterative count controls
indexed DO statement, 9-3 to 9-6
Iterative processing controls
see DO statements
/14 qualifier, 3-11

J
JOB logical name table, 1-18 to 1-19
.JOU files
see journal files
Journal files (EDT)
recovery operations, 2-5 to 2-6

K
'KEEP'
file disposition, 13-18
KEY
INQUIRE statement specifier, 13-19,
13-22 to 13-22
key-field-value specifier
in I/0 statements, 11-19 to 11-20
OPEN statement keyword, 13-4, 13-12 to
13-13
KEYx specifier (KEY, KEYEQ, KEYGE,
KEY GT)
see key-field-value specifier
KEYID specifier
see key-of-reference specifier
Keys, access
specified in OPEN statement, 13-12 to
13-13
Keys, primary and alternate
see key fields

'KEYED'
OPEN statement keyword value, 13-3,
13-6
Keyed access mode, 11-15
general discussion, 15-1 to 15-8
see also indexed organization files
Key fields
primary and alternate
definition, 15-2
discussion of use, 15-2 to 15-5
Key-field-value specifier
control list parameter (KEY, KEYEQ,
KEYGE, KEYGT)
in I/0 statements, 11-19 to 11-20
Key-of-reference specifier
control list parameter (KEYID)
in I/0 statements, 11-20 to 11-21
Keypad diagrams
VT52, 2-8
VTlOO, 2-8
VTlOO, Debug command layout, 17-7
VT200, 2-9

L
L edit descriptor, 12-18
Labels
see statement labels
.LIST
see relational operators
LEN function, 10-24, 10-26, 16-6
Length
default for INTEGER and LOGICAL (/I4),
3-11
of records
see fixed-length records, variable-length
records, segmented records,
stream records
of source lines (/EXTENDSOURCE), 3-9
affect on sequence number fields, 5-11
specifier in data type declarations, 6-2
Lexical comparison library functions
LLT, LLE, LGT, LGE, 10-26 to 10-27,
16-7
LGE function, 10-26 to 10-27, 16-7
LGT function, 10-26 to 10-27, 16-7
Libraries
see text file libraries, intrinsic functions
LIBRARY command (DCL), 3-15 to 3-17

/LIBRARY qualifier
FORTRAN command, 3-11
LINK command, 4-3, 4-5
Library search order
during compilation, 3-18
%LINE prefix
SET BREAK command (Debug), 17-29
Lines, FORTRAN source code
all blank, 6-10
entry methods
fixed format, 5-7 to 5-8
tab format, 5-9 to 5-10
format requirements
continuation indicator field, 5-11
sequence number field, 5-11
statement field, 5-11
statement label field, 5-10
space characters embedded in, 5-7
Line mode editing (EDT), 2-1, 2-12 to 2-23
command summary, 2-12 to 2-14
deleting text, 2-19
displaying text, 2-17 to 2-18
getting text from other files, 2-21 to 2-22
inserting text, 2-18 to 2-19
line positioning, 2-18
moving text, 2-20
replacing text, 2-19
range specification, 2-14 to 2-17
string substitution, 2-20 to 2-21
writing text to other files, 2-21 to 2-22
Line speed
see SET TERMINAL command
LINK command
format, 4-2
options, 4-2 to 4-5
Linker
compiler input for, 3-1 to 3-2
messages, 4-6
LIS
file type, 3-11
Lists, implied-DO
use in DATA statements, 8-5
List-directed formatting
I/0 statement specifier, 11-17 to 11-18
List-directed I/0 statements
ACCEPT statement, 11-52
general description, 11-3
READ statements
internal READ, 11-39, 11-40

Index-17

List-directed I/0 statements, (Cont.)
sequential READ, 11-26, 11-28 to 11-30
WRITE statements
internal WRITE, 11-49, 11-50
sequential WRITE, 11-41, 11-43 to
11-44
List elements, simple
I/0 list parameter
in 1/0 statements, 11-23 to 11-24
Listing file
see output listing
LLE function, 10-26 to 10-27, 16-7
LLT function, 10-26 to 10-27, 16-7
%LOC built-in function, 10-8
Local symbols
assignment operations 1-8, 1-29
controlling availability of, 3-8
local symbol definitions
effect of /DEBUG, 3-8
Locked records
freeing locked records
UNLOCK statement, 13-30
Logical
constants
.TRUE. and .FALSE., 6-13
representation in memory, C-1
setting default length, 3-11
storage requirement, 6-2
data type
definition, 6-1
relationship to BYTE data type, 8-7
see also arrays, constants, data types,
logical values, variables
LOGICAL*n
see logical
Logical assignment statement, 7-3 to 7-4
Logical editing (L), 12-18
Logical elements
see logical expressions
Logical expressions, 6-39 to 6-40
compile-time logical expressions
use in PARAMETER statements, 8-21,
8-22
Logical IF statement, 9-13 to 9-14
Logical 1/0 units
CLOSE statement options, 13-18
connection method
explicitly by means of OPEN, 13-17
implicitly by system default, 11-7 to 11-8

