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Document:	VAX-11 PASCAL User's Guide (Ver 1.2)
Order Number:	AA-H485B-TE
Revision:	000
Pages:	239
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VAX-11- PASCAL
User's Guide
Order No. AA-H485B-TE

March 1981
This document describes how to compile, link, execute, and debug VAX-11
PASCAL programs on the VAX/VMS operating system. It also contains information useful to VAX-11 PASCAL programmers, dealing with input and output,
procedure calling, error processing, and storage allocation.

VAX-11- PASCAL
User's Guide
Order No. AA-H485B-TE

SUPERSESSION/UPDATE INFORMATION:

This revised document supersedes the
VAX-11 PASCAL User's Guide
(Order No. AA-H485A-TE)

SOFTWARE VERSION:

VAX-11 PASCAL V1.2

To order additional copies of this document, contact the Software Distribution
Center, Digital Equipment Corporation, Maynard, Massachusetts 01754

digital equipment corporation . maynard, massachusetts

First Printing, November 1979
Revised, March 1981
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 or its affiliated companies.

@ 1979, 1981 by Digital Equipment Corporation.
All Rights Reserved.

The postage prepaid READER'S COMMENTS form on the last page of this
document requests the user's critical evaluation to assist us in
preparing future documentation.
The following are trademarks of Digital Equipment Corporation:

DEC
DEC US
DIGITAL
PDP
UNIBUS
VAX
DECnet

DECsystem-10
DECSYSTEM-20
DECwriter
DIBOL
Edusystem
IAS
MASSBUS

PDT
RSTS
RSX
VMS

momoomo
ZKA25-81

3111-15

CONTENTS

Page
PREFACE

SUMMARY OF TECHNICAL CHANGES

xiii

CHAPTER

USING VAX-11 PASCAL

1-1

1.1
1. 2

CREATING AND EXECUTING A PROGRAM
VAX/VMS FILE SPECIFICATIONS AND DEFAULTS

1-1
1-2

COMPILING A PROGRAM

2-1

2.1
2.2
2.2.1

2-1
2-2

2.2.2
2.3
2.4
2.4.1
2.4.2
2.4.3
2.4.4

THE PASCAL COMMAND
PASCAL COMPILER QUALIFIERS
Specifying Qualifiers with the PASCAL
Command
Specifying Qualifiers in the Source Code
SPECIFYING OUTPUT FILES
COMPILER LISTING FORMAT
Source Code Listing
Cross-Reference Listing
Machine-Code Listing
A Compiler Listing Example

2-4
2-6
2-7
2-8
2-9
2-11
2-12
2-15

LINKING A PROGRAM

3-1

3.1
3.2
3. 2. 1
3.2.2
3. 2. 3
3.3
3.3.1
3.3.2

THE LINK COMMAND FORMAT
COMMAND QUALIFIERS
Image-File Qualifiers
Map-File Qualifiers
Debugging and Traceback Qualifiers
FILE QUALIFIERS
/LIBRARY Qualifier
/INCLUDE Qualifier

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

EXECUTING A PROGRAM

4-1

4.1
4. 1. 1
4. 1. 2
4.2

FINDING AND CORRECTING ERRORS
Error-Related Command Qualifiers
Specifying Command Qualifiers
SAMPLE TERMINAL SESSION

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

DEBUGGING PASCAL PROGRAMS

5-1

VAX-11 SYMBOLIC DEBUGGER
5.1
Debugger Symbol Table
5. 1. 1
5.1. 2
VAX-11 Symbolic Debugger Command Syntax
Debugger Operations
5.1. 3
5. 1. 4
Specifying Addresses
Specifying Data Addresses
5.1.4.1
Specifying Current, Previous, and
5.1.4.2
Next Locations

iii

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

CONTENTS
Page
Specifying Program Addresses
5.1.4.3
5-4
Special Symbols
5.1. 5
5-5
USING THE DEBUGGER
5.2
5-6
Debugging a PASCAL Program
5.2.1
5-6
General Description of the Debugger Commands 5-9
5.2.2
Preparing to Debug a Program
5.2.2.1
5-9
Controlling Program Execution
5.2.2.2
5-10
Examining and Modifying Locations
5.2.2.3
5-12
5·. 2. 2. 4
Specifying Scope
5-13
VAX-11 SYMBOLIC DEBUGGER COMMANDS
5.3
5-15
CANCEL ALL Command
5.3.1
5-16
CANCEL BREAK Command
5.3.2
5-17
CANCEL EXCEPTION BREAK Command
5.3.3
5-18
CANCEL MODE Command
5.3.4
5-19
CANCEL MODULE Command
5.3.5
5-20
CANCEL SCOPE Command
5.3.6
5-21
CANCEL TRACE Command
5.3.7
5-22
CANCEL TYPE/OVERRIDE Command
5.3.8
5-23
CANCEL WATCH Command
5.3.9
5-24
5.3.10
CTRL/Y Command
5-25
DEPOSIT Command
5.3.11
5-26
EVALUATE Command
5.3.12
5-29
EXAMINE Command
5.3.13
5-31
5.3.14
EXIT Command
5-34
5.3.15
GO Command
5-35
HELP Command
5.3.16
5-36
5.3.17
SET BREAK Command
5-38
SET EXCEPTION BREAK Command
5.3.18
5-40
SET LANGUAGE Command
5.3.19
5-41
5.3.20
SET LOG Command
5-42
SET MODE Command
5.3.21
5-43
5.3.22
SET MODULE Command
5-45
5.3.23
SET OUTPUT Command
5-46
5.3.24
SET SCOPE Command
5-48
5.3.25
SET STEP Command
5-50
SET TRACE Command
5.3.26
5-52
SET TYPE Command
5.3.27
5-54
5.3.28
SET WATCH Command
5-56
SHOW BREAK Command
5.3.29
5-57
SHOW CALLS Command
5.3.30
5-58
5.3.31
SHOW LANGUAGE Command
5-59
SHOW LOG Command
5.3.32
5-60
SHOW MODE Command
5.3.33
5-61
SHOW MODULE Command
5.3.34
5-62
SHOW OUTPUT Command
5.3.35
5-63
SHOW SCOPE Command
5.3.36
5-64
SHOW STEP Command
5.3.37
5-65
SHOW TRACE Command
5.3.38
5-66
SHOW TYPE Command
5.3.39
5-67
5.3.40
SHOW WATCH Command
5-68
5.3.41
STEP Command
5-69
5.3.42
@file-spec Command
5-71
A DEBUGGING EXAMPLE
5.4
5-72
CHAPTER

INPUT AND OUTPUT

6-1

6.1
6.2
6.2.1

LOGICAL NAMES
FILE CHARACTERISTICS
File Organization

6-1
6-2
6-3

CONTENTS
Page

6.4.4
6.4.5
6.5
6.6

Record Access
RECORD FORMATS
Fixed-Length Records
Variable-Length Records
OPEN PROCEDURE PARAMETERS
File Status or History
Record Length
Record-Access Mode
Record Type
Carriage Control
LOCAL INTERPROCESS COMMUNICATION: MAILBOXES
COMMUNICATING WITH REMOTE COMPUTERS: NETWORKS

6-3
6-3
6-4
6-4
6-4
6-4
6-5
6-5
6-5
6-5
6-6
6-7

CALLING CONVENTIONS

7-1

6.2.2
6.3
6.3.1
6.3.2
6.4
6.4.1
6.4.2
6. 4. 3

CHAPTER

VAX-11 PROCEDURE CALLING STANDARD
7.1
Argument Lists
7. 1. 1
Parameter Passing Mechanisms
7. 1. 2
By-Reference Mechanism
7.1.2.l
By-Immediate-Value Mechanism
7.1.2.2
By-Descriptor Mechanism
7.1.2.3
Passing Functions and Procedures
7. 1. 3
as Parameters
Function Return Values
7 .1. 4
Passed Arguments to PASCAL Subprograms
7 .1. 5
CALLING VAX/VMS SYSTEM SERVICES
7.2
Calling System Services by Function
7.2.1
Reference
Calling System Service as Procedures
7.2.2
Passing Parameters to System Services
7.2.3
Input and Output By-Reference Parameters
7.2.3.l
Optional Parameters
7.2.3.2
Passing Character Parameters
7.2.3.3
CALLING RUN-TIME LIBRARY PROCEDURES
7.3
COMPLETE SYSTEM SERVICE EXAMPLE
7.4
CHAPTER

CHAPTER

7-1
7-1
7-2
7-2
7-3
7-4
7-5
7-6
7-6
7-6

7-7
7-9
7-9
7-9
7-11
7-11
7-12
7-12

ERROR PROCESSING AND CONDITION HANDLERS

8-1

8.1
8.2
8.2.1
8.2.2
8.3
8.3.1
8.3.2
8.3.3
8.3.4
8.3.5
8.4

RUN-TIME LIBRARY DEFAULT ERROR PROCESSING
OVERVIEW OF VAX-11 CONDITION HANDLING
Condition Signals
Handler Responses
WRITING CONDITION HANDLERS
Establishing and Removing Handlers
Parameters for Condition Handlers
Handler Function Return Values
Condition Values and Symbols
Floating-Point Operation
CONDITION HANDLER EXAMPLE

8-2
8-3
8-3
8-4
8-4
8-5
8-5
8-7
8-8
8-9
8-10

VAX-11 PASCAL SYSTEM ENVIRONMENT

9-1

9.1
9.2
9.3
9.4
9.4.1
9.4.2
9.4.3

USE OF PROGRAM SECTIONS
STORAGE OF SCALAR AND POINTER TYPES
STORAGE OF UNPACKED STRUCTURED TYPES
STORAGE OF PACKED STRUCTURED TYPES
Storage of Packed Sets
Storage of Packed Arrays
Storage of Packed Records

9-1
9-2
9-3
9-4
9-4
9-4
9-6

CONTENTS
Page
REPRESENTATION OF FLOATING-POINT DATA
Single-Precision Floating-Point Data
(SINGLE, REAL Types)
Double-Precision Floating-Point Data
(DOUBLE Type)

9-9

DIAGNOSTIC MESSAGES

A-1

A.l
A.2

COMPILER DIAGNOSTICS
RUN-TIME ERROR MESSAGES

A-1
A-19

CONTENTS OF RUN-TIME STACK DURING PROCEDURE
CALLS

B-1

9.5
9.5.1
9.5.2
APPENDIX

APPENDIX

9-8
9-8

APPENDIX

VAX-11 SYMBOLIC DEBUGGER COMMAND SUMMARY

C-1

APPENDIX

VAX-11 SYMBOLIC DEBUGGER AND PASCAL-SPECIFIC
MESSAGES

D-1

INDEX

Index-1

FIGURES
FIGURE

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

5-4
9-1
9-2
9-3
9-4
9-5
B-1

Program Development Process
VAX-11 PASCAL Compiler Listing
Source Program Listing and Traceback List
Sample PASCAL Program
Sample Debugging Session
Source Program for the Program
Flight Reservations
Interactive Debugging Session for the Program
Flight Reservations
Storage of Sample Record
Storage of Sample Record
Storage of Sample Packed Record Containing
Packed Ar ray
Single-Precision Floating-Point Data
Representation
Double-Precision Floating-Point Data
Representation
Contents of Run-Time Stack During Procedure
Calls

1-2
2-16

4-3
5-6
5-7
5-72

5-76
9-4
9-7
9-8
9-8

9-9
B-2

CONTENTS
TABLES
Page
TABLE

1-1
2-1
2-2
2-3
3-1
3-2

4-1
5-1
5-2
6-1
6-2
7-1
9-1

9-2
9-3
9-4

File Specification Defaults
PASCAL Compiler Qualifiers
PASCAL Command Qualifiers
Source Code Qualifiers
Command Qualifiers
File Qua 1 if i ers
/DEBUG and /TRACEBACK Qualifiers
Debugger Command Qualifiers
Special Symbols
Predefined System Logical Names
Carriage Control Characters
Suggested Variable Data Types
Program Section Attributes
Program Section Usage and Attributes
Storage of Scalar and Pointer Types
Storage of Packed Array Elements

vii

1-3
2-2
2-5
2-6
3-1
3-2
4-2

5-3
5-5
6-2
6-6
7-10
9-1

9-2
9-3

9-5

PREFACE

MANUAL OBJECTIVES
The VAX-11 PASCAL User's Guide is intended for use in developing and
debugging new PASCAL programs, and in compiling and executing existing
PASCAL programs on VAX/VMS systems.
PASCAL
language
elements
supported on VAX/VMS are described
in the VAX-11 PASCAL Language
Reference Manual.

INTENDED AUDIENCE
This manual is designed for programmers who have a working knowledge
of
PASCAL.
Detailed knowledge of VAX/VMS is helpful but not
essential;
familiarity with the VAX/VMS Primer is recommended.
Some
sections of this book, however, (condition handling, for instance)
require more extensive understanding of the operating system.
In such
sections, you are directed to
the appropriate manual(s) for the
required additional information.

STRUCTURE OF THIS DOCUMENT
This manual is organized as follows:
•

Chapter 1 provides an overview of the steps you must follow to
create, compile, link, and execute a VAX-11 PASCAL program.

•

Chapter 2 describes how to compile your program
the options available at compile time.

•

Chapter 3 supplies information on the VAX-11
options, as they apply to PASCAL programs.

•

Chapter 4 describes the commands used to run a program.

Chapter 5 describes how to use the VAX-11 Symbolic Debugger.

•

Chapter 6 provides information about
including
details
on
the use of
conventions, and record structure.

and

Linker

explains
and

its

PASCAL input/output,
logical names,
file

•

Chapter 7 discusses the conventions followed
in calling
procedures, especially the conventions for passing parameters.

•

Chapter 8 describes error processing, in particular, how to
use the condition handling facility.
This chapter is intended
for users with in-depth knowledge of VAX/VMS.

•

Chapter 9 describes the relationship between VAX-11 PASCAL and
the VAX/VMS operating system, with particular emphasis on
program section
usage,
storage
allocation,
and
data
representation.

•

Appendix A summarizes diagnostic messages.

•

Appendix B illustrates the
during procedure calls.

•

Appendix C summarizes in alphabetical order all
commands.

the

debugger

•

Appendix D summarizes in alphabetical order all
and PASCAL specific error messages.

the

debugger

contents

the

run-time

stack

ASSOCIATED DOCUMENTS
The following documents are relevant to VAX-11 PASCAL programming:
•

VAX/VMS Primer

•

VAX-11 PASCAL Primer

•

VAX-11 PASCAL Language Reference Manual

•

VAX/VMS Command Language User's Guide

•

VAX-11 Run-Time Library Reference Manual

•

VAX-11 Linker Reference Manual

•

VAX/VMS System Services Reference Manual

•

VAX-11 Architecture Handbook

•

VAX-11 PASCAL Installation Guide/Release Notes

For a complete list of VAX-11 software
Information Directory and Index.

documents,

see

the

VAX-11

CONVENTIONS USED IN THIS DOCUMENT
This document uses the following conventions.
Convention

{}

Meaning
Braces enclose lists from which you must choose
one item, for example:
expr
}
{ statement
A horizontal ellipsis means that the preceding
item can be repeated as indicated, for example:
filename,

•••

Convention

Meaning
A vertical ellipsis means that not all of the
statements in a figure or example are shown.

[ ]

Double
brackets
in
statement
format
descriptions enclose items that are optional,
for example:
[PACKED]
Double brackets in statement
format
description enclose
optional, for example:

and declaration
items that are

WRITE ( [OUTPUT,] print list)
[ ]

Square brackets mean that the statement syntax
requires the square bracket characters.
This
notation is used with arrays and sets,
for
example:
ARRAY [subscriptl]

items in uppercase
letters and special
symbols

Uppercase
letters
and special symbols in
format descriptions indicate PASCAL reserved
words that you must not
abbreviate,
for
example:
BEGIN

END
items in lowercase
letters

Lowercase letters represent elements that you
must replace according to the description in
the text.

$ PASCAL
$ File:

In examples of commands you enter and system
responses, all output lines and
prompting
characters that the system prints or displays
are shown in black letters. All the lines you
type are shown in red letters.
A symbol with a 1- to 3-character abbreviation
indicates that you press a key on the terminal,
for example, IB@.

SUMMARY OF TECHNICAL CHANGES

This section summarizes the technical
PASCAL compiler for Version 1.2.

changes

made

the

•

Debugger records are now generated to allow for
the _VAX-11 Symbolic Debugger.

•

An enhanced machine-code listing is now generated.

•

Nonabortive run-time errors are signaled when issued.

xiii

full

VAX-11
use

CHAPTER 1
USING VAX-11 PASCAL

VAX-11 PASCAL is an extended implementation of the
PASCAL language.
The VAX-11 PASCAL compiler executes in native mode under the VAX/VMS
operating system.
This manual describes how you interact with the VAX/VMS operating
system using VAX-11 PASCAL.
It contains instructions for compiling,
linking, executing, and debugging
a
PASCAL program, and provides
information on the following topics:
•

Performing input and output operations

•

Calling VAX/VMS system services and Run-Time Library routines

•

Using the VAX/VMS condition handling facility

•

Writing efficient VAX-11 PASCAL programs

This chapter provides an overview of the steps in creating and
executing a VAX-11 PASCAL program.
It also describes the standard
VAX/VMS file specification and defaults.

1.1

CREATING AND EXECUTING A PROGRAM

Figure 1-1 illustrates the program development process, from inception
to execution.
You specify the steps shown in Figure 1-1 by entering
commands strings to the VAX/VMS operating system.

$ EDIT file-spec @.ITl
$ PASCAL file-spec @_ITJ
$ LINK file-spec @.ITl

$ RUN file-spec

@_ITJ

With each command, you include information that further defines what
you want the system to do.
Of prime importance is the file
specification, indicating the file to be processed.
You can also
specify qualifiers that modify the processing performed by the system.
Each ~ommand string is terminated by pressing the RETURN key.

1-1

USING VAX-11 PASCAL

INPUT/OUTPUT Fl LES

COMMANDS

$EDIT AVERAGE. PAS
Use the file type of PAS to
indicate that the file contains
a VAX-11 PASCAL program.

Create a
source program

AVERAGE.PAS

$PASCAL AVERAGE
The PASCAL command
assumes that the file type
of an input file is PAS.

:::::

Compile the
source program

(If you use the /LIST
qualifier, the compiler
creates a listing file.)

AVERAGE.OBJ
(AVERAGE. LIS)
Ii braries

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

AVERAGE.EXE
(AVERAGE.MAP)

Link the
object module

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

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

Run the
executable
image
ZK-063-80

Figure 1-1

1.2

Program Development Process

VAX/VMS FILE SPECIFICATIONS AND DEFAULTS

A VAX/VMS file specification indicates the input file to be processed
or the output file
to be produced.
File specifications have the
following form:
node::device: [directory]filename.type;version
The punctuation
required syntax
specification.

are
marks
(colons, brackets, period, semicolon)
that separate the various components of the file

node
Specifies a network node name.
systems that support DECnet-VAX.

This

applicable

only

device
Identifies the device on which the file is stored
written.

1-2

USING VAX-11 PASCAL
directory
Identifies the name of the directory under which the file is
cataloged,
on the device specified.
You can delimit the
directory name with square brackets, as shown, or with angle
brackets {< >) •
filename
filename

Identifies the file by its name;
alphanumeric characters long.

Describes the kind of data in the file;
alphanumeric characters long.

type

can

version
Specifies which version of the file is desired.
Versions are
identified by a decimal number, which is incremented by 1 each
time a new version of a file is created. Either a semicolon or a
period can be used to separate type and version.
You need not explicitly state all elements of a file specification
each time you compile, link, or execute a program. The only part of
the file specification that is usually required is the file name.
If
you omit any other part of the file specification, a default value is
used. Table 1-1 summarizes the default values.
Table 1-1
File Specification Defaults
Default
Value

Optional
Element
node

Local network node

device

User's current default device

directory

User's current default directory

f iletype

Depends on usage:
Input to PASCAL compiler
Output from PASCAL com pi 1 er
Input to linker
Output from linker
Input to RUN command
Compiler source listing
Linker map listing
Input to executing program
Output from executing program

version

PAS
OBJ
OBJ
EXE
EXE
LIS
MAP
DAT
DAT

Input:

highest existing version

Output:

highest existing version
plus 1

1-3

USING VAX-11 PASCAL
If you request compilation of a PASCAL program and you specify only a
file name,
the compiler can process the source program if it finds a
file with the specified file name that:
•

Is stored on the default device

•

Is cataloged under the default directory name

•

Has a file type of PAS

If more than one file meets these conditions, the compiler chooses the
one with the highest version number.
For example, assume that your default device
is
DBAO, your default
directory is SMITH, and you supply the following file specification to
the compiler:
$ PASCAL (@.!)
$ File: Circle (@.!)

The compiler will search device DBAO in directory SMITH, seeking the
highest verion of Circle.PAS.
If you do not explicitly specify an
object file, the compiler will generate the file Circle.OBJ, store
it
on device DBAO in directory SMITH, and assign it a version number 1
higher than any other version of Circle.OBJ currently cataloged
in
directory SMITH on DBAO.

1-4

CHAPTER 2
COMPILING A PROGRAM

After creating a VAX-11 PASCAL source program, you compile it.
At
compile time,
you specify the name of the file(s) containing the
source code and indicate which qualifiers you want to use.
At your option, the compiler produces one or more object files,
which
can be input to the linker {see Chapter 3), and one or more listing
files.
The listing files contain source and object code listings,
information about compilation errors, and optional
items such as
cross-reference listings.

2.1

THE PASCAL COMMAND

To compile a source program, use the PASCAL command in
form:
PASCAL [/cornmand-qua·lifier {s)]

the

following

file-spec-list [/file-qualifier {s)]

/cornmand-qualifier{s)
Indicates special processing is to be performed by
on all files being compiled {see Section 2.2).

the

compiler

f il e-spec-1 i st
Specifies the source file(s) containing the program or module 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.
/file-qualifier(s)
Indicates special processing is to be performed by
on the file(s) in the file-spec-list.

the

compiler

In interactive mode, you can also enter the file specification on a
separate line by pressing the RETURN key after you type PASCAL.
The
system responds with a prompt for the file specification:
$ PASCAL ffi)
$ File:

Type the file specification and any file qualifiers immediately
the $ File: prompt.

2-1

after

COMPILING A PROGRAM
2.2

PASCAL COMPILER QUALIFIERS

In many cases, the simplest form of the PASCAL command
is sufficient
for compilation.
Sometimes, however, you will need to use qualifiers
to specify special processing.
Table 2-1 lists the qualifiers you can
use with the VAX-11 PASCAL compiler.
You specify the qualifiers on
the command line. Some qualifiers may be specified
in source code
comments.
This section describes the effect of each qualifier on a
PASCAL program.
Section 2.2.1 describes how to specify command line
qualifiers.
Section 2.2.2 deals with specifying qualifiers in source
code comments.
Table 2-1
PASCAL Compiler Qualifiers

Qualifier

Purpose

Can Be Specified
in Source Code?

CHECK

Generates code to perform
run-time checks

Yes

CROSS REFERENCE

Produces a cross-reference
listing of identifiers

Yes

DEBUG

Generates records for
VAX-11 Symbolic Debugger

Yes

ERROR LIMIT

Terminates compilation
after 30 errors

LIST

Produces source listing
file

Yes

MACHINE CODE

Includes representation of
machine code in the
source listing file

Yes

OBJECT

Specifies name of
object file

STANDARD

Prints messages indicating
use of PASCAL extensions

Yes

WARNINGS

Prints diagnostics for
warning-level errors

Yes

CHECK
The CHECK qualifier directs the compiler to generate code to perform
run-time checks. This code checks for invalid assignments to sets and
subranges, and out-of-range array bounds and case labels. The system
issues an error message and normally terminates execution if any of
these conditions occur.
When this qualifier is disabled, the compiler generates nq check code.
By default, CHECK is disabled.

2-2

COMPILING A PROGRAM
CROSS REFERENCE
The CROSS REFERENCE qualifier produces a
cross-reference listing of
all identTfiers.
The compiler generates separate cross-references for
each procedure and function.
To get complete cross-reference listings
for
a program, the qualifier must be in effect for all modules of the
program.
This qualifier is
ignored
if no listing
file
is being
generated.
By default, CROSS REFERENCE is disabled.
You can specify this qualifier in the source code, as described
in
Section 2.2.2.
Note, however, that the cross-reference listing for a
portion of a procedure or function may be incomplete.
DEBUG
The DEBUG qualifier specifies that the compiler
is to generate
information for
use by the VAX-11 Symbolic Debugger and the run-time
error traceback mechanism.
When you enable the option,
the compiler
generates the debugger and
Traceback records for each procedure or
1program for which the qualifier is in effect.
When this qualifier is disabled, the compiler generates only Traceback
records.
By default, the debugger is disabled.
Refer to Chapter 5 for more information on the debugger.
ERROR LIMIT
The ERROR LIMIT qualifier
terminates compilation after 30 errors,
excluding warning-level
errors.
If
this qualifier
is disabled,
compilation continues through the entire unit.
You cannot specify
this qualifier in the source code.
By default, ERROR_LIMIT is enabled.
Note that after it finds 20 errors (including warning messages) on any
one source line, the compiler generates the error code 255 -- too many
errors on this source line.
Compilation of the line continues, but no
further error messages are printed for that line.
LIST
The LIST qualifier produces a source listing file.

It has the form:

/LIST [=file-spec]
If you omit the file specification, the listing file defaults to
the
name of the first source file, your default directory, and a file type
of LIS.
The compiler does not produce a
listing
file
in
interactive mode
unless you specify 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 DIGITAL Command
Language (DCL) PRINT command to obtain a
line printer copy of the
listing file.
A sample listing is explained in Section 2.4.

2-3

COMPILING A PROGRAM
MACHINE CODE
The MACHINE CODE qualifier places in the listing file a representation
of the object code generated by the compiler.
The compiler ignores this q~alifier
enabled.

~he

LIST

qualifier

not

The OBJECT qualifier can be used when you want to specify the name
the object file.
It has the form:

By default, MACHINE CODE is disabled.

OBJECT

/OBJECT [=file-spec]
If you omit the file specification, the object file defaults to the
name of the first source file, the default directory, and a file type
of OBJ.
You cannot specify this qualifier in the source code.
You can disable this qualifier to suppress object code;
for example,
when you only want to test the source program for compilation errors.
By default, OBJECT is enabled.

STANDARD
The STANDARD qualifier tells the compiler to print warning-level
messages wherever the program uses "nonstandard" PASCAL features.
Nonstandard PASCAL features are the extensions to the PASCAL language
that are incorporated in VAX-11 PASCAL.
Nonstandard features include
VALUE declarations and the exponentiation operator.
Refer to the
VAX-11 PASCAL Language Reference Manual for a list of all the
extensions.
By default, STANDARD is enabled.

WARNINGS
The WARNINGS qualifier directs the compiler to generate
messages in response to warning-level (W) errors.

diagnostic

By default, WARNINGS is enabled.
A warning diagnostic message
indicates that the compiler has detected acceptable but unorthodox
syntax or has performed some corrective action;
in either case,
unexpected
results
may occur.
To suppress warning diagnostic
messages, disable this qualifier. Note that messages generated when
the STANDARD qualifier is enabled appear even if WARNINGS is disabled.
Appendix A lists the compiler diagnostic messages.

2.2.1

Specifying Qualifiers with the PASCAL Command

A PASCAL command qualifier has the form:
/qualifier [=file-spec]
Table 2-2 lists the qualifiers, and their negative form that you can
use on the PASCAL command line.
The optional file specification
indicates the name of an output file for the /OBJECT and /LIST

2-4

COMPILING A PROGRAM
qualifiers only.
To enable the qualifier, specify its name.
disable the qualifier, specify the negative form.

You can abbreviate all command line qualifiers by truncating them on
the right.
All qualifiers are unique when truncated to their first
four characters, not including the NO of the negative form.
You can
truncate further as long as the resulting qualifier is unique.
For
example, you can truncate /CROSS REFERENCE to /CR, /CHECK to /CH,
and
/DEBUG to /D.
It is recommended that you use the full qualifier names in command
procedure files,
to ensure readability. To guarantee compatibility
with future releases of the system, you should not abbreviate
qualifiers in command procedures to fewer than four characters.
Table 2-2
PASCAL Command Qualifiers
Negative Form

Qualifier

Default

/CHECK

/NOC HECK

/CROSS_REFERENCE

/NOCROSS_REFERENCE

/DEBUG

/NODEBUG

/ERROR_LIMIT

/NOERROR_LIMIT

/ERROR_LIMIT

/LIST [=file-spec]

/NOLIST

/NOLIST (interactive)
/LIST (batch)

/MACHINE_CODE

/NOMACHINE_CODE

/NOMACHINE _CODE

/OBJECT [=file-spec]

/NOOBJECT

/OBJECT

/STANDARD

/NOSTANDARD

/STANDARD

/WARNINGS

/NOWARNINGS

/WARNINGS

Examples
1.

$ PASCAL Cal c

The source file Cale.PAS is compiled. By default, the /OBJECT,
/STANDARD, /WARNING, and /ERROR_LIMIT qualifiers are enabled.
2.

$ PASCAL/CHECK/NOSTANDARD Cale
The source file Cale.PAS is compiled, and check code
is
generated.
The compiler does not issue warnings for the use of
language extensions.

$ PASCAL/LIST/CR Cale
The source file Cale.PAS
Cale.LIS
is
generated.
cross-reference listing.

compiled and the
The
listing
file

2-5

1 isting
file
includes
a

COMPILING A PROGRAM
2.2.2

Specifying Qualifiers in the Source Code

You can use qualifiers in the source code to enable and disable
special processing during compilation. When specified in the source
code, qualifiers have the form:
(*$qualifier{±}

[,qualifier{±}, ••• ]

;comment*)

The first character after the comment delimiter must be a dollar sign
($);
the dollar sign cannot be preceded by a space.
Table 2-3 lists
the qualifiers you can specify in your source program. Note that you
can optionally use a 1-character abbreviation for each qualifier.
The
abbreviation is simply the first character of the qualifier name,
except for CROSS_REFERENCE, whose abbreviation is X.
Table 2-3
Source Code Qualifiers
Qualifier

Abbrev ia ti on

CHECK
CROSS REFERENCE

DEBUG

LIST

MACHINE CODE
-

STANDARD

WARNINGS

To enable a qualifier, specify a plus sign
(+)
after
its name or
abbreviation.
To disable a qualifier, specify a minus sign (-).after
its name or abbreviation.
You can specify any number of qualifiers.
You can also
include a text comment after the qualifiers, separated
from the list of qualifiers by a semicolon.
When specified in the source code, the LIST qualifier cannot contain a
file
specification.
The
listing
file will have the default
specification as described in Section 2.2 above.
For example, to generate check code for only one procedure in a
program,
enable the CHECK qualifier before the procedure declaration
and disable it at the end of the procedure, as follows:
(*$C+; enable CHECK for Testl only*)
PROCEDURE Testl;

END;
(*$C-;disable CHECK*)
Command line qualifiers override source code qualifiers.
If, for
example,
the
source
code
specifies
DEBUG+,
but you enter
PASCAL/NODEBUG, the DEBUG option will not be in effect.

2-6

COMPILING A PROGRAM
2.3

SPECIFYING OUTPUT FILES

The compiler produces object files and listing files. You can control
the production of these files by using the /LIST and /OBJECT
qualifiers with the PASCAL command. Unless you specify otherwise, the
compiler generates an object file.
In interactive mode, the compiler,
by default, does not generate a listing file; you must use the /LIST
qualifier to explicitly specify a listing file.
In batch mode,
however, the opposite is true: by default, the compiler produces a
listing file.
To suppress the listing file, you specify the /NOLIST
qualifier.
During the early stages of program development, you may find it
helpful to suppress the production of object files until your source
program compiles without errors.
To do so, specify the NOOBJECT
qualifier on the PASCAL command line.
If you do not specify
/NOOBJECT, 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 plus signs,
the source files are concatenated and compiled, and 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.
• You can use both plus signs and commas in the same command line
to produce different combinations of concatenated and separate
object files (see Example 4 below).
To produce an object file with an explicit file specification, you
must specify /OBJECT on the PASCAL command line (see Section 2.2).
Otherwise, the object file will have 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 attributes (node, device,
directory, and version) assume the default attributes.
Examples
1.

$ PASCAL/LIST A, B, C

Source files A.PAS, B.PAS, and C.PAS are compiled as separate
files, producing object files named A.OBJ, B.OBJ, and C.OBJ; and
listing files named A.LIS, B.LIS, and C.LIS.
2.

$ PASCAL X + Y + Z

Source files X.PAS, Y.PAS, and Z.PAS are concatenated and
compiled as one file, producing an object file named X.OBJ.
In
batch mode, this command also produces the listing file X.LIS.
3.

$ PASCAL/OBJECT=Square <RET>
$ File: Circle

The system issues the $ File: prompt because the PASCAL command
does not specify a source file. The file Circle.PAS is compiled,
producing an object file named Square.OBJ, but no listing file.
{This example applies to interactive mode only.)

2-7

COMPILING A PROGRAM
4.

$ PASCAL A + B/LIST,C
Two object files are produced: A.PAS and B.PAS are concatenated
to become A.OBJ and C.PAS becomes C.OBJ.
In interactive mode,
this command produces the listing file A.LIS.
In batch mode,
it
produces two listing files:
A.LIS and C.LIS.

$ PASCAL A + Circ/NOOBJECT + X

When you include a qualifier in a list of files that are to be
concatenated, the qualifier affects all files in the list. Thus,
the command shown above completely suppresses the object file.
That is, source files A.PAS, Circ.PAS, and X.PAS are concatenated
and compiled, but no object file is produced.
6.

$ PASCAL/LIST [DIR)M

The source file M.PAS in directory [DIR] is compiled, producing
an object file named M.OBJ and a listing file named M.LIS.
The
compiler places the object and
listing files in the default
directory.

2.4

COMPILER LISTING FORMAT

This section explains the format of the compiler listing.
Each section of a compiler listing is shown and described
in
A complete compiler listing is illustrated in Section 2.4.4.

detail.

The compiler listing contains the following three sections:
•

Source code listing -- When you specify the
the source code is listed by default.

/LIST

qualifier,

•

Cross-reference listing -- To generate cross references for
all
identifiers used
in the program, you must specify the
/CROSS_REFERENCE and /LIST qualifiers.

•

Machine code listing -- To generate the machine code listing,
you must specify the /MACHINE_CODE and /LIST qualifiers.

The numbers in the section below are keyed to the circled numbers in
the examples that appear above each discussion and to the complete
listing in Section 2.4.4.
Title line

Each page of the compiler listing contains a title line.

EXAMPLE 15-AUG-1980 13:47:41

VAX-11 PASCAL Vl.2-80

Page 1

The title line consists of four parts:

0
0
0
0

The module name:

EXAMPLE

The date (day, month, year) and time (hour,
compilation:
15-AUG-1980 13:26:37
The PASCAL compiler name and version number:
The page number:

Page 1

2-8

minute,

second)

VAX-11 PASCAL Vl.2

COMPILING A PROGRAM
2 •. 4.1

Source Code Listing

Each page of the source code listing contains a line under
line.