Index-18

Logical I/0 units, (Cont.)
default FORTRAN logical unit numbers,
11-7 to 11-8
defining logical unit numbers
DEFINE FILE statement, A-1, A-3 to
A-4
general discussion, 11-2
inquiring about properties
INQUIRE statement, 13-19 to 13-26
OPEN statement options, 11-8, 13-2
system unit numbers and names, 11-5 to
11-6
see also system logical names
Logical names
see FORTRAN logical names, system
logical names, logical I/0 units
Logical name tables, 1-18 to 1-19
Logical operators, 6-39, 6-40
Logical scalar memory reference
see scalar memory reference
Logical units
see logical I/0 units, UNIT
Logical unit specifier
control list parameter
in I/0 statements, 11-17
Logical values
representation in memory, C-8 to C-9
Log-in command file, 1-38
Log-in procedure, 1-4
accessing other nodes, 1-6 to 1-7
Log-out procedure, 1-4
Loops, DO
DO statements, 9-3 to 9-10
Lowercase characters
flagging in output
SOURCEFORM parameter
(/STANDARD), 3-14
in character and Hollerith constants, 5-7
supported by VAX FORTRAN, 5-6
see relational operators

M
Machine code listing
general description, 3-29 to 3-31
representation in MACRO, 3-12
/MACHINE_CODE qualifier, 3-12
MACRO code
use to represent object code, 3-12

MACRO code, (Cont.)
unsupported codes generated by
FORTRAN; 3-12
Main program
see program unit
Map declaration
general description, 8-31 to 8-33
use to establish variables, 6-16
MAP parameter
/SHOW qualifier, 3-13
LINK command, 4-2, 4-4 to 4-5
MAP statement, 8-31, 8-32
Mathematical functions, intrinsi~
see subprograms
MAXREC
OPEN statement keyword, 13-4, 13-13
Memory diagrams
structured records, 6-25, 6-26
Messages
compiler-fatal diagnostic messages, E-26
to E-27
CDD and CDDL error messages, E-41
CRX error messages, E-41 to E-43
linker messages, 4-6
run-time messages, E-28 to E-40
sending to terminal
see PAUSE statement
source program diagnostic messages, E-1
to E-26
warning and informational
/STANDARD qualifier, 3-14
/WARNING qualifier, 3-15
Minus operator (-), 6-33 to 6-34, 6-40,
17-34
MOUNT command (DCL)
logical name assignment, 1-20 to 1-21
MTH$
prefix for condition symbols
for FORTRAN run-time errors, 18-5
Multiplication operator (*), 6-33 to 6-34
MVBITS subroutine, D-42 to D-43

N
NAME
INQUIRE statement specifier, 13-19, 13-23
OPEN statement keyword, 13-4, 13-13
NAMED
INQUIRE statement specifier, 13-19, 13-23

Names
see symbolic names, entry names
Named common blocks
establishing order of contents, 8-3 to 8-4
initializing values in, 8-2 to 8-3
Namelist specifier
control list parameter
in I/0 statements, 11-18
NAMELIST statement
general description, 8-20
use of unsubscripted arrays with, 6-21
Namelist-directed VO statements
ACCEPT statement, 11-52
general description, 11-3
sequential READ statement, 11-27,
11-30 to 11-34
sequential WRITE statement, 11-41,
11-44 to 11-45
see also NAMELIST statement
.NE.
see relational operators
.NEQV.
see logical operators
Nested block IF constructs, 9-19 to 9-20
Nested DO loops, 9-6 to 9-8
Nested structured declarations
see substructure declarations
Networks
accessing other nodes, 1-6 to 1-7
SET HOST, 1-7
SHOW NETWORK, 1-6
NEXTREC
INQUIRE statement specifier, 13-19,
13-24
NML specifier
in I/0 statements, 11-18
Nodes
file spec default, 1-16, 11-5
see also networks
Nonexecutable statements
definition, 5-2
NOSPANBLOCKS
OPEN statement keyword, 13-4, 13-13
.NOT.
see logical operators
NUMBER
INQUIRE statement specifier, 13-19,
13-24
Numbers, sequence, 5-11
Number generator, random, D-42
Index-19

Numeric scalar memory reference
see scalar memory reference
Numeric storage unit, 6-2
Numeric type declarations
general description, 8-7 to 8-8

0
0 field descriptor, 12-8
Object files
naming (/OBJECT), 3-12
see also compilation options
/OBJECT qualifier, 3-3, 3-4, 3-12
Octal constants, 6-11 to 6-12
data typing of, 6-12
Octal notation (")
for integer constants, A-1, A-6
Octal values
1/0 transfers
by 0 field descriptor, 12-8
ON ... THEN command (DCL), 1-36, 1-37
OPEN statement
general description, 13-1 to 13-18
I/O statement interdependencies, 11-2,
11-8 to 11-9, 11-17
file organization, 11-10
file specification, 11-8, 11-9
logical unit specifier, 11-17
OPENED
INQUIRE statement specifier, 13-19,
13-24
Operators
in DCL expressions, 1-30
expression operators
summary of, D-1 to D-2
precedence in logical expressions, 6-40
see also arithmetic operators, relational
operators
Optimization
affect on debugging, 3-8
effect of VOLATILE statement, 8-34
/OPTIMIZE qualifier, 3-12
/OPTIMIZE qualifier, 3-12
/OPTIONS qualifier (LINK), 4-3
OPTIONS statement, 3-26
.OR.
see logical operators
Order
required statement order, 5-3

Index-20

ORGANIZATION
INQUIRE statement specifier, 13-19,
13-24 to 13-25
OPEN statement keyword, 13-4, 13-13
OUT
Debug screen display, 17-38, 17-39
Output files
see listing files
Output listing, 3-28 to 3-35
qualifiers affecting output
see compilation options
Output options
see compilation options
Overflow
see arithmetic overflow
OWNER file access, 1-25

p
P edit descriptor, 12-16 to 12-17
Parameters
passing to command procs, 1-32 to 1-33
PARAMETER statement, 8-21 to 8-22
alternate version of, A-1, A-5 to A-6
Passed-length character arguments, 6-17,
10-5 to 10-6, 16-4 to 16-5
Passed-length format, *(*)
for dummy arguments or character
functions, 6-3
Passwords
changing, 1-5
Pathname prefixes (Debug)
making symbolic references unique, 17-30
Pathnames (CDD), 3-27
PAUSE statement, 9-20 to 9-21
Period (.)
current location indicator (Debug), 17-28
operand contents specifier (Debug), 17-34
Plus operator(+), 6-33 to 6-34, 6-40, 17-34
Positional editing (X,T,TL,TR), 12-22 to
12-23
Precedence, operator
within arithmetic expressions, 6-33
Prefixes (Debug)
making symbolic references unique, 17-29
to 17-30
PREPROCESSOR parameter
of /SHOW qualifier, 3-13

Pretested indefinite DO statement
DO WHILE, 9-9
Primary key fields
see key fields
'PRINT'
file disposition, 13-18
PRINT command (DCL), 1-26 to 1-27
PRINT statement, 11-53
PROCESS logical name table, 1-18
Programs, main
see program unit
Program debugging
see de bugger
Program execution, 4-6 to 4-11
controlling during debug session, 17-17
to 17-23
interrupting
<CTRL/C> and <CTRL/Y>, 4-7 to 4-8
temporarily suspending (PAUSE), 9-20 to
9-21
terminating
EXIT, D-40
STOP, 9-23
Program section (PSECT), 3-32
PROGRAM statement
general description, 8-23
Program unit
assigning symbolic name
to main program unit, 8-23
block data program unit, 8-2
definition of, 5-2
Protection
codes (RWED), 1-25
handling file protections, 1-25 to 1-27
for source files when creating (EDT), 2-5
PSECT, 3-32
PURGE command (DCL), 1-23 to 1-24

a
Q edit descriptor, 12-24
Qualifiers
rules for specifying, 1-3
Question mark
namelist prompt, 11-32
Quotation marks (")
octal notation for integer constants, A-1,
A-6