•

01 SOURCE LISTING

0
0

19-JUN-1980 14:10:08

The Module Identifier:

the

title

_DBAl: [SMITH]EXAMPLE.PAS;2(1}

The subtitle describing the listing:
SOURCE LISTING or (CROSS REFERENCE or GENERATED CODE)

The date (day, month, year) and time (hour, minute,
source file creation:
19-JUNE-1980
14:10:08

(»

The VAX/VMS file specification of the source file:

second)

_DBAl: [SMITH]EXAMPLE.PAS;2 (1)
Source Code Listing
LINE
NUMBERS

•

100
200
300
400
500
600
700
800
900
1000

3
4
5
6
7
8
9
10

llOO

1200
1300
1400
1500

12
13
14
15

1
2

LEVEL
PROC STMT

G
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1

G0
0
0
0
0
0
0
0
0
0
2
2
2
2
2

STATEMENT.
PROGRAM EXAMPLE(INPUT, OUTPUT)
LABEL 10 ;
VAR
A, B, C,

REAL

BEGIN
REPEAT
WRITELN ( 'Enter triangle sides')
IF EOLN(INPUT} THEN
GOTO 10 ;
READLN(A, B) ;
c := ( SQR(A} + SQR(B) }· ** 0.5 ;

The lines of the source code are printed in the source code listing.

SOS line numbers -- If you created or edited the source lines in
a PASCAL module with the SOS editor, SOS line numbers appear in
the leftmost column of the source code listing. SOS line numbers
are irrelevant to the PASCAL compiler.

Line numbers -- The compiler assigns unique line numbers to the
source lines in a PASCAL module.
The symbolic traceback that is
printed if your program encounters an exception at run time
refers to these line numbers. These line numbers are used when
executing a program under the VAX-11 Symbolic Debugger.

Procedure level -- Each line that contains a declaration lists
the procedure level of that declaration.
Procedure level 1
indicates declarations in the outermost block.
The procedure
level number increases by one for each nesting level of functions
or procedures.

Statement level -- The listing specifies a statement level for
each line of source code after the first BEGIN delimiter.
The
statement level starts at 0 and increases by 1 for each nesting

2-9

COMPILING A PROGRAM
level of PASCAL structured statements. The statement level of a
comment is the same level as that of the statement that follows
it.

Error and Warnings
2000

WRITELN ( 'Done' ;

%PAS-F-DIAGN
2100
2200

21
22
23

*** ERROR
*** ERROR

II )

20:
1
1
1

*** 20== > 15

Jlro

expected
expected G)

END.

1
0

The source code listing includes information on any errors or warnings
detected by the compiler.
A line beneath the source code line in
which the error is detected specifies whether the diagnostic is a
warning or an error.

41)

A circumflex (A) that points to the
line where the error was detected.

A numeric code, following
particular error.

the

character

circumflex,

position

that

the

specifies

the

On the following lines of the source listing, the compiler prints
the text that corresponds to each numeric error code.

An asterisk (*) shows
after the error.

where

the

compiler

resumed

translation

Note that one source program error often
compiler to detect more than one error.

causes

the

PASCAL

error

The following line numbers are indicated:

The line number in which the error was detected
The line number in the last previous
diagnostic

You can use these error numbers to
backwards through the source listing.

line

trace

containing
the

error

diagnostics

Summary -2 Errors 1 Nonstandard feature
Last error (warning) on line

Active options at end of compilation:
NODEBUG,STANDARD,LIST,NOCHECK,WARNINGS,CROSS REFERENCE,
MACHINE_CODE,OBJECT,ERROR_LIMIT = 30
If your program generated warning
prints a summary of:

error

messages,

All the errors

The source line number of the last message

The compiler
options.

then

lists

the

2-10

status

all

the

compiler

compilation

COMPILING A PROGRAM
Compilation Statistics
COMPILATION STATISTICS
Total Space Allocated:
Stack Frame Size Total:
Run Time:
Page Faults:

874 bytes, 363 Code+ 511 Data G)
64 bytes
.50 seconds.
(1452 lines/minutes)G)
990 fl)

The source code listing contains
current compilation.

•
•

the

following

statistics

for

the

Total Space Allocated -- The number of bytes of static storage
the program occupies. The total number of bytes is listed first
followed by the amount of space required by the code, and data,
respectively.
Stack Frame Size Total -- This number is the total size of all
This number
the stack frames for all procedures and functions.
is only an estimate of the maximum stack size since the number
does
not take
into account recursion or conformant array
parameters •
CPU

time

used

during

Page Faults -- This number reflects the
that occurred during com pi 1 ation.

number

page

14
14
15
12

15
15

Run Time -- This time reflects
compilation •

2.4.2

the

faults

Cross-Reference Listing

A fD

6
6
6

c
INPUT
OUTPUT

G)l

GLOBALLY DEFINED IDENTIFIERS:
EOLN
FALSE fD
READLN
REAL
SQR
WRITELN

0
0
0
0
0
0

17
14
6
15
11

l5
16

The cross-reference listing (if requested with the /CROSS REFERENCE
qualifier)
appears before the machine code listing.
lt contains two
sections.
section

lists

Globally defined identifiers
This section
predefined identifiers that the program uses.

lists

User-specified
identifiers -- This
identifiers you declared.

all

the

the
PASCAL

Each line of the cross-reference listing contains:

An identifier

A list of the source line numbers where the identifier is used.

2-11

COMPILING A PROGRAM
The first line number indicates where the
identifier
is declared.
Predefined
identifiers are listed as if they were declared on line O.
The cross-reference listing does not specify pointer type
identifiers
that are used before they are declared.

2.4.3

Machine-Code Listing

.TITLE
• !DENT

EXAMPLE
\01 \

• EXTRN
.EXTRN
.EXTRN
.EXTRN
.EXTRN
.EXTRN
.EXTRN
.EXTRN
.EXTRN
.EXTRN

PAS$CLOSEINOUT
OTS$POWRR
PAS$EOLN
PAS$READLN
PAS$READREAL
PAS$WRITEREALE
PAS$WRITELN
PAS$WRITESTR
PAS$0UTPUT
PAS$INPUT

•

00000001
00000000
7FFFFFFF

00000000

PREDEFINED SYMBOLS
TRUE = 1
FALSE = 0
MAXINT = 2147483647
NIL = 0

The machine-code listing (if requested with the MACHINE CODE and
qualifiers) follows the cross-reference listing.
-

G
G

f.D

LIST

The object module title and ident fields are listed first.
All external routines called by the program are listed.
Definitions of the PASCAL predeclared constants TRUE,
FALSE,
MAXINT,
and NIL.
The hexadecimal equivalent of each constant
appears on the left side of the listing.

00000100
00000104
00000108
00000008
OOOOOOEC

SYMBOLS FOR EXAMPLE
464
B = 468
c = 472
INPUT = 8
OUTPUT = 236
A

0006
0006
0006
0001
0001

Definitions of user-declared identifiers -- These identifiers are
used
in the listing of generated code as either register offsets
or constant values.
The hexadecimal
equivalent of each name
appears on the left side of the listing.

The comment column, on the right side contains
number where each identifier was declared.

2-12

the

source

line

COMPILING A PROGRAM

•

00000

6S 64 69 73 20 6S 6C 67 6E 61 69 72 74 20 72 6S 74 6E 4S
73
20 3A 73 69 20 6S 73 7S 6E 6S 74 6F 70 79 48

The current location counter value appears in the center
listing and divides the listing into 2 parts.
The hexadecimal representation of the code appears
side of the counter and is read right to left.

•

00000

.PSECT

00000
00013
00014

C.AAA:
C.AAB:

.ASCII
• ASCII
.ASCII

the

1 eft

G $PDATA, PIC,REL,SHR,NOEXE RD,NOWRT
0011 G

G) \Enter triangle side\
\s\
\Hypotenuse is: \

0016

The symbolic representation of the code appears on the right side
of the counter and is read left to right.

Each program section in the object module has a corresponding location
counter.

The $PDATA program section -- This section contains any constants
longer than 4 bytes.

The compiler generates names for literal
the form C.AAA, C.AAB, etc.

Cl)

The source line numbers where the constants were
declared appear as comments on the right •

(anonymous) constants of
first

used

• PSECT(D$CODE, PIC,REL,SHR,EXE,RD NOWRT,2
4FAC

CD . ENTRY

00000
00002

EXAMPLE, CDAM<R2,R3,RS,R7,R8,R9,Rl0, 11,IV>

THE $CODE program section -- This program section
machine instructions generated by the compiler.

contains

the

Each procedure and function starts with:

CD
CD

The entry point
The register save mask definition

08
00000000'
00000000'
00000000'

AE
EF
SA

OOEC

EF
SA

EF
SA
03

14
OS
CB
SA
01
AB
SA
01

SA
OOA8

DO
FB
9E
DD
FB
9E
DD
FB
DO
E9
31

00049 CD
0004D
OOOS4
OOOS9
OOOSB
00062
00066
00068
0006F
00072
0007S
00078 2$:

The listing formats of the generated
similar to the VAX-11 MACRO listings.

2-13

MOVL
CALLS
MOVAB
PUSHL
CALLS
MOVAB
PUSHL
CALLS
MOVL
BLBC
BRW

#20, 8 (SP)
#S, PAS$WRITESTR
OUTPUT(Rll), RlO
RlO
#1, PAS$WRITELN
INPUT(Rll), RlO
RlO
#1, PAS$EOLN
RO, RlO
RlO, 2$
.10

machine

instructions

are

0012

0013

COMPILING A PROGRAM

MOVL
CALLS
MOVAB
PUSHL
CALLS
MOVAB

#20, 8 (SP)
#S, PAS$WRITESTR
OUTPUT(Rll), RlO
RlO
#1, PAS$WRITELN
INPUT (Rll), RlO

•

0012

The right side of the listing contains:

The symbolic opcode

A set of symbolic operands
A comment section that can follow the symbolic operand and
contains a source line number if the corresponding instruction is
the first one generated for that source line.

908

00000000'
•

QQOQOQOQ I

AE
EF
SA

OOEC

EF
SA

14
OS
CB
SA
01
AB

DO 00049
FB 0004D
9E OOOS4
DD OOOS9
FB OOOSB
9E 00062

The left side of the listing c!tains the following:

The hexadecimal opcode

The hexadecimal operands

Each operand consists of:

A register/mode part

An offset or literal value

Operands whose values are supplied by the linker are flagged with
a single quote.

so
SA
OOA8

DO 0006F
E9 00072
31 0007S
00078 2$:.

MOVL
BLBC
BRW

RO, RlO
RlO, 2$ C)
.10

Compiler generated labels are designated by
targ~ts of the branch instructions.

and

are

Branch instructions point to the compiler-generated labels.

2-14

the

COMPILING A PROGRAM
50
SA
OOA8

DO 0006F
MOVL
E9 00072
BLBC
31 00075
BRW
00078 2$:

CB
58
01
00
FFlO

9E
DD
FB
E8
31

RO, RlO
RlO, 2$
.10

MOVAB
OOlOC
PUSHL
00111
CALLS
00113
BLBS
OOllA
BRW
00110
00120 .10: •

OUTPUT (Rll) , R8
R8
#1, PAS$WRITELN
#FALSE, .+3
1$

Branch instructions generated
user-defined labels as targets.

for

GOTO

statements

User-defined labels are represented by a period followed
label value •

Routine Size:

•

363 bytes,

Routine Base:

use
by

the
the

$CODE + 00000, 9

Stack Frame Size (exclusive of conformant array ) :

64 bytes.

A summary line is printed for each procedure and function.
contains:

The routine size in bytes

The ro.utine base in terms of an offset
$CODE program section.

The stack frame size in bytes

from

the

start

CD
The

1 ine

the

The stack frame size
includes any saved registers, but does not
include copies of conformant arrays or any transient information such
as parameter values pushed on the stack prior to a CALLS instruction.
.PSECT
.BLKB

$GLBL, PIC,OVL,REL,GBL,NO HR,NOEXE,RD,WRT
476

The definition of the $GLBL program section -- This program
section contains the storage for all program level variables.
Conceptually, it is the stack frame for the main program,
exclusive of saved
registers.
Register 11 always contains the
base address of this program section.

2.4.4

A Compiler Listing Example

The examples
Figure 2-1 illustrates a complete compiler listing.
described
in Sections 2.4.1,
2.4.2, and 2.4.3 are segments of this
listing.

2-15

EXAMPLE

019

SOURCE LISTING

I
I-'

°'

100
200
300

1
2
3

400

500
5
6
600
7
700
8
800
900
9
1000
10
1100
11
12
1200
13
1300
1400
14
15
1500
%PAS-W-DIAGN
16
1600
1700
17
1800
18
1900
19
2000
20
%PAS-F-DIAGN

Page 1

G G
l
l
1
1
1
l
1
1
1
1
1
1
1
1
1

PROGRAM EXAMPLE( INPUT, OUTPUT )

0
0
0
0
0
0
0
0
0
0

LABEL 10
VAR
A,

REAL

BEGIN
REPEAT
WRITELN ( 'Enter triangle sides'
IF EOLN( INPUT ) THEN
GOTO 10 ;
READLN( A, B) ;

2
2
2

2
2

( S QR (A)

+ S QR ( B)

)

(')

** 0 • 5 ;

t'of

l
l

2
2

l
l

*** ERROR
*** ERROR
21
22
23

•

VAX-11 PASCAL Vl.2-80
DBAl: [SMITH]EXAMPLE.PAS;2 (1)

STATEMENT.

*** WARNING 450:

2100
2200

0
LEVEL
PROC STMT

LINE
NUMBERS

15-AUG-1980 13:47:41
19-JUN-1980 14:10:08

l
1
l

***

==>

Nonstandard Pascal: Exponentiation
WRITELN ( 'Hypo ten use is: ', C ) ;
UNTIL FALSE ;

Gl
::i::-

tt:t

10:
WRITELN(
4:
20:

l
l
0

")II
II

'Done'

expected
expected

***

4'1'~4-

==>

END.

fl!>

2 Errors
l Nonstandard feature
Last error (warning) on line
20.

fJ»

Active options at end of compilation:~
NODEBUG,STANDARD,LIST,NOCHECK,WARNINGS,CROSS REFERENCE,
MACHINE_CODE,OBJECT,ERROR_LIMIT = 30
COMPILATION STATISTICS
Total Space Allocated:
Stack Frame Size Total:
Run Time:
Page Faults:

874 bytes, 363 Code + 511 Data 6)
64 bytes
.50 seconds.
(
1452 lines/minute)
990

Figure 2-1

f1)

VAX-11 PASCAL Compiler Listing

ZK-064-80

EXAMPLE
01

A.
B

c
INPUT
OUTPUT

6
6
6
1

14
14
15
12

0
0
0
0
0
0

12
17
14
6
15
11

G)1

Page 2

VAX-11 PASCAL Vl.2-80

15-AUG-1980 13:47:41
19-JUN-1980 14:10:08

CROSS REFERENCE

- DBAl: [SMITHJ EXAMPLE. PAS; 2

( 1)

15
15
16

GLOBALLY DEFINED IDENTIFIERS:

fl)

EOLN
FALSE
READLN
REAL
SQR
WRITELN
EXAMPLE
01

15
16

VAX-11 PASCAL Vl.2-80
DBAl: [SMITH]EXAMPLE.PAS;2 ( l)

15-AUG-1980 13:47:41
19-JUN-1980 14:10:08

GENERATED CODE

Page 3

(')

s:
'U
H

t""

z(j)

.TITLE EXAMPLE
. IDENTe\01 \

,_.I

:x:.i

.EXTRN
.EXTRN
.EXTRN
.EXTRN
.EXTRN
.EXTRN
.EXTRN
.EXTRN
.EXTRN
.EXTRN
00000001
00000000
7FFFFFFF
00000000
00000100
00000104
00000108
00000008
OOOOOOEC

PAS$C LOSE IN OUT
OTS$POWRR
PAS$EOLN
PAS$READLN
PASSREADREAL
PAS$WRITEREALE
PAS$WRITELN
PAS$WRITESTR
PASSOUTPUT
PAS$INPUT

; PREDEFINED SYMBOLS
TRUE: = 1
FALSE = 0
MAXINT = 2147483647
NIL=O

= 4 72

INPUT = 8
OUTPUT = 236

(j)

•

SYMBOLS FOR EXAMPLE
A = 164
B = 468

Figure 2-1 (Cont.) VAX-11 PASCAL Compiler Listing

0006
0006
0006
0001
0001

•

00000

69 73 20 6S 6C 67 6E 61 69 72 74 20 72 GS 74 6E 4S
73
20 3A 73 69 20 6S 73 7S 6E 6S 74 nF 70 79 48

00000 C.AAA:
00013
00014 C.AAB:

00000004'

SB 00000000'
EF

00000000'

08
08
OOEC
00000000'
F4

EF
AD
SA
SE

....I

CX)

OOEC

S9 00000000'
AE
AE

EF
SD
7E
7E
AB
01
AB
CB
02
SE
CB
10
SA
EF
S9
14

$PDATA, PIC,REL,SHR,NOEXE,RD,NOWRT

fD
• b.SCII \Enter triangle side\

;

. ASCII \s\
.b.SCII(D\Hypotenuse is: \

: 0016

00000
00002
9E 00002
DO 00009
04 00010
7C 00012
OF 00014
FB 00017
OF OOOlE
OF 00021
FB 0002S
DO 0002C
00030 1$:
9E 00030
C2 0003S
DD 00038
9E 0003A
DO 00041
DO 00045

0011 •

$CODE, PIC,REL,SHR,EXE,RD,NOWRT,2

• PSECT

00000
4FAC

•

. PSECT

CD .ENTRY EXAMPLE, -

CD~M<R2,R3,RS,R7,R8,R9,Rl0,Rll,IV>

MOVAB
MOVL
CLRL
CLRD
PUS HAL
CALLS
PUS HAL
PUS HAL
CALLS
MOVL

$GLBL, Rll
FP, $GLBL+4
-(SP)
-(SP)
INPUT (Rll)
1, PAS$INPUT
INPUT (Rll)
OUTPUT (Rll)
2, PAS$0UTPUT
SP, -12(FP)

MOVAB
SUBL2
PUSHL
MOVAB
MOVL
MOVL

OUTPUT (Rll), RlO
lfi' SP
RlO
C.AAA, R9
R9, 4 (SP)
20' 12 (SP)

(')

0
;

OOll

::s:

ttJ

t""
H

zGl
):I

ttJ

:;tj

EXAMPLE
01

•

r---G~

08
00000000'

AE
EF
SA

00000000 1

EF
5A

00000000'

EF
5A
03
5A
59

00000000'

EF
59

•

VAX-11 PASCAL Vl.2-S9
DB Al: f SM ITH] EXAMPLE. PAS; 2

lS-AUG-1980 13:47:41
19-JUN-1980 14:10:08

GENERATED CODE
14
OS
CB
OOEC
SA
01
AB
08
5A
01
50
5A
OOA8

08
0100

0104

AB
CB
59
SA
02
CB
59
SA

CD
DO 00049
FB
9E
DD
FB
9E
DD
FB
DO
E9
31
9E
9E
DD
DD
FB
9E
DD
DD

00040
00054
OOOS9
OOOSB
00062
00066
00068
0006F
00072
00075
00078 2S:
00078
0007C
00081
00083
00085
0008C
00091
00093

-e

MOVL
CALLS
MOVAB
PUSHL
CALLS
MOVAB
PUSHL
CALLS
MOVL
BLBC
BRW

20, 8 (SP)
s, PAS$WRITESTR
OUTPUT(Rll), RlO
RlO
1, PASSWRITELN
INPUT (Rll), RlO
RlO
1, PAS$EOLN
RO, RlO
RlO, 2 $ .
.10.

MOVAB
MOVAB
PUSHL
PUSHL
CALLS
MOVAB
PUSHL
PUSHL

INPUT (Rl l), Rl()
A(Rll), R9
R9
RlO
2, PAS$READREAL
B(Rll), R9

R9
RlO

Figure 2-1 (Cont.) VAX-11 PASCAL Compiler Listing

Page 4
( l)

0
Gl

CD
0012

: 0013
: 0014

00000000'
00000000'
S2
S8

00000000'
OlD8

08
00000000'

EF
SA
EF
SA
SA
S3
S3
S8
S7
EF
S2
CB
S8
SE
SS
AE
AE
AE
EF
SE

I:\.)

I
I-'
\,0

04
08
00000000'

AE
AE
EF
S8

00000000'

EF
03

02
AB
SA
01
CB
SA
CB
S3
S2
00
S7
S8
02

FB
9E
DD
FB
SO
4S

S2
OOEC
CB
10
S8
EF
00000014'
SS
OF
OF
OS
10
S8
S2
10
OS
OOEC
CB
SB
01
00
FFlO

SO
9E
C2
DD
9E
DO
DO
DO
FB
C2
DD
DO
DO
FB
9E
DD
FB
E8
31

08
OlDO
0104

4S
40
SO
DD
DD
FB

CALLS
MOVAB
PUSHL
CALLS
MOVF
MULF3
MOVF
MULF3
ADDF2
MOVF
PUSHL
PUSHL
CALLS
MOVF
MOVF
MOVAB
SUBL2
PUSHL
MOVAB
MOVL
MOVL
MOVL
CALLS
SUBL2
PUSHL
MOVL
MOVL
CALLS
MOVAB
PUSHL
CALLS
BLBS
BRW

0009S
0009C
OOOAO
OOOA2
OOOA9
OOOAE
OOOB2
OOOB7
OOOBB
OOOBE
OOOCl
OOOC3
OOOC S

so ooocc

OOOCF
OOOD4
OOOD9
OOODC
OOODE
OOOES
OOOE9
OOOED
OOOF l
OOOF8
OOOFB
OOOFD
00101
OOlOS
OOlOC
00111
OOll 3
OOllA
001 lD
00120

2, PAS$READREAL
INPUT (Rll), RlO
RlO
1, PAS$READLN
A(Rll), RlO
RlO, RlO, R2
B(Rll), R3
R3, R3, R8
R 2, R8
~ FO. 5,
R7
R7
R8
2, OTS$POWRR
RO, R2
R2, C(Rll)
OUTPUT (Rll) , R8
16, SP
R8
C.AAB, RS
RS, 4 (SP)
l S, 12 (SP)
l S, 8 (SP)
S, PAS$WRITESTR
16, SP
R8
R2, 4 (SP)
16, 8 (SP)
S, PAS$WRITEREALE
OUTPUT (Rll), RB
R8
1, PAS$WRITELN
FALSE, .+3
1$

.1o:G

Figure 2-1 (Cont.) VAX-11 PASCAL Compiler Listing

;

OOlS

;

0016

(')

s:
"ti
H

ti
H

"ti
:::ti
0
G)

;

0017

EXAMPLE
01

lS-AUG-1980 13:47:41
19-JUN-1980 14:10:08

GENERATED CODE
SA
SE
04

oc
08
00000000'

OOEC

S9 6S6E6F44
AE
AE
AE
EF
OOEC
SA

00000000'

Routine Size:

I
N
0

•

363 bytes,

Routine Base:

OOEC

CB
10
SA
8F
S9
04
04
OS
CB
SA
01
AB
01
CB
01
01

$CODE + 00000,

9E
C2
DD
DO
DO
DO
DO
FB
9E
DD
FB
DF
FB
DF
FB
DO
04

00120
0012S
00128
0012A
00131
0013S
00139
0013D
00144
00149
0014B
001S2
OOlSS
OOlSC
00160
00167
0016A

MOVAB
SUBL2
PUSHL
MOVL
MOVL
MOVL
MOVL
CALLS
MOVAB
PUSHL
CALLS
PUS HAL
CALLS
PUS HAL
CALLS
MOVL
RET

VAX-11 PASCAL Vl.2-80
_DBAl: [SMITH]EXAMPLE.PAS;2 (1)
OUTPUT(Rll), RlO
16, SP
RlO
A\Done\, R9
R9, 4 (SP)
4, 12 (SP)
4, 8 (SP)
S, PAS$WRITESTR
OUTPUT(Rll), RlO
RlO
1, PAS$WRITELN
INPUT (Rll)
1, PAS$CLOSEINOUT
OUTPUT (Rll)
1, PAS$CLOSEINOUT
SS$_NORMAL, RO

Page S
;

0020

;

0022

CD Stack Frame Size (exclusive of conformant arrays):

(')

64 bytes. G!)

~
H

OOOOOlDC

00000
00000
OOlDC

Rll-BASED PROGRAM LEVEL STATIC STORAGE
PSECT $GLBL, PIC,OVL,REL,GBL,NOSHR,NOEXE,RD,WRT
.BLKB
476

CD .

.END

t'1
H

Gl
~

Figure 2-1 (Cont.) VAX-11 PASCAL Compiler Listing

CHAPTER 3
LINKING A PROGRAM

After a VAX-11 PASCAL program is compiled, you link the object
module(s)
to produce an executable image file.
Linking resolves all
references in the object code and establishes absolute addresses for
symbolic locations.

3.1

THE LINK COMMAND FORMAT

To link an object module, the LINK command is issued in the
general form:
LINK/[command-qualifiers(s)]

following

file-spec-list [/file-qualifier(s)]

/command-qualifier(s)
Specify output file options.
Table 3-1 lists the command
qualifier options in their positive and negative forms, and the
default options.
f il e-spec-1 ist
Specifies the input object file to be linked.
/file-qualifier(s)
Specify input file options.
options.

Table 3-2 lists the

file

qualifier

Table 3-1
Command Qualifiers
Command
Qualifier
/BRIEF

Negative Form

Default
Not applicable

None

/CROSS REFERENCE

/NOCROSS REFERENCE

/NOCROSS_REFERENCE

/DEBUG

/NODEBUG

/NOEXECUTABLE

/EXECUTABLE

[=file-spec]

(continued on next page)

3-1

LINKING A PROGRAM
Table 3-1 (cont.)
Command Qualifiers
Command
Qualifier

Negative Form

Default

/FULL

None

Not applicable

/MAP =file-spec

/NOMAP

/NOMAP (interactive)
/MAP (batch)

/SHAREABLE

/NOSHAREABLE

/NOTRACEBACK

/TRACEBACK

[=file-spec]

/TRACEBACK

Table 3-2
File Qualifiers
File
Qualifier

Negative Form

Default

/INCLUDE=module-name(s)

None

Not applicable

/LIBRARY

None

Not applicable

In
interactive mode, you can
accompanying file specification.

issue the LINK command with
no
The system responds with the prompt:

$ File:
The file specification must be typed on the same line as the prompt.
If the file specification does not fit on one line, type a hyphen (-)
as the last character of the line and continue on the next line.
Multiple file specifications are entered separated by commas or plus
signs. When used with the LINK command, the comma has the same effect
as the plus sign:
the linker creates a single executable image from
the several
input files.
If no output file is specified, the linker
produces an executable image with the same name as the
first object
module and a file type of EXE.
The following sections describe in detail the LINK command options.

3.2

COMMAND QUALIFIERS

The command qualifiers, in the LINK command, modify the output of the
linker and specify the debugging or traceback facility.
Linker output
consists of an image file and, optionally, a map file.
The following
qualifiers, control the image file generated by the linker:
/EXECUTABLE
[=file-spec]
/NOEXECUTABLE
/SHAREABLE
[=file-spec]

3-2

LINKING A PROGRAM
These qualifiers are referred to
described in Section 3.2.1.

image-file

qualifiers

and

are

The following qualifiers control the map file generated by the linker:
/BRIEF
/CROSS REFERENCE
/FULL /MAP [=file-spec]
These qualifiers are referred
described in Section 3.2.2.

map-file

qualifiers

and

are

The following qualifiers specify the debugging or traceback facility.
/DEBUG
/TRACEBACK
These qualifiers are described in Section 3.2.3.

3.2.1

Image-File Qualifiers

The image-file qualifiers are:
/EXECUTABLE and /NOEXECUTABLE
/SHAREABLE
To produce an executable image, you specify the /EXECUTABLE qualifier.
To suppress production of an image file, you specify the /NOEXECUTABLE
qualifier. If no image-file qualifier is specified, the default is
/EXECUTABLE.
For example:
$ LINK/NOEXECUTABLE Circle

The file Circle.OBJ is linked, but no image is generated.
The
/NOEXECUTABLE qualifier is useful to verify the results of linking an
object file without actually producing the image.
To designate a file specification
/EXECUTABLE in the form:

for

executable

image,

use

generated

/EXECUTABLE=file-spec
For example:
$ LINK/EXECUTABLE=Test Circle

The file Circle.OBJ is linked, and the executable image
named Test.EXE.

A shareable image is one that can be used in a number of different
applications;
as a private image for your own applications, or
installed for use by all users in the system by the system manager.
To create a shareable image, specify /SHAREABLE. For example:
$ LINK/SHAREABLE Circle

3-3

LINKING A PROGRAM
To include a shareable image as input to the linker, use an options
file and specify the /OPTIONS file qualifier in the LINK command.
Refer to the VAX-11 Linker Reference Manual for details.
If /NOSHAREABLE is
image.

3.2.2

specified,

the

linker

generates

executable

Map-File Qualifiers

The map-file qualifiers control the generation of a map file
contents of the map file.

and

the

/FULL,

The map-file qualifiers are:
/MAP

[=file-spec]

[/FULL]

[/BRIEF]

Note that the /MAP option must
/CROSS_REFERENCE is specified.

[/CROSS REFERENCE]

used

/BRIEF,

The linker uses defaults to generate or suppress a map file.
In
interactive mode, the default is to suppress the map; in batch mode,
the default is to generate the map.
If no file specification is included with /MAP qualifier, the map file
has the name of the first input file and a file type of MAP. The map
file is stored on the default device, in the default directory.
The optional qualifiers /BRIEF and /FULL define
information included in the map file, as follows:

the

type

•

/BRIEF produces a summary of the image's characteristics and a
list of contributing modules.

•

/FULL produces (1) a summary of the image's characteristics
and a list of contributing modules (as produced by /BRIEF),
(2) listings of global symbols by name and by value, and (3) a
summary of characteristics of image sections in the linked
image.

By default, if neither /BRIEF nor /FULL is specified, the map file
contains a summary of the image's characteristics and a list of
contributing modules (as produced by /BRIEF), plus a list of global
symbols and values, in symbol name order. For a complete description
of the map file's contents, refer to the VAX-11 Linker Reference
Manual.
The /CROSS REFERENCE qualifier can be used with either the default or
/FULL map-qualifier 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.

3.2.3

Debugging and Traceback Qualifiers

The /DEBUG qualifier indicates that the VAX-11 Symbolic Debugger is to
be included in the executable image and a symbol table is to be
generated. If /DEBUG is specified at 1ink time, the program executes
under the control of the debugger, unless /NODEBUG is specified with
the RUN command. The default at link time is /NODEBUG.

3-4

LINKING A PROGRAM
The /TRACEBACK qualifier causes error messages accompanied by symbolic
traceback information showing the sequence of calls that transferred
control to the program unit in which the error occurred to be
generated. /NOTRACEBACK specifies that no traceback information is to
be produced. The default is /TRACEBACK.
If you specify both /DEBUG
and /NOTRACEBACK, the traceback capability is automatically included,
and /NOTRACEBACK has no effect.

3.3

FILE QUALIFIERS

The file qualifiers /LIBRARY and /INCLUDE are used as modifiers on the
input file specification. Input files can be object files, shareable
images specified in an options file, or library files.

3.3.1

/LIBRARY Qualifier

The /LIBRARY qualifier has the form:
/LIBRARY
The /LIBRARY qualifier specifies that the input
file
is
an
object-module library that the linker must search to resolve undefined
symbols referenced in other input modules. The default file type is
OLB.

3.3.2

/INCLUDE Qualifier

The /INCLUDE qualifier has the form:
/INCLUDE=module-name(s)
The /INCLUDE qualifier specifies that the input
file
is
an
object-module library, and that the modules named are the only modules
in that library that are to be explicitly included as input. At least
one module name is required. To specify more than one, enclose the
module names in parentheses, and separate them with commas.
The
/LIBRARY qualifier can be used with the /INCLUDE qualifier to modify a
single input file specification.
If /INCLUDE and /LIBRARY are
specified for the same input file, the specified library is also
searched for unresolved references.

3-5

CHAPTER 4
EXECUTING A PROGRAM

After you have compiled and linked your program,
the system can
execute it. The RUN command initiates execution.
It has the form:
RUN /NODEBUG file-spec
You must specify the file name;
default values are
omit optional elements of the file specification.
type is EXE.

applied
if you
The d e fa u 1 t f i l e

The DEBUG qualifier allows you to use the VAX-11 Symbolic Debugger,
even if you omitted this qualifier from the PASCAL and LINK commands
(see Sections 2.2 and 3.2).
If you specify /NODEBUG,
the program
executes without debugger intervention. This qualifier allows you to
override a /DEBUG qualifier specified at link time.

4.1

FINDING AND CORRECTING ERRORS

Both the compiler and the Run-Time Library include facilities for
detecting and reporting errors.
VAX/VMS also provides the debugger to
help you locate and correct errors.
In addition to the debugger, you
can use a
traceback facility to track down errors that occur during
program execution.

4.1.1

Error-Related Command Qualifiers

At each step in compiling, linking, and executing your program, you
can specify command qualifiers that affect how errors are reported.
At compile time, you can use the /DEBUG qualifier to ensure that
symbolic
information is preserved for use by the debugger. At link
time, you can also specify the /DEBUG qualifier to make the symbolic
information available to
the debugger.
The same qualifier can be
specified with the RUN command to invoke the debugger at run time.
Table 4-1 summarizes the /DEBUG and /TRACEBACK qualifiers.
If you use qualifiers at any point in the compile-link-execute
sequence, and an execution error occurs, you receive a traceback list
by default.

4-1

EXECUTING A PROGRAM
Table 4-1
/DEBUG and /TRACEBACK Qualifiers
Effect

Default

Qualifier

Command

/DEBUG

PASCAL

The PASCAL compiler
creates symbolic data
needed by the debugger.

/NODEBUG

/DEBUG

LINK

Symbolic data created by the
compiler is passed to the
debugger.
Traceback list is
also produced.

/NODEBUG

/TRACEBACK

LINK

Traceback information is
passed to the debugger.
Traceback list is produced.

/TRACEBACK

/DEBUG

RUN

Invokes the debugger. The
DBG> prompt is displayed.
Not needed if $ LINK/DEBUG
was specified.

None

/NODEBUG

RUN

If /DEBUG was specified in
the LINK command, RUN/NODEBUG
suppresses the DBG> prompt.

None

4.1.2

Specifying Command Qualifiers

To perform symbolic debugging, you must specify the /DEBUG qualifier
with both the PASCAL command and the LINK command.
It then is
unnecessary to specify /DEBUG with the RUN command.
If you omit
/DEBUG from either the PASCAL command or the LINK command, you can use
it with the RUN command to
invoke the debugger.
However, the
executable image does not contain debugger records or symbol tables
used in debugging. You must express addresses as absolute values,
rather than symbolically.
If you specify LINK/NOTRACEBACK combination, a traceback list is not
produced
in event of an error.
Figure 4-1 shows an example of a
source program listing and a traceback list.
The traceback list is interpreted as follows.
When the error is detected, you receive the appropriate message,
followed by the traceback information.
In this example, a message is
displayed by the system, indicating the nature of the error, the
address at which the error occurred (the Program Counter, PC), and the
contents of the processor status longword
(PSL).
This message is
followed by the traceback information.
The traceback information is presented in inverse order to the routine
or subprogram calls.
Of particular interest are the values listed
under routine name and line, the first of which shows which routine or
subprogram generated the error. The value given for line corresponds
to a compiler-generated line number in the source program listing (not
to be confused with editor-generated line numbers).
The line number
indicates the nearest previous line on which a statement begins.
Using this information, you can usually isolate the error in a short
time.

4-2

EXECUTING A PROGRAM
If you specify either LINK/DEBUG or RUN/DEBUG,
the debugger assumes
control of execution.
If an error occurs, control reverts to the
debugger;
the traceback list is not automatically printed.
For more
information on using the debugger, refer to Chapter 5.
TRACETEST
01

20-AUG-1980 13:32:07
20-AUG-1980 13:31:50

SOURCE LISTING

LINE
NUMBERS

LEVEL
PROC STMT
1
1
2
2
2
2
2
2
2
2
2
2
1
1
1
1

1
2

3
4
5
6
7

8
9
10
11
12
13
14
15
16

0
0
0
0
0
1
0
0
0
0
1
0
0
0
1
0

VAX-11 PASCAL Vl.2-59
_DBAl: fSMITH]TRACE.PAS;l

Page
(l)

STATEMENT.
PROGRAM TRACETEST;
PROCEDURE Pl (VAR X
BEGIN
x := 1.0/X;
END;
PROCEDURE P2
BEGIN
Pl(Y);
END;

REAL);

BEGIN
P2 (0. 0);
END.

Active options at end of compilation:
NODEBUG,STANDARD,LIST,NOCHECK,WARNINGS,NOCROSS REFERENCE,
NOMACHINE_CODE,OBJECT,ERROR_LIMIT = 30
COMPILATION STATISTICS
Total Space Allocated:
Stack Frame Size Total:
Run Time:
Page Faults:

140 bytes, 128 Code+ 12 D~ta
144 bytes
0.13 seconds.
451 lines/minute)
983

%SYSTEM-F-FLIDIV, arithmetic trap, floating/decimal divide by zero at PC=00000429, PSL=03C0002A
%TRACE-F-TRACEBACK, symbolic stack dump follows
module name

routine name

line

relative PC

absolute PC

TRACETEST
TRACETEST
TRACETEST

Pl
P2
TRACETEST

5
10
14

00000029
00000030
0000004E

00000429
0000045D
000004AC

Figure 4-1
4.2

Source Program Listing and Traceback List

ZK-065-80

SAMPLE TERMINAL SESSION

A simple dialog between you and the system might appear as follows:
(BTIJ

Username: SMITH (ffi)
Password:
(ffi)
(Your password is not displayed)
WELCOME TO VAX/VMS VERSION 1.2
$EDIT CIRCLE.PAS (BTIJ
Input:DBA2: [SMITH]CIRCLE.PAS
00100
(enter source program)
*E
(ffi)
(terminate edit session and write file to disk)
[DBA2: [SMITH]CIRCLE.PAS;l]
$ PASCAL/LIST Circle
$ LINK Circle
$ RUN Circle
$ ENTER VALUE:

4-3

CHAPTER 5
DEBUGGING PASCAL PROGRAMS

This chapter describes how to
debug
VAX-11
interactively using the VAX-11 Symbolic Debugger.

PASCAL

programs

Section 5.1 describes some features of the VAX-11 Symbolic Debugger.
Section 5.2 describes the debugging of a simple PASCAL
gives a functional description of the debugger commands.

program

and

Section 5.3 describes in detail each debugger command in
order.

alphabetical

Section 5.4 describes the debugging of a complex PASCAL program.
For a detailed description of the
Symbolic Debugger Reference Manual.

5.1

debugger,

refer

the

VAX-11

VAX-11 SYMBOLIC DEBUGGER

The VAX-11 Symbolic Debugger provides the following:

5.1.1

•

Access to the symbol table generated by the PASCAL compiler

•

A set of debugger commands and qualifiers
specific control of an executing program

that

allow

for

Debugger Symbol Table

The debugger maintains a table of symbols that can be referenced by a
program during a debugging session.
The symbol
table provides
information on all scalar
(real, subrange,
integer,
character,
Boolean, double, enumerated) and structured (array, record, file, set,
pointer) variables, user-defined types, labels, procedures, functions,
main programs, and modules.
To place the symbols from a program into the symbol
table you must
first specify the /DEBUG qualifier in the PASCAL and LINK commands.
This makes the symbols available in the executable program image file.
To copy a module's symbols from the image file to the symbol table you
use a SET MODULE command.
The debugger will place the symbols from
the main program into the symbol table at the beginning of a debugging
session.
(Refer to Section 5.3.22 for more information on the SET
MODULE command.)

5-1

DEBUGGING PASCAL PROGRAMS
VAX-11 Symbolic Debugger Command Syntax

5.1.2

You control the execution
Debugger commands.

program

using

VAX-11

Symbolic

Section 5.3 describes the debugger commands in detail.
In addition,
Appendix
C
contains
a
list of all debugger commands, with
abbreviations and syntax, for quick reference.
The debugger commands resemble other DIGITAL Command
commands and observe the same language conventions.

Language

(DCL)

Format
COMMAND [/qualifier(s)] [parameters][DO(cornmand-string; ... )] [!comment]
COMMAND
Specifies the command name.
/qualifier(s)
Modifies some debugging commands.
Qualifiers change the defaults 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
/HEXADECIMAL.
Table 5-1 summarizes the command
qualifiers of particular significance in PASCAL debugging.
Refer to the VAX-11 Symbolic Debugger Reference Manual
information on qualifiers.

for

parameter
Specifies the object of the command. The parameter can
address, constant, name of a variable, or an expression.

DO (command-string; ••• )
Tells the debugger to perform the specified command.
command-string can be a series of debugger commands.)
!comment
Contains user remarks about the intent of the command.
Separate the command and parameter fields by one or more spaces.

5-2

(The

DEBUGGING PASCAL PROGRAMS
Table 5-1
Debugger Command Qualifiers

5.1.3

Qualifier

Commands

Function

/ADDRESS

EVALUATE

Indicates that an address
value is desired

/HEXADEC !MAL
/OCTAL

EVALUATE
EXAMINE
DEPOSIT

Overrides the default
(decimal)

/BYTE
/WORD
/LONG
/ASCII

EXAMINE
EVALUATE
DEPOSIT

Specifies a type

Debugger Operations

The EVALUATE.command evaluates expressions and performs operations on
integer,
real,
double-precision, character, Boolean, enumerated
scalar, record, file, array, and set types. The PASCAL operators used
in your programs that are supported by the debugger are listed below
in decreasing order of precedence:
NOT

**
*,/, DIV, MOD, AND
+,-, OR

=,<>, <, <=, >, >=,

The debugger evaluates expressions in the same way as PASCAL.
Spaces
are used to separate elements of the debugger commands, and are
significant to the debugger;
therefore,
variable
names
and
multicharacter operators must contain no embedded spaces.
The debugger accepts constants in PASCAL syntax, with the following
exception:
constructors cannot be deposited into ar~ays or records
nor can they be evaluated.
For more information on constructors,
refer to the VAX-11 PASCAL Language Reference Manual.

5.1.4

Specifying Addresses

The debugger allows you to specify addresses as symbolic names in the
debugger commands.
For example, to examine a variable you need only
refer to it by its name;
you need not know its actual memory
location.
This form of symbolic expression applies to data addresses
(such as variables, array elements, or record fields),
to program
addresses
(such as program line numbers, or labels) and to program
unit names.
When you are debugging more than one program unit, you should be aware
of the concept of scope (see Section 5.2.2.4), since it affects how
the debugger interprets symbols. The following sections describe how
to specify data and program addresses using the debugger commands.

5-3

DEBUGGING PASCAL PROGRAMS
5.1.4.1 Specifying Data Addresses - You can specify
symbolically as variables names.
For example:
DBG> DEPOSIT ISSUE

data

addresses

= 100

DBG> EXAMINE PURCH[I,J+l]
The first command deposits the value 100 in the
integer
identifier
ISSUE, and
the second command examines the contents of an element of
the array PURCH.
You can reference array elements with subscripts that are constants or
expressions.
If you reference a variable or array element that is not
in the symbol table, or if you attempt to reference an element that is
out of the array bounds, the debugger issues a warning.

5.1.4.2 Specifying Current,
Previous, and
Next
Locations - The
debugger provides a quick method for referencing any of three relative
data addresses, or locations:
A period (.) references the current location, that is,
the
• location
most recently referenced by an EXAMINE or DEPOSIT
command.
•

A circumflex {~) references the
current location.

•

A carriage return {RET) references the logical successor.

logical

predecessor

the

For example:
DBG> DEPOSIT .=100
This command puts a value of 100 in the current location. The current
location is the last address used by an EXAMINE or DEPOSIT command.
To specify the previous location, type:
DBG> EXAMINE

This command displays the the contents of the previous location.
To specify the next location, type:
DBG> EXAMINE IBru
This command displays the contents of the next location.

5.1.4.3 Specifying Program Addresses - You can
specify
program
addresses by program unit name, routine name, line number, statement
label, or {nonsymbolic) virtual address.
To specify a
procedure by
name, give the command followed by the name of the procedure.
For
example:
DBG> SET BREAK procedl
This command sets a breakpoint at the entry to procedl.

5-4

DEBUGGING PASCAL PROGRAMS

To specify an address using a compiler-generated line number, use
%LINE prefix, as follows:

the

DBG> SET BREAK %LINE 6
This command sets a breakpoint at line 6, corresponding
compiler-generated line number shown in the source listing.

the

You can also set a breakpoint at a line number within a particular
program unit. For example, to stop execution at line 11 in the module
MOD2, you could set a breakpoint as follows:
DBG> SET BREAK MOD2\%LINE 11
To specify a
example:

GOTO

statement

label,

use

the

%LABEL

prefix.

For

DBG> SET BREAK %LABEL 7
This command sets a breakpoint at statement label 7.
To specify a virtual address, issue the command without a modifier
(for example, %LABEL).
This causes the address you specify to be
interpreted as the Program Counter (PC) value at which to perform the
debugging function. For example:
DBG> SET BREAK %X700
This command sets a breakpoint at the hexadecimal address 700.

5.1.5

Special Symbols

The debugger accepts the special symbols listed in Table 5-2.
These
symbols are used in the debugger commands in place of an address or
value.
Table 5-2
Special Symbols
Symbol

Definition

Example

A hexadecimal number

DEPOSIT TOT = %XFF

An octal number

EVALUATE %077

A binary number

DEPOSIT TOT

The last value displayed
by EXAM !NE or EVALUATE

EXAMINE \

Current location

EVALUATE

Logical predecessor

EXAMINE "

ffiJ

Logical successor

EXAMINE ffiJ

= %Bl01

(continued on next page)

5-5

DEBUGGING PASCAL PROGRAMS
Table 5-2 (Cont.)
Special Symbols

5.2

Symbol

Definition

Example

%RO-%Rll

General registers 0-11

EXAMINE %RS

%AP

Argument Pointer

EXAMINE %AP

%FP

Frame Po inter

EXAMINE %FP

%SP

Stack Po inter

EXAMINE %SP

%PC

Program Counter

EXAMINE %PC

%PSL

Processor Status Longword

EXAMINE %PSL

USING THE DEBUGGER

The following sections illustrate how to debug a simple PASCAL program
and describe in general terms the use of the debugger.

5.2.1

Debugging a PASCAL Program

Figure 5-1 is a program that requires debugging.
The program was
compiled and linked without diagnostic messages from either the
compiler or the linker.
However, the program produces erroneous
results because of the missing asterisk in the exponentiation operator
(Radius*2 should be Radius**2).
1
2
3
4
5
6
7

8
9
10
11
12
13
14
15
16
17
18
19

PROGRAM Circle(INPUT,OUTPUT);
CONST Pi = 3.1415927;
VAR Radius, Area : REAL;
LABELl;
BEGIN
WRITE ('ENTER T.HE RADIUS VALUE: ');
WHILE NOT EOF
DO
BEGIN
WHILE NOT EOLN
DO
BEGIN
READLN (Radius);
1: Area := Pi * Radius * 2;
WRITELN ('AREA OF CIRCLE EQUALS ',Area : 4);
WRITELN ('ENTER RADIUS VALUE OR CTRL/Z : ');
END;
END
END.
Figure 5-1

Sample PASCAL Program

5-6

DEBUGGING PASCAL PROGRAMS
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 determine
whether 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.
To look at the contents of a location, use the EXAMINE
resume execution, use either the GO or STEP command.

command.

The debugger commands relevant to PASCAL are described in Section 5.3.
Figure 5-2 is an example of a simple terminal dialog for a debugging
session.
The circled numbers are keyed to notes that follow the
figure and explain the dialog.

$ PASCAL/LIST/DEBUG CIRCLE
$ LINK/DEBUG CIRCLE 0
$ RUN CIRCLE C)

VAX-11 DEBUG VERSION 2.3
%DEBUG-I-INITIAL, language is PASCAL, module set to 'CIRCLE'
DBG> SET BREAK %LINE 14 (»
DBG> GO C)
routine start at CIRCLE
ENTER RADIUS VALUE : 24
break at CIRCLE\CIRCLE\%LINE 14 C.

DBG> STEP
start at CIRCLE\%LINE 14
stepped to CIRCLE\%LINE 15

DBG> EXAMINE Area
CIRCLE\CIRCLE\AREA: l.507964478E+02
DBG> EXAMINE Radius 0
CIRCLE\CIRCLE\RADIUS: 2.400000000E+Ol

DBG> GO
start at CIRCLE\%LINE 15
AREA OF CIRCLE EQUALS 1. 4E+02
ENTER RADIUS VALUE OR CTRL/Z :

.. z
%DEBUG-I-EXITSTATUS, is '%SYSTEM-S-NORMAL, normal successful completion'
DBG> EXIT G
$

Figure 5-2

Sample Debugging Session

5-7

DEBUGGING PASCAL PROGRAMS

t»
f»

Invoke the PASCAL
qualifiers.

compiler,

specifying

the

/LIST

Link the program using the /DEBUG qualifier to include
table for the debugger.

and

/DEBUG

symbol

Issue the RUN command.
In response, 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 settings from the first main program specified in
the LINK command.

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.
which execution starts.

The

debugger

displays

the

point

The program request for
input for
the variable Radius is
displayed.
The debugger displays
that program execution was
suspended at the specified breakpoint.

f»

The STEP command causes the equation to be executed.

(»

Examine the variable Area.
Area.

Examine the variable Radius.

4D
~

4D
G)

The debugger displays

the

value

Resume execution.
The debugger displays a message indicating the
point at which program execution resumed.
The Area is calculated and displayed.
A request for
displayed, and a CTRL/Z is entered to end the program.

input

Successful completion of the program is indicated by
message.
However, as you can see, the result is incorrect.

is
this

Exit from the debugger.

By examining the variables Radius and Area as the program is
executing, you can determine that the values being
entered or
calculated are being stored correctly.
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,
recompile,
and
relink
the
source
program, with the exponentiation operator properly
specified in the formula expression.

5-8

DEBUGGING PASCAL PROGRAMS
5.2.2

General Description of the Debugger Commands

The debugger's
function:

commands

can

broken

down

into

four

areas

•

The commands that allow you to control the environment
(the
language, where the output is to go) in which the debugger is
to operate

•

The commands that allow you to control the execution
program

•

The commands that allow you to examine and modify locations in
your program

•

The commands that allow you to specify scope

Each of these areas and the commands that perform these functions
discussed in the following sections.

your

are

5.2.2.l Preparing to Debug a Program - The commands used to establish
the proper environment for debugging PASCAL programs are:
SET LANGUAGE
SHOW LANGUAGE
SET LOG
SHOW LOG
SET MODE
SHOW MODE
CANCEL MODE
SET MODULE
SHOW MODULE
CANCEL MODULE
SET OUTPUT
SHOW OUTPUT
SET TYPE
SHOW TYPE
CANCEL TYPE/OVERRIDE
The LANGUAGE commands let you establish or determine
language.

the

programming

•

SET LANGUAGE indicates to the debugger that the debugging
session should be conducted according to the conventions of
the specified language.

•

SHOW LANGUAGE displays the current language.

The LOG commands let you establish or determine the
and whether it is being written to.

log

file's

•

SET LOG specifies the name of the log file.

•

SHOW LOG displays the log file name and whether the
is active.

5-9

log

name

file

DEBUGGING PASCAL PROGRAMS
The MODE commands let you establish, display, and cancel default entry
and display modes.
•

SET MODE establishes entry and display modes.

•

SHOW MODE displays the current entry and display modes.

•

CANCEL MODE cancels all modes and sets
values for the current language.

them

the

default

The MODULE commands let you control the contents of the symbol table
when the program you want to debug consists of multiple program units
(a program and module(s}}.
•

SET MODULE places the symbols defined in the specified program
unit or units in the debugger's internal symbol table.

•

SHOW MODULE displays the names of all
symbols are available to the debugger.

•

CANCEL MODULE removes the
from the symbol table.

specified

The OUTPUT commands control where the
written.

output

program

program
from

units

unit's
the

•

SET OUTPUT specifies whether the debugger output
written to the terminal or to the log file.

•

SHOW OUTPUT displays the output configuration.

The TYPE commands let you establish or determine
types for the DEPOSIT and EXAMINE commands.
data

type

whose
symbols

debugger

the

default

data

ASCII,

BYTE,

SET TYPE specifies the default
INSTRUCTION, LONG, or WORD.

•

SHOW TYPE displays the current default data type.

•

CANCEL TYPE/OVERRIDE cancels the current default data type.

5.2.2.2 Controlling Program Execution - To control the execution of
your program, you must be able to suspend and resume execution at
specific points.
The following
commands are available for
these
purposes:
SET BREAK
SET EXCEPTION BREAK
SHOW BREAK
CANCEL BREAK
CANCEL EXCEPTION BREAK
SET TRACE
SHOW TRACE
CANCEL TRACE
SET WATCH
SHOW WATCH
CANCEL WATCH

5-10

DEBUGGING PASCAL PROGRAMS
SHOW CALLS

GO
SET STEP
SHOW STEP
STEP

EXIT
The BREAK commands let you select
suspension, so you can examine
variables in the program.

specified locations for program
and/or modify structured or scalar

•

SET BREAK defines a procedure's line number, statement
or address at which to suspend execution.

label,

•

SET EXCEPTION BREAK defines exceptions
(conditions
interrupt execution of your program) as breakpoints.

that

•

SHOW BREAK displays
program.

•

CANCEL BREAK removes selected breakpoints.

•

CANCEL EXCEPTION BREAK removes the exception breakpoint.

all

breakpoints

currently

set

the

The TRACE commands let you set, examine, and
remove tracepoints in
your program.
A tracepoint is similar to a breakpoint in that it
suspends program execution and displays the address at the point of
suspension.
However,
in the case of a tracepoint, program execution
resumes immediately after a message is displayed.
Thus,
tracepoints
let you follow the sequence of program execution to ensure that
execution is carried out in the proper order.
Note that if you set a tracepoint at the same location as
breakpoint, the breakpoint is canceled, and vice versa.

current

The TRACE commands perform the following functions:
•

SET TRACE establishes points within
execution is momentarily suspended.

the

program

which

•

SHOW TRACE displays the locations
tracepoints are currently set.

the

program

which

•

CANCEL TRACE removes one or more tracepoints currently set
the program.

The WATCH commands let you monitor specified locations to determine
when attempts are made to modify their contents, so you can take the
appropriate action.
These locations are called watchpoints. When an
attempt is made to change the value of a watchpoint, the debugger
suspends program execution, displays the old and new contents of the
location, and prompts for a command.
Watchpoints are monitored
continuously.
Thus, you can determine whether locations are being
modified inadvertently during program execution.

5-11

DEBUGGING PASCAL PROGRAMS
The WATCH commands perform the following functions:
•

SET WATCH defines the location(s)

to be monitored.

•

SHOW WATCH displays the location(s)

•

CANCEL WATCH disables monitoring of the specified locations.

currently being monitored.

The SHOW CALLS command is used to produce a traceback of procedure and
function calls, and
is particularly useful when you have returned
control to the debugger following a CTRL/Y command.
The GO command lets you resume program execution.
•

GO initiates execution at the current location and continues
to the conclusion of the program or to the next breakpoint or
watchpoint.

The STEP commands give you specific control over how much of a program
is to be executed at one time.
A program can, for example, be
executed line by line or instruction by instruction.
The STEP commands perform the following functions:
•

SET STEP establishes the
INSTRUCTION, and so on).

current

step

conditions

•

SHOW STEP displays the current step conditions.

•

STEP initiates execution from the current
continues for a specified number of lines.

location

The CTRL/Y command returns control to DCL command level but
terminate the debugging session.
The EXIT command lets you exit from the debugger
debugging session.

(LINE,

and

does

not

terminating

the

5.2.2.3 Examining and Modifying Locations - Once you set breakpoints
and begin program execution, the next step is to determine whether
correct values are assigned
to
the identifiers and, possibly,
to
change the contents of locations as execution proceeds. You may also
want to calculate the value of an expression that appears in your
program.
You can use the following commands:
DEPOSIT
EVALUATE
EXAMINE
The DEPOSIT command lets you place a new value into a variable
the debugging session.

5-12

during

DEBUGGING PASCAL PROGRAMS
The EVALUATE command lets you determine the value of an expression.
The EXAMINE command
specific location.

lets

you

display

the

current

contents

Refer to Section 5.1.5 for information on special symbols that can
used with these commands.

5.2.2.4 Specifying Scope - If the program you are debugging consists
of more than one program unit, your symbolic references should be
unambiguous.
Usually you can let the debugger specify scope, that is,
the module in which a symbol is unique.
Sometimes, however, you must
tell the debugger how to resolve symbolic references.
For example,
suppose you are debugging
two program units and both units use the
variable I, and both variables are defined
in the symbol
table.
Unless you explicitly specify scope, the debugger may not be able to
determine which variable I you want to use. You can make a symbol
unique by specifying scope in one of three ways:
•

By using the debugger default scope

•

By explicitly specifying the desired scope
name in the command

•

By explicitly specifying the desired scope in the SET SCOPE
command
(once scope has been set, it is in effect for all
subsequent commands until you issue another SET SCOPE command)

and

the

symbolic

When you begin a debugging session, the debugger automatically defines
the main program unit as the default scope.
However, this default
scope is dynamic;
that is, as you debug your program,
the default
scope is always the routine you are currently executing.
The
debugger's default scope rules are:
•

If the specified symbol name is unique within
symbol table, the debugger uses that name.

the

debugger

•

If the specified symbol is ambiguous (not unique within the
symbol table), but one of its declarations is within the
current scope, the debugger uses that particular declaration.

•

If the specified symbol is not defined in the symbol table, or
if it is ambiguous with no declarations defined within the
current scope, the debugger issues an error message.

You can specify scope explicitly by providing the name of the symbol
and the name of the routine in which it is accessible, separated by a
backslash (\) character, as shown in these examples:
DBG> SET WATCH MOD1\ARRMN[l2]
DBG> SET BREAK MODl\%LINE10
In addition, if you want to make a number of symbolic
references
within the same program unit, you can eliminate the need to specify
scope with each symbolic address by using the SET SCOPE command.

5-13

DEBUGGING PASCAL PROGRAMS
You specify the scope of a name explicitly by providing both the
symbol name and the names of the module and routine in which it is
located, separated by a backslash
(\)
character.
This type of
specification is called a pathname, because it consists of a path of
names for several nested routines.
For example:
PROGRAM Main(INPUT, OUTPUT);

PROCEDURE Check Table (X,Y
VAR Z-: CHAR;

INTEGER);

PROCEDURE Put Table (R : REAL);
VAR-Z : CHAR;

To change the value of Z,
which is the variable defined
procedure Put_Table, the following debugger command is given:

the

DBG> DEPOSIT MAIN \Check_Table \Put_Table \Z = 'a'
By specifying· this pathname you change only the value of Z in the
procedure Put Table.
The variable Z in the procedure Check Table
remains unchanged.
Another way of altering
follows:

the

variable

the

routine

Put Table

DBG> SET SCOPE Put Table
DBG> DEPOSIT Z
'a'
This method does not use a pathname, but defines the scope
Put_Table and then deposits a value directly into the variable z.

You can also use a pathname to specify an address reference that is in
a routine not under the current scope setting. This is done by giving
the address a pathname qualifier:
DBG> SET BREAK MOD1\%LINE 7
This command sets a breakpoint at line 7 of the module MODl.
The following commands can be used to specify scope:
SET SCOPE
SHOW SCOPE
CANCEL SCOPE

5-14

DEBUGGING PASCAL PROGRAMS
These commands let you explicitly control how
symbolic references.

5.3

the

debugger

resolves

•

SET SCOPE explicitly establishes the specified unit or
as the scope to be used fo.r the translation of symbols.

units

•

SHOW SCOPE displays the current setting of scope.

•

CANCEL SCOPE revokes the program unit previously established
in a SET SCOPE command and establishes as the default scope
the currently active program unit.

VAX-11 SYMBOLIC DEBUGGER COMMANDS

The following sections describe the VAX-11 Symbolic Debugger commands
that can be used to debug a PASCAL program. The commands are listed
in alphabetical order for ease of reference.

5-15

DEBUGGING PASCAL PROGRAMS

CANCEL ALL
CANCEL ALL Command

5.3.1

The CANCEL ALL command cancels
all
breakpoints,
tracepoints,
watchpoints, and restores scope and user-set entry/display modes to
their default values.
CANCEL ALL does not affect the modules included in the debugger symbol
table or the current language.

Format
CANCEL ALL

Command Parameters
None.

Command Qualifiers
None.

Examples
DBG> CANCEL ALL
All breakpoints, tracepoints, watchpoints, are
and modes are set to their default values.

5-16

canceled.

Scope

DEBUGGING PASCAL PROGRAMS

CANCEL BREAK
5.3.2

CANCEL BREAK Command

The CANCEL BREAK
breakpoints.

command

cancels

specific

breakpoint

Format
CANCEL BREAK

[/qualifier]

[address-expression]

Command Qualifiers
/ALL
Command Parameters
address-expression
Specifies the address at which a breakpoint is to be canceled.
Command Qualifiers
/ALL
Cancels all breakpoints in the program.
Examples
DBG> CANCEL BREAK %LINE 110
The break located at line 110 is canceled.

5-17

all

DEBUGGING PASCAL PROGRAMS

CANCEL EXCEPTION BREAK
5.3.3

CANCEL EXCEPTION BREAK Command

The CANCEL EXCEPTION BREAK command cancels the exception breakpoint.
Format
CANCEL EXCEPTION BREAK
Command Parameters
None.
Command Qualifiers
None.
Examples
DBG> CANCEL EXCEPTION BREAK
All exception breakpoints are canceled.

5-18

DEBUGGING PASCAL PROGRAMS

CANCEL MODE
5.3.4

CANCEL MODE Command

The CANCEL MODE command cancels all modes and types and sets
the default values.

them

The CANCEL MODE command sets the default address display mode to
the
PASCAL default of symbolic and the radix mode to the default radix of
decimal.
Format
CANCEL MODE
Command Parameters
None.
Command Qualifiers
None.
Examples
DBG> CANCEL MODE
The current modes are
default values.

canceled

5-19

and

are

reset

the

PASCAL

DEBUGGING PASCAL PROGRAMS

CANCEL MODULE
CANCEL MODULE Command

5.3.5

The CANCEL MODULE command removes the specified program unit's symbols
from the debugger's internal symbol table.

Format
CANCEL MODULE

[/qualifier]

[module

[,module ••• ]]

Command Qualifiers
/ALL

Command Parameters
module
Specifies the name of the program unit for which symbols
be removed from the active symbol table.

are

Command Qualifiers
/ALL
Specifies that all information is to be deleted
symbol table.

fro~

the

active

Examples
1.

DBG> CANCEL MODULE MODl
The symbols from the program
active symbol table.

unit

MODl

are

removed

DBG> CANCEL MODULE/ALL
All the symbols in the active symbol table are removed.

5-20

from

the

DEBUGGING PASCAL PROGRAMS

CANCEL SCOPE
5.3.6

CANCEL SCOPE Command

The CANCEL SCOPE command cancels all previous settings for scope and
resets the scope to the current scope, the scope of the program unit
within which the PC is currently located.
The current scope changes as different sections of the program are
executed.
CANCEL SCOPE is the same as setting the scope equal to O
{refer to Section 5.3.24).
Format
CANCEL SCOPE
Command Parameters
None.
Command Qualifiers
None.
Examples
DBG> CANCEL SCOPE
The scope{s) currently set are canceled.

5-21

DEBUGGING PASCAL PROGRAMS

CANCEL TRACE
5.3.7

CANCEL TRACE Command

The CANCEL TRACE command specifies an address at which the
is to be removed.

tracepoint

Format
CANCEL TRACE

[/qualifier]

[address]

Command Qualifiers
/ALL
Command Parameters
address
Specifies the address from which a tracepoint is to be removed.
Command Qualifiers
/ALL
Removes all tracepoints in the program.
Examples
1.

DBG> CANCEL TRACE %LABEL 140
The tracepoint at label 140 is canceled.

DBG> CANCEL TRACE/ALL
All existing tracepoints are canceled.

5-22

DEBUGGING PASCAL PROGRAMS

CANCEL TYPE/OVERRIDE
5.3.8

CANCEL TYPE/OVERRIDE Command

The CANCEL TYPE/OVERRIDE command cancels the current override type and
resets the override type to none.
Format
CANCEL TYPE/OVERRIDE
Command Parameters
None.
Command Qualifiers
/OVERRIDE
The /OVERRIDE qualifier must be specified.
Examples
DBG> CANCEL TYPE/OVERRIDE
The current override type is canceled and the
reset to none.

5-23

override

type

DEBUGGING PASCAL PROGRAMS

CANCEL WATCH
CANCEL WATCH Command

5.3.9

The CANCEL WATCH command
session.

cancels

watchpoint

during

debugging

Format
CANCEL WATCH [/qualifier]

[var]

Command Qualifiers
/ALL

Command Parameters
var
Specifies the location at which monitoring is to be disabled.

Command Qualifiers
/ALL
Removes all watchpoints from the program.

Examples
1.

DBG> CANCEL WATCH AREA
This example cancels the monitoring of location AREA.

DBG> CANCEL WATCH/ALL
All existing watchpoint$ are canceled.

5-24

DEBUGGING PASCAL PROGRAMS

CTRL/Y
5.3.10

CTRL/Y Command

You can use the CTRL/Y command at any time to
return to
the system
command
level.
To issue this command, press the Y key while holding
down the CTRL key.
The dollar sign ($) prompt is displayed on the
terminal.
To return control to the debugger, type DEBUG.
This brings
you back to the debugger in your old program with the same set of
command defaults.
You can use the CTRL/Y command if your program
loops or otherwise fails to stop at a breakpoint.
To determine the
point at which CTRL/Y was executed, use the SHOW CALLS command
(Section 5.3.30) after you return to the debugger.
Format

Command Parameters
None.
Command Qualfiers
None.
Examples
DBG > G0

(CTRL/Y)

$DEBUG
VAX-11 DEBUG VERSION 2.3
DBG>

5-25

DEBUGGING PASCAL PROGRAMS

DEPOSIT
5.3.11

DEPOSIT Command

The DEPOSIT command places the contents of the value
specified variable:

field

into

the

•

If the value is the same size as the specified variable,
value is deposited in the variable with no conversion.

the

•

If the value is larger than the specified variable, the
is truncated on the left and deposited in the variable.

value

•

If the value is smaller than the specified variable, the value
is zero-filled on the left and deposited in the variable.

If you assign a value to a variable that does not conform to the rules
of assignment compatibility, an informational message is displayed.
(For more information on assignment compatibility, refer to the VAX-11
PASCAL Language Reference Manual.)
Format
DEPOSIT

[/qualifier]

address-expression

value

Command Qualifiers
/ASCII: 1 eng th
/BYTE
/DECIMAL
/HEXADECIMAL
/INSTRUCTION
/LONG
/OCTAL
/WORD
Command Parameters
address-expression
Specifies the variable reference into which the value
deposited.

value
Specifies the value to be deposited.
Command Qualifiers
/ASCII: 1 ength
Specifies that the data value is to be interpreted as an ASCII
string.
The length specifies the number of bytes of ASCII data
to be deposited for each data item.
It is interpreted in the
radix specified by a command qualifier that precedes the /ASCII
qualifier or in the current radix mode.
If length is omitted,
the debugger assumes a length of 4.

5-26

DEBUGGING PASCAL PROGRAMS

/BYTE
Specifies that the data value is to be interpreted as a byte
integer.
For each data item specified, the debugger deposits 1
The data is interpreted in the radix mode
byte of data.
specified by a command qualifier or in the current radix mode.
Any value that cannot be stored in a byte (greater than 255,
unsigned)
is left-truncated (that is, the high-order bits are
dropped) •
/DECIMAL
Specifies that all numbers following the qualifier in the command
are to be interpreted in decimal radix.
/HEXADEC !MAL
Specifies that all numbers following the qualifier in the command
are to be interpreted in hexadecimal radix.
/INSTRUCTION
Specifies that the data is instructions enclosed in quotation
marks or apostrophes.
The debugger deposits the binary opcode
and operands. The length of the instruction deposited depends on
the opcode and the addressing modes used.
/LONG

Specifies that the data value is to be interpreted as a longword
integer.
For each data item specified, the debugger deposits 4
The data is interpreted in the radix mode
bytes of data.
specified by a command qualifier or in the current radix mode.
Any value that cannot be stored in a longword
will
be
1 eft-truncated.
/OCTAL

Specifies that all numbers following the qualifier in the command
are interpreted in octal radix.
/WORD
Specifies that the data value is to be interpreted as a word
integer.
For each data item specified, the debugger deposits 2
bytes of data.
The data is interpreted in the radix mode
specified by a command qualifier or in the current radix mode.
Any value that cannot be stored in a word (greater than 65,535,
unsigned) is left-truncated.

5-27

DEBUGGING PASCAL PROGRAMS

Examples
1.

DBG> DEPOSIT Hair Color = Brown
DBG> DEPOSIT Married = True
These examples place the values Brown and True into the variables
Hair Color and Married.

DBG> DEPOSIT AA.Name= 'SMITH'
The name 'SMITH' is deposited into the name field of
A.

5-28

the

record

DEBUGGING PASCAL PROGRAMS

EVALUATE
5.3.12

EVALUATE Command

The EVALUATE command functions as a calculator to determine the
of an expression.

value

Format
EVALUATE

[/qualifier]

expression

Command Qualifiers
/ADDRESS
/DECIMAL
/HEXADECIMAL
/OCTAL
Command Parameters
expression
Specifies the expression whose value is to be determined.
A
backslash
(\) can also be used in an expression to reference the
last expression evaluated. A function reference is the only
PASCAL expression that cannot be evaluated. An expression must
contain only variables or constants in the active symbol table to
be evaluated.
Command Qualifiers
/ADDRESS
Indicates that an address value is desired.
/DECIMAL
Specifies that decimal is the default radix for
in the command and for the display of values.

numbers

entered

Specifies that hexadecimal
is the default radix for
entered in the command and for the display of values.

numbers

/HEXADECIMAL

/OCTAL
Specifies that octal is the default radix for numbers entered
the command and for the display of values.

5-29

DEBUGGING PASCAL PROGRAMS
Examples
1.

DBG> EVALUATE Pi*Radius
6.28
The value of the expression Pi*Radius is displayed.

DBG> EVALUATE/ADDRESS /HEX I
007F3AA4
This command calculates and displays the hexadecimal
the variable I.

address

DBG> EVALUATE/ADDRESS A[J]
1600
This command calculates the decimal address of the Jth element o~
array A and displays it.