R
Radix
specifying during debug session,
17-36 to 17-37
Radix-50
constants and character sets, B-:-3
to B-4
RAN function, D-42
Random number generator
RAN function, D-42
Range specifications (EDT), 2-14 to
2-17
READ command (DCL), 1-35
READ statements
direct access READ, 11-35
formatted, 11-36
unformatted, 11-37
indexed READ, 11-37
formatted, 11-38
unformatted, 11-38 to 11-39
internal READ, 11-39
formatted, 11-40
list-directed, 11-41 to 11-42
sequential READ, 11-26
formatted, 11-27
list-directed, 11-28 to 11-30
namelist-directed, 11-30 to 11-34
unformatted, 11-34 to 11-35
relationship to DECODE statement, A-1,
A-2
READONLY
OPEN statement keyword, 13-4, 13-14
REAL
see REAL*4
REAL*4
constants, 6-6 to 6-7
data type
default for undeclared symbolic names,
8-17
definition, 6-1
representation in memory, C-2 to C-3
storage requirements, 6-2
see also arrays, constants, data types,
variables
REAL*8
constants, 6-7 to 6-8
G_f1oating vs. D_f1oating, 3-10, 6-3
data type
definition, 6-1

Index-21

REAL*8, (Cont.)
representation in memory (G_ and
D_floating), C-2, C-3 to C-4
storage requirement, 6-2
see also arrays, constants, data types,
variables
REAL*l6
constants, 6-8 to 6-9
data type
definition, 6-1
representation in memory, C-2, C-4 to
C-5
storage requirements, 6-2
see also arrays, constants, data types,
variables
Real editing (F,E,D,G), 12-10 to 12-16
complex data editing, 12-15 to 12-16
relationship to DECODE statement, A-1,
A-2
REC
DELETE statement keyword, 13-28, 13-29
specifier in I/0 statements, 11-19
RECL
INQUIRE statement specifier, 13-19, 13-25
OPEN statement keyword, 13-4, 13-14
to 13-15
Records
I/0 records
general description, 11-3
deleting records from a file (DELETE),
13-28 to 13-29, 15-7
freeing locked records (UNLOCK), 13-30
in internal files, 11-11
ISAM record pointers (current and
next), 15-7
record formats (fixed-length, segmented,
stream, variable-length), 11-12 to
11-14
record operations on indexed files, 15-3
to 15-7
RECORDTYPE keyword (INQUIRE
statement), 13-19, 13-25
RECORDTYPE keyword (OPEN
statement), 13-15 to 13-16
sizes (OPEN statement keywords), 13-14
to 13-15
structured data items
arrangement in memory, 6-24 to 6-26
contrasted 'vith arrays, 6-23

Index-22

Records, (Cont.)
overview, 6-23, 14-3 to 14-4
Record access modes
direct, 11-15
keyed, 11-15
sequential, 11-14 to 11-15
Record and field references
aggregate field reference
definition, 6-27 to 6-28
use in unformatted I/0, 6-29
scalar field reference
definition, 6-27 to 6-28
Record specifier
control list parameter
in I/0 statements, 11-19
RECORDSIZE
OPEN statement keyword, 13-4, 13-15
RECORD statement
general description, 8-23 to 8-24, 14-3
RECORDTYPE
INQUIRE statement specifier, 13-19, 13-25
OPEN statement keyword, 13-4, 13-15 to
13-16
Recovery
source files (EDT), 2-5
%REF built-in function, 10-7 to 10-8
use with Debug, 17-19
References, function
see function references
References, generic or specific
see function references
REG
Debug screen display, 17-38, 17-39
Relational expressions, 6-38 to 6-39
Relational operators, 6-38, D-1
avoiding use as field names
in structure declarations, 6-29
Relative files
see relative organization files
Relative organization files
deleting records from
DELETE statement, 13-28 to 13-29
defining size and structure
DEFINE FILE statement, A-1,
A-3 to A-4
freeing locked records in
UNLOCK statement, 13-30
general description, 11-10 to 11-11
see also direct access