You can also use EVALUATE to perform address arithmetic, such as
computing an offset or array element address, as in this
following example.
DBG> EVALUATE/ADDRESS I+4
3000
This command calculates the decimal address of the data stored at
a location 4 bytes after the address of I.

DBG> EVALUATE \
3000
The last scalar value
command is displayed.

resulting

5-30

from

EVALUATE

DEPOSIT

DEBUGGING PASCAL PROGRAMS

EXAMINE
5.3.13

EXAMINE Command

The EXAMINE command displays the contents of specified locations.
Note you cannot examine variables of an array, record, or file type,
except when the variable is a packed or unpacked array [l •• n] of CHAR,
where n is less than 65535.
The following predefined locations can be examined:

• %RO - %Rll
• \
•
•
• IBm

General registers 0-11

• %AP

Argument Po inter

•

%FP

Frame Po inter

• %SP
• %PC
• %PSL

Stack Po inter

Last value
Current location
Logical predecessor
Logical successor

Program Counter
Processor Status Longword

Format
EXAMINE

[/qualifier]

[address-expression]

Command Qualifiers
/ASCII: 1 ength
/BYTE
/DECIMAL
/HEXADEC !MAL
/INSTRUCTION
/LONG
/NOSYMBOLIC
/OCTAL
/SYMBOLIC
/WORD
Command Parameters
address-expression
Specifies the address whose contents are to be examined.
The
address is usually given symbolically as a scalar variable name
or component of a structured variable type.
You can examine
array elements or record fields but not whole arrays or records;
except for variables of the type PACKED ARRAY
[l •• n]
OF CHAR,
which are displayed as ASCII strings.
5-31

DEBUGGING PASCAL PROGRAMS

Command Qualifiers
/ASCII:length
Specifies that the data value is to be interpreted as an ASCII
string.
The length specifies the number of bytes of memory to be
examined and the number of characters to be displayed.
It is
interpreted in the radix specified by a command qualifier that
precedes the /ASCII qualifier or in the current radix.
If length
is omitted, the debugger assumes a length of 4.
The number of
characters actually displayed is limited by the maximum size of
the debugger's output line, 132 characters.
/BYTE
Specifies that the data value is to be interpreted as a byte
integer.
The contents of each byte of the value examined is
displayed in the radix mode specified by a command qualifier or
in the current radix mode.
/DECIMAL
Specifies that the radix is decimal.
The debugger displays all
numbers and
interprets all numbers in the command in decimal
radix.
/HEXADECIMAL
Specifies that the radix is hexadecimal.
The debugger displays
all numbers and
interprets all numbers in the command
in
hexadecimal radix.
/INSTRUCTION
Specifies that the contents of memory should be displayed as
VAX-11 MACRO instructions. The debugger attempts to decode the
address specified as an instruction.
If the debugger can decode
the
instruction,
it displays the instruction.
If the debugger
cannot decode the instruction, it displays a warning message.
The length of the instruction displayed varies depending on the
opcode and addressing modes.
/LONG
Specifies that the data value is to be interpreted as a
longword
integer.
The contents of each longword (4 bytes) of the value
examined is displayed in the radix mode specified by a command
qualifier or in the current radix mode.
/NOSYMBOLIC
Specifies that addresses should be displayed as absolute virtual
addresses.
The debugger displays the addresses being examined
and any addresses in decoded
instructions as absolute virtual
addresses.
/OCTAL
Specifies that the radix is octal.
The debugger displays all
numbers and interprets all numbers in the command in octal radix.

5-32

DEBUGGING PASCAL PROGRAMS
/SYMBOLIC
Specifies that addresses should be displayed as symbols or
offsets from symbols.
The debugger displays the addresses being
examined and any addresses in decoded instructions as symbols or
offsets from symbols.
/WORD
Specifies that the data value is to be interpreted as a word
integer.
The contents of each word
(2 bytes) of the value
examined is displayed in the radix mode specified
in a command
qualifier or in the current radix mode.

Examples
1.

DBG> EXAMINE Flight Number
FLIGHT\FLIGHT FLIGHT_NUMBER:lO
The contents of variable Flight_Number are displayed.

DBG> EXAMINE Entered Flight
FLIGHT\FLIGHT Entered_Flight:O
The contents of Entered_Flight are displayed.

DBG> EXAMINE Flights[l].Reservations~.Name
FLIGHT\FLIGHT FLIGHTS[l].Reservation ~.Name : Jones
The contents of the field Reservation~.Name in the record
specified by the first element of the array Flights are examined.

DBG> EXAMINE 600
600: 1
The contents of the nonsymbolic virtual address 600 (decimal)
examined.

are

DBG> EXAMINE
ARRVAR[2]:2.5
The contents of the logical successor
(the next
here} of the current location are displayed.

5-33

array

element

DEBUGGING PASCAL PROGRAMS

EXIT
5.3.14

EXIT Command

The EXIT command lets you exit from the debugger when you are ready to
terminate a debugging session. You must use this command to return to
DCL command level.
Format
EXIT
Command Parameters
None.
Command Qualifiers
None.
Examples
DBG> GO
%DEBUG-I-EXITSTATUS is %SYSTEM-S-NORMAL, normal successful completion
DBG> EXIT
The debugging session is terminated by the EXIT
end of normal program execution.

5-34

command

the

DEBUGGING PASCAL PROGRAMS

GO
5.3.15

GO Command

The GO command starts the execution
session.

program

for

debugging

Format
GO

[address-expression]

Command Parameters
address-expression
Specifies the address at which execution is to begin;
if no
address is specified, execution begins at the current location.
Command Qualifiers
None.
NOTE
You must not restart a program from the
beginning unless you first exit from the
debugger.
Otherwise,
unpredictable
results may occur.
Examples
DBG> GO
routine start at MAIN\MAIN
break at MOD1\MOD1\%LINE 3
The debugger responds to the GO command by indicating that
execution started at the routine MAIN\MAIN and that a breakpoint
has been reached in module MODl\MODl .at line 3.

5-35

DEBUGGING PASCAL PROGRAMS

HELP
5.3.16

HELP Command

The HELP command displays a description of the command specified.
can also get descriptions of command parameters and qualifiers.

You

The HELP command displays a description of debugger commands, their
format, and the parameters and qualifiers you can use with them. You
can find out the topics that have help descriptions by entering the
HELP ~ommand with no topics.
Format

HELP topic

[subtopic ••• ]

Command Parameters

topic
Specifies the command that you want information about.
subtopic
Specifies the command keyword, qualifier, or parameter that you
want information about. If you want information about a specific
qualifier, specify the qualifier (including the initial slash) as
the subtopic.
If you want information about all qualifiers or
all parameters, specify QUALIFIER or PARAMETER, respectively. If
you want all the information about a command, specify an asterisk
(*) as the subtopic.
Command Qualifiers

None.

5-36

DEBUGGING PASCAL PROGRAMS
Examples
DBG> HELP GO
GO
Starts or continues program execution.
If the GO command is specified without an address-expression as a
parameter, execution resumes at the point of suspension or, in
the case of debugger start-up, at the transfer address.
If the GO command is specified with an address-expression as a
parameter, execution resumes at the location denoted by the
address-expression.
Note that using an address-expression as a
parameter
in the GO command can produce unpredictable results if
the state of your program required to commence execution at the
location specified by the address-expression is not identical to
the state of your program at the time the GO command is issued.
Format:

GO [[address-expression]]
Additional information available:
Parameters

5-37

DEBUGGING PASCAL PROGRAMS

SET BREAK
5.3.17

SET BREAK Command

The SET BREAK command specifies a label, line number, or address at
which program execution is to be suspended. This location is called a
breakpoint. The DO command-string specifies one or more of the
debugger commands that are to be performed when the breakpoint is
reached.
Note that you cannot set breakpoints, tracepoints, or watchpoints at
the same location.
The most recently issued command overrides any
other.
Format
SET BREAK [/qualifier] address-expression [DO(command-string [;command-string] ••• )]

Command Qualifiers
/AFTER: count
.Command Parameters
address-expression
Specifies the address at which the program
execution
is
suspended.
Note that execution is suspended just before the
specified address.
Section 5.1.4 describes how addresses are
specified.
DO{command-string)
Tells the debugger to perform the specified debugger command{s)
specified by the command-string when the breakpoint is reached.
Command Qualifiers
/AFTER:count
Specifies that the debugger should not stop execution until
the
breakpoint is reached the number of times specified by count.
Examples
1.

DBG> SET BREAK %LINE 100 DO(EXAMINE Total;

EXAMINE Area)

In this example, the values of the variables Total and Area are
displayed when the breakpoint at line 100 is reached. The line
number is located on the source and machine-code listings.

5-38

DEBUGGING PASCAL PROGRAMS
2.

DBG> SET BREAK/AFTER:3 %LINE 20
You can use the /AFTER qualifier to control when a breakpoint
takes effect.
For instance, if you set a breakpoint on a line
that is in the body of a WHILE loop, and you want the breakpoint
to occur the third time through the loop, specify the /AFTER
qualifier with a value of 3, as shown in this example.
Note that if you use the /AFTER qualifier, the breakpoint is
reported not only the nth time it is encountered, but also every
time it is encountered thereafter.

5-39

DEBUGGING PASCAL PROGRAMS

SET EXCEPTION BREAK
5.3.18

SET EXCEPTION BREAK Command

The SET EXCEPTION BREAK command specifies exceptions (conditions that
interrupt execution of your program)
as breakpoints.
For more
information on exceptions,
refer to the VAX/VMS System Services
Reference Manual and the VAX-11 Run-Time Library Reference Manual.
Format
SET EXCEPTION BREAK
Command Parameters
None.
Command Qualifiers
None.
Examples
DBG> SET EXCEPTION BREAK
A breakpoint will occur when an exception occurs
execution.

5-40

during

program

DEBUGGING PASCAL PROGRAMS

SET LANGUAGE
5.3.19

SET LANGUAGE Command

The SET LANGUAGE command tells the debugger to conduct
according to the conventions of the specified language.
language is the language of the main program.
Format
SET LANGUAGE language-name
Command Parameters
language-name
Specifies the language to be used.
Command Qualifiers
None.
Examples
DBG> SET LANGUAGE PASCAL
The current language is set to PASCAL.

5-41

the dialog
The default

DEBUGGING PASCAL PROGRAMS

SET LOG
5.3.20

SET LOG Command

The SET LOG command specifies the name of the log file that the
debugger uses when the output is directed to the log file.
A log file
contains a copy of all the user's commands and the debugger responses
during a debugging session.
The SET LOG command controls only the name of the log file;
it does
not control whether a log file
is being written. The SET OUTPUT
command (5.3.23) does this.
By default, the debugger uses the file
name DEBUG and the file type LOG.
If the debugger is currently
creating a log file and you enter SET LOG,
the debugger closes the
existing log
file.
A new file is opened using the newly specified
file name and all subsequent debugger commands are recorded in the new
log file.
Format
SET LOG file-spec
Command Parameters
file-spec
Specifies the name of the log file.
You must enclose the file
specification in quotation marks or apostrophes only if the file
specification begins with a special symbol
(such as a square
bracket) •
Command Qualifiers
None.
Examples
DBG> SET LOG CALC.DBG
DBG> SET LOG "[CODEPROJ]FEB29.TMP"
Log
files
are
created
"[CODEPROJ]FEB29.TMP."

with

5-42

the

names

CALC. DBG

and

DEBUGGING PASCAL PROGRAMS

SET MODE
5.3.21

SET MODE Command

The SET MODE command sets the default entry and display modes.
The
entry and display modes control the current radix and whether
addresses and instruction operands are displayed symbolically or as
absolute virtual addresses.
The default radix controls how the
debugger interprets numbers· that you enter and how it displays
numbers.
You can override the current radix mode by using a
radix mode
qualifier
in a DEPOSIT, EVALUATE, or EXAMINE command or by specifying
a radix control operator (%X, %0, %B).
In SYMBOLIC mode, addresses are displayed as symbols,
virtual
addresses or offsets from symbolic locations.
The debugger first
looks for an exact match with a local symbol or a global symbol.
If
no exact match can be found, the debugger searches for the sym_bol
whose value is less than the address and closest to it.
If it cannot
find
any symbolic definition,
it displays the address as a virtual
address in the current radix mode.
Probable causes of the debugger
displaying a virtual address are that-the module's symbols are not
included in the the debugger symbol
table or that the address is
outside the program's address space.
In NOSYMBOLIC mode, addresses are displayed as virtual addresses in
the current radix mode.
Note that you can always enter symbolic
addresses even when the mode is NOSYMBOLIC.

Format
SET MODE mode-keyword

[,mode-keyword]

Command Parameters
mode-keyword
Specifies the entry and display mode.

Mode-keyword can be:

•

DECIMAL -- Sets the current radix to decimal

•

HEXADECIMAL -- Sets the current radix to hexadecimal

•

OCTAL -- Sets the current radix to octal

•

NOSYMBOLIC -- Specifies that addresses should be displayed
absolute virtual addresses

•

SYMBOLIC -- Specifies that addresses should
offsets from symbolic locations

Command Qualifiers
None.

5-43

displayed

DEBUGGING PASCAL PROGRAMS

Examples
DBG> SET MODE DEC,NOSYM
The modes decimal and nosymbolic are set as the current entry and
display modes.

5-44

DEBUGGING PASCAL PROGRAMS

SET MODULE
5.3.22

SET MODULE Command

The SET MODULE command 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 local
symbols of the main program unit which contains the entry point or the
point at which execution begins.
Format
SET MODULE

[/qualifier]

['module-name

[,module-name ••• ]]

Command Qualifiers
/ALL
Command Parameters
module-name
Specifies the name of the module whose symbols are to be included
in the symbol table. A PASCAL module-name is either a program or
a module.
Command Qualifiers
/ALL
Tells the debugger to use the symbols of all known
(linked)
modules.
If there is insufficient space, the debugger displays
an error message.
Examples
1.

DBG> SET MODULE MAIN, MODI
The symbols from the program units MAIN and MODI are added to the
active symbol table.

DBG> SET MODULE/ALL
All the symbols from the programs and modules are included in the
active symbol table.

5-45

DEBUGGING PASCAL PROGRAMS

SET OUTPUT
5.3.23

SET OUTPUT Command

The SET OUTPUT command controls whether the debugger displays output
on the terminal or writes it to a log file and controls whether the
debugger echoes commands in command procedures.
When the debugger is initiated, all responses are displayed on the
terminal, no log file
is created, and command procedures and DO
command-string sequences are not echoed on the terminal.
The log file contains all the commands that you enter at a
terminal
and all the responses of the debugger. The log file does not contain
the DBG> prompt.
The debugger's responses are preceded by an
exclamation mark.
To reproduce a debugging session, you can use the
log file as a command procedure.
Format
SET OUTPUT option

[,option ••• ]

Command Parameters
option
Specifies the mode of output.
Option can be
VERIFY, or the negative form of each.

LOG,

TERMINAL,

•

LOG -- starts writing output to the log file.
The log file
contains all the commands that you enter at the terminal and
all debugger responses.
The debugger responses are preceded
by an exclamation mark (comment indicator) to allow you to use
the log file as a command procedure.
The default setting,
NOLOG, inhibits output to the log file.

•

TERMINAL -- starts writing output to the terminal.
The
default setting, TERMINAL, causes all the debugger responses
to be displayed on the terminal.
The NOTERMINAL parameter
causes the debugger to stop displaying all responses except
error messages on the terminal. The NOTERMINAL parameter is
useful when you want to write output only to a log file.
If
you specify SET OUTPUT NOLOG, NOTERMINAL,
the
debugger
displays a warning message telling you that output is being
lost.

•

VERIFY -- causes the debugger to echo commands executed from
command procedures and DO command-string sequence of SET BREAK
commands. The commands are displayed on the terminal and
written to the log file depending on the other options
specified for the SET OUTPUT command.
The default setting,
NOVERIFr, causes the debugger to not echo commands as they are
executed in a command procedure or DO command-string sequence.

Command Qualifiers
None.

5-46

DEBUGGING PASCAL PROGRAMS
Examples
1.

DBG> SET OUTPUT NOLOG ,TERMINAL ,VERIFY
The output is displayed on the terminal, commands, procedures,
and DO command-string sequence of SET BREAK commands are echoed,
and a log file is not produced.

DBG> SET OUTPUT LOG
The log file is to be created.

5-47

DEBUGGING PASCAL PROGRAMS

SET SCOPE
5.3.24

SET SCOPE Command

The SET SCOPE command specifies scopes to be searched to find a
symbol.
By default, the debugger searches for symbols (specified
without pathnames) in the current scope (the scope that contains the
current PC).
If the debugger does not find the symbol, it searches
its symbol table for a unique symbol. When you enter SET SCOPE,
the
debugger modifies its search rules:
it searches the scopes in the
order you specify.
If it does not find the symbol in these scopes, it
then searches for a unique symbol.
SET SCOPE command allows you to modify the default symbol search. You
can specify the default scope (scope 0) in any position in the scope
list. You can also specify that global symbols be searched in any
position in the scope list by using the backslash (\) character.
If the debugger cannot find a symbol in the scopes specified with the
SET SCOPE command,
it searches all the modules in the active symbol
table for a unique symbol. There is no way to suppress the search for
a unique symbol.

Format
SET SCOPE scope-element

[,scope-element ••• ]

Command Parameters
scope-element
Specifies the name of a scope, the digit O, a backslash
(\), or
the number of a scope. These scope elements have the following
meanings:
•

Name of scope -- in general, consists of a module name and
block or routine names separated by backslashes. The simplest
case is a scope consisting of a module name. When you specify
a name of scope, the debugger adds the symbols for the module
specified to the symbol table if they are not already
included.

•

0 -- specifies the current scope, the scope that contains the
current PC.
The current scope is used as the default scope if
you enter the CANCEL SCOPE command. The current scope changes
as different sections of your program are executed.

•

\ -- specifies the scope consisting of all the global
defined in your image.

•

Number of scope -- specifies scope by the level of active
calls.
The number 0 represents the scope currently being
executed;
the number 1 represents the scope that contained
the call to the current scope; the number 2 represents the
scope that contained the call before that.

Command Qualifiers
None.

5-48

symbols

DEBUGGING PASCAL PROGRAMS

Examples
1.

DBG> SET SCOPE MOD3
This command sets the scope to MOD3

You can also define a scope list to specify the
the debugger should search for symbols.

order

which

DBG> SET SCOPE MOD1\MAR,MOD2\JAN,MOD2\FEB
The command above instructs the debugger to search for symbols
first in the context of routine MAR.
If the debugger cannot find
a specified symbol in MAR, the debugger continues the search in
JAN and, if necessary, FEB.
The scope defined in a SET SCOPE command becomes the default
scope for all symbolic addresses until you explicitly change or
cancel the scope.
Note that when you explicitly use SET SCOPE to set the scope to a
program unit name, the debugger implicitly performs a SET MODULE
command. Therefore, symbols for the program unit specified
in
your SET SCOPE command are placed in the symbol table.
However,
if you use the debugger's default scope, you must also use the
SET MODULE command
(Section 5.3.22)
to place symbols for the
program unit other than the main program in the symbol table.

5-49

DEBUGGING PASCAL PROGRAMS

SET STEP
5.3.25

SET STEP Command

The SET STEP command specifies the current default step conditions.
The SET STEP command controls how the unit of the program is to be
executed (INSTRUCTION or LINE), whether a called procedure or a
subroutine is treated as a series of instructions or as a single
instruction (INTO or OVER). You can override the current default step
condition by specifying a mode qualifier in the STEP command.
Format
SET STEP

[qualifier(s)]

Command Qualifiers
INSTRUCTION
INTO
LINE
[NO] SYSTEM
OVER
Command Parameters
None.
Command Qualifiers
INSTRUCTION
Tells the debugger to step
instruction by instruction.

through

the

program

VAX-11

MACRO

INTO
Tells the debugger to step through routines when one
that is, it is to step into the subprogram.

called;

LINE
Tells the debugger to step through the
This is the default for VAX-11 PASCAL.

program

line

line.

[NO] SYSTEM
Tells· the debugger to count steps wherever they occur,
system address space. The default is NOSYSTEM.

including

OVER
Tells the debugger to ignore calls to routines as it steps
through the program. That is, it is to step over the call.

5-50

DEBUGGING PASCAL PROGRAMS
Examples
DBG> SET STEP INTO
The debugger is to step into routines when it encounters
calls.

5-51

routine

DEBUGGING PASCAL PROGRAMS

SET TRACE
5.3.26

SET TRACE Command

The SET TRACE command specifies the location at which the debugger
is
to suspend program execution, display that the tracepoint has been
reached, and resume execution.
Note that you cannot set tracepoints, watchpoints or breakpoints at
the same location.
The most recently issued command overrides any
other.

Format
SET TRACE

[/qualifier]

[address-expression]

Command Qualifiers
/BRANCH
/CALL

Command Parameters
address-expression
Specifies the location at which the tracepoint is located.

Command Qualifiers
/BRANCH
Traces all branch, jump, and case instructions in the image.
/CALL
Traces all instructions that call routines in the image.

5-52

DEBUGGING PASCAL PROGRAMS
Examples
DBG> SET TRACE %LABEL 10
DBG> GO
routine start at MAIN\MAIN
trace at %label 10

The tracepoint is established at label 10.
In response to the GO
command, the debugger displays the routine it is in and the
starting point of the trace.
DBG>

SET TRACE CIRCLE

DBG> SET TRACE/BRANCH
DBG> SET TRACE/CALL
DBG> SHOW TRACE
tracepoint at CIRCLE\CIRCLE
tracing
tracing

/CALL instructions: CALLS, CALLG, BSBW, BSBB, JSB, RSB
and RET
/BRANCH instructions: BNEQ, BEQL,
BGTR,
BLEQ,
BGEQ,
BLSS,
BGTRU,
BLEQU, BVC, BVS, BGEQU, BLSSU, BRB, BRW,
JMP, BBS, BBC, BBSS, BBCS, BBSC,
BBCC,
BBSSI,
BBCCI,
BLBS, BLBC, ACBB~ ACBW, ACBL, ACBF, ACBD, AOBLEQ,
AOBLSS, SOBGEQ, SOBGTR, CASEB, CASEW and CASEL

5-53

DEBUGGING PASCAL PROGRAMS

SET TYPE
5.3.27

SET TYPE Command

The SET TYPE command sets the default types for
EXAMINE commands.
The SET TYPE command sets the
in the symbol
there is no assigned data type
TYPE/OVERRIDE command sets the default type for
DEPOSIT and EXAMINE commands.

the DEPOSIT and
default type when
table.
The SET
all data items in

Format
SET TYPE

[/qualifier]

type-keyword

Command Qualifiers
/OVERRIDE
Command Parameters
type-keyword
Specifies the default
data
type.
Type-keyword
ASCII:length, BYTE, INSTRUCTION, LONG, or WORD.

can

•

ASCII:length -- Specifies that the default data type
is an
ASCII string.
The number of characters in the string is
specified by length.
If you do not specify length, the
debugger assumes a length of 4.

•

BYTE -- Specifies that the default data type is byte integer.

•

INSTRUCTION -- Specifies
instruction.

•

LONG -- Specifies that
integer.

•

WORD -- Specifies that the default data type is word integer.

that
the

the

default

data

data
type

type
is

longword

Command Qualifiers
/OVERRIDE
Specifies that the specified data type should be used even when a
symbol has an assigned data type in the symbol table.
The CANCEL
TYPE/OVERRIDE command cancels the effects of SET TYPE/OVERRIDE
and specifies that the debugger should use the symbol's assigned
default data type.

5-54

DEBUGGING PASCAL PROGRAMS
Examples
1.

DBG> SET TYPE ASCII:8
The type is set ASCII with a string length of 8 characters.

DBG> SET TYPE/OVERRIDE LONG
The type LONG is to be used even if the symbol
data type.

5-55

has

assigned

DEBUGGING PASCAL PROGRAMS

SET WATCH
5.3.28

SET WATCH Command

The SET WATCH command allows you to monitor a specific
determine ·when that location's value is changed.

location

Note that you cannot set watchpoints, tracepoints, and breakpoints at
the same location.
The most recently issued command overrides any
other.

Format
SET WATCH var

Command Parameters
var
Specifies the location to be monitored.
You cannot monitor
variables declared
in a procedure or function because these
variables are allocated on the stack.
However,
variables
declared at the program or module level or variables dynamically
allocated by the NEW procedure can be monitored because these
variables are allocated
in static storage.
If a variable is
located on the same memory page as a PASCAL file variable, a file
system error can occur when the file variable is accessed.
If the value of the location being monitored changes, the
debugger stops program execution and displays the modifying
statement, the location's old value, and
its new value.
The
debugger then prompts for another command.

Command Qualifiers
None.

Examples
DBG> SET WATCH Area
DBG> GO
write to MAIN\AREA at PC=000002C4
old value
12
new value = 16
DBG>
A watchpoint is set for the location Area in module MAIN.
During
execution of the program, the value of Area changed from 12 to
16.

5-56

DEBUGGING PASCAL PROGRAMS

SHOW BREAK
5.3.29

SHOW BREAK Command

The SHOW BREAK command displays
currently set in the program.

the

location

Format
SHOW BREAK
Command Parameters
None.
Command Qualifiers
None.
Examples
DBG> SHOW BREAK
breakpoint at MOD1\MOD1\%LINE 3
The breakpoint is at LINE 3 of module MODl.

5-57

all

breakpoints

DEBUGGING PASCAL PROGRAMS

SHOW CALLS
5.3.30

SHOW CALLS Command

The SHOW CALLS command displays a traceback list of procedures and
function calls.
This traceback list shows you the sequence of calls
leading to the current subprogram from the most recent call to
the
first call.
Format
SHOW CALLS

[integer]

Command Parameters
integer
Specifies the number of most recent calls to be displayed.
call count is not specified, all the calls are displayed.

Command Qualifiers
None.
Examples
D8G> SHOW CALLS
module name

routine name

line

relative PC

absolute PC

MAIN

MOD2

00000002

00000880

MAIN

MODl

0000006C

00000863

The first line in the report refers to the
One call, at line 10, preceded this level.

5-58

current

call

level.

DEBUGGING PASCAL PROGRAMS

SHOW LANGUAGE
5.3.31

SHOW LANGUAGE Command

The SHOW LANGUAGE command displays the current language
is currently interpreting.

the

Format
SHOW LANGUAGE
Command Parameters
None.
Command Qualifiers
None.
Examples
DBG> SHOW LANGUAGE
language:
PASCAL
The debugger displays the current language as PASCAL.

5-59

debugger

DEBUGGING PASCAL PROGRAMS

SHOW LOG
5.3.32

SHOW LOG Command

The SHOW LOG command displays the log
debugger is writing to the log file.

file

Format
SHOW LOG
Command Parameters
None.
Command Qualifiers
None.
Examples
DBG> SHOW LOG
logging to FEB29.TMP
The log file being used is FEB29.TMP.

5-60

name

and

whether

the

DEBUGGING PASCAL PROGRAMS

SHOW MODE
5.3.33

SHOW MODE Command

The SHOW MODE command displays the current radix mode and the
symbolic or nonsymbolic mode.

current

The current modes are those last established by the SET MODE
or the default modes associated with the current language.

command

Format

SHOW MODE
Command Parameters

None.
Command Qualifiers

None.
Examples

DBG> SHOW MODE
modes: symbolic, hexadecimal
The debugger displays that the mode is symbolic, hexadecimal.

5-61

DEBUGGING PASCAL PROGRAMS

SHOW MODULE
5.3.34

SHOW MODULE Command

The SHOW MODULE command displays the names of all program units
symbols are potentially available to the symbol table.

whose

The SHOW MODULE command displays the following information about each
program or module in the image compiled with the /DEBUG qualifier.
•

The module's name

•

The symbols that are or are not in
(yes/no)

•

The language the module is written in

•

The size of the module's active symbol table in bytes

•

The total number of modules

•

The amount of memory that
symbol table

can

the

still

active

symbol

allocated

for

table

the

Format
SHOW MODULE
Command Parameters
None.
Command Qualifiers
None.
Examples
DBG> SET MODULE Main, Modl
DBG> SHOW MODULE
Symbols

Language

Size

MAIN

yes

PASCAL

204

MODI

yes

PASCAL

164

MOD2

PASCAL

184

total modules:

Module Name

remaining size:

61568.

In this example, there are three PASCAL modules.
Modules Main
and Modl have symbols in the active symbol table: Mod2 symbols
are not included in the symbol table.
The run-time symbol table
has 61568 bytes of remaining space allocated.

5-62

DEBUGGING PASCAL PROGRAMS

SHOW OUTPUT
5.3.35

SHOW OUTPUT Command

The SHOW OUTPUT command displays the output configurations and reports
whether the debugger is displaying output on the terminal, writing
output to a log file, or verifying command procedures or
DO
command-string sequences.
Format
SHOW OUTPUT
Command Parameters
None.
Command Qualifiers
None.
Examples
DBG> SHOW OUTPUT
output:

no verify, terminal, not logging into DEBUG.LOG

The debugger is not verifying command
procedures
or
DO
command-string sequences, the log file is not in use, and output
is to a terminal.

5-63

DEBUGGING PASCAL PROGRAMS

SHOW SCOPE
5.3.36

SHOW SCOPE Command

The SHOW SCOPE command displays the routines that are currently set as
scope.

Format
SHOW SCOPE

Command Parameters
None.

Command Qualifiers
None.

Examples
1.

DBG> SHOW SCOPE
scope: MOD2,MOD1
The message the debugger returns shows that the current scope
is
set first to MOD2,
then to MODI.
The debugger checks for a
symbol in the module MOD2 first.

DBG> SHOW SCOPE
scope: 0 [ = MOD2\MULT]
The symbol 0 shows that the current scope is the default
the default scope is routine MULT in program unit MOD2.

5-64

scope;

DEBUGGING PASCAL PROGRAMS

SHOW STEP
5.3.37

SHOW STEP Command

The SHOW STEP command displays the current default step conditions.
Format
SHOW STEP
Command Parameters
None.
Command Qualifiers
None.
Examples

DBG> SHOW STEP
step type: no system, by instruction, over routine calls
The debugger is skipping address reserved for the system,
is
stepping through the program by instruction, and is skipping over
routines calls.

5-65

DEBUGGING PASCAL PROGRAMS

SHOW TRACE
5.3.38

SHOW TRACE Command

The SHOW TRACE command displays either the location (as a line number,
label, or hexadecimal address) of all active tracepoints or a message
indicating there are no active tracepoints.
Format
SHOW TRACE
Command Parameters
None.
Command Qualifiers
None.
Examples
DBG> SHOW TRACE
tracepoint at %LINE 20
tracepoint at %LINE 25
The tracepoints are located at lines 20 and 25.

5-66

DEBUGGING PASCAL PROGRAMS

SHOW TYPE
5.3.39

SHOW TYPE Command

The SHOW TYPE command displays the current default data type. If you
specify the /OVERRIDE qualifier, the debugger displays the current
default override data type.
If the data type is /ASCII:length, the debugger displays length
decimal number even if the current radix is not decimal.
Format
SHOW TYPE

[/qualifier]

Command Qualifiers
/OVERRIDE
Command Parameters
None.
Command Qualifiers
/OVERRIDE
Displays the current override default data type.
Examples
DBG> SHOW TYPE
type: long integer
The data type now being used is long integer.

5-67

DEBUGGING PASCAL PROGRAMS

SHOW WATCH
5.3.40

SHOW WATCH Command

The SHOW WATCH command displays all the watch points that are active
and
the size of each watchpoint in number of bytes. A watchpoint
remains active until a CANCEL WATCH command is issued, or a SET BREAK
or SET TRACE command is given for the same location, or the debugging
session ends.
Format
SHOW WATCH
Command Parameters
None.
Command Qualifiers
None.
Examples
DBG> SHOW WATCH
Watchpoint at MOD\ROUT\AREA for 4 bytes
A watchpoint has been established for AREA in the routine ROUT in
the module MOD.
AREA is 4 bytes long.

5-68

DEBUGGING PASCAL PROGRAMS

STEP
5.3.41

STEP Command

The STEP command allows you
statements.

execute

predetermined

number

You can specify the qualifiers each time you issue a STEP command, or
you can use one SET STEP command to set the conditions for a series of
STEP commands.
Refer to Section 5.3.25 for the SET STEP command.
Format
STEP [qualifier(s)]

[integer]

Command Qualifiers
INSTRUCTION
INTO
LINE
[NO]SYSTEM
OVER
Command Parameters
integer
Specifies the number of statements to be executed.
If you
specify 0 or omit the integer, a default of 1 is assumed.
Note,
however, that if you issue a STEP command while your program is
stopped
in a module whose symbols are not in the active symbol
table, VAX-11 MACRO instructions
(not PASCAL statements)
are
executed.
Command Qualifiers
INSTRUCTION
Tells the debugger to step through
instruction.

the

program

instruction

INTO
Tells the debugger to step through routines when one
That is, it is to step into the subprogram.

called.

LINE
Tells the debugger to step through the
This is the default for VAX-11 PASCAL.

program

line

line.

[NO] SYSTEM
Tells the debugger to count steps wherever they occur,
system address space.
The default is NOSYSTEM.

5-69

including

DEBUGGING PASCAL PROGRAMS

OVER
Tells the debugger to ignore calls to routines as it steps
through the program. That is, it is to step over the call.

Examples
1.

DBG> SET STEP INSTRUCTION, INTO, SYSTEM
In this example, the debugger overrides the defaults applicable
to PASCAL programs. When you subsequently issue a STEP command
without qualifiers, these qualifiers (INSTRUCTION, INTO, and
SYSTEM)
are in effect.
You can, however, supersede them
individually by including a qualifier in a STEP command.

DBG> STEP/LINE 10
This example tells the debugger to execute 10
of the SET STEP command.

lines,

regardless

Sometimes it is advisable to use STEP to execute only a few
instructions at a time. To execute many instructions and stop,
use a SET BREAK command to set a breakpoint, and then issue a GO
command to execute all statements up to the breakpoint.

5-70

DEBUGGING PASCAL PROGRAMS

@file-spec
5.3.42

@file-spec Command

The @file-spec command directs the debugger to begin
from a specified command procedure.

taking

commands

Format
@file-spec
Command Parameters
file-spec
Specifies the name of a VAX/VMS file containing
commands. The default file type is COM.

the

debugger

Command Qualifiers
None.
Examples
The command procedure DBGPROG.COM contains the following debugger
commands:
SET BREAK %LINE 10
GO
EXAMINE A" .NAME
EXAMINE A"'.ADDRESS
EXAMINE A"'.SSNUMBER
GO
During a debugging session to execute the commands in this
you would enter:

file,

DBG> @DBGPROG.COM
The commands from this file are executed as if
each of the commands yourself.

5-71

you

had

entered

DEBUGGING PASCAL PROGRAMS

5.4

A DEBUGGING EXAMPLE

This section presents a debugging example
using
the
program
Flight Reservation to track reservations for 10 different flights.
The program prompts for input of a flight number, passenger name, and
class of reservation desired.
When 0 is entered for the flight
number, the program should terminate. A bug has been included in this
program for the purpose of demonstrating how to use the VAX-11
Symbolic Debugger to find a logic error in a program.
Figure 5-3 is the source listing for Flight Reservation and Figure 5-4
is an actual interactive debugging session.
The circled numbers
correspond to the text that follows the figures and gives a detailed
description of the debugging session.
PROGRAM Flight Reservations (INPUT, OUTPUT);
CONST
Alfa Length
3 O;
Maximum length of a name }
Max Flights
10 different flights possible }
= 10;
Max-Reservations
100;
Maximum number of reservations per flight
TYPE
Alfa
=PACKED ARRAY[l •• Alfa_Length] OF CHAR;
Flight Class
= (Standby,Coach,Business,First);
Reservation Pointer = AReservation Record;
Reservation-Record = RECORD
Name
: Alfa;
Class
: Flight Class;
Next_Reservation: Reservation_Pointer;
END;
Flight_Description = RECORD
Flight Number
Number-Of Reservations
Reservations

INTEGER;
INTEGER;
Reservation_Pointer;

END;
Flight Range
Flight=List

1. • Max Flights;

ARRAY[Flight_Range] OF Flight_Description;

VAR
Current Reservation
Entered-Flight
Accepting Reservations
Flights -

Reservation Pointer;
INTEGER;
-{ Requested flight number }
BOOLEAN;
{ True = Still accepting reservations
Flight_List;

PROCEDURE Initialize Flights;
{ PURPOSE:
Initialize the flight reservation array}
VAR
Flight

: Flight_Range;

{ Current flight record }

BEGIN { Initialize_Flights }
FOR Flight := 1 TO Max Flights DO
WITH Flights[Flight] DO
BEGIN
Flight Number
:= Flight;
{The array index is the flight number }
Number Of Reservations
:= O;
Reservations
:= Nil;
END;
END; { Initialize_Flights }

Figure 5-3

Source Program for the Program Flight_Reservations

5-72

DEBUGGING PASCAL PROGRAMS
FUNCTION Flight Available (Flight To Check : INTEGER) : BOOLEAN;
{ PURPOSE:
.
- Check whether or not a particular flight is open
PARAMETERS:
Flight_To_Check - Flight number to check for }
LABEL l;
VAR
Flight

{ Index into Flights array }

: INTEGER;

BEGIN { Flight_Available
Fl ight_Available : = False; { Assume the flight won't be available }
FOR Flight := 1 TO Max Flights DO
WITH Flights[Flight] DO
IF Flight To Check = Flight Number
THEN
- IF (Number Of Reservations + 1) <= Max Reservations
THEN
- BEGIN
Flight Available := True;
GOTO lT
{ Exit
.END;
1:

END; { Flight_Available }
FUNCTION Reservations Available : BOOLEAN;
PURPOSE:
Check whether or not all flights are full
FUNCTION VALUE:
True
There are still open flights
False = There are no more open flights}
LABEL l;
VAR
Flight

: INTEGER;

. { Index in Flights array }

BEGIN { Reservations_Available
Reservations_Available := False;

{ Assume no more open flights }

FOR Flight := 1 TO Max Flights DO
WITH Flights[Flight] DO
IF Number Of Reservations < Max_Reservations
THEN
- BEGIN
Reservations Available := True;
GOTO 1;
{ Exit }
END;
1:

END;

Reservations Available

Figure 5-3(Cont.)

Source Program for the Program Flight_Reservations

5-73

DEBUGGING PASCAL PROGRAMS
FUNCTION Read Reservation (VAR Reservation : Reservation_Pointer)
BOOLEAN;
{ PURPOSE:
Read reservation information from the terminal.
PARAMETERS:
Reservation - Pointer to a reservation record (output parameter)
FUNCTION VALUE:
True = The reservation can be made
False
= The reservation cannot be made }
BEGIN { Read_Reservation
Allocate space for the reservation }
NEW(Reservation);
WITH ReservationA DO
BEGIN
Next Reservation := Nil;
{ Prompt for and read reservation information }
WRITELN;
WRITE ('Enter Flight Number:');
READ (Entered Flight);
IF Entered FlTght = 0 THEN
Read Reservation := False
ELSE IF NOT Flight Available(Entered Flight)
THEN
BEGIN
WRITELN('
Flight•, Entered Flight: 1,
Read Reservation := False;
END
ELSE

is full.');

{ Read the rest of the reservation information }
BEGIN
WRITELN;
WRITE ('
Name: ') ;
READ (Name);
WRITE('
Class:');
READ(Class);
Read Reservation := True;
END;
END; { WITH Current_ReservationA
END; { Read_Reservation }

Figure 5-3(Cont.)

Source Program for the Program Flight_Reservations

5-74

DEBUGGING PASCAL PROGRAMS
PROCEDURE Enter Reservation (Reservation : Reservation Pointer);
- { PURPOSE:
Enters a reservation in the reservation data base
PARAMETERS:
Reservation

- Pointer to the reservation to enter }

LABEL l;
VAR
Flight

: INTEGER;

{ Index into Flights array }

BEGIN { Enter_Reservation
FOR Flight := 1 TO Max Flights DO
WITH Flights[Flight) DO
IF Flight Number = Entered_Flight
THEN
BEGIN
Number Of Reservations
:= Number Of Reservations + l;
ReservationA.Next Reservation :=Reservations;
Reservations
:= Reservation;
GOTO l;
{ Exit }
END;
1:

END; { Enter_Reservation }
BEGIN { Flight_Reservations
Initialize_Flights;
Accepting Reservations := True;
WHILE Accepting Reservations DO
BEGIN
IF Read Reservation(Current Reservation)
THEN
Enter Reservation(Current Reservation);
IF Accepting Reservations
THEN
Accepting_Reservations := Reservations_Available;
END;
END. { Flight_Reservations }

Figure 5 - 3 (Cont • )

Source Program for the Program Flight_Reservations

5-75

DEBUGGING PASCAL PROGRAMS
$RUN FLIGHT
VAX-11 DEBUG VERSION 2.3
%DEBUG-I-INITIAL, language is PASCAL, module set to 'FLIGHT_RESERVATIONS'

«»

DBG> GO
ENTER

Flight Number : 1
Name
Smith
Class : First

ENTER
ENTER

Flight Number : 0
Flight=Number :~z

%PAS-F-ERRACCFIL, error in accessing file PAS$INPUT
%RMS-F-EOF, end of file detected
DBG> EXIT . ,
$RUN FLIGHT
VAX-11 DEBUG VERSION 2.3
%DEBUG-I-INITIAL, language is PASCAL, module set to 'FLIGHT RESERVATIONS'
DBG> SET BREAK Read Reservation
DBG> SET BREAK Enter Reservation

DBG> SET BREAK Reservations Available

DBG> GO
routine start at FLIGHT RESERVATIONS
routine break at FLIGHT=RESERVATIONS\FLIGHT_RESERVATIONS\READ RESERVATION
DBG> STEP 7
routine start at

FLIGHT RESERVATIONS\READ RESERVATION
ENTER Flight Number: 1
stepped to FLIGHT_RESERVATIONS\READ_RESERVATION %LINE 140

DBG> STEP
start at FLIGHT RESERVATIONS\READ RESERVATION %LINE 140
stepped to FLIGHT_RESERVATIONS\READ_RESERVATION %LINE 142
DBG> EXAMINE Entered Flight
FLIGHT_RESERVATIONS\~LIGHT_RESERVATIONS\ENTERED_FLIGHT:

•

DBG> STEP 16
start at FLIGHT RESERVATIONS\READ RESERVATION %LINE 142
-Name: Smith
Class: First
routine break at FLIGHT_RESERVATIONS\FLIGHT_RESERVATIONS\ENTER_RESERVATION

Figure 5-4

Interactive Debugging Session for the
Program Flight_Reservations

5-76

DEBUGGING PASCAL PROGRAMS

The program Flight Reservations is compiled and linked using the
/DEBUG qualifier.- The debugger is entered by using the command
RUN FLIGHT.
The debugger responds with its version number, the date, a
message that the initial programming language is PASCAL and the
main module is Flight_Reservations.
The debugger now has control of the program, and the prompt
replaces the dollar sign ($) prompt on the screen.

•
0

DBG>

In this first session, the program Flight Reservations
is
executed using only the debugger command GO. This allows you to
observe the functioning of the program without interruption.
After receiving the GO command, the debugger gives control to the
program which executes as it would normally. The program prompts
for
input (the flight number, name, class). On the next request
for a flight number, a 0 is entered which should signal the
program to stop requesting
input and to terminate execution.
However, the program fails to act as expected because another
prompt for
input occurs. The CTRL/Z command is issued to exit
from the program and return control to the debugger •
To reenter the program, first exit from the debugger
EXIT command and then, reissue the RUN command.

using

the

To debug the program, the next step is to set breakpoints at
places where results need to be verified, such as functions and
procedures.
In this session, the breakpoints are set
at
Read_Reservation, Enter_Reservation, and Reservations_Available.
Once the breakpoints have been established, the command GO is
issued.
The debugger responds with the starting point address
and execution of the program stops when a breakpoint is reached.
The address of the first breakpoint is then displayed.

The debugger halts at the breakpoint and prompts for a command.
The command STEP 7 is issued.
This command instructs the
debugger to continue program execution. The next seven lines of
code from the routine Read Reservation are processed.
Program
execution starts at the BEGIN instruction of the function
Read Reservation.
The
debugger
displays
the
starting
address
in
the
Read Reservation module.
The program requests input for the
variable Entered Flight. The value assigned to the variable
Entered Flight Ts verified using the EXAMINE command.
The
debugger responds with the value 1.

The command STEP 16 continues execution of the program until
the
16th line of executable code from the current address is reached.
The debugger responds with the starting address in the module and
the program prompts for a name and class.

5-77

DEBUGGING PASCAL PROGRAMS

DBG> STEP
routine start at FLIGHT RESERVATIONS\ENTER RESERVATION
stepped to FLIGHT_RESERVATIONS\ENTER_RESERVATION %LINE 178
DBG> EXAMINE ReservationA.Name
FLIGHT_RESERVATIONS\FLIGHT_RESERVATIONS\ENTER_RESERVATION\RESERVATIONA.NAME: 'Smith'
DBG> EXAMINE ReservationA.Class
FLIGHT_RESERVATIONS\FLIGHT_RESERVATIONS\ENTER_RESERVATION\RESERVATIONA.CLASS: FIRST
DBG> SET BREAK Enter_Reservation\%LABEL 1
DBG> GO
start at FLIGHT RESERVATIONS\ENTER RESERVATION %LINE 178
break at FLIGHT=RESERVATIONS\FLIGHT_RESERVATIONS\ENTER_RESERVATION\%LABEL 1
DBG> EXAMINE Flights[l].Number Of Reservations
FLIGHT_RESERVATIONS\FLIGHT_RESERVATIONS\FLIGHTS[l].NUMBER_OF_RESERVATIONS: 1
DBG> EXAMINE Flights[l].ReservationsA.Name
FLIGHT_RESERVATIONS\FLIGHT_RESERVATIONS\FLIGHTS(l].RESERVATIONSA.NAME:

' Smith'~

DBG> EXAMINE
FLIGHT_RESERVATIONS\FLIGHT_RESERVATIONS\FLIGHTS[l].RESERVATIONSA.CLASS: FIRST
DBG> GO
start at FLIGHT RESERVATIONS\ENTER RESERVATION %LINE 189
routine break at FLIGHT_RESERVATIONS\FLIGHT_RESERVATIONS\RESERVATIONS_AVAILABLE
DBG> STEP 6
A
routine start at FLIGHT RESERVATIONS\RESERVATIONS AVAILABLE
"'
stepped to FLIGHT_RESERVATIONS\RESERVATIONS_AVAILABLE %LINE 108
DBG> EXAMINE Reservations Available
FLIGHT_RESERVATIONS\FLIGHT_RESERVATIONS\RESERVATIONS_AVAILABLE:

TRUE

DBG> GO
start at FLIGHT RESERVATIONS\RESERVATIONS AVAILABLE %LINE 108
routine break at FLIGHT_RESERVATIONS\FLIGHT_RESERVATIONS\READ_RESERVATION
DBG> STEP 7
routine start at FLIGHT RESERVATIONS\READ RESERVATION
ENTER Flight Number : 0
stepped to FLIGHT_RESERVATIONS\READ_RESERVATION %LINE 140
DBG> STEP
start at FLIGHT_RESERVATIONS\READ_RESERVATION %LINE 140
stepped to FLIGHT_RESERVATIONS\READ_RESERVATION %LINE 141

DBG> EXAMINE Entered Flight
FLIGHT_RESERVATIONS\FLIGHT_RESERVATIONS\ENTERED_FLIGHT: 0
DBG> GO
start at FLIGHT RESERVATIONS\READ RESERVATION %LINE 141
routine break at FLIGHT_RESERVATIONS\FLIGHT_RESERVATIONS\RESERVATIONS_AVAILABLE

Figure 5-4 (Cont.)
Interactive Debugging Session for the
Program Flight_Reservations

5-78

DEBUGGING PASCAL PROGRAMS

The STEP command is given.

C»

The fields ReservationA.Name and ReservationA.Class are examined.

A new
breakpoint
is
set
at
LABEL 1
in
the
module
Enter Reservation and the GO command continues execution of the
procedure Enter Reservation.
The contents of the array Flights
are verified by-the EXAMINE command when LABEL 1 is reached.

C»

The contents of the array Flights are displayed by the use of
EXAMINE commands.
In each case, the debugger responds with the
pathname, array element name, and the value contained
in that
element.
The field ReservationsA.Class is examined by simply entering
EXAMINE followed by a return.
The debugger displays the contents
of the next logical successor, which is ReservationA.Class.
Program execution is resumed with the GO command and continues
until
the debugger encounters the next breakpoint.
The debugger
responds with the starting point address and the address of the
breakpoint reached in Reservation_Available.
The function Reservations Available is executed when the command
STEP 6 is given.
The command EXAMINE displays the contents of
the field Reservations Available as TRUE.
the
Program execution is resumed with the GO command until
breakpoint at the beginning of the routine Read Reservation is
encountered.
The command STEP 7 is given to step through seven lines of
executable code of the routine Read Reservations to the point
where the prompt for input is displayed~
The program requests
the
input for Flight Number. A 0 is entered indicating that the
last reservation has been entered.
The debugger displays the
current
address after executing six lines in the routine
Read Reservation.

The STEP command is given and the contents of Entered_Flight
examined.
Entered_Flight contains a O.

are

The GO command causes program execution to
resume
breakpoint Reservations Available is encountered.

the

5-79

until

DEBUGGING PASCAL PROGRAMS
DBG> EXAMINE Accepting_Reservations
FLIGHT_RESERVATIONS\FLIGHT_RESERVATIONS\ACCEPTING_RESERVATIONS: TRUE

41»

DBG> SET BREAK Reservations_Available\%LABEL 1 Cl!)

DBG> GO
routine start at FLIGHT RESERVATIONS\RESERVATIONS AVAILABLE
break at FLIGHT_RESERVATIONS\FLIGHT_RESERVATIONS\RESERVATIONS_AVAILABLE\%LABEL 1
DBG> EXAMINE Reservations_Available
FLIGHT_RESERVATIONS\FLIGHT_RESERVATIONS\RESERVATIONS_AVAILABLE\RESERVATIONS_AVAILABLE: TRUE
DBG> DEPOSIT Reservations_Available = FALSE ~
DBG> EXAMINE Reservations Available
FLIGHT_RESERVATIONS\FLIGHT_RESERVATIONS\RESERVATIONS_AVAILABLE\RESERVATIONS_AVAILABLE: FALSE
DBG> CANCEL BREAK/ALL ~
DBG> GO
•
start at FLIGHT RESERVATIONS\RESERVATIONS AVAILABLE %LINE 111
%DEBUG-I-EXITSTATUS, is '%SYSTEM-S-NORMAL~ normal successful completion'
DBG> EXIT
$

Fig u r e 5 - 4 ( Cont • ) Interactive Debugging Session for the
Program Flight_Reservations

5-80

DEBUGGING PASCAL PROGRAMS
The contents of the field Accepting Reservations are examined.
The debugger displays the contents-of Accepting Reservations as
TRUE.
The bug has been found because this field should have been
set to FALSE when the flight number 0 was entered in the module
Read Reservation.
To verify that this is the bug, the contents of the field
Reservations Available are changed and the program is run to
completion as described below.

Cl)

A breakpoint at LABEL 1 is
established
in
the
module
Reservations Available.
The module and label names are used as
the address Tn a SET BREAK command.

Program execution is started with the GO command.
The
of Reservations Available are displayed as being TRUE.
The
DEPOSIT
command
Reservations Available.
command.

contents

places
the
value
FALSE
into
The change is verified by the EXAMINE

The CANCEL BREAK/ALL command terminates all breakpoints, to allow
the program to run to completion without halting.
The program must be edited,
recompiled, and relinked to
test
whether this error was in fact the only incorrect logic in the
program.

To verify, the program execution is started with the GO command.
At completion of the run, the debugger responds with the message
that normal and successful completion of the program
has
occurred.

The EXIT command is given to end the debugger session.

5-81

CHAPTER 6
INPUT AND OUTPUT

This chapter describes input and output (I/O) for VAX-11 PASCAL.
In
particular,
it provides information about PASCAL I/O in relation to
VAX-11 Record Management Services (VAX-11 RMS).
The topics covered
include:

6.1

•

Logical names

•

PASCAL file characteristics

•

PASCAL record formats

•

OPEN procedure parameters

•

Local interprocess communication by means of mailboxes

•

Remote communication by means of DECnet-VAX

LOGICAL NAMES

The VAX/VMS operating system provides the logical name mechanism as a
way of making programs device and file independent.
If you use
logical names, your program need not specify the particular device on
which a
file resides or the particular file that contains data.
Specific devices and files can be defined at run time.
A logical name is an alphanumeric string, .up to 63 characters long,
that you specify in place of a file specification. The operating
system provides a number of predefined logical names,
already
associated with file specifications.
Table 6-1 lists the logical
names of special interest to PASCAL users.
Logical names provide great flexibility because they can be associated
not only with a complete file specification, but also with a device, a
device and a directory, or even another logical name.

6-1

INPUT AND OUTPUT

Table 6-1
Predefined System Logical Names
Meaning

Name

Default

SYS$DISK

Current default device

As specified by the
user

SYS$ERROR

Default error message file

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

SYS$COMMAND

Default command input stream

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

SYS$INPUT

Default input file

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

SYS$0UTPUT

Default output file

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

You can create a logical name and associate it with a
file
specification by means of the ASSIGN command. Thus, before program
execution, you can associate the logical names in your program with
the file specifications appropriate to your needs.
For example:
$ ASSIGN

DBAO: [SMITH]Test.DAT;2

Data

This command creates the logical name Data and associates it with the
file specification DBAO: [SMITH]Test.DAT;2.
The system uses this file
specification when it encounters the logical name Data during program
execution. For example:
OPEN (Indata, 'Data' ,HISTORY:= OLD);
In executing this PASCAL statement, the system uses the
file
specification DBAO: [SMITH]Test.DAT;2 for the logical name Data. To
specify a different file when you execute the program again,
issue
another ASSIGN command.
For example:
$ ASSIGN DBA2: [JONES]Real.DAT;7

Data

This command associates the logical name Data with a different file
specification and replaces the previous logical name assignment. The
OPEN
statement
above
will
now
refer
to
the
file
DBA2: [JONES]Real.DAT;7.
You can also assign logical names with the MOUNT and
(see the VAX/VMS Command Language User's Guide).

6.2

DEFINE

commands

are

organized

FILE CHARACTERISTICS

A clear distinction must be made between the way files
and the way records are accessed.

6-2

INPUT AND OUTPUT
The term "file organization" applies to the way records are physically
arranged on a storage device.
The term "record access" refers to the
method used
to read
records from or write records to a file,
regardless of the file's organization.
A file's organization is
specified when the file is created and cannot be changed.
Record
access is specified each time the file is opened and can vary.

6.2.1

File Organization

VAX-11 PASCAL supports sequential file organization.
Sequential files
consist of records arranged in the order 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).
Records can only be added at the end of a new file,
with a
HISTORY equal to NEW.

6.2.2

Record Access

You specify record access mode as a parameter to the OPEN
VAX-11 PASCAL provides two ways of accessing records:
•

Sequential

•

Direct

procedure.

If you select sequential access mode, records are written to or read
from the file,
starting at the beginning and continuing through the
file one record after another.
Sequential access to a file means that you can read a particular
record only after reading all the records preceding it. New records
can be written only at the end of a file that is open for sequential
access.
If you select direct access mode, you can specify the order in which
records are accessed;
Each FIND procedure call must include the
relative record number indicating the record to be read.
You can
directly access a
file only if it contains fixed-length records,
resides on disk, and is open for input (reading).

6.3

RECORD FORMATS

Records are stored in one of two formats:
o

Fixed length

Variable length

You can access fixed-length records in either sequential or direct
mode.
Variable-length records can be accessed only in sequential
mode.

6-3

INPUT AND OUTPUT
6.3.1

Fixed-Length Records

When you specify fixed-length records (see Section 6.4.4), you are
specifying that all
records in the file contain the same number of
bytes.
A file opened for direct access must contain fixed-length
records, to allow the record location to be computed correctly.

6.3.2

Variable-Length Records

Variable-length records can contain any number of bytes, up to
the
buffer size specified when the file was opened. Variable-length
records are prefixed by a count field, indicating the number of bytes
in the record.
The count field comprises 2 binary bytes on a disk
d.evice and 4 decimal digits on magnetic tape.
The value stored in the
count field indicates the number of data bytes in the record.

6.4

OPEN PROCEDURE PARAMETERS

This section supplements the description of the OPEN procedure that
appears
in
the
VAX-11 PASCAL Language Reference Manual.
In
particular, it describes how the VAX-11 Record Management Services
(VAX-11 RMS) affect VAX-11 PASCAL.
For more information, refer to the
VAX-11 Record Management Services Reference Manual.
The OPEN procedure has the following formats:
1.

OPEN (file-variable, 'VAX/VMS-file-spec',
file-status,
record-length,
record-access-mode,
record-type,
carriage-control);

OPEN (FILE VARIABLE := file-variable
[,FILE NAME := file-name]
[,HISTORY := file-status]
[,RECORD LENGTH :=record-length]
[,RECORD-ACCESS MODE := record-access-mode]
[,RECORD=TYPE :~record-type]
[,CARRIAGE_CONTROL := carriage-control]

File status, record
length,
record-access mode,
record type, and
carriage control are VAX-11 RMS-dependent attributes described in this
section.

6.4.1

File Status or History

The file-status or history parameter indicates whether the specified
file exists or must be created.
The possible values for this
parameter are:
NEW
OLD
A file status of NEW indicates that a new file must be created
the specified characteristics. NEW is the default value.

6-4

with

INPUT AND OUTPUT
A file status of OLD indicates that an existing file is to be opened.
An error occurs if the file cannot be found. A type of OLD is illegal
for internal files, which are newly created each time the declaring
program unit is executed.

6.4.2

Record Length

The record length parameter is an integer that specifies the maximum
record size in bytes for a text file.
The default for a VAX-11 PASCAL
text file is 133 bytes. For a nontext file this parameter has no
meaning.

6.4.3

Record-Access Mode

The record-access mode parameter specifies the mode of access
records in the file.
The possible values for this parameter are:

SEQUENTIAL
DIRECT
The default record access mode is SEQUENTIAL.
In SEQUENTIAL mode, you
can access files that have fixed- or variable-length records.
DIRECT mode allows you to use the FIND procedure to read files with
fixed-length records.
You cannot access a file with variable-length
records in DIRECT mode.

6.4.4

Record Type

The record-type parameter specifies the structure
file.
The possible values for this parameter are:

records

FIXED
VARIABLE
A value of FIXED indicates that all records in the file have the same
length.
A value of VARIABLE indicates that the records within the
file can vary in length. VARIABLE is the default for a new file.
For
an existing file, the default is the record type associated with the
file at its creation.

6.4.5

Carriage Control

The carriage-control parameter specifies the type of carriage control
in effect for an output text file.
The possible values for this
parameter are:
LIST
CARRIAGE
FORTRAN
NOCARRIAGE
NONE

6-5

INPUT AND Otrl'PUT
A value of LIST indicates that each record is preceded by a line feed
and followed by a carriage return when the file is output to a
terminal or line printer.
LIST is equivalent to the VAX-11 RMS record
attribute CR.
LIST is the default for all text files.
The values of CARRIAGE or FORTRAN indicate that the first byte of each
record contains a carriage control character. CARRIAGE or FORTRAN is
equivalent to the VAX-11 RMS record attribute FTN.
Table 6-2 lists
the carriage-control characters.
Table 6-2
Carriage Control Characters
Meaning

Character

starts output at the beg inning of the

'+'

Overprinting:
current line

space

Single spacing:
the next line

starts output at the

'0'

Double spacing:

skips a line before starting output

'1'

Paging:

'$'

Prompting: starts output at the beg inning of the
next line, and suppresses carriage return at the end
of the line

beginning

starts output at the top of a new page

Characters other than those in Table 6-2 are ignored.
The values of NOCARRIAGE or NONE indicate that the record contains no
carriage control information. NOCARRIAGE or NONE is equivalent to the
VAX-11 RMS record attribute PRN with all bits equal to zero.

6.5

LOCAL INTERPROCESS COMMUNICATION: MAILBOXES

The exchange of data between processes is often useful;
to synchronize execution or to send messages.

for

example,

A mailbox is a record-oriented, pseudo-I/O device that allows data to
be passed from one process to another. Mailboxes are created by the
Create Mailbox (SYS$CREMBX) system service (see Section 7.2.1 for an
example using SYS$CREMBX).
This section describes how to send and
receive data using mailboxes.
Data transmission by means of mailboxes is synchronous;
that is, a
PASCAL program that writes a message to a mailbox must wait until that
message is read, and a program that reads a message from a mailbox
must wait until a message is written. When the writing program closes
the mailbox, an end-of-file condition is returned to the reading
program. VAX-11 RMS ensures that the message transmission is complete
before it returns control to the user program.

6-6

INPUT AND OUTPUT
For example:
PROGRAM Mail (MBX, OUTPUT);
VAR MBX : TEXT;
BEGIN
OPEN (MBX, 'Mailbox', HISTORY:= OLD, ACCESS METHOD:= SEQUENTIAL);
RESET (MBX);
WHILE NOT EOF (MBX) DO
BEGIN
WHILE NOT EOLN (MBX) DO
BEGIN
WRITE (MBXA);
GET (MBX)
END;
WRITELN;
GET (MBX)
END;
CLOSE (MBX)
END.

This program reads messages from a mailbox known by the logical name
Mailbox.
The messages are lines of text, which are then printed at
the user's terminal.

6.6

COMMUNICATING WITH REMOTE COMPUTERS:NETWORKS

If your computer is one of the nodes in a DECnet network, you can use
VAX-11 PASCAL I/O procedures to communicate with other nodes in the
network.
These procedures allow you to exchange data with a program
at the remote computer
(task-to-task communication) and to access
files at the remote computer (resource sharing).
Both task-to-task communication and resource sharing between systems
are transparent.
That is, these intersystem exchanges do ·not appear
to be different from local interprocess and file-access exchanges.
To communicate across the network, specify a node name
element of a file specification.
For example:

the

first

Boston::DBAO: [SMITH]Test.DAT;2
Remote task-to-task communication requires a special form of file
specification.
You must use the notation TASK= in place of the device
name and supply the task name, as in the following example:
Boston::"TASK=UNA"
The example specifies the task named UNA on the
network.

BOSTON

node

the

The following program fragment shows how messages can be received from
a remote program by means of VAX-11 PASCAL I/O procedures.
OPEN (FILE VARIABLE:=Netjob,
FILE NAME:;'Boston::"TASK=UNA"' ,HISTORY:=OLD);
RESET (Netjob);
Rdat := NetjobA;
NET Proc (Rdat,Wrtdat);
CLOSE (Netjob);

6-7

INPUT AND OUTPUT
The effect of these statements is to establish a link with a job
(TASK) named UNA at the node BOSTON and to receive a component from
the file variable associated with the remote program.
The variable
RDAT contains the data.
Then the procedure Net Proc is called to
process the data and the link is broken.
The next example shows how you can write a remote
PASCAL I/O procedures.

file

using

VAX-11

PROGRAM UPDATE (Newdat, Branch);
VAR Newdat
Branch

FILE OF INTEGER;
FILE OF INTEGER;

BEGIN
OPEN (Newdat,'NEWDAT.DAT',HISTORY:=OLD);
RESET (Newdat);
OPEN (Branch,'Nashua"PLUGH XYZZY"::Master.Dat',HISTORY:=NEW);
REWRITE (Branch);
WHILE NOT EOF(Newdat) DO
BEGIN
BranchA:=NewdatA;
GET (Newdat);
PUT (Branch)
END;
CLOSE (Branch);
CLOSE (Newdat)
END.
The sample program writes records in a remote file at the node Nashua.
It reads data from a local file known by the logical name Newdat and
writes the data across the network to the remote file Master.DAT in
the directory [PLUGH] with password XYZZY.
If you use logical names in·your program, you can equate the logical
names with either local or remote files.
Thus, if your program
normally accesses a remote file, and the remote node
becomes
unavailable, you can bring the volume set containing the file to the
local site. You can then mount the volume set and assign the
appropriate logical name. For example:
Remote Access
$ASSIGN REM::APPLIC SET:file-name

LOGIC

Local Access
$ MOUNT device-name APPLIC SET
$ ASSIGN APPLIC SET:file-name LOGIC
The MOUNT and ASSIGN commands are described in detail in
Command Language User's Guide.

the

VAX/VMS

DECnet capabilities are described in the DECnet-VAX Reference Manual.

6-8

CHAPTER 7
CALLING CONVENTIONS

In the context of the VAX/VMS operating system, a procedure is a
routine entered by a CALL instruction.
In a PASCAL program, such a
routine can be a function or procedure written in PASCAL, a
function
or procedure written in some other language, a VAX/VMS system service,
or a VAX-11 Run-Time Library procedure.
In many cases, procedures
perform calculations that are used widely and repeatedly in many
applications.
In PASCAL, you can write each procedure once and call
it from many other programs.
This chapter describes how to call procedures that are not written in
PASCAL and provides information on calling VAX/VMS system services and
VAX-11 Run-Time Library procedures. See the VAX-11 PASCAL Language
Reference Manual for
information on defining and invoking PASCAL
functions and procedures.
The material presented here assumes some knowledge of procedure
calling and argument passing mechanisms. You should be familiar with
these subjects before you attempt to use the features described
in
this chapter.
Refer to the VAX-11 Run-Time Library Reference Manual
and the VAX-11 Architecture Handbook for more information.

7.1

VAX-11 PROCEDURE CALLING STANDARD

Programs compiled by the VAX-11 PASCAL compiler conform to the
standard defined for VAX-11 procedure calls (see Appendix C of the
VAX-11 Architecture Handbook). This standard prescribes how arguments
are passed, how function values are returned, and how procedures
receive and return control. VAX-11 PASCAL also provides features that
allow programs to call system services and procedures written in other
native-mode languages supported by VAX/VMS.
VAX-11 PASCAL uses the VAX-11 CALLS instruction to call procedures.
Appendix B illustrates the events that occur during a procedure call
and show the structure of the run-time stack after each event.

7.1.1

Argument Lists

Each time you call a procedure, VAX-11 PASCAL constructs an argument
1 ist.
The VAX-11 procedure calling standard defines an' argument 1 ist
as a sequence of longword (4-byte) entries. The first byte of the
first entry in the list is an argument count, which indicates how many
arguments follow in the list.

7-1

CALLING CONVENTIONS
The arguments in the list are based on the passing mechanisms
specified in the formal parameter list and the values in the actual
parameter list. The argument list contains the arguments actually
passed to the procedure.

7.1.2

Parameter Passing Mechanisms

Non-PASCAL procedures require arguments as addresses,
immediate
values, or descriptors. The VAX-11 procedure calling standard defines
three mechanisms by which arguments are passed to procedures:
1.

By-reference -- The argument list entry is the address of the
value.

By-immediate-value -- The argument list entry is the value.

By-descriptor -- The argument list entry is the address of
descriptor of the value.

The following sections describe what you must specify in your VAX-11
PASCAL program to correctly pass arguments to non-PASCAL subprograms
using each of these mechanisms. Note that this information pertains
only to subprograms written in languages other than PASCAL. For
information about passing arguments to PASCAL subprograms
from
non-PASCAL programs, see Section 7.1.5.
Refer to the VAX-11 PASCAL
Language Reference Manual for a description of parameter passing
between PASCAL subprograms.

7.1.2.l By-Reference Mechanism - The by-reference mechanism passes
the address of the actual parameter. By default, PASCAL uses this
mechanism to pass all parameters except dynamic array parameters. You
can invoke the by-reference mechanism in two ways:
1.

By omitting the mechanism specifier from the formal parameter
list. This syntax implies PASCAL by-value semantics.

By using the VAR specifier in the formal parameter
This syntax implies PASCAL by-reference semantics.

list.

If you omit the mechanism specifier, PASCAL passes the address of the
actual parameter.
PASCAL expects the called procedure to copy the
value from the specified address to local storage.
You should use
this method only if the called procedure does not change the value of
the corresponding actual parameter.
When you omit the mechanism
specifier, the actual parameter can be an expression.
For example, the following
function
function call use this method:

declaration

FUNCTION MTH$TANH (Angle : REAL):REAL;

and

corresponding

EXTERN;

Tanh := MTH$TANH (Radians);
This example declares the VAX-11 Run-Time Library function MTH$TANH as
an external subprogram.
The MTH$TANH function returns, as a real
value, the hyperbolic tangent of its argument. The input parameter to
this function is the size of the angle (in radians), and it must be
passed by-reference. Because the function MTH$TANH does not change
the value of the angle, you can omit the mechanism specifier when you
declare the function.
The returned value is assigned to the variable

7-2

CALLING CONVENTIONS
Tanh by the assignment statement shown.
(See Section 7.3 for more
information on calling Run-Time Library procedures.)
Use the VAR specifier to pass an actual parameter that can be changed
by the execution of the procedure. You must use VAR when passing a
file variable as a parameter. The VAR specifier is also useful
to
prevent the copying of large parameters.
Specify VAR in the following
format:
VAR formal-parm-list : type;
The formal parameter list specifies one or more formal parameters of
the indicated type.
Each of these parameters will be passed using the
by-reference mechanism and with by-reference semantics.
When you call the procedure, the argument list contains the address of
the value to be passed.
The actual parameter must be a variable or a
component
of
an
unpacked,
structured
variable;
constants,
expressions, procedure names, and function names are not allowed.
The following declarations and corresponding function call show how to
pass an address to an external routine.
TYPE Bit64 =PACKED ARRAY [1 •• 2] OF INTEGER;
VAR Systime : Bit64;
FUNCTION SYS$GETTIM (VAR Bintim

Bit64)

INTEGER;

EXTERN;

STATUS := SYS$GETTIM (Systime);
This example declares the Get Time (SYS$GETTIM) system service, which
returns the system time.
The actual parameter Systime is a 64-bit
variable into which the system service writes the time.

7.1.2.2 By-Immediate-Value Mechanism - VAX/VMS system services and
Run-Time Library procedures sometimes require that the calling program
pass an immediate value, that is, the value itself. To direct PASCAL
to pass a value
instead of an address, use the %IMMED mechanism
specifier, as follows:
%IMMED formal-parm-list : type;
The formal parameter list specifies one or more formal parameters of
the
indicated type.
Variables that require more than 32 bits of
storage, including all file variables, cannot be passed as immediate
values.
%IMMED can be used for value parameter only.
You can use
%IMMED only when declaring external non-PASCAL routines.
When you call the routine, the actual parameter list contains the
value of each parameter for which you specified %IMMED.
The actual
parameter can be a constant, a variable, or an expression. Note that
%IMMED can also modify procedure and
function formal
names, as
described in Section 7.1.3.