RENAME command (DCL), 1-22, 1-25
Repeat counts
in FORMAT statements, 12-3
Return argument, alternate, 10-6 to 10-7
RETURN statement
general description, 9-21 to 9-22
use with CALL statements, 9-21, 9-22
use with FUNCTION statement, 10-11
use with SUBROUTINE statement, 10-14,
10-16
when to avoid, 4-8
Returning completion status values
to a command proc, 4-8
REWIND statement
general description, 13-26
see also BACKSPACE statement
REWRITE statements, 11-50 to 11-52
RTL
see Run-Time Library
RUN command (DCL), 4-6 to 4-7
using to invoke the debugger, 17-3
Running FORTRAN programs, 4-6 to 4-11
Run-time formats, 12-27 to 12-28
Run-Time Library
error processing performed by, 18-1 to 18-7
RWED
file protection codes, 1-25

s
S edit descriptor, 12-6
'SAVE'
file disposition, 13-18
SAVE statement
general description, 8-24 to 8-25
use of unsubscripted arrays with, 6-21
Scalar field reference
see record and field references
Scalar memory reference
definition and examples, 6-31 to 6-32
Scalar reference
definition and examples, 6-31 to 6-32
Scale factor editing (P), 12-16 to 12-17
Scope (Debug)
making symbolic references unique, 17-29
to 17-30, 17-31
Screen displays (Debug), 17-39 to 17-43
SCROLL command (Debug), 17-41

SEARCH command (DCL), 1-26
SEARCH command (Debug), 17-23, 17-24
Search lists, 1-21
SECNDS function subprogram, D-41
Segmented records
format, 11-13
RECORDTYPE keyword (OPEN
statement), 13-4, 13-15 to 13-16
SELECT/SCROLL command (Debug), 17-41
key used in keypad mode, 17-43
Separators
external field separators, 12-27
format specification separators, 12-26
Sequence numbers, 5-8, 5-11
'SEQUENTIAL'
OPEN statement keyword value, 13-3,
13-6
SEQUENTIAL
INQUIRE statement specifier, 13-19,
13-25 to 13-26
Sequential access mode, 11-14 to 11-15
for indexed organization files, 15-1
Sequential files
see sequential organization files
Sequential 1/0 statements
READ statements, 11-26 to 11-35
WRITE statements, 11-41 to 11-46
Sequential organization files
repositioning
BACKSPACE statement, 13-27
REWIND statement 13-26
general description, 11-10
writing end-of-file records
ENDFILE statement, 13-27 to 13-28
SET commands (DCL)
SET DEFAULT, 1-15
SET HOST, 1-7
SET [NOJON, 1-37, 1-38
SET PASSWORD, 1-5
SET PROTECTION, 1-25
SET TERMINAL, 1-5 to 1-6
SET VERIFY, 1-36
SET commands (Debug)
SET BREAK, 17-20 to 17-22
SET DISPLAY, 17-41to17-42
SET LOG, 17-10
SET MODE radix, 17-36 to 17-37
SET MODE SCREEN, 17-23, 17-24,
17-39

Index-23

SET commands (Debug), (Cont.)
SET MODULE, 17-26 to 17-27
SET OUTPUT LOG, 17-10
SET SCOPE, 17-31
SET TRACE, 17-20, 17-23
SET TYPE/OVERRIDE, 17-35
SET WATCH, 17-20 to 17-22
SET WINDOW, 17-40
/SHAREABLE qualifier (LINK), 4-2, 4-4
SHARED
OPEN statement keyword, 13-4, 13-16
SHOW commands (DCL)
SHOW DEFAULT, 1-15
SHOW NETWORK, 1-6
SHOW QUOTA, 1-15
SHOW commands (Debug)
SHOW BREAK, 17-22
SHOW CALLS, 17-19 to 17-20
SHOW KEY, 17-7, 17-8
SHOW MODULE, 17-26, 17-27
SHOW STEP, 17-18
SHOW SYMBOL, 17-31 to 17-32
SHOW TRACE, 17-22
SHOW TYPE, 17-36
SHOW WATCH, 17-23
SHOW WINDOW, 17-40
/SHOW qualifier, 3-13 to 3-14
Sign control editing, 12-6
Simple list elements
1/0 list parameter
in 1/0 statements, 11-23 to 11-24
SINGLE parameter (/SHOW), 3-13
Slash (/)
division operator, 6-33 to 6-34,
6-40, 17-34
record terminators
in FORMAT statements, 12-1
Source code listing
general description, 3-28 to 3-29
qualifiers affecting output
/LIST, 3-11
/SHOW, 3-13
Source code
allowable characters, 5-7 to 5-7
coding restrictions/limits
summary of, E-27 to E-28
comments, 3-9, 5-5
debugging statements in, 5-10

lndex-24

Source code, (Cont.)
field descriptions, 5-7 to 5-11
format requirements
fixed-format lines, 5-7 to 5-8
tab-format lines, 5-9 to 5-10
see also source programs
Source files
creating (EDT), 2-6
input to compiler, 3-2 to 3-3
protecting (EDT), 2-5 to 2-6
recovering (EDT), 2-5 to 2-6
see also files
SOURCE_FORM parameter
(/STANDARD), 3-14
Source programs
compile options
continuation line limits, 3-7
D in column 1, 3-9, 5-10
maximum line length, 3-9
program unit
definition, 5-2
statement order, 5-2 to 5-3
symbolic names
rules, conventions, and use, 5-4 to 5-5
see also source code
Source program diagnostic messages, E-1 to
E-26
SP
edit descriptor, 12-6
Space characters
effect of FORMAT descriptors, 12-3, 12-5
in character and Hollerith constants, 5-7
in source code in general, 5-7
in statement label fields, 5-10
Special characters
FORTRAN supported, 5-6
Specification statements, 8-1 to 8-34
SRC
Debug screen display, 17-38, 17-39
SS
edit descriptor, 12-6
SS$
prefix for condition symbols for
FORTRAN run-time errors, 18-4 to 18-5
/STANDARD qualifier, 3-14
Standards
see ANSI standards, FORTRAN-66,
FORTRAN-77

Startup command files (EDT), 2-25 to 2-26
Statements, FORTRAN
see FORTRAN statements
Statement function subprograms
see subprograms
Statement labels
rules governing use, 5-2, 5-8, 5-10, 7-6
Statement label references
use in FORMAT and GOTO statements,
7-6 to 7-7
STATUS
CLOSE statement keyword, 13-18
OPEN statement keyword, 13-4, 13-16 to
13-17
Status values, completion
returning to a command proc, 4-8
STEP commands (Debug), 17-18 to 17-19
STEP/SOURCE, 17-23, 17-24
STOP statement
affect on program execution, 4-7
general description, 9-23
when not to use, 4-8
Storage allocation, file
OPEN statement keywords
EXTENDSIZE, 13-3, 13-10
INITIALSIZE, 13-4, 13-11
Storage map listing
general description, 3-32 to 3-35
qualifiers affecting output
/SHOW, 3-13
Storage units
character, 6-2
numeric, 6-2
Stream records
format, 11-13 to 11-14
RECORDTYPE keyword (OPEN
statement), 13-4, 13-15 to 13-16
Structures
general description, 14-2
see also records (structured data items),
structure declaration blocks,
substructure declarations
Structure declaration blocks
CDD data definitions, relationship to,
3-20, 3-21
data type declaration rules, 8-28
field declarations within, 8-25,
8-26, 8-27 to 8-33
general description, 8-25 to 8-33

Structure declaration blocks, (Cont.)
overview, 6-23 to 6-24, 14-2
use of %FILL, 6-24, 8-28
see also substructure declarations
STRUCTURE statement
general description, 8-25, 8-26, 14-2
Subdirectories, 1-14 to 1-17
creating, 1-15
deleting, 1-17
'SUBMIT'
file disposition, 13-18
SUBMIT command (DCL), 1-37 to 1-38
/PARAMETERS qualifier, 1-33
Subprograms
definition of, 5-2
bit functions
general discussion about, D-43 to D-45
CALL statement, 9-2
CHARACTER FUNCTION statement,
10-12
ENTRY statement, 10-16 to 10-19
FUNCTION statement, 10-11to10-14
functions, built-in
argument list functions (%VAL, %REF,
%DESCR), 10-7 to 10-8
%LOC function, 10-8
function references, 10-13 to 10-14
RETURN statement, 9-21 to 9-23
system-supplied FORTRAN intrinsic
functions
algorithms used in, D-30
complete list of, D-30 to D-38
character comparison functions, 10-24 to
10-26
description of types, 10-1
duplicating external procedure names,
8-17
lexical comparison functions, 10-26 to
10-27
references, generic, 10-20 to
10-21, 10-22 to 10-24
references, specific, 10-19 to 10-20,
10-22 to 10-24
use of names as arguments, 8-18
system-supplied subroutines and functions
list and descriptions of, D-38 to D-43
user-written functions
function subprograms, 10-11 to 10-14
ENTRY statements in, 10-17 to 10-18