7-3

CALLING CONVENTIONS
The following declarations and cerresponding function call show how to
pass an immediate value to a system service procedure.
VAR Event_Flag : INTEGER;
FUNCTION SYS$WAITFR (%IMMED EFN : INTEGER)

INTEGER; EXTERN;

STATUS := SYS$WAITFR (Event_Flag);
This example declares the wait for Single Event Flag
(SYS$WAITFR)
system service, which waits for a single event flag.
SYS$WAITFR
requires one value parameter, the number of the event flag
for which
to wait.
This number is passed as an immediate value, copied from the
integer variable Event_Flag.

7.1.2.3 By-Descriptor Mechanism - The by-descriptor mechanism passes
the address of a string, array, or scalar descriptor, as described in
Appendix C of the VAX-11 Architecture Handbook.
VAX-11 PASCAL
includes
the
%STDESCR
mechanism specifier for passing string
descriptors and the %DESCR mechanism specifier for passing array and
scalar descriptors. You cannot pass a component of a packed structure
using either of these specifiers. You can use these specifiers only
with non-PASCAL subprograms. Note that, by default, PASCAL passes an
array descriptor to a formal dynamic array parameter.
To pass a string descriptor, specify %STDESCR as follows:
%STDESCR formal-parm-list : type;
The formal parameter list specifies one or more parameters of the
indicated type.
Only string constants, packed character arrays with
subscripts from 1 to n, and packed dynamic character arrays with
subscripts of an integer or integer subscript type can be passed by
string descriptor.
When you call the procedure, the argument list contains the address of
each string descriptor.
For example, the Broadcast {SYS$BRDCST)
system service requires two string descriptors as parameters:
TYPE Msgtype =PACKED ARRAY[l •• 80] OF CHAR;
PACKED ARRAY[l •• 6] OF CHAR;
Dev type
VAR Message : Msgtype;
Terminal : Devtype;
FUNCTION SYS$BRDCST {%STDESCR MSG
MSGTYPE;
%STDESCR DEV
DEVTYPE):
INTEGER; EXTERN;
STATUS := SYS$BRDCST (Message, Terminal);
The %STDESCR specifier indicates that both parameters must be passed
by string descriptor. The actual parameters Message and Terminal are
packed arrays of 80 and 6 characters, respectively.
Routines written in other high-level languages may require array or
scalar descriptors. To pass an array or scalar descriptor, use %DESCR
in the following format:
%DESCR formal-parm-list

type;

7-4

CALLING CONVENTIONS
The formal parameter list specifies one or more parameters of the
indicated scalar or array type. The type can be any predefined scalar
type or an unpacked array (fixed or dynamic) of a predefined scalar
type.
The argument list contains the address of the descriptor of an
array or scalar variable.
The following example shows how an array descriptor might be passed to
a FORTRAN subroutine.
TYPE Foray= ARRAY [1 •• 10,1 •• 10] OF CHAR;
PROCEDURE Formatrix (%DESCR ARRDES : Foray); FORTRAN;
The FORTRAN subroutine Formatrix expects the array to be
by-descriptor. A call to Formatrix might be the following:

passed

Formatrix (Chararr);
The actual parameter Chararr specifies a character array, and the
argument list contains the address of a descriptor for this array.
(Note that VAX-11 FORTRAN treats character parameters as CHARACTER*l
variables.)

7.1.3

Passing Functions and Procedures as Parameters

You can pass procedure and function names as immediate values
routines written in other languages, using the following format:

%IMMED PROCEDURE procedure-name-list;
%IMMED FUNCTION function-name-list :

type;

The procedure name list specifies the name of one or more formal
procedure parameters.
The function name list specifies the name of
one or more formal function parameters of the
indicated type.
The
corresponding actual parameter lists specify the names of the actual
procedures and functions to be passed as parameters.
For example:
PROCEDURE Forcaller (%IMMED PROCEDURE Utility);

FORTRAN;

The FORTRAN subroutine Forcaller calls a PASCAL procedure and requires
that the name of the procedure be passed as an immediate value.
The
argument list contains the address of the PASCAL procedure's entry
mask. A call to the FORTRAN procedure might be:
Forcaller (Printer);
Any subprogram passed with %IMMED should access only its own variables
and those declared at program level.
For information on passing procedure and function names between PASCAL
subprograms, see the VAX-11 PASCAL Language Reference Manual.

7-5

CALLING CONVENTIONS
7.1.4

Function Return Values

A function returns a value to the calling program by assigning
that
value to the function's name. The value must be a scalar, subrange,
or pointer type; structured types are not allowed.
The method by
which a value is returned depends on its type, as listed below.

7.1.5

Type

Return Method

Integer, real,
single, character,
Boolean, pointer,
user-defined scalar

General Register RO

Double

RO: Low-order result
Rl: High-order result

Passed Arguments to PASCAL Subprograms

When calling a PASCAL subprogram from a non-PASCAL subprogram, you
must ensure that the arguments are in the correct form.
By default,
VAX-11 PASCAL expects most parameters to be passed by-reference.
For a PASCAL value parameter (declared without a mechanism specifier),
the argument list must contain the address of the value.
The PASCAL
subprogram will copy the value from the passed address upon entry.
For a VAR parameter, the argument list must contain the address of the
variable.
The subprogram does not copy the value, but instead uses
the address to access the actual parameter variable. Actual parameter
variables that can change in value as a result of subprogram execution
must be passed in this manner.
In addition, all files must be passed
as PASCAL VAR parameters.
For a
formal
procedure or function parameter
(indicated by the
PROCEDURE or FUNCTION specifier), the argument list must specify the
address of the bound procedure value, which consists of two longwords.
The first longword contains the address of the entry mask for the
subprogram;
the second longword contains the environment pointer.
(This process implements the VAX-11 by-reference mechanism for a
procedure or function.)
For a formal dynamic array parameter, the argument list
the address of an array descriptor.

7.2

must

contain

CALLING VAX/VMS SYSTEM SERVICES

You can declare any VAX/VMS system service as an external function or
procedure and then call it from your PASCAL program. When declaring a
system service, specify an identifier in the following form:
SYS$service-name
For example, the name of the $FAQ system service is SYS$FAO.

7-6

CALLING CONVENTIONS
You pass parameters to the system service according to its particular
requirements: a value, an address, or the address of a descriptor may
be needed, as described
in Section 7.1.2.
To
invoke the system
service, use a function or procedure call in your PASCAL program.
See
the VAX/VMS System Services Reference Manual for a full description of
each system service.
The system provides three
files
containing
condition
symbol
definitions.
When you declare a system service or Run-Time Library
procedure, you should specify the appropriate file
in the CONST
section to define the condition values in your PASCAL program.
Use
the %INCLUDE directive to specify the file name, as described
in the
VAX-11 PASCAL Language Reference Manual.
The ·three files are SYS$LIBRARY:LIBDEF.PAS,
SYS$LIBRARY:MTHDEF.PAS,
and SYS$LIBRARY:SIGDEF.PAS, as described below.
SYS$LIBRARY:LIBDEF.PAS
This file contains definitions for all condition symbols from the
general
utility Run-Time Library procedures.
These symbols have the
form:
LIB$_xyz
For example:
LIB$ NOTFOU
SYS$LIBRARY:MTHDEF.PAS
This file contains definitions for all condition symbols from
mathematical procedures library. These symbols have the form:

the

MTH$_xyz
For example:
MTH$_SQUROONEG
SYS$LIBRARY:SIGDEF.PAS
This file contains miscellaneous symbol definitions used in
handlers.
These symbols have the form:

condition

SS$_xyz
For example:
SS$ FLTOVF

7.2.1

Calling System Services by Function Reference

In most cases, you will want to declare a system service as a function
so that you can check its return status.
Each system service returns
a VAX-11 condition value indicating whether completion was successful.
These condition values can be interpreted as integer codes that
correspond to symbolic names such as SS$ ACCVIO.
Odd numbered codes
indicate successful completion and even numbered codes indicate
failure.

7-7

CALLING CONVENTIONS
For example, the following procedure
Mailbox (SYS$CREMBX) system service.

defines

and

calls

the

Create

PROCEDURE Create_Mailpox;
CONST %INCLUDE 'SYS$LIBRARY:SIGDEF.PAS'
TYPE Status = (Int Stat, Bool_Stat);
Word= 0 •• 65535;
Sub63 = 1 •• 63;
Chan Stat = (Int Chan,Dummy_Chan);
Chan-Type = PACKED RECORD
-CASE Chan Stat OF
Int Chan : (Chan No : INTEGER);
Dummy_Chan
(Bot_Chan : Word)
END;
VAR Mbx Rec : RECORD
CASE Status OF
Int Stat : (Mbx Int : INTEGER);
BooT Stat : (Mbx_Bool : BOOLEAN)
END;
Chan_Rec : Chan_Type;
FUNCTION SYS$CREMBX (%IMMED PRMFLG : INTEGER;
Var Chan : Chan Type;
%IMMED Maxmsg, Bufquo, Promsk, Acmode : INTEGER;
%STDESCR Lognam : PACKED ARRAY [Sub63] OF CHAR):
INTEGER; EXTERN;
BEGIN
WITH Mbx Rec DO BEGIN
Mbx-Int := SYS$CREMBX(O,Chan Rec,O,O,O,O,'Mailbox');
IF NOT Mbx Bool THEN BEGIN WRITELN ('Error when trying to create mailbox');
HALT
END
END
END;
The function reference allows a return status to be stored
in the
record Mbx Rec.
If the function's return status is false (represented
by any even integer), indicating failure, an error occurs and error
processing can be undertaken.
You can also check for a particular
return status, such as lack of privileges, by comparing the return
status to one of the status codes defined by the system. For example:
IF Mbx Rec.Mbx Int = SS$ NOPRIV THEN
WRITELN (1 No privilege to create mailbox');
Refer to the VAX/VMS System Services Reference Manual for
information
about return status codes.
The relevant return status codes are
described with each system service.

7-8

CALLING CONVENTIONS
7.2.2

Calling System Service as Procedures

If you do not need to check the return status, you can declare a
system service as an external procedure rather than as an external
function.
Procedure calls to system services are made in the same way
that calls are made to any other procedure.
For example, to use the
Create Mailbox system service, define and call
the
procedure
SYS$CREMBX, as follows:
PROCEDURE SYS$CREMBX (%IMMED PRMFLG : INTEGER;
VAR Chan : Chan Type;
%IMMED MAXMSG, Bufquo, Promsk, Acmode : INTEGER;
%STDESCR Lognam : ARRAY [Sub63] OF CHAR);
EXTERN;
SYS$CREMBX (0,Chan_Rec,O,O,O,O,'Mailbox');
You should declare Chan Rec and Chan_Type as in the previous section.
This procedure call corresponds to the function reference, but does
not a~low you to test the status code returned by the system service.

7.2.3

Passing Parameters to System Services

Most system services require input parameters to be passed as
immediate values.
When declaring these parameters, you must use the
%IMMED mechanism specifier.
Some system services, however,
require
input parameters to be passed by-reference. For input parameters
passed by-reference, you should use the default
(that is, omit the
mechanism specifier) so that the actual parameters can be expressions.
In addition, most system services require output parameters to be
passed by-reference.
For these parameters, you must use the VAR
mechanism specifier to ensure that PASCAL correctly interprets the
output data.
The VAX/VMS System Services Reference Manual lists the
mechanism by which each parameter to a system service must be passed.

7.2.3.l Input and Output By-Reference Parameters - You may need
to
tell
the system service where to find input values and where to store
output values.
Thus, you must ascertain the hardware data type of the
parameter: byte, word, longword, or quadword.
For input parameters that refer to byte, word, or longword values, you
can specify either constants or variables.
If you specify a variable,
it must be of a type that is allocated an equal or greater amount of
storage than is allocated to the hardware data type required.
For output parameters, you must declare a variable of exactly the
length required, to avoid including extraneous data.
For example, if
the system returns a byte value in a word-length variable,
the
leftmost 8 bits of the variable will not be overwritten on output and
the variable will not contain the data you expect.
Table 7-1 lists
the suggested input and output variable types.

7-9

CALLING CONVENTIONS
Table 7-1
Suggested Variable Data Types
Input Parameter
Declaration

VAX/VMS Hardware
Type Required

Output Parameter
Declaration

Byte

INTEGER, CHAR

CHAR

Word

INTEGER

Appropriate packed
record

Longword

INTEGER

Quadword

Properly dimensioned
array

To store the output produced by a system service, you must allocate
sufficient space to contain the output. You can do so by declaring
variables of the proper size.
For example, the Create Mailbox
(SYS$CREMBX) system service returns a 2-byte value. Thus, you can set
up storage space as follows:
TYPE Word= 0 •• 65535;
Sub63 = 1. .63;
Chan Type
PACKED RECORD
Bot Chan : WORD
END;
VAR Chan Rec

Chan_Type;

VALUE Chan Rec := (0);
FUNCTION SYS$CREMBX (%IMMED PRMFLG : INTEGER;
VAR Chan : Chan Type;
%IMMED Maxmsg, Bufquo, Promsk, Acmode : INTEGER;
%STDESCR Lognam : PACKED ARRAY [Sub63] OF CHAR):
INTEGER; EXTERN;
Mbx Rec.Mbx Int := SYS$CREMBX (0,Chan_Rec, O, O, O, O,'Mailbox');
If the output is a quadword value, you must declare an array or record
of the proper size.
For example, the Get Time (SYS$GETTIM) system
service returns the time as a quadword binary value. Thus, you would
need to specify the following:
TYPE Quad= ARRAY [1 •• 2] OF INTEGER;
VAR Systim : Quad;
!stat : INTEGER;
FUNCTION SYS$GETTIM (VAR F_Systim
ISTAT := SYS$GETTIM (Systim);

7-10

Quad) : INTEGER; EXTERN:

CALLING CONVENTIONS
7.2.3.2 Optional Parameters - VAX-11 PASCAL does not allow you to
omit parameters from proc~dure or function calls.
If you choose not
to supply an optional parameter, you should pass the value zero using
the immediate value
(%IMMED) mechanism.
For example, the Translate
Logical Name
(SYS$TRNLOG)
system
service
has
three
optional
parameters.
If you do not specify values for these parameters, you
must include zeros in their places, as follows:
!stat := SYS$TRNLOG ('Cygnus', Namlen,Namdes, 0,0,0);

7.2.3.3 Passing Character Parameters - Some VAX/VMS system services
require character parameters for either input or output.
For example,
the Translate Logical Name
(SYS$TRNLOG)
system service accepts a
logical name as input and returns the associated logical name or file
specification, if any, as output.
VAX/VMS system services usually require strings to be passed by string
descriptor.
Specify %STDESCR in the function or procedure declaration
to pass the required string parameters by string descriptor.
On
input, a character constant or packed array of characters must be
passed to the system service by descriptor.
On output, two parameters
are required:
(1)
a packed array of characters to hold the output
string and (2) an INTEGER variable, which is set to the actual length
of the output string.
For example:
TYPE Word= 0 •• 65535;
Sub63 = 1 •• 63;
string_Buf =PACKED ARRAY [1 •• 128] OF CHAR;
VAR

Icode : INTEGER;
Namlen
WORD;
Namdes : String_Buf;

PROCEDURE Error;

FUNCTION SYS$TRNLOG (%STDESCR Cygnus : PACKED ARRAY [Sub63] OF CHAR;
VAR Rsllen : Word;
stdescr rslbuf : String Buf;
%IMMED Table, Acmode, Dsbmsk : INTEGER) : INTEGER; EXTERN;
BEGIN

Icode := SYS$TRNLOG ('Cygnus', Namlen,Namdes,0,0,4);
IF NOT ODD (Icode) THEN Error;

The logical name Cygnus is translated to its associated name or file
specification, and the output values (length and associated name or
file specification) are stored
in the locations you specified
Namlen and Namdes, respectively.
The last parameter, with the value
4, causes the system to disable its search of the process logical name
table; only the system and group tables are searched.
Section 7.4 presents another, complete system service example.

7-11

CALLING CONVENTIONS
7.3

CALLING RUN-TIME LIBRARY PROCEDURES

The VAX-11 Run-Time Library provides mathematical procedures that you
can call from PASCAL programs.
These procedures are described in the
VAX-11 Run-Time Library Reference Manual.
You can invoke a Run-Time Library procedure from a PASCAL program by
defining
it as an external
function and including the appropriate
function reference.
For example:
VAR Seed Val : INTEGER;
Rand=Rslt : REAL;
FUNCTION MTH$RANDOM (Seed : INTEGER)

REAL; EXTERN;

Rand Rslt := MTH$RANDOM(SEED_VAL);
This example· uses
(MTH$RANDOM) •

the

uniform

pseudo random

number

generator

When defining a function for a Run-Time Library procedure, you
note the following:
•

The
mechanism
by
which
each
parameter
is
(by-immediate-value, by-reference, or by-descriptor)

•

The types appropriate for the parameters and the result

should
passed

In the pseudorandom number generator, the seed parameter is passed
reference and the result is a real number, as shown.

7.4

COMPLETE SYSTEM SERVICE EXAMPLE

This section presents a sample PASCAL procedure that declares and
calls the Get Job/Process Information (SYS$GETJPI) system service.
The procedure declares SYS$GETJPI as an INTEGER function, so that upon
return, it can check for successful completion.
SYS$GETJPI is used here to get the process identification and name of
the current process. When used for this purpose, SYS$GETJPI requires
information in only the fourth of seven parameters.
The first,
second, third, fifth, sixth, and seventh parameters must be null.
The
fourth parameter contains the address of a list of descriptors that
describe the specific
information requested and point to buffers to
receive the information.
In this example, the list is constructed as
a
record.
It contains fields corresponding to each required item as
noted in the description of SYS$GETJPI in the VAX/VMS System Services
Reference Manual.
PROCEDURE Getjpinfo

(VAR Name: Prcnam; VAR ID: INTEGER);

(*This procedure calls the SYS$GETJPI system service to
get the process ID and process name, which are
used as formal parameters.
It uses these types
and variables:
Word -- 16 bits to contain buffer length and request code
Ptr Pid -- Address of process ID
Ptr-Pidlen -- Address of process ID length
Ptr-Prcnarn -- Address of process name string
Ptr-Prcnarnlen -- Address of length of process name string
Jpirec -- Record containing item list parameter
!code -- Status returned by SYS$GETJPI function

7-12

CALLING CONVENTIONS
The following type is declared in the main program:
PRCNAM =PACKED ARRAY [1 •• 15] OF CHAR*)
CONST Null = O;
TYPE Word= 0 •• 65535;
Recj = RECORD
Pidinfo

PACKED RECORD
Pidlen, Jpi$ Pid
Word
END;
Ptr Pid : AINTEGER;
Ptr-Pidlen
AINTEGER;
Prcnaminfo : PACKED RECORD
Prcnamlen, Jpi$ Prcnam
END;
Ptr Prcnam : APrcnam;
Ptr-Prcnamlen : AINTEGER;
Endlist : INTEGER

WORD

END;
VAR !code : INTEGER;
Jpirec : Recj;
FUNCTION SYS$GETJPI (%IMMED A,B,C : INTEGER; VAR Itmlst : Recj;
%IMMED X,Y,Z : INTEGER) : INTEGER; EXTERN;
(*A,B,C and X,Y,Z are null parameters*)
BEGIN
(*Set up record parameter*)
WITH Jpirec DO
BEGIN
Pidinfo.Pidlen := 4;
(*length of ID buffer*)
Pidinfo.Jpi$ Pid := %x319;
(*Hex of JP!$ PID*)
NEW (Ptr Pidf;
(*Get address-of ID*)
Ptr PidA-:= O;
(*Zero ID variable*)
NEW-(Ptr Pidlen);
(*Get address of length*)
Ptr PidlenA := O;
(*Zero ID length variable*)
Prcnaminfo.Prcnamlen := 15; (*Length of name buffer*)
Prcnaminfo.Jpi$_Prcnam := %x31C;
(*Hex of JP!$ PRCNAM*)
NEW (Ptr Prcnam);
(*Get address-of name*)
Ptr PrcnamA := •
•;
(*Blank-fill name string*)
NEW (Ptr Prcnamlen);
(*Get address of length*)
Ptr PrcnamlenA := O;
(*Zero name length variable*)
ENDLIST := 0
(*List must end with 0*)
END;
(*Call function and return status in STATUS variable*)
!code := SYS$GETJPI (Null, Null, Null, Jpirec, Null, Null, Null);
IF NOT ODD(Icode'jTHEN
(*If error, *)
BEGIN
I
WRITELN ('Error in GETJPI process'); (*print error message*)
HALT
(*and halt*)
END
ELSE
BEGIN
(*If successful,*)
NAME := Jpirec.Ptr PrcnamA;
(*assign name to Name param*)
ID := Jpirec.Ptr PTdA
(*and assign id to ID param*)
END
END;

7-13

CHAPTER 8

ERROR PROCESSING AND CONDITION HANDLERS

During the execution of a VAX-11 PASCAL program, various conditions,
including errors or exceptions can occur. These conditions result
from errors during I/O operations, invalid input data, incorrect calls
to library routines, errors in arithmetic, or system-detected errors.
VAX-11 PASCAL provides two methods of error control and recovery:
•

Run-Time Library default error-processing procedures

•

VAX-.11 Condition Handling
condition handlers)

Facility

(including

These error-processing methods are complementary and can
the same program.

user-written
be

used

The Run-Time Library can provide all condition handling needed by an
application program.
The Run-Time Library provides default error
processing by generating error messages for all error or exception
conditions that occur during
the execution of a PASCAL program.
Section 8.1 describes error processing by the Run-Time Library as
applied
to VAX-11 PASCAL.
Appendix A describes the error messages
that can be generated for a PASCAL program.
·
The VAX-11 Condition Handling Facility provides, at the lowest level,
all condition handling for the Run-Time Library and can provide
routines (user-written condition handlers) for processing conditions
that occur during your program's execution. The use of condition
handlers requires considerable programming experience and should not
be undertaken by novice users.
You should understand the condition
handling descriptions in the VAX/VMS System Services Reference Manual,
the
VAX-11
Run-Time
Library Reference Manual, or the VAX-11
Architecture Handbook before attempting to write a condition handler.·
The following terms are used in this chapter:

•

Condition handler -- A function that has been specified by a
particular routine as the handler to be called when an
exception condition is signaled.

•

Condition value -- An
particular condition.

•

Establish -- The process of placing the address of a condition
handler in the stack frame of the current routine activation.
A condition handler established for a routine activation is
automatically called when a condition occurs.
In PASCAL,
condition handlers are
established
by
means
of
the
LIB$ESTABLISH routine.

INTEGER

8-1

value

that

identifies

ERROR PROCESSING AND CONDITION HANDLERS
•

•

Routine activation -- The environment in which a routine
executes.
This environment includes a unique stack frame on
the run-time stack;
the stack frame contains the address of a
condition handler for the routine activation. A new current
routine activation is created every time a routine is called;
the routine activation is deleted when the routine returns.
Program

Exit

Status -- The

program

completion

status

program completion.

•

Resignal -- The means by which a condition

handler indicates
that the signaling facility is to continue searching for a
condition handler to process a previously signaled error.
To
resignal, a condition handler returns the SS$ RESIGNAL value.

•

Signal -- The means by which the occurrence of an exception
condition is made known.
Signals are generated by the
operating system in response to
I/O events and hardware
errors, by the system supplied library routines and by user
routines. All signals are initiated by calling the signaling
facility.
There are two entry points to the signaling
facility.
- LIB$SIGNAL -- Used to signal a condition
to continue program execution

and,

possibly,

- LIB$STOP -- Used to signal a severe error and discontinue
program execution, unless a condition handler performs an
unwind operation

8.1

•

Stack frame -- A standard data structure built on the stack
during a procedure call, starting from the location addressed
by .the FP to lower addresses and popped off during a return
from procedure.

•

Unwind -- To return
control
to
a
particular
routine
activation, bypassing any intermediate procedure activations.
For example, if X calls Y and Y calls Z and Z detects an
error, a condition handler associated with X or Y can unwind
to x, bypassing Y.
Control returns to X immediately following
the point at which X called Y.

RUN-TIME LIBRARY DEFAULT ERROR PROCESSING

The Run-Time Library, by default, prints a message and terminates
PASCAL program execution when a run-time error occurs. These default
actions occur unless your program includes a condition handler.
Run-time errors are reported by default in the following format:
%PAS-F-code, text
The code is an abbreviation of the error message text. VAX-11 PASCAL
run-time errors and recovery procedures are described in Appendix A.
Most Run-Time Library routines provide their own error messages, as
described in the VAX-11 Run-Time Library Reference Manual.

8-2

ERROR PROCESSING AND CONDITION HANDLERS
8.2

OVERVIEW OF VAX-11 CONDITION HANDLING

When the VAX/VMS system creates a
user process, a system-defined
condition handler is established in the absence of any user-written
condition handler.
The system-defined handler processes errors that
occur during execution of the user image when no user-defined handlers
are present.
Thus, by default, a
run-time error
causes
the
system-defined condition handler to print one of the standard error
messages and
to terminate or continue execution of the image,
depending on the severity code associated with the error.
When a condition is signaled, the system searches for condition
handlers to process the condition.
The system conducts the search for
condition handlers by proceding down the stack, frame by frame,
(see
Section 8.2.1 for definition) until a condition handler is found that
does not resignal.
The default handler calls the system's message
output routine to send the appropriate message to the user. Messages
are sent to the SYS$0UTPUT file and to the SYS$ERROR file,
if both
files are present.
If the condition is not a severe error, program
execution continues.
If the condition is a severe error the default
handler forces program termination and the condition value becomes the
program exit status.
You can create and establish your own condition handlers according to
the needs of your applications.
For example, your condition handler
could create and display messages
that.
specifically
describe
conditions encountered during execution of an application program,
instead of relying on the standard system error messages.

8.2.1

Condition Signals

A condition signal consists of a call to one of the two signaling
facility entry points,
LIB$SIGNAL and LIB$STOP.
These entry points
must be declared external, for example:
PROCEDURE LIB$SIGNAL (%IMMED Condition : INTEGER); EXTERN;
PROCEDURE LIB$STOP (%IMMED Condition : INTEGER); EXTERN;
If a condition occurs in a routine that cannot handle it, notification
is passed to other active routines by issuing a signal.
If the
current routine can continue after the signal
is
propagated,
LIB$SIGNAL is called.
A higher-level
routine can then determine
whether program execution is to continue.
If the nature of the
condition does not allow the current routine to continue, LIB$STOP is
called.
Condition values are
example:

usually

expressed

condition

provide

symbols,

for

LIB$SIGNAL (MTH$_FLOOVEMAT);
Additional parameters can be
information about the error.

included

supplementary

When called, the signaling facility searches for condition handlers by
exam1n1ng the preceding stack frames until it activates a condition
handler that does not resignal.

8-3

ERROR PROCESSING AND CONDITION HANDLERS
8.2.2

Handler Responses

A conditioD handler responds
action in three major areas:
•

Condition correction

•

Condition reporting

•

Condition control

exception

condition

taking

First, the handler determines whether the condition is correctable.
If possible, the handler takes the appropriate action, and execution
continues. If the handler cannot correct the condition, the condition
may be resignaled.
That is, the handler requests that another
condition handler be located to process the condition.
Condition reporting performed by handlers can involve one or
the following actions:
Maintaining a count of exceptions encountered
execution

•

Resignaling the same condition to send the appropriate message
to your terminal or log file

•

Changing the severity field
resignaling the condition

•

Signaling a different condition, for example,
message oriented to a specific application
numb~r

the

during

•

Execution can be affected in a

8.3

condition
to

program

value

and

produce

of w~ys:

•

Continuing from the signal. If the signal was issued
a call to LIB$STOP, the program exits.

through

•

Unwinding to the establisher at the point of the call that
resulted in the exception.
The handler can determine the
function value returned by the called routine.

•

Unwinding to the establisher's caller (the routine that called
the routine that established the handler). The handler can
determine the function value returned by the called routine.

WRITING CONDITION HANDLERS

The following sections describe how to code and establish condition
handlers
and
provide
some
simple examples.
See the VAX-11
Architecture Handbook, the V_A~X_-_l_l~R_u_n_-_T~im~e~L_i_b_r_a_r_y__~R_e_f_e_r_e_n_c_e~~M_a_n_u_a_l,
and the VAX/VMS System Services Reference Manual for more details on
condition handlers.

8-4

ERROR PROCESSING AND CONDITION HANDLERS
Establishing and Removing Handlers

8.3.1

When a routine
is called, a condition handler is not initially
established.
To use a condition handler, first define both the
Run-Time Library procedure LIB$ESTABLISH and the condition handler as
follows:
FUNCTION HANDLER : INTEGER;
EXTERN;
PROCEDURE LIB$ESTABLISH (%IMMED FUNCTION Handler
EXTERN;

INTEGER);

LIB$ESTABLISH (ERR_HANDLER)
To establish the handler, call LIB$ESTABLISH.
To
remove
an
established handler, define the Run-Time Library procedure LIB$REVERT,
and call as follows:
PROCEDURE LIB$REVERT; EXTERN;

LIB$REVERT
As a result of this call, the condition handler established
in the
current stack frame is removed. When a routine returns, any condition
handler established during that activation is automatically removed.
Note that condition handlers written in PASCAL can access only
own local data and data declared at program or module level.

their

Parameters for Condition Handlers

8.3.2

A PASCAL condition handler is an INTEGER function that is called when
a condition is signaled. Two formal VAR parameters must be defined
for a condition handler:
1.

An integer array to refer to the parameter list from the call
to the signal routine (the signal parameters);
that i'S(, the
1 ist of parameters included in calls to
LIB$SIGNAL----0-r-LIB$STOP (see Section 8.2.1).

An integer array to
refer to
information concerning the
routine activation that established the condition handler
(the mechanism array).

For example, a condition handler may be defined as follows:
TYPE Mecharr = ARRAY[0 •• 4] OF INTEGER;
Sigarr =ARRAY [0 •• 9] OF INTEGER;

FUNCTION HANDLER (VAR Sigargs
VAR Mechargs
BEGIN

Sigarr;
Mecharr)

END;

8-5

INTEGER;

ERROR PROCESSING AND CONDITION HANDLERS

PROCEDURE LIB$ESTABLISH (%IMMED FUNCTION Handler

INTEGER); EXTERN;

BEGIN

LIB$ESTABLISH (HANDLER);

END.
The array Sigargs receives the values listed
procedure.

below

from

the

signal

being

passed

Meaning

Value
Sigargs[O]

Indicates how many parameters are
in this array (parameter count).

Sigargs[l]

Indicates
the
condition
being
signaled
(condition value).
See Section 8.3.4 for a
discussion of condition values.

Sigargs[2 to n]

Indicates optional parameters supplied
in the
call
to
LIB$SIGNAL or LIB$STOP; note that the
dimension bounds for the Sigargs array should
specify as many entries as necessary to refer to
the optional parameters.

The array Mechargs receives information about the procedure activation
status of the routine that established the condition handler.
The
values from this routine are listed below.

Value

Meaning

Mecha rg s [ 0]

Specifies the number of parameters in this array
( 4) •

Mechargs[l]

Contains the address of the
established the handler.

Mechargs[2]

Contains the number of calls that have been .made
(that is, the stack frame depth)
from the
routine activation, up to the point at which the
condition was signaled.

Mechargs[3]

Contains the value of register RO at the time of
the signal.

Mechargs[4]

Contains the value of register Rl at the time of
the signal.

8-6

stack

frame

that

ERROR PROCESSING AND CONDITION HANDLERS
Handler Function Return Values

8.3.3

Condition handlers specify
subsequent execution.
The
are listed below.

function return
values
to
control
function return values and their effects

Value

Effect

SS$ CONTINUE

If the
Continues execution from the signal.
signal was issued by a call to LIB$STOP, the
program exits.

SS$ RESIGNAL

Resignals to continue the search for a condition
handler to process the condition.

In addition, a condition handler can request a stack unwind by calling
SYS$UNWIND before returning.
Declare SYS$UNWIND as follows:
FUNCTION SYS$UNWIND (Depth : INTEGER; %IMMED Newpc : INTEGER):
INTEGER; EXTERN;
When SYS$UNWIND is called, the function return value is ignored.
The
handler modifies the saved
registers RO and Rl in the mechanism
parameters to specify the called procedure's function value.
A stack unwind can be made to one of two places:
•

Unwind to the establisher, at the point
resulted in the exception.
Specify:

the

call

that

Status := SYS$UNWIND (Mechargs[2],0);
•

Unwind to the routine that called the establisher.
Status := SYS$UNWIND (Mechargs[2]+1,0);

8-7

Specify:

ERROR PROCESSING AND CONDITION HANDLERS
8.3.4

Condition Values and Symbols

VAX-11 uses condition values to indicate that a called routine has
either executed successfully or failed, and to report exception
conditions. Condition values are 32-bit packed records (usually
interpreted as integers), consisting of fields that indicate which
system component generated the value, the reason the value was
generated, and the severity of the condition. The definition of a
condition value has the form:
TYPE Condition Value=PACKED RECORD
(* Field

Bits

Meaning*)

Severity:0 •• 7;

(*2:0

Specifies a severity
follows:
0 - warning
1 - success
2 - error
3 - information
4 - severe error
5,6,7 - reserved *)

code

Message:0 •• 8191;

(*15:3

Describes the
condition
that
occurred.
Bit 15 = 1 indicates
that the message is specific to a
single
facility.
Bit 15 = O
indicates
a
system-wide
message.*)

Facility:0 •• 4095;

(*27:16

Identifies the software component
that
generated
the condition
value. Bit 27 = 1 indicates a
customer facility.
Bit 27 = O
indicates a DIGITAL facility.*)

Control:0 •• 15

(*31:28

Control bits.*)

END;
A warning severity code (0) indicates that output was produced, but
the results may be unpredictable.
An error severity code (2)
indicates that output was produced even though an error was detected.
Execution can continue, but the results may not be correct. A severe
error code (4) indicates that the error was of such severity that
output was not produced. An even-numbered error code is a warning. A
condition handler can alter the severity code of a condition value to
allow execution to continue or to force an exit, depending on the
circumstances.
In the example in Section 8.3.2 the condition value is passed as the
second element of the array Sigargs.
Occasionally, a condition
handler may require a particular condition be identified by an exact
match. That is, each bit of the condition value (31:0) must match the
specified condition. For example, you may want to process a floating
overflow condition only if the severity code is still 4 (that is, if
no previous congition handler has changed the severity code).
As
noted above; a typical condition handler response is to change the
severity code and resignal.

8-8

ERROR PROCESSING AND CONDITION HANDLERS
In many cases, however, response to a condition, regardless of the
value of the severity code is desired.
To ignore the severity and
control
fields of a condition value,
declare
and
call
the
LIB$MATCH_COND function, as follows:
FUNCTION LIB$MATCH COND (Condval,Compval
BOOLEAN;EXTERN;

INTEGER):

IF LIB$MATCH COND (Sigargs [ 1], PAS$ Erraccfil)
THEN...
-

8.3.5

Floating-Point Operation

Some conditions involving floating-point operations require special
action to continue execution.
Operations that involve, for example,
floating overflow, dividing by O, or computing the square root of a
negative number, storing a unique result known as a floating reserved
operand.
If a
subsequent floating-point operation accesses this
result, a hardware reserved operand fault is generated and signaled.
This can continue indefinitely if the condition handler does not
change the reserved operand, because the operand is accessed each time
the computation is retried.
To allow computation to continue, change the reserved operand by
defining and calling the Run-Time Library routine LIB$FIXUP_FLT, as
follows:
FUNCTION LIB$FIXUP FLT (VAR Sigadr : Sigvector;
VAR Mechadr : Mechvector; VAR Op : DOUBLE):
INTEGER; EXTERN;

Status:= LIB$FIXUP_FLT(Sigargs,Mechargs,Newoperand);
The types Sigvector and Mechvector in this example refer to the types
of the signal and mechanism argument vectors, which are assumed to be
defined in the calling procedure. The third parameter is specified as
a double-precision variable to ensure that the reserved operand is
changed correctly regardless of precision. Specify O.ODO if there is
no special value for this parameter.
For more information on
LIB$FIXUP_FLT, see the VAX-11 Run-Time Library Reference Manual.

8-9

ERROR PROCESSING AND CONDITION HANDLERS
8.4

CONDITION HANDLER EXAMPLE

The following example illustrates how to declare and use a condition
handler with a typical PASCAL procedure.
A condition handler is
established, that is called when an error occurs in a file opening
procedure.
If the error is the general "Error opening/creating the
file," signified by the PAS$ ERROPECRE code, an unwind operation is
performed. Any other error Ts resignaled.
PROCEDURE Openhand;
(*This procedure shows how to establish and call a
from a PASCAL program.
It uses these types:

condition

handler

Datarec -- a record type for the accounting file
Datafile -- a file type with components of type Datarec
Sigarr -- an array type for signal parameters
Mecharr -- an array type for mechanism parameters
It declares these global variables:
Flag -- a Boolean variable set to TRUE when an error occurs
New Accounts -- a file variable of type Datafile
Status -- an all-purpose function return status variable *)
CONST %INCLUDE 'SYS$LIBRARY:SIGDEF.PAS'
(*This file contains the PASCAL declarations of the condition
signals*)
TYPE Datarec = RECORD
Name :
Amount
Cost
Date :
END;

PACKED ARRAY [l •• 30) OF CHAR;
: REAL;
REAL;
PACKED ARRAY [l. .11) OF CHAR

Datafile = FILE OF Datarec;
Sigarr =ARRAY [0 •• 9] OF INTEGER;
Mecharr =ARRAY [0 •• 4) OF INTEGER;
VAR Flag : BOOLEAN;
New Accounts : DATAFILE;
Status : INTEGER;
PROCEDURE LIB$ESTABLISH (%IMMED FUNCTION Fixer : INTEGER); EXTERN;
(*The Run-Time Library procedure LIB$ESTABLISH will be called to
establish the condition handler*)
PROCEDURE Opener (VAR Accounts : Datafile);
(*This procedure will be called to open the file and write new
records in it.
It also performs data entry and cleanup.
Only
the OPEN processing is shown here for simplicity*)
(*Local variable declarations*)
FUNCTION HANDLER (VAR Sigargs : Sigarr; VAR Mechargs : Mecharr):
INTEGER;
(*This function will be called to handle a file opening error during
the OPENER procedure.
It uses only globally declared variables,
except for the SYS$UNWIND and LIB$MATCH_COND functions.*)
FUNCTION SYS$UNWIND (Depth : INTEGER; %IMMED Newpc : INTEGER):
INTEGER; EXTERN;
FUNCTION LIBSMATCH COND (Condval, Compval : INTEGER):
BOOLEAN; EXTERN;
BEGIN

END;

IF (LIBSMATCH COND (Sigargs{l), PasS_Erropecre)) THEN
BEGINFlag := True;
Status := SYS$UNWIND(Mechargs[21+1, 0)
END;
HANDLER :=SS$ RESIGNAL
(*end HANDLER*)

(*If error opening file,*)
(*set file error flag*)
(*and unwind*)
(*If some other error, resignal*)

BEGIN
LIB$ESTABLISH (HANDLER); (*establish condition handler*)
OPEN (Accounts, '[DATA)Accounts.DAT',OLD, SEQUENTIAL);
(*Data entry, storage, and cleanup*)
END;

(*End OPENER*)

BEGIN
(*This is the start of the outermost procedure*)

END;

Flag :=FALSE;
(*initialize Flag to FALSE for test below*)
OPENER (New Accounts);
(*open the file*)
IF Flag THEN WRITELN ('Error in opening file')
(*Print message if error handler was called*)
(*End Openhand*)

8-10

CHAPTER 9
VAX-11 PASCAL SYSTEM ENVIRONMENT

This chapter describes the relationship between the VAX/VMS operating
system and the VAX-11 PASCAL compiler.
It covers the following
topics:

•
•
•
•
•
9.1

Use of program sections
Storage of scalar and pointer types
Storage of unpacked structured types
Storage of packed structured types
Representation of floating-point data

USE OF PROGRAM SECTIONS

The VAX-11 PASCAL compiler uses contiguous areas of memory, called
program sections, to store information about the program. The VAX-11
Linker controls memory allocation and sharing according to the
attributes of each program section.
Table 9-1 lists the possible
program section attributes.
Table 9-1
Program Section Attributes
Attribute

Meaning

PIC/NOPIC

Position independent or position dependent

CON/OVR

Concatenated or overlaid

REL/ABS

Relocatable or absolute

GBL/LCL

Global or local scope

SHR/NOSHR

Shareable or nonshareable

EXE/NO EXE

Executable or nonexecutable

RD/NORD

Readable or nonreadable

WRT/NOWRT

Writeable or nonwriteable

9 .... 1

VAX-11 PASCAL SYSTEM ENVIRONMENT
VAX-11 PASCAL implicitly declares three program sections:
$GLBL,
$CODE, and $PDATA.
Table 9-2 summarizes the usage and attributes of
these program sections.
Table 9-2
Program Section Usage and Attributes
Program
Section
Name

Attributes

Usage

$GLBL

Read/write static data
declared at module or
program level

PIC, OVR, REL, GBL,
NOSHR, NOEXE, RD, WRT

$CODE

Read-only generated
executable code

PIC, CON, REL, LCL,
SHR, EXE, RD, NOW RT

$PDATA

Read-only constants
that need storage

PIC, CON, REL, LCL,
SHR, NOEXE, RD, NOW RT

Each module in your PASCAL program is named according to the
identifier specified in the program or module header.
You can use the
module name to qualify the program section name in LINK commands.
For
more information, refer to the VAX-11 Linker Reference Manual.
When the linker constructs an executable image, it divides the
executable image into sections. Each image section contains program
sections that have the same attributes. The linker controls memory
allocation by arranging
image sections according to program section
attributes.
The linker allows you to use special options to change program section
attributes and
to influence the memory allocation in the image. You
include these options in an options file, which is input to the
linker.
The options and the file are described in the VAX-11 Linker
Reference Manual.

9.2

STORAGE OF SCALAR AND POINTER TYPES

When not part of a packed structure, the scalar types
allocated storage space as summarized in Table 9-3.

PASCAL

are

Variables of scalar types, with the exception of DOUBLE variables, are
aligned on a boundary corresponding to their sizes. DOUBLE variables
are aligned on longword boundaries rather than on quadword boundaries.
Variables of subrange types are allocated and aligned in the same way
as variables of the associated scalar types. For example, an integer
subrange variable is allocated 1 longword and is aligned on a longword
boundary.
A subrange of an enumerated type Days Of Week (with values
Sunday, Monday, Tuesday, and so on) is stored in T byte and aligned on
a byte boundary.
A pointer is simply a longword containing an address.

9-2

VAX-11 PASCAL SYSTEM ENVIRONMENT
Table 9-3
Storage of Scalar and Pointer Types
Type

Storage Allocation

Alignment Boundary

Character

8 bits (1 byte)

Byte

Boolean

8 bits (1 byte)

Byte

Integer, single, real

32 bits (1 longword)

Longword

Double

64 bits (1 quadword)

Longword

Enumerated

8 bits (1 byte) if
type contains 256
elements or less;
16 bits (1 word) if
type contains more
than 256 elements

Byte if type contains
256 elements or less;
word if type contains
more than 256 elements

Pointer

32 bits (1 longword)

Longword

9.3

STORAGE OF UNPACKED STRUCTURED TYPES

The unpacked structured types (sets, arrays, and records)
are stored
and aligned as described below. Note that this description applies
only to data items that are not part of another structure.
A set consists of
boundary.

bytes

longwords)

aligned

longword

An array is stored and aligned according to the type of its elements.
For example, each element of an array of integers is stored in 1
longword and aligned on a longword boundary. Similarly, each element
of a character array is stored
in 1 byte and aligned on a byte
boundary.
Records are stored field by field according to the type of each field.
The type of the first field in the record establishes the alignment of
the entire record.
Subsequent fields in the record are always aligned
on byte boundaries,
regardless of the type of the first field.
For
example:
VAR A

RECORD
X
INTEGER
Y :
BOOLEAN
Z :
INTEGER
END;

Record A is aligned on a longword boundary because its first field, X,
contains an integer value, which is stored in a longword.
Figure 9-1
shows how this record is stored.
Bytes O through 3 (bits 0 through 31)
contain the first field,
X,
which is an integer longword value.
Byte 4 (bits 32 through 39)
contains the Boolean value of Y,
and bytes 5 through 8
(bits 40
through 71) contain the other integer longword value, Z.

9-3

VAX-11 PASCAL SYSTEM ENVIRONMENT
0

X(INTEGER)
Z(INTEGER)

Y(BOOLEAN)
Z(INTEGER)

64
ZK-066-80

Figure 9-1

9.4

Storage of Sample Record

STORAGE OF PACKED STRUCTURED TYPES

Although you can pack any structured type, packing saves storage space
only for sets, arrays, and records.
Packing files has no effect on
their storage.
In general, storage space for packed types is allocated
the "32-bit rule," as followi:

according

•

Any data item that is 32 bits or less in length is packed into
as few bits as possible.

•

Any data item over 32 bits long
is allocated the smallest
possible number of bytes and is aligned on a byte boundary.

The sections below describe exactly how storage is allocated to each
packed type and note any exceptions to the general 32-bit rule. The
descriptions apply only to data items that are not part of another
structure.

Storage of Packed Sets

9.4.1

A packed set that is not a component of another packed structure is
byte-aligned.
Each packed set is allocated space according to the
32-bit rule, based on the ordinal value of its largest element:
•

If the ordinal value is less than or equal to 31, the set is
allocated the number of bits equal to the ordinal value plus
1.
For example, a packed set of 2 •• 19 is allocated 20 bits.

•

If the ordinal value is greater than 31, the set is allocated
the number of bits equal to the ordinal value plus 1, rounded
up to the nearest byte boundary.
For example, a packed set of
subrange type 100 •• 101 is allocated 13 bytes (101+1 bits
rounded up to a byte boundary).

Since the size of a set is limited to 256 elements, with ordinal
values from 0 to 255, a packed set can occupy at most 32 bytes (8
longwords) of memory.

9.4.2

Storage of Packed Arrays

A packed array that is not a component of another packed structure is
aligned on a byte boundary. The elements of the array are packed to
the nearest bit. Table 9-4 lists the space requirements for elements
of packed arrays.

9-4

VAX-11 PASCAL SYSTEM ENVIRONMENT
Table 9-4
Storage of Packed Array Elements
Storage
Allocation

Type

Boolean

1 bit

Character

8 bits (1 byte)

Integer, real, single

32 bits (1 longword)

Double

64 bits (1 quadword)

Subrange of integer,
character, or
enumerated type

Minimum number of bits in which the
largest and smallest possible values
can be expressed

Enumerated types

Number of bits required for
ordinal value

Po inters

32 bits (1 longword)

All structured types

Same as structured types not in
packed array.
However, if the total
size of the structu-r-ed type
is
greater than 32 bits, the array
element is allocated
a
m1n1mum
number of bytes, that is, the 32-bit
rule applies.
Structured
types
requiring 32 bits or less space are
bit-aligned.

largest

Note that integer subranges are packed into the minimum amount of
space needed to hold the largest or smallest value, whichever needs
[1 •• 10]
OF
more space. For example, each element of PACKED ARRAY
-128 •• 127 is allocated 8 bits.
Each element of PACKED ARRAY [1 •• 64]
OF 0 •• 7 is allocated 3 bits.
Enumerated types are packed into the number of bits required to hold
the largest ordinal value.
For example, an enumerated type with 16
values is allocated 4 bits, because its ordinal values are 0 through
15.
A packed array of an unpacked structured type saves no storage space.
The only effect of such a specification is to byte-align the array.
Instead, specify a packed array of a packed structured type.
The
following two examples illustrate this difference.

Examples
1.

TYPE Int Set= SET OF 0 •• 14;
VAR Int Arr
PACKED ARRAY [1 •• 5] OF Int_Set;
An unpacked set of type
Int Set is stored as 8 longwords.
Consequently, each element of Int Arr requires 8 longwords, for a
total of 40 longwords (640 bits) of space.

9-5

VAX-11 PASCAL SYSTEM ENVIRONMENT
2.

TYPE Int Set= PACKED SET OF 0 •• 14;
VAR Int Arr : PACKED ARRAY [1 .• 5] OF Int_Set;
A packed set of type Int Set is allocated 15 bits. Each element
of Int Arr therefore requires 15 bits, for a total of 75 bits for
the entire array.

Storage for packed arrays of records and arrays of packed
allocated similarly.

records

Multidimensional arrays can also be packed.
As for the other
structured types, you must specify packing at the innermost level to
gain any significant space advantage. For a 2-dimensional array, an
array of a packed array generally takes less space than a packed array
of an array, as in the following examples.
Examples
1.

TYPE Internal Arr= Array [1 •• 5] of 0 •• 6;
VAR Sampl_Arr-: PACKED ARRAY [1 •• 5] OF Internal_Arr;
Each element of an array of type Internal Arr is stored in a
longword.
Each element of Sampl Arr, in turn, requires 5
longwords -- enough storage space -for 5 elements
of
type
Internal Arr.
The entire array Sampl Arr therefore occupies 25
longwords (800 bits).

VAR Sampl Arr
PACKED ARRAY [1 •• 5,1 •• 5] OF 0 •• 6;
VAR Sampl=Arr : ARRAY [1 •• 5] OF PACKED ARRAY [1 •• 5] OF 0 •• 6;
Specifying PACKED for an array with multiple subscripts results
in packing only at the innermost level. Therefore, the two array
declarations in this example are equivalent.
Each
PACKED
ARRAY[l •• 5] of 0 •• 6 requires 15 bits. Because the packed arrays
are elements of an unpacked array, their size is rounded up to an
even 16 bits. The total size of each SAMPl ARR is therefore 80
bits.
Example 3 shows a slightly more -efficient way
of
allocating this array.

TYPE Internal Arr= PACKED ARRAY [1 •• 5] OF 0 •• 6;
VAR Samp2_Arr-: PACKED ARRAY [1 •• 5] OF Internal_Arr;
In this example, each element of Internal Arr requires only 3
bits because the array is packed. Each element of Samp2 Arr can
be stored in 15 bits, and the entire array occupies 75 bits.

TYPE Internal Arr= PACKED ARRAY [1 •• 5] OF 0 •• 6;
Samp3 Arr= PACKED ARRAY [1 •• 5] OF Internal Arr;
VAR Sample-: PACKED ARRAY [1 •• 5] OF Samp3_Arr; This example shows how you can maximize space savings for arrays
of more than two dimensions by specifying PACKED at every level.
As in Example 3, each element of Internal Arr requires 3 bits,
and each element of Samp3 Arr requires 15-bits. The entire array
Sample, then, requires 375 bits.

9.4.3

Storage of Packed Records

A packed record that is not a component of another packed structure is
aligned on a byte boundary.
The fields within the record are
allocated space depending on their sizes and types.

9-6

VAX-11 PASCAL SYSTEM ENVIRONMENT
Fields of scalar types, if less than or equal to 32 bits long,
are
packed to the nearest bit.
A field that requires more than 32 bits is
aligned on a byte boundary and is allocated space as for a field of an
unpacked record.
Except for its alignment, a field that contains an unpacked
array,
set, or record occupies the same amount of space in a packed or
unpacked record.
To pack such a field, you must explicitly declare
the type of the field to be packed.
For example:
VAR Sample! :

PACKED RECORD
A
-128 •• 127;
B :
BOOLEAN;
C :
ARRAY [1 •• 5] OF 0 •• 30
END;

This record is byte-aligned and is allocated storage as follows:

Field

Storage Allocation
8 bits
1 bit
160 bits

A
B

Field A, an integer subrange,
is stored
in the smallest possible
amount of space,
7 data bits plus a sign bit.
Field B, a Boolean,
takes up 1 bit, leaving 7 bits unused.
Field C is an unpacked array,
which is allocated storage as for integers, 32 bits (1 longword) for
each of 5 elements.
Figure 9-2 shows how this record is stored.
8 7

unused

Cl 1]

I BI

C[2)

C[1]

C[3)

C[2]

C[4]

C[3]

C(5]

C[4]

0
A

C[5]

175

167
ZK-067-80

Figure 9-2

Storage of Sample Record

This record requires a total of 176 bits (11 words) of storage.
Compare the preceding example with the next
packed array.
VAR Sample2

one,

which

PACKED RECORD
A
-128 •• 127;
B :
BOOLEAN;
C :
PACKED ARRAY [1 •• 5] OF 0 •• 30
END;

9-7

specifies

VAX-11 PASCAL SYSTEM ENVIRONMENT
This record is byte-aligned and is allocated storage as follows:

Field

Storage Allocation

A
B

8 bits
1 bit
25 bits

Fields A and B are allocated the same amount of space in both sample
records.
Field c, however,
requires much less space in SAMPLE2
because it is packed.
Each element of the packed array C occupies
only 5 bits. Figure 9-3 shows how this record is stored.
31

C[5)

24
C[4)

C[3)

C[l]

C[2)

9 8 7

C[5)

......._
33

ZK-068-80

Figure 9-3

Storage of Sample Packed Record Containing Packed Array

This record requires a total of 34 bits of storage.

REPRESENTATION OF FLOATING-POINT DATA

9.5

The following sections summarize the
internal
representation of
single-precision
(REAL and SINGLE types) and double-precision (DOUBLE
type) floating-point numbers.
For more detailed information, see the
VAX-11 Architecture Handbook.

9.5.1

Single-Precision Floating-Point Data (SINGLE, REAL Types)

A single-precision floating-point value is represented by
four
contiguous bytes. The bits are numbered from the right O through 31,
as shown in Figure 9-4.
76

15 14

EXPONENT

0
FRACTION

FRACTION
31

16
ZK-069-80

Figure 9-4

Single-Precision Floating-Point Data Representation

9-8

VAX-11 PASCAL SYSTEM ENVIRONMENT
A single-precision floating-point value is specified by its address A,
the address of the byte containing bit O.
The form of the value is
sign magnitude with bit 15 the sign bit, bits 14 through 7 an excess
128 binary exponent, and bits 6 through 0 and 31 through 16 a
normalized 24-bit fraction with the redundant most
significant
fraction bit not represented. Within the fraction, bits of increasing
significance go from 16 through 31 and 0 through 6.
The 8-bit exponent field
encodes the values 0 through 255.
An
exponent value of O,
with a sign bit of O, indicates that the
floating-point value has a value of O.
Exponent values of 1 through
255 indicate binary exponents of -127 through +127.
An exponent value
of O, with a sign bit of 1,
is taken as a
reserved operand.
Floating-point instructions processing a reserved operand take a
reserved operand fault.
The value of a floating-point number is in the approximate range of
.29*(10**-38)
through
l.7*(10**38).
The
precision
of
a
s~ngle-precision value is
approximately one part in 2**23, or 7
decimal digits.

9.5.2

Double-Precision Floating-Point Data (DOUBLE Type)

A double-precision floating-point value is represented by 8 contiguous
bytes. The bits are numbered from the right 0 through 63, as shown in
Figure 9-5.
15 14

76
EXPONENT

0
FRACTION

FRACTION
FRACTION
FRACTION

ZK-070-80

Figure 9-5

Double-Precision Floating-Point Data Representation

A double-precision floating-point value is specified by its address A,
the
address
of
the byte containing bit O.
The form of a
double-precision
floating-point
value
is
identical
to
a
single-precision floating-point .value except for an additional 32
low-significance fraction bits.
Within the fraction,
bits
of
increasing significance are numbered 48 through 63, 32 through 47, 16
through 31, and 0 through 6.
The exponent conventions and approximate range of values are the same
for double-precision floating-point values as for single-precision
floating-point values.
The
prec1s1on
of
a
double-precision
floating-point value is approximately one part in 2**55, or 16 decimal
digits.

9-9

APPENDIX A
DIAGNOSTIC MESSAGES

This appendix summarizes the error messages that can be generated by a
PASCAL program at compile time and at run time.

A.l

COMPILER DIAGNOSTICS

VAX-11 PASCAL reports compile-time diagnostics in the source listing
(if
one is created) and summarizes them on the terminal
(in
interactive mode)
or in the batch log file (in batch
mode).
Compile-time diagnostics are preceded by the following:

w
%PAS {

} DIAGN
F

A level of W indicates a warning-level error which will not prevent
your program from linking or executing. A level of F indicates a
fatal error which you must correct for your program to link and
execute properly.
The diagnostic messages that the PASCAL compiler can print are listed
below.
All messages are printed with both number and text. Messages
with numbers less than 400 indicate serious syntax errors that you
must correct for proper compilation. Messages with numbers greater
than 400 indicate the use of VAX-11 PASCAL extensions and illegal
compiler options.
1

Error in simple type
The declaration for a base type of a set or the index type of
array contains a syntax error.

Identifier expected
The statement syntax requires an
found.

identifier,

but

the

word

none

can

PROGRAM

PROGRAM or MODULE expected
The statement
MODULE.

syntax

requires

A-1

reserved

DIAGNOSTIC MESSAGES
4

')' expected
The statement syntax requires the right-parenthesis character.

' : ' expected
The statement syntax requires a colon character.

Illegal symbol
The statement contains an illegal symbol, such
reserved word or illegal character.

misspelled

such

Error in parameter list
The parameter list contains a syntax error,
comma, colon, or semicolon character.

missing

OF expected
The statement syntax requires the reserved word OF.

'(' expected
The statement syntax requires the left-parenthesis character.

Error in type
The statement syntax requires a data type, but no type identifier
is present.

' [ ' expected
The statement syntax requires the left square bracket character.

' 1 ' expected
The statement syntax requires the right square bracket character.

END expected
The compiler cannot find the delimiter END, which marks
of a compound statement, subprogram, or program.

the

end

expected

The statement syntax requires the semicolon character.
15

Integer expected
The statement syntax requires
statement label.

A-2

integer,

for

example,

DIAGNOSTIC MESSAGES
16

'=' expected
The statement syntax
requires the equal sign to separate a
constant identifier from a constant value or to separate a type
identifier from a type definition.

BEGIN expected
The compiler cannot find the delimiter
beginning of an executable section.

BEGIN,

which

marks

the

• •• • expected
The compiler cannot find the range symbol ( •• ),which is required
between the endpoints of the subrange.

Error in field-list
The field list in a record declaration contains a syntax error.

expected

The statement syntax requires a comma character.
21

Empty parameter (successive ',') not allowed
The parameter list attempts to specify a null or missing
In PASCAL, you cannot
parameter, or contains an extra comma.
omit optional parameters.

Illegal (nonprintable) ASCII character
The program contains a character that is not
character.

printable

ASCII

Error in constant
A constant contains an illegal character or is improperly formed.

':=' expected
The statement syntax requires the assignment operator.

THEN expected
The compiler cannot find the reserved word THEN to
IF-THEN statement.

complete

the

The compiler cannot find the reserved word UNTIL to complete
REPEAT statement.

the

UNTIL expected

A-3

DIAGNOSTIC MESSAGES
54

DO expected
The compiler cannot find the reserved word DO to complete the FOR
statement or the WHILE statement.

TO/DOWNTO expected
The compiler cannot find the reserved word TO or
FOR statement.

DOWNTO

the

Invalid expression
The statement syntax requires an expression, but the first symbol
the compiler finds is not valid in an expression.

Error in variable
A reference to an array element or record field contains a syntax
error.

ARRAY expected
The compiler cannot find the reserved
definition.

ARRAY

the

type

Strings in excess of 65535 characters not allowed in comparisons
Relational operators. cannot be applied
65535 bytes.

word

strings

longer

than

Parameter count exceeds 255
The number of parameters to a procedure or function cannot exceed
255.

End of input encountered
aborted.

before

The end of the input file
program had been parsed.

100

was

end

program.

encountered

before

entire

Array size too large
A declared array is larger than
2,147,483,647
2,147,483,647 bits for a packed array.

101

Compilation

bytes

Identifier declared twice
An identifier is declared twice within a
You can redeclare identifiers only in
sections.

A-4

declaration section.
different declaration

DIAGNOSTIC MESSAGES
102

Lowbound exceeds highbound
The lower limit of a subrange is greater than the upper limit of
the subrange, based on their ordinal values in their base type.

103

Identifier is not of appropriate class
The identifier names the wrong class of data.
For example,
it
names a constant where the syntax of the statement requires a
procedure.

104

Identifier not declared
The program uses an identifier that has not been declared.

105

Sign not allowed
A plus or minus
nonnumeric type.

107

sign

has

occurred

before

expression

Incompatible subrange types
The subrange types are not compatible according to the
type compatibility.

108

rules

File not allowed in variant part
A file type cannot appear in the variant part of a record.

109

Type must not be REAL or DOUBLE
You cannot specify a real value here. Real values cannot be used
as array subscripts, control values for FOR loops, tag fields of
variant records, elements of set expressions, or boundaries of
subrange types.

110

Tagf ield type must be scalar or subrange
The tag field for a variant record must be a scalar
type.

111

subrange

Incompatible with tagfield type
The case label and the tag
These two
items must be
compatibility rules.

112

field are
compatible

of incompatible types.
according to the general

Index type must not be REAL or DOUBLE
Array subscripts cannot be real values;
integer or integer subrange values.

A-5

if numeric, they must be

DIAGNOSTIC MESSAGES
113

Index type must be scalar or subrange
Array subscripts must be scalar or subrange values, and cannot be
of a structured type.

114

Base type must not be REAL or DOUBLE
The base type of this set or subrange cannot be one of
types.

115

the

Base type must be scalar or subrange
The base type of this set or subrange must be scalar or
values, and cannot be of a structured type.

116

real

subrange

Actual parameter must be a set of correct size
The actual parameter must be of correct size when passed as a VAR
parameter.

117

Undefined forward reference in type declaration:

<name>

The base type of a pointer was not defined in the TYPE section.
118

VALUE initialization must be in main program
A VALUE initialization statement can appear only in the main
program block; you cannot initialize variables in subprograms.

119

Forward declared; repetition of parameter list not allowed
You cannot repeat the parameter
declaration of a subprogram.

120

list

after

the

forward

Function result type must be scalar, subrange, or pointer
The function specifies a result that is not a scalar, subrange,
or pointer type.
Function results cannot be structured types.

121

File value parameter not allowed
A file cannot be passed as a value parameter.

122

Forward declared function;

repetition of result type not allowed

The
result of the function appears in both
the
forward
declaration and
in the later complete declaration.
The result
can appear only in the forward declaration.
123

Missing result type in function declaration
The function heading does not declare the type of the
the function.

A-6

result

DIAGNOSTIC MESSAGES
124

F-format for REAL and DOUBLE only
You can specify two integers in the field width (such
for real, single, and double values only.

125

R:3:2)

Error in type of predeclared function parameter
A parameter passed to
correct type.

126

predeclared

function

not

the

Number of parameters does not agree with declaration
The number of actual parameters passed to
the subprogram is
different from the number of formal parameters declared for that
subprogram.
You cannot add or omit parameters.

127

Parameter cannot be element of a packed structure
You cannot
subprogram;
use it.

128

pass
you

one element of a packed structure to
a
must pass the entire structure if you want to

Result type of actual function
declaration

parameter

does

The result of an actual function parameter is
specified in the formal parameter list.
129

not
not

agree

with

the

type

Operands are of incompatible types
Two or more of the operands in an expression are of incompatible
types.
For example, the program attempted to compare a numeric
and a character variable.

130

Expression is not of set type
The operators you specified are valid only for set expressions.

131

Type of variable is not set
The statement syntax requires a set variable.

132

Strict inclusion not allowed
You must use the <= and >= operators to test set inclusion.
PASCAL does not allow you to use the less than (<) and greater
than (>) signs.

133

File comparison not allowed
Relational operators cannot be applied to file variables.

A-7

DIAGNOSTIC MESSAGES
134

Illegal type of operand(s)
You cannot perform the specified operation on data items
specified types.

135

the

Type of operand must be Boolean
This operation requires a Boolean operand.

136

Set element must be scalar or subrange
The elements of a set must be scalar or subrange
cannot have elements of structured types.

137

types.

Sets

Set element types not compatible
The elements of this set are not all of the same type.

138

Type of variable is not array
A variable that is not of an array type is followed
square bracket or a comma inside square brackets.

139

left

the

type

Index type is not compatible with declaration
The specified array subscript is not
specified in the array declaration.

140

compatible

with

Type of variable is not record
A period appears following a variable that is not a record type.

141

Type of variable must be £ile or pointer
A circumflex character appears after the name of a variable
is not a file or pointer.

142

Illegal parameter substitution
The type of an actual parameter is not compatible with
of the corresponding formal parameter.

143

the

type

Loop control variable must be an unstructured, non-floating point
scalar
The control variable in a FOR loop must be
subrange, or user-defined scalar type;
variable.

144

that

an integer, integer
it cannot be a real

Illegal type of expression
The specified expression evaluates to a type that is incompatible
in this position.

A-8

DIAGNOSTIC MESSAGES
145

Type conflict between control variable and loop bounds
The type of the control variable in a FOR loop
with the type of the bounds you specified.

146

incompatible

Assignment of files not allowed
You cannot assign one file to another.
used to give values to files.

147

Output procedures must be

Label types incompatible with selecting expression
The type of a case label is incompatible with the type to which
the selecting expression evaluates. Case labels and selecting
expressions must be of compatible types.

148

Subrange bounds must be scalar
You can specify subranges of scalar
specify a real or string subrange.

149

types

only.

You

Index type must not be integer
The index type of a nondynamic array cannot be integer,
it can be an integer subrange.

150

the

name

formal

function

No such field in this record
You attempted to access a record by an incorrect
field name.

153

function

Assignment to formal function parameter is not allowed
You cannot assign a value
parameter.

152

although

Assignment to this function is not allowed
You cannot assign a value to an external or predeclared
identifier.

151

cannot

Error count exceeds error limit.

nonexistent

Compilation aborted

The number of errors exceeds 30, the limit set by the ERROR LIMIT
option.
154

Type of parameter must be integer
The actual parameter passed to this function or procedure must be
an integer.

A-9

DIAGNOSTIC MESSAGES
155

Recursive %INCLUDE not allowed.
The %INCLUDE directive cannot
directive appears.

156

Compilation aborted
include

the

file

which

Multidefined case label
The same case label refers to more than one statement.
label can be used only once within the CASE statement.

157

the

Each case

Case label range exceeds 1000
The range of ordinal values between the largest and smallest case
labels must not exceed 1000.

158

Missing corresponding variant declaration
In a call to NEW or DISPOSE, more tagfield constants were
specified than the number of nested variants in the record type
to which the pointer refers.

159

Double, real or string tagfields not allowed
Tag fields cannot be
scalar.

160

real

string

variables,

but

Previous declaration was not forward
The reiteration of a procedure or function that was
declared is illegal.

161

must

not

forward

Procedure/function has already been forward declared
The subprogram has already been forward declared.

162

Undeclared procedure or function:

<name>

A procedure or function was forward-declared but
never declared.
163

block

was

Type of parameter must be real or integer
The subprogram
parameter.

164

its

requires

real

integer

expression

This procedure/function cannot be an actual parameter
The specified predeclared procedure or function cannot be an
actual parameter.
If you must use it in the subprogram, call it
directly.

A-10

DIAGNOSTIC MESSAGES
165

Multidefined label
A label appears in front of more than one statement in
executable section.

166

single

Multideclared label
The program declares the same label more than once.

167

Undeclared label
The program contains a label that has not been declared.

168

Undefined label:

<label>

The program defines a label, but does not use the
executable section.
169

the

between

and

Set element value must not exceed 255
The ordinal value of an element of a set must be
255.

170

label

Value parameter expected
A subprogram that is passed as an actual parameter can have
value parameters.

171

Type of variable must be textfile (FILE OF CHAR)
The specified operation or subprogram
variable as an operand or param~ter.

172

173

only

requires

text

file

The program heading specifies an external file that has not
declared at program or module level.

been

Undeclared external file

Negative set elements not allowed
The value of an integer set element must be between 0 and 255.

174

Type of parameter must be file
The specified subprogram requires a file as a parameter.

175

INPUT not declared as an external file
The program makes an implicit reference to the file variable
INPUT, but INPUT is either not declared or has been redeclared at
an inner level.

A-11

DIAGNOSTIC MESSAGES
176

OUTPUT not declared as an external file
The program makes an implicit reference to the file variable
OUTPUT, but OUTPUT is either not declared or has been redeclared
at an inner level.

177

Assignment to function identifier not allowed here
Assignment to a function identifier is allowed
function block.

178

within

the

Multidefined record variant
A constant tag field value appears
definition of a record variant.

179

only

than

once

the

File of file type not allowed
You cannot declare a file that has components of a file type.

181

Array bounds too large
The bounds of an array are too large to allow the elements of the
array to be accessed correctly.

182

Expression must be scalar
The expression must specify a scalar value;
a re not 1 eg a 1 •

183

%IMMED,
%DESCR,
procedure/function

%STDESCR

allowed

structured variables

only

external

These extended parameter specifiers are allowed
procedures and functions which are declared EXTERN.
184

only

for

can

have

External procedure has same name as main program
Program and procedure names must be unique.

185

Formal procedures may have at most 20 parameters
A procedure name that is defined as a formal parameter
at most 20 value parameters.

186

Formal procedures may not have dynamic array parameters
You cannot pass a dynamic array as a parameter
that is itself passed as a parameter.

187

procedure

assignment

involving

Illegal dynamic array assignment
The program attempts to perform an illegal
dynamic arrays.

A-12

DIAGNOSTIC MESSAGES
188

Parameter must be scalar and not real or double
The parameters to the predeclared functions SUCC and PRED must be
scalar types, and cannot be one of the real types.

189

Actual parameter must be a variable
When you use VAR ~ith a formal parameter, the corresponding
actual parameter must be a variable and not a general expression.

190

READLN/WRITELN/PAGE are defined only for textfiles
The predeclared procedures READLN, WRITELN, and PAGE operate only
on text files.

191

READ/WRITE require input/output parameter list
The READ and WRITE procedures require
you cannot omit the parameter list.

192

least

one

parameter;

Illegal type of input/output parameter
Arrays, sets, records, and pointers cannot be parameters
READ and WRITE procedures.

193

the

Field width parameter must be of type INTEGER
The field width you specify must be an integer.

194

Variable must be of type PACKED ARRAY[l •• 11] OF CHAR
The DATE and TIME procedures require a parameter of this type.

195

Type of variable must be pointer
The statement syntax requires a variable of pointer type.