Index-25

RETURN state·ment, (Cont.)
statement functions, 10-9 to 10-11
subroutine subprograms, 10-14 to 10-16
ENTRY statements in, 10-18 to 10-19
Subprogram arguments (actual and dummy
arguments)
general description, 10-2 to 10-8
overview, 10-2
adjustable arrays, 10-3 to 10-4
alternate return arguments, 10-6 to 10-7
assumed-size arrays, 10-4 to 10-5
character arrays, 10-5 to 10-6
defaults for arguments passing, 10-7 to
10-8
Hollerith and character constants, 10-6
passed-length character arguments, 10-5
to 10-6, 16-4 to 16-5
associating variables with, 6-16
bit function arguments, D-43 to D-45
use of aggregate field references, 6-29
use of built-in functions
argument list functions (%VAL, %REF,
%DESCR), 10-7 to 10-8
%LOC function, 10-8
use of external procedure names, 8-16 to
8-17
use of intrinsic function names, 8-18
Subroutine arguments
see subprogram arguments
SUBROUTINE statement, 10-14 to 10-15
see also subprograms
Subscripts
see arrays
Substrings, character
see character substrings
Substring equivalence, 8-13 to 8-16
Substring references
checking boundaries
FORTRAN command option, 3-6
Substructure declarations
general description, 6-24, 8-25, 8-31
Summary listing, compilation, 3-35
Symbolic names
assigning to constants
with PARAMETER statement, 8-21 to
8-22
assigning to main program unit, 8-23
default data types assigned, 8-17
reference information in listing file, 3-7

Index-26

Symbolic names, (Cont.)
referencing during debug session,
17-25 to 17-27
rules, conventions, and use, 5-4 to 5-5
use as arguments to subprograms
external procedure names, 8-16 to 8-17
intrinsic function names, 8-18 to 8-19
use with arrays, 6-18
use with variables, 6-15
Symbols
assignment operations 1-8, 1-29
controlling availability of, 3-8
local symbol definitions
effect of /DEBUG, 3-8
Symbols (DCL)
use in commands procs, 1-28 to 1-32
Symbol map
MAP parameter (/SHOW), 3-13
SYNTAX parameter (/STANDARD), 3-14
SYS$COMMAND, 1-19, 1-34
SYS$DISK, 1-19
SYS$ERROR, 1-19
SYS$INPUT, 1-19, 1-34
SYS$LIBRARY, 3-19
SYS$LOGIN, 1-19
SYS$NODE, 1-19
SYS$0UTPUT, 1-19, 1-34
SYS$SCRATCH, 1-19
/SYSLIB qualifier (LINK), 4-3
/SYSSHR qualifier (LINK), 4-3
System access, 1-3 to 1-6
see also log-in procedure, log-out
procedure
System definition modules, 3-19
SYSTEM file access, 1-25
System logical names
assigning with MOUNT, 1-20
defaults, 1-19
defining, 1-18
deleting, 1-20
displaying, 1-20
search lists, 1-21
using to identify devices, 1-11
System logical name table, 1-18 to 1-19
System time
function subprogram for calculating
SECNDS, D-41
subroutine for calculating
TIME, D-41 to D-42

T
T edit descriptor, 12-=22 to 12-23
Tab character, 5-6
Tab formatting
EDT set-up, 2-25 to 2-26
flagging in output
SOURCE_FORM (/STANDARD), 3-14
general description, 5-9 to 5-10
Terminals
assigning SYS$COMMAND, SYS$1NPUT,
or SYS$0UTPUT, 1-34 to 1-35
setting speed, 1-6
setting type, 1-5
Text editor (EDT), 2-1 to 2-26
Text file libraries
general discussion, 3-15 to 3-19
accessing (INCLUDE), 3-24 to 3-25
creating and modifying
LIBRARY command (DCL), 3-15 to
3-17
defining defaults, 3-18 to 3-19
/LIBRARY qualifier, 3-11
search order, 3-18
system-supplied default library
FORSYSDEF. TLB,_ 3-19
TIME subroutine, D-41 to D-42
Time, system
function subprogram for calculating
SECNDS, D-41
subroutine for calculating
TIME, D-41 to D-42
TL
edit descriptor, 12-22, 12-23
TLB
file type, 3-15
TR
edit descriptor, 12-22, 12-23
Trace back mechanism
effect of /DEBUG
FORTRAN command, 3-8
LINK command, 4-2, 4-5
!rRACEBACK qualifier (LINK), 4-2, 4-5,
4-9 to 4-11
Tracepoints
setting during debug session, 17-20
to 17-22
Transfer, control
FORTRAN control statements, 9-1 to 9-23
see also CALL, RETURN

Transfer, data
see 1/0
Transfer-of-control specifier
control list parameter
in 1/0 statements, 11-21 to 11-22
.TRUE.
see logical constants
Type
see file type, data type
TYPE
OPEN statement keyword, 13-4, 13-17
TYPE command (DCL), 1-26 to 1-27
TYPE command (Debug), 17-23, 17-24
TYPE command (EDT), 2-17
Type declaration statement
see data type declaration statement
TYPE statement, 11-53

u
Unary plus and minus operators ( + and - ) ,
6-33 to 6-34, 6-40
Unconditional GOTO statement, 9-10 to
9-11
Undeclared symbolic names
default data types, 8-17
UNFORMATTED
INQUIRE statement specifier, 13-26
Unformatted 1/0 statements
general description, 11-3
relationship to ENCODE statement, A-1,
A-2
use of aggregate field references, 6-29
READ statements
direct access, 11-35, 11-36
indexed, 11-37, 11-38 to 11-39
sequential, 11-27, 11-34 to 11-35
REWRITE statements, 11-50, 11-51 to
11-52
WRITE statements
direct access, 11-46, 11-47
indexed, 11-47, 11-49
sequential, 11-41, 11-45 to 11-46
Union declarations
contrasted with EQUIVALENCE, 8-32
definition, 8-25 to 8-26
general description, 8-31 to 8-33
UNION statement, 8-31
Index-27

Units, logical
see logical I/0 units
UNIT
specifier in VO statements, 11-17
BACKSPACE statement keyword, 13-27
CLOSE statement keyword, 13-18
DELETE statement keyword, 13-28, 13-29
ENDFILE statement keyword, 13-27,
13-28
INQUIRE statement keyword, 13-19
OPEN statement keyword, 13-4, 13-17
REWIND statement keyword, 13-26
UNLOCK statement keyword, 13-30
UNLOCK statement, 13-30
Unnamed fields
use of %FILL
in structure declarations, 6-24
Unsubscripted arrays
statements used in, 6-21
Uppercase characters
in character and Hollerith constants, 5-7
supported by VAX FORTRAN, 5-6
USER logical name table, 1-18
/USERLIBRARY qualifier (LINK), 4-3
US ERO PEN
OPEN statement keyword, 13-17 to 13-18
User-written subroutines
see subprograms

Variables, (Cont.)
initializing character variables, 8-4
to 8-6, 16-4
scalar reference, 6-31
use in structure declarations, 6-24
Variable-length records
format, 11-13
RECORDTYPE keyword (OPEN
statement),
13-4, 13-15 to 13-16
VAX DEBUG
see de bugger
VAX FORTRAN
extensions to ANSI standard, v, 5-1
VAXNMS commands
see DCL commands
Virtual memory locations
defining symbolically (Debug), 17-31
specifying program addresses (Debug),
17-29
VIRTUAL statement, 8-10
VOLATILE statement
general description, 8-34
VT52 keypad, 2-8
VTlOO keypad, 2-8
keypad layout for Debug commands, 17-7
VT200 keypad, 2-9

w
v
%VAL built-in function, 10-7 to 10-8
use with Debug, 17-19
Variables
definition of, 6-15 to 6-16
assigning values to
with DATA statements, 8-4 to 8-6
association of two or more
with EQUIVALENCE statement, 6-16
character substrings, 6-22 to 6-23
data typing of
by implication, 6-17
by specification, 6-16 to 6-17
defining in memory, 6-16
establishing with subprogram references
actual and dummy arguments, 6-16
implied-DO variables '
in DATA statements, 8-5

Index-28

\Varning messages
see messages
/\VARNINGS qualifier, 3-15
\Vatch points
setting during a debug session,
17-20 to 17-22
\VHILE command (Debug), 17-25
\Vildcards
use in filespecs, 1-14
\Vindows (Debug)
defining, 17-40
\VORLD file access, 1-25
\VRITE command (DCL), 1-35
\VRITE statements
direct access \VRITE
formatted, 11-46, 11-47
unformatted, 11-46, 11-47
indexed \VRITE
formatted, 11-47, 11-48

WRITE statements, (Cont.)
unformatted, 11-47, 11-49
internal WRITE
formatted, 11-49, 11-50
list-directed, 11-49, 11-50
sequential WRITE
formatted, 11-41, 11-42 to 11-43
list-directed, 11-41, 11-43 to 11-44
namelist-directed, 11-41, 11-44
to 11-45
unformatted, 11-41, 11-45 to 11-46

x
X edit descriptor, 12-22
.XOR.
see logical operators

z
Z field descriptor, 12-9

Index-29

Programming in VAX FORTRAN
AA-D034D-TE
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