196

Type of variable does not agree with tagfield type
The type of a variable in a tag value list is
the tag field type.

197

with

(single-

Type of parameter must be REAL or DOUBLE
The
statement
syntax
double-precision) value.

198

incompatible

requires

real

Type of parameter must be DOUBLE
The statement syntax requires a double-precision value.

A-13

DIAGNOSTIC MESSAGES
199

Parameter must be of numeric type
The ~rocedure or function requires
value.

200

integer

real

number

Parameter must be scalar or pointer and not real
The procedure or function requires an integer, user-defined
scalar, Boolean, integer subrange, user-defined scalar subrange,
or pointer parameter.

201

Error in real constant:

digit expected

A real constant contains a nonnumeric character where
is required.

202

numeral

String constant must not exceed source line
The end of the line occurs before the apostrophe that closes a
string.
Make sure that the second apostrophe has not been left
out.

203

Integer constant exceeds range
An integer constant is outside the permitted
(that is, -2**31 to 2**31-1).

204

integers

Actual parameter is not of correct type
The actual parameter is not
corresponding formal parameter.

205

range

compatible

type

with

the

Zero length string not allowed
You cannot specify a string that has no characters.

206

Illegal digit in octal or hexadecimal constant
An octal or hexadecimal constant contains an illegal digit.

207

Real or double constant out of range
A single- or double-precision real number is outside
the
permitted range -- 0.29*10**(-38)
to l.7*(10**38) for positive
for
negative
numbers and -0.29*10**(-38)
to -1.7*(10**38)
numbers.

208

Data type cannot be initialized
This variable contains a type that cannot be initialized, such as
a file.

A-14

DIAGNOSTIC MESSAGES
209

Variable has been previously initialized
You can specify only one VALUE declaration for a variable.

210

variable is not array or record type
The VALUE initialization for a variable that is not a
an array contains a constructor.

211

record

Incorrect number of values for this variable
The VALUE declaration contains too many or too few values for the
variable being initialized.

212

Repetition factor must be positive integer constant
The repetition factor in an
positive integer constant.

213

214

array

initialization

must

The optional type identifier must be compatible with the type
variable to be initialized.

Type identifier does not match type of variable

Incorrect type of value element
A constant appearing in a VALUE initialization has a type other
than that of the variable, record field, or array element to be
initialized.

215

RMS record size is out of range
The record size specified in the OPEN procedure call exceeds
maximum.

216

the

Type OLD is not allowed for this file
You cannot specify OLD for an internal file.

217

%DESCR, %STDESCR not allowed for procedure or function parameters
The only extended mechanism specifier that can
PROCEDURE and FUNCTION parameters is %IMMED.

218

applied

Array must be unpacked
An array parameter to PACK or UNPACK is not unpacked correctly.

219

Array must be packed
An array parameter to PACK or UNPACK is not packed correctly.

A-15

DIAGNOSTIC MESSAGES
220

Packed bounds must not exceed unpacked bounds
The bounds of the packed array exceed the unpacked bounds.

221

%STDESCR not allowed for this type
This mechanism specifier can be applied only to strings
packed dynamic arrays of CHAR indexed by integer.

222

%DESCR not allowed for this type
This mechanism specifier can be applied only to the
scalar types and to unpacked arrays of these types.

223

and

predefined

%IMMED not allowed for this type
This mechanism specifier can be applied only to types that occupy
4 bytes or less, or to PROCEDURE or FUNCTION parameters.

224

%DESCR, %IMMED, %STDESCR not allowed for VAR parameters
You cannot combine the %DESCR,
%STDESCR,
specifiers with the VAR specifier.

225

OPEN

statement

mechanism

that

not

Too many nested scopes of identifiers
You can have only 20 levels of nesting.
occurs with each block or WITH statement.

251

%IMMED

Illegal file attribute specification
You specified an attribute in the
recognized by the compiler.

250

and

new

nesting

level

Too many nested procedures and/or functions
Subprograms can be nested no more than 20 levels deep.

252

Assignment to function not
conflict

allowed

This error is generated when
function with the same name.
255

259

here.

function

Probable

name/scope

nested

inside

The PASCAL compiler diagnoses only the first 20
source line.

errors

each

The expression is too deeply nested. To correct this error,
should separately evaluate some parts of the expression.

you

Too many errors on this source line

Expression too complicated

A-16

DIAGNOSTIC MESSAGES

260

Too many nonlocal labels
The subprogram contains more than 1000 labels that
at a higher level, that is, not locally declared.

261

are

declared

Declarations out of order or repeated declaration sections
The declarations must be in the following order:
constants, types, variables, values, and subprograms.
main program can contain value declarations.

263

Program segment too large:
bytes

branch

displacement

labels,
Only the

32767

exceeds

A statement is too large to allow the generation of a branch
instruction to span the statement. Use subprogram calls to break
the program into smaller units.
300

Division by zero·
The program attempts to divide by zero.

302

Index expression out of bounds
The value of the expression
subscripts of this array.

303

outside

the

range

the

Value to be assigned is out of bounds
The value to the right of the assignment operator is out of range
for the variable to which it is being assigned.

304

Element expression out of range
The value of the expression is out of range for the array element
to which you are assigning it.

305

Dimension specification out of range
The second argument to UPPER or LOWER specifies an array
dimension greater than the number of dimensions of the first
argument.

306

Index type
declaration

dynamic

array

parameter

exceeds

range

The index type of the actual dynamic array parameter
beyond the range declared in the formal parameter list.

401

Warning:

extends

Identifier exceeds nn characters

Identifiers can be any length, but PASCAL scans only the first 15
characters for uniqueness.

A-17

DIAGNOSTIC MESSAGES
402

Warning: Error in option specification
A compiler option is incorrectly specified in the source code.

403

Warning:

Source input after •END.• ignored

The compiler ignores any characters after the END that terminates
the program.

404

Warning:

Duplicate external procedure name

Two external procedures or functions have been declared with the
same
name.
They
refer to the same externally compiled
subprogram.

405

Warning:

LABEL Declaration in module ignored

The compiler ignores label declarations at the outermost level in
a module.

450

Nonstandard Pascal:

Exponentiation

451

Nonstandard Pascal:

Value declaration

452

Nonstandard Pascal:

OTHERWISE clause

453

Nonstandard Pascal:

%INCLUDE directive

454

Nonstandard Pascal:

MODULE declaration

456

Nonstandard Pascal:

'$' OR '

457

Nonstandard Pascal:

Dynamic arrays

458

Nonstandard Pascal:

%IMMED, %DESCR, or %STDESCR parameter

459

Nonstandard Pascal:

Octal or hexadecimal constant

460

Nonstandard Pascal:

Double precision constant

461

Nonstandard Pascal:

External procedure declaration

462

Nonstandard Pascal:

Octal or hexadecimal data output

463

Nonstandard Pascal:

Output of user-defined scalar

' in identifier(s)

A-18

DIAGNOSTIC MESSAGES
464

Nonstandard Pascal:

Input of string or user-defined scalar

465

Nonstandard Pascal:

Input/output of double precision data

466

Nonstandard Pascal:
procedure

Implementation-defined

A.2

RUN-TIME ERROR MESSAGES

type,

function,

When an error occurs at run-time, VAX-11 PASCAL issues an error
message and aborts execution. The run-time error messages appear in
the format:
%PAS-F-code, Text
code
An abbreviation of the message text.
by this code.

Messages

are

alphabetized

Text
The explanation of the error.
Some conditions, particularly I/O errors, may cause several messages
to be printed. The first message is a general diagnostic specifying
the file being accessed (if any) when the error occurred. Then a more
specific PASCAL message may be issued to clarify the nature of the
error. Finally, a VAX-11 RMS error message may be printed.
In most
cases, you should be able to understand .the error by looking up the
first two messages in the list below.
If not, refer to the VAX/VMS
System Messages and Recovery Procedures Manual for an explanation of
the VAX-11 RMS error message.
ATTDISINV Attempt to dispose invalid pointer value xxx at user PC xxx
The DISPOSE procedure was called with an illegal parameter value,
probably because of an uninitialized pointer. You should use the
NEW procedure to correctly allocate the pointer.
CASSELBOU CASE selector out of bounds at user PC xxx
In a CASE statement, the case selector expression does not
correspond to one of the case label values, and no OTHERWISE
clause is specified. This message occurs only when the CHECK
option is in effect.
ERRACCFIL Error in accessing file nnnnnn
This message identifies the file being accessed when an I/O error
occurred.

A-19

DIAGNOSTIC MESSAGES
ERRCLOFIL Error closing file
An error occurred while a file was being closed.
This is an
internal PASCAL error and should be reported to DIGITAL. Please
submit a Software Performance Report (SPR), including an example
program if possible.
ERROPECRE Error opening/creating file
An error occurred when the system attempted to open or create the
file.
The parameters specified in the OPEN procedure (or the
defaults, if the OPEN procedure was not used) are probably
incorrect for this file.
ERRRESFIL Error resetting file
An error occurred during execution of the RESET procedure.
This
is an internal PASCAL error and should be reported to DIGITAL.
Please submit a Software Performance Report (SPR), including an
example program if possible.
ERRREWFIL Error rewriting file
An error occurred during execution of the REWRITE procedure.
This is an internal PASCAL error and should be reported to
DIGITAL. Please submit a Software Performance Report (SPR),
including an example program if possible.
FILBUFNOT File buffer not. allocated
The system could not find enough space to allocate the file
buffer.
This means that too many files are open or too many
pointers are in use.
FILNOTCLO Files INPUT and OUTPUT cannot be closed by user
You cannot call CLOSE for the predeclared
and OUTPUT.

file

variables

INPUT

FILOUTINV File OUTPUT opened with invalid parameters
You can specify only a carriage control option when you open
predeclared file variable OUTPUT.

the

FILTYPNOT File type not appropriate
You tried to open for direct access (DIRECT) a file of type TEXT,
or a file with variable-length records.
INPCONERR Input conversion error
The system found erroneous input when reading a text file.

A-20

DIAGNOSTIC MESSAGES
INVASGINC Invalid assignment of incompatible dynamic arrays at user pc
xxx
The program tried to assign incompatible dynamic arrays to one
another.
For the assignment to be legal, the arrays must have
the same element type and the same upper and lower bounds for
each dimension. This message appears only if CHECK is enabled.
LINLENEXC Line length exceeded, line length = xxx
The length of an output line was greater than the maximum allowed
by the record size for this file.
Check to be sure that you did
not omit a call to the WRITELN procedure.
If you must write
lines of this length, increase the record size in the OPEN
statement.
LINLIMEXC LINELIMIT exceeded, LINELIMIT = xxx
The number of lines output to the specified file exceeds the
limit.
Make sure that the excessive output was not caused by an
infinite loop and increase the line limit if necessary.
OUTCONERR Output conversion error
The program tried to write data of an incorrect type to a text
file.
Make sure that all output values are properly defined.
PROEXCHEA Process exceeds heap maximum size at user PC xxx
The system could not find enough space to allocate storage for a
pointer variable.
This error is probably caused by an infinite
loop that calls the NEW procedure, thus attempting to allocate an
infinite amount of heap storage.
If the program does not include
an infinite loop, your process may actually require more heap
storage than the maximum process size allows.
In this case, try
to make your program smaller; if you cannot, ask your system
manager about increasing the maximum process size.
PROEXCSTA Process exceeds stack maximum size at user PC xxx
The system could not expand the stack to make room for the last
procedure or function called. This error is probably caused by
infinite recursion, where a number of procedures and functions
call each other without returning. Make sure that the program
does not include this type of logic error.
If the program logic
is sound, the process may actually require more space than the
maximum process size allows.
In this case, try to make your
program smaller;
if you cannot, ask your system manager about
increasing the maximum process size.
RESREQACC RESET required before accessing file
You can use the FIND procedure only on files that
input.

A-21

are

open

for

DIAGNOSTIC MESSAGES
RESREQREA RESET required before reading the file
The program did not call the RESET
read the file.

procedure

before

trying

The program did not call the REWRITE procedure before
write to the file.

trying

REWREQWRI REWRITE required before writing to file

SETASGBOU Set assignment out of bounds at user PC xxx
The program tried to assign an illegal value to a set variable.
Make sure that all set assignments specify values that are within
the bounds of the set. This message appears only if CHECK is
enabled.
SUBASGBOU Subrange assignment out of bounds at user PC xxx
The program tried to assign an illegal value to a subrange
variabls. Make sure that all subrange assignments specify values
that are within the bounds of the subrange. This message appears
only if CHECK is enabled.

A-22

APPENDIX B
CONTENTS OF RUN-TIME STACK DURING PROCEDURE CALLS

The illustrations in this appendix outline the events that occur
during a
procedure call, and show the contents of the run-time stack
after each event.

B-1

CONTENTS OF RUN-TIME STACK DURING PROCEDURE CALLS

0 Before procedure call:
lower addresses

:SP
Stack grows
toward lower
addresses

calling
procedure local
data area

:FP

higher addresses
SP = Stack Pointer
FP = Frame Pointer

@ The calling procedure's actions:

First:
Decrements SP by 4 times
number of parameters &
stores actual parameters
on stack.
parameter 1

called
procedure
parameters

parameter n

calling
procedure
local data
area

:FP

Second:
Calculates "static link"
to allow the called procedure
to find the stack frame
of its declaring procedure.
Stores static link in R1.

Finally:
Issues CALLS instruction.
ZK-071-80

Figure B-1

Contents of Run-Time Stack During Procedure Calls

8-2

CONTENTS OF RUN-TIME STACK DURING PROCEDURE CALLS

6) The CALLS instruction's actions:
Finally:
Creates and pushes
stack frame.

First:

Condition handler

Pushes parameter count &
fills with zero-bytes to a
longword size.

:FP

Second:
Sets new argument pointer
(AP) equal to current SP.

...
'--~

PSW

old AP

called
procedure
stack
frame

mask

FP
PC
R2-R11 saved
as needed

parameter count
and zeros
called
procedure
parameters

Third:
Adjusts stack to a
longword boundary.

calling
procedure
data area

G) The called procedure's actions:
First:

Third·

Loads base register R11 with the
address of the program-level
variables.

Allocates space for
local data and
copies value parameters.

Second:

I-{

local
data

Pushes static link (R1) and
local AP on stack.

SP
local AP

_ _ _1_o_c:-'1_A_P_ _ _

static link
·condition handler

mask
called
procedure
stack frame

value parameters
& local data

Finally:
Saves SP at -12(FP).

:FP

PSW

old AP
FP
PC
R2-R11
as needed
parameter count
and zeros

:AP

calling procedure
parameters
calling procedure
data area

- ....

-Figure B-1 (Cont.)

Contents of Run-Time Stack During Procedure Calls

B-3

APPENDIX C

VAX-11 SYMBOLIC DEBUGGER COMMAND SUMMARY

This appendix lists in alphabetical order each debugger command with a
format description, a list of qualifiers, a list of parameters, and a
brief description of the command's function.
The boldface letters
indicate the minimum abbreviation that you must type for the debugger
to recognize the command name, qualifier, or parameter.

C-1

VAX-11 SYMBOLIC DEBUGGER COMMAND SUMMARY

Function

Format
CANCEL BREAK[/ALL]
[address-expression]

Cancels specified breakpoint or all breakpoints.

CANCEL EXCEPTION BREAK

Cancels effects of SET EXCEPTION BREAK.

CANCEL MODE

Sets all modes and types to their default values for the current
language.

CANCEL MODULE [/ALL] [module [,module ... ]]

Cancels specified modules or all modules.

CANCEL SCOPE

Sets scope to its default value (PC scoping).

CANCEL TRACE [/qualifier]
[address-expression]
/ALL
/BRANCH
/CALL

Cancels the specified tracepoint or the specified opcode tracing or all tracepoints and opcode tracing.

CANCEL TYPE/OVERRIDE

Sets the override type to none.

CANCEL WATCH [/ALL]
[variable-reference]

Cancels the specified watchpoint or all watchpoints.

Interrupts execution of the program.

DEPOSIT [lqualifier] ... variable-reference =data
/ASCll:length
/BYTE
/DECIMAL
/HEXADECIMAL
/INSTRUCTION
/LONG
/OCTAL
/WORD

Stores the specified value(s) at the specified location.

EVALUATE[/ qualifier ] ... expression
/ADDRESS
/LONG
/DECIMAL
/BYTE
/HEXADECIMAL
/WORD
/OCTAL
/ASCII

Evaluates expressions or bit ranges, and displays value.

EXAMINE [/qualifier] ... addr-expr
/ASCll:length
/BYTE
/DECIMAL
/HEXADECIMAL
/INSTRUCTION
/LONG
/NOSYMBOLIC
/OCTAL
/SYMBOLIC
/WORD

Displays the contents of the specified addresses and range of
addresses.

EXIT

Ends a debugging session or specifies the end of a command
procedure.

GO [address-expression]

Starts or continues program execution.

HELP topic [subtopic ... ]

Displays a description of the specified command.

SET BREAK[/AFTER:count] address-expression
[DO (cmd[;cmd ... ])]

Establishes a breakpoint at the specified address.

SET EXCEPTION BREAK

Requests that the debugger treat external exception conditions
as breakpoints.

SET LANGUAGE language-name

Sets the current language.

SET LOG file-specification

Sets the file specification of the log file.

SET MODE mode-keyword [,mode-keyword]

Sets the entry/display modes. Mode-keyword can be:
DECIMAL, HEXADECIMAL, OCTAL, NOSYMBOLIC, or
SYMBOLIC.
(continued on next page)

C-2

VAX-11 SYMBOLIC DEBUGGER COMMAND SUMMARY

Format

Function

SET MODULE [/ALL] [module-name
[,module-name] ... ]

Adds the symbols in the specified modules or all modules to
the debugger symbol table.

SET OUTPUT option [,option ... ]

Controls the debugger's output configuration. Option can be
LOG, NOLOG, TERMINAL, NOTERMINAL, VERIFY, or
NOVERIFY.

SET SCOPE scope [,scope ... ]

Specifies scopes to be searched to find a symbol.

SET STEP condition [,condition ... ]

Specifies the step conditions. Condition can be INSTRUCTION, LINE, INTO, OVER, SYSTEM, or NOSYSTEM.

SET TRACE [/qualifier] [address-expression]
/BRANCH
/CALL

Establishes a tracepoint at the specified address or establishes
the specified opcode tracing.

SET TYPE [/OVERRIDE] type-keyword

Sets the default data type for the DEPOSIT and EXAMINE
commands. Type-keyword can be ASCII:length, BYTE, INSTRUCTION, LONG, or WORD.

SET WATCH variable-reference

Establishes a watchpoint at the specified address.

SHOW BREAK

Displays current breakpoints.

SHOW CALLS [integer]

Displays current location and previous calls.

SHOW LANGUAGE

Displays current language.

SHOW LOG

Displays the name of the log file.

SHOW MODE

Displays current entry/display modes.

SHOW MODULE

Lists the modules in the image and shows which are currently
included in the debugger symbol table.

SHOW OUTPUT

Displays the debugger's output configuration.

SHOW SCOPE

Displays the current scope search list.

SHOW STEP

Displays current STEP conditions

SHOW TRACE

Displays current tracepoints and opcode tracing.

SHOW TYPE

Displays current default type or override type.

SHOW WATCH

Displays current watchpoints.

STEP [/qualifier] [integer]
/LINE
/INTO
/OVER
/NOSYSTEM
/SYSTEM
/INSTRUCTION

Executes one or a specified number of instructions or lines.

@file-spec

Accepts commands from specified command procedure.

C-3

APPENDIX D
VAX-11 SYMBOLIC DEBUGGER AND PASCAL-SPECIFIC MESSAGES

If the debugger encounters an error, it displays a message
terminal. The general format of a debugger message is:

the

%DEBUG-l-code, text
1

A severity level indicator.
It has a value
of
I
for
informational messages, W for warning messages, E for error
messages, and F for fatal messages.
code
An abbreviation of the message text; the message descriptions in
this appendix are alphabetized by this code.
text
The explanation of the message.
For example:
%DEBUG-W-DIVBYZERO, attempted to divide by zero
Listed below are the messages displayed by the debugger. Each message
is accompanied by an explanation of the cause of the error and the
recommended user action to correct the error.
BADOPCODE, opcode xxx is unknown
Explanation: The opcode xxx specified in the DEPOSIT command is
unknown to the debugger. If the opcode is a valid VAX-11 MACRO
opcode, it is an opcode that has a synonomous opcode.
These
opcodes, such as MOVAF and MOVAL, generate the same instruction.
The debugger only recognizes one of them. Severity is warning.
User Action: Specify a valid opcode
synonym that the debugger accepts.

specify

the

opcode's

BADSCOPE, invalid pathname xxx, SCOPE not changed
Explanation: The scope xxx specified in the SET SCOPE command
contained a pathname that does not exist. Severity is warning.
User Action:

Specify a valid scope.

D-1

VAX-11 SYMBOLIC DEBUGGER AND PASCAL-SPECIFIC MESSAGES
BADSTARTPC, cannot access start PC

= xxx

Explanation: Location xxx is not an accessible address and
This is often caused when a GO
therefore cannot be executed.
command with no address specification is entered after the
The debugger tries to execute an
program has terminated.
instruction at location O, which is not accessible. Severity is
warning.
User Action: Specify a different address specification in the GO
command or, if the program has terminated, you can exit from the
debugger and initiate the program with the DCL RUN command.
BADTARGET, target location protected, cannot perform deposit
Explanation: The target specified as the location of a deposit
is protected. The deposit operation is not performed. Severity
is warning.
User Action:

Check the target location specified.

BADWATCH, cannot watch protected address xxx
Explanation: A SET WATCH command specified a protected address.
Note that you cannot set a watchpoint for a dynamically allocated
variable because these variables are stored on the stack.
In
PASCAL,
argument
lists
for functions and procedures are
dynamically allocated on the stack. Severity is warning.
User Action:
BITRANGE,

bi~

Do not set a watchpoint for this address.

range out of limits

Explanation: The EVALUATE command specified a bit field that
too wide. Severity is warning.

The low limit of the bit field is 0
the maximum range is <0:31>.

high

User Action:
limit is 31;

and

the

BRTOOFAR, destination xxx is too far for branch operand
Explanation: The DEPOSIT command specified a branch instruction
with a destination, xxx, too far from the current PC. Severity
is warning.
User Action: Change a BRB instruction to BRW or a BRW to JMP
specify a closer address.
DBGBUG, internal DEBUG coding error, please report no.
Explanation: An internal debugger error
Severity is informational.

has

been

nnn
encountered.

User Action: If the error is reproducible, submit a Software
Performance Report (SPR) to DIGITAL and, if possible, enclose
both a copy of the program being debugged and a logged debugging
session that reproduces the error.

D-2

VAX-11 SYMBOLIC DEBUGGER AND PASCAL-SPECIFIC MESSAGES
DBGERR, internal DEBUG coding error

Explanation:

An internal debugger error
Severity is error.

has

been

encountered.

User Action:

If the error is reproducible, submit a Software
Performance Report
(SPR)
to DIGITAL and, if possible, enclose
both a copy of the program being debugged and a logged debugging
session that reproduces the error.
DEBUGBUG, internal DEBUG coding error, please report no.

Explanation:

An internal debugger error
Severity is error.

has

been

nnn
encountered.

User Action:

Explanation:

An expression contained a division by O.

Severity

is warning.

User Action:

Reformulate the expression.

EXARANGE, invalid range of addresses

Explanation: The range of addresses specified was in the wrong
order.
The higher address preceded the lower address.
Severity
is warning.
User Action:

Reenter the command with a valid address range.

EXITSTATUS, is xxx

Explanation:

The program has exited with the status xxx.
See
the VAX/VMS System Services Reference Manual for more information
about the VAX/VMS exit status codes.
Severity is informational.

User Action:

None.

EXPSTKOVR, expression exceeds maximum nesting level

Explanation:

The

expression

too

complex.

Severity

Reduce the nesting of parentheses and simplify

the

warning.

User Action:
expression.

EXPTDOPR, expected operator but found operand xxx

Explanation:
found instead.

An operator was expected
Severity is warning.

User Action:

Reenter the command with a correct operator.

D-3

but

the

value

xxx

was

VAX-11 SYMBOLIC DEBUGGER AND PASCAL-SPECIFIC MESSAGES
FILEASGN, assignment of files not allowed
Explanation: A file cannot appear as the
command. Severity is warning.
User Action:

target

DEPOSIT

None.

FILEVERS, unsupported file version
Explanation: The file version number generated by the
is not supported by the debugger.
Severity is warning.

compiler

User Action:
DIGITAL.

Report

(SPR)

Explanation: A floating-point overflow occurred at or
location xxx. Severity is warning.

near

the

User Action:
to occur.

overflow

Submit

Software

Performance

FLTOVER, floating overflow at or near xxx

Correct the calculations that caused

the

FLTUNDER, floating underflow at or near xxx
Explantion: A floating-point underflow occurred at or
location xxx. Severity is warning.
User Action:

near

the

Correct the calculation that caused the underflow.

PRERANGE, storage package range error
Explanation: Data used to control internal storage allocation is
corrupt.
Severity is error.
User Action:
If DEPOSIT commands or your program has
not
modified
the
debugger's
storage area, submit a Software
Performance Report (SPR) to DIGITAL.
FRESIZE, storage package size error
Explanation: Data used to control internal storage allocation is
corrupt. Severity is error.
User Action:
If DEPOSIT commands or the user program
modified
the
debugger's
storage area, submit a
Performance Report (SPR) to DIGITAL.

has not
Software

ILLINDTYPE, index type must be scalar or subrange
Explanation: An index for an array must be a scalar variable,
constant, or variable of a scalar subrange type.
Severity is
warning.
User Action:
subrange.

Change the index to a scalar variable or

D-4

scalar

VAX-11 SYMBOLIC DEBUGGER AND PASCAL-SPECIFIC MESSAGES
ILLINSET, expression preceding 'IN' incompatible with set base type
Explanation: The expression specified before the IN operator
not compatible with the set base type. Severity is warning.
User Action:
type.

Specify an

expression

compatible

with

the

base

one.

Severity

Explanation:
warning.

The pathname element xxx is illegal.

Severity

User Action:

Correct the pathname.

ILLOPER, xxx is an illegal operator
Explantion:
warning.

The operator xxx is an

illegal

User Action:

Specify a legal operator.

ILLPATH, illegal pathname element xxx

ILLREF, xxx is not a legal reference
Explanation: The reference xxx is not understood in the
stated. Severity is warning.

context

User Action: Make sure the symbols for the module being debugged
are present in the active symbol table and that they are
correctly spelled when referenced.
ILLSCALAR, scalar variable xxx has an out of range value of

yyy

(hex

ZZZ)

Explanation: The scalar variable xxx has a value that is out of
range.
The variable has the value yyy or in hexadecimal zzz.
Severity is warning.
User Action:

Correct the value assigned to the variable.

ILLSETELEM, set element type must be scalar or subrange
Explanation: A set element must be
subrange type. Severity is warning.

scalar

User Action: Correct the type of the set element
scalar subrange.

scalar

ILLTAGVAL, tag field aaa has an illegal or uninitialized value of
xxx, decimal xxx

hex

Explanation: The tag field aaa has an illegal
value xxx. Severity is informational.
User Action:

uninitialized

Check the state of the object you are referencing.

D-5

VAX-11 SYMBOLIC DEBUGGER AND PASCAL-SPECIFIC MESSAGES
ILLTYPE, illegal type of operand(s)
Explanation: The type of the operand is illegal for the operator
specified. Severity is warning.
User Action:

Change the operand.

IMPTERMNO, improperly terminated numeric string nnn
Explanation: Numeric string nnn with radix control did not have
a
terminating apostrophe or was followed by a nonnumeric
character. Severity is warning.
User Action:

Terminate the string with an apostrophe.

INCDSTNES, incorrect DST nesting in module xxx, compiler error
Explanation:
incorrectly.

The compiler is generating
Severity is error.

debugger

information

User Action: Check that your PASCAL source program is correctly
written.
Submit a Software Performance Report (SPR) to DIGITAL,
enclosing your source program.
INDNOTCOMP, index type not compatible with declaration
Explanation: The index type used to subscript an array
compatible with its declaration. Severity is warning.
User Action:

not

Change the index type.

INITIAL, language is xxx, module set to yyy
Explanation: This message is displayed when the debugger is
invoked by the image activator. The language is set to xxx and
the module to yyy.
Module yyy is the first module linked
containing an entry point and language xxx is the language used
in that module. Severity is informational.
User Action:

None.

INTEGER, this operation only valid on integers
Explanation: The command specified an operation with operands
that did not have integer values when integer values are
required. Severity is warning.
User Action: Use only
specified operation.

operands

that

have

integer

values

INTMEMMER, internal memory-pool error at location xxx
Explanation: An error occurred in memory at
Severity is fatal.

the

location

User Action: Submit a Software Performance
enclosing your source program.

Report

D-6

xxx.

DIGITAL,

VAX-11 SYMBOLIC DEBUGGER AND PASCAL-SPECIFIC MESSAGES
INTOVER, integer overflow at or near xxx
Explanation: An integer calculation overflowed at
location xxx. Severity is warning.
User Action: Correct any calculations in the
cause an integer overflow.

near

the

program

that

may

INVCHAR, invalid character
Explanation: The command contained a character that
in the command's context. Severity is warning.
User Action:

invalid

Reenter the command.

INVDIM, subscript error, was declared dimension (string)
Explanation: A reference to an array contained either
an
incorrect number of subscripts or the value of the subscripts is
outside of the bounds of the array. The dimension of the array
was specified by string. Severity is warning.
User Action: Specify the correct
values in the correct range.

number

subscripts

symbol

table

with

INVDSTREC, invalid DST record
Explanation:
encountered.

An invalid debugger
Severity is error.

record

was

User Action: If DEPOSIT commands or your program has
not
modified
the
debugger's
storage area, submit a Software
Performance Report (SPR) to Digital.
INVEXPR, invalid expression detected at or near xxx
Explanation: An invalid expression
location xxx. Severity is warning.
User Action:

was

detected

near

Correct the expression.

INVFLOAT, variable has invalid floating point format
Explanation: A floating-point number has an invalid bit pattern.
This error can be caused by depositing a value with a type
qualifier into an address associated with a floating-point type
variable. Severity is informational.
User Action: Examine the value of the symbol
qualifier to override the floating-point format.

with

type

INVNUMBER, invalid numeric string 'nnn'
Explanation: The numeric string 'nnn' is invalid in the
language. Severity is warning.

current

User Action: Specify the value in another numeric format or set
the language to one that accepts this type of numeric string.

D-7

VAX-11 SYMBOLIC DEBUGGER AND PASCAL-SPECIFIC MESSAGES
INVOPR, unrecognized operator in expression
Explanation: An expression
debugger does not recognize.
User Action:

contained a character
Severity is warning.

that

the

Reenter the command with a valid expression.

INVPATH, improperly terminated pathname beginning with xxx
Explanation: The pathname beginning with
pathname. Severity is warning.
User Action:
command.

Check the

pathname

for

xxx

not

valid

errors

and

reenter

the

LABNOTFND, search for %label xxx using scope failed
Explanation: The label xxx could not be found
specified pathname or the current default scope.
warning.
User Action:

using
the
Severity is

Reenter the command with the correct pathname.

LASTCHANCE, stack exception handlers lost, re-initializing stack
Explanation: Error in user program caused the exception handling
mechanism to fail. Can be caused when the stack is overwritten
by the user program or by DEPOSIT commands. Severity is warning.
User Action:

Identify and correct the error in your program.

LINNOTFND, search for %line nnn using scope failed
Explanation: The line nnn specified does not exist in the
default scope{s).
Note that the debugger does not search for a
unique line number but only searches the current default scope
list. Severity is warning.
User Action:
number.

Specify the scope of the line or the

correct

line

Explanation: There are too many modules in the image for
debugger to keep track of. The excess modules are ignored.
cannot set the module to any of the ignored modules.

the
You

LONGDST, too many modules, some ignored

User Action: Use the SHOW MODULE command to determine which
modules are included.
If crucial modules were omitted, relink
the image, specifying first the modules needed for debugging.
MAXDIMSN, maximum number of subscripts is nnn
Explanation: An array reference specified too few or too many
subscripts. The array has nnn subscripts. Severity is warning.
User Action:
subscripts.

Reenter

the

command

D-8

with

correct

number

VAX-11 SYMBOLIC DEBUGGER AND PASCAL-SPECIFIC MESSAGES
MISMODBEG, missing Module-Begin record in DST, compiler error
Explanation: The compiler has incorrectly generated
for the debugger.
User Action: Submit a Software Performance
DIGITAL, enclosing your source program.

information

Report

(SPR)

MISMODEND, missing Module-End in DST for xxx, compiler error
Explanation: The compiler has incorrectly generated
for the debugger.
User Action: Submit a Software Performance
DIGITAL, enclosing your source program.

information

Report

(SPR)

specified
Severity

in
is

MODNOTADD, no space to add module yyy
Explanation: There was no room to add the modules
the SET MODULE command to the symbol table.
'y informational.

User Action: Use the SHOW MODULE command to show the modules
currently in the symbol table and the remaining space, and then
use the CANCEL MODULE command to free the needed space.
MULTOPR, multiple successive operators in expression
Explanation: There were two adjacent operators
Severity is warning.

expressions.

User Action: Use angle brackets or parentheses (depending on the
current language)
to separate the operators or enter a valid
expression.
NEEDMORE, unexpected end of command line
Explanation: The command entered was not complete.
part of a command was omitted. Severity is warning.
User Action:

required

Reenter the complete command.

NEEDOPR, expected operator but found operand:

xxx

Explanation: The operand xxx was found instead of
Severity is warning.
User Action:

operator.

Supply an operator.

NILDEREF, attempt to dereference a nil or null pointer value
Explanation: An attempt to dereference a
value was made. Severity is warning.
User Action: A nil or null pointer
correct the value of the pointer.

D-9

NIL

null

pointer

cannot

dereferenced,

VAX-11 SYMBOLIC DEBUGGER AND PASCAL-SPECIFIC MESSAGES
NILREF, NIL or an untyped pointer referenced at or near xxx
Explanation: The NIL pointer or untyped pointer
at or near the point xxx. Severity is warning.

was

referenced

User Action: Expressions containing NILA cannot be used.
Also
do not attempt to dereference untyped pointers defined by other
languages.
NOACCESSR, no read access to virtual address nnn
Explanation: The debugger does not have read access to the
address specified.
This error can be caused when an EXAMINE
command with no address specification is entered at the beginning
of a debugging session. Severity is warning.
User Action:

Specify an address that is within the image.

NOACCESSW, no write access to virtual address nnn
Explanation: A DEPOSIT, SET BREAK, or SET
TRACE
command
specified the address nnn, but the debugger does not have write
access to the page.
The debugger requires write access for
setting up breakpoints and tracepoints. Severity is warning.
User Action:

You cannot perform the requested operation.

NOANGLE, unmatched angle brackets in expression
Explanation: An expression did not have a
bracket. Severity is warning.
User Action:

closing

right

angle

Reenter the command with a ?omplete expression.

NOBRANCH, instruction requires branch-type operand
Explanation: A DEPOSIT command specified a branch
using an invalid addressing mode as the operand.
warning.

instruction
Severity is

User Action: Reenter the command using a valid branch operand in
the destination field.
NOBREAKS, no breakpoints are set
Explanation: The SHOW BREAK command was
entered
breakpoints were set. Severity is informational.
User Action:

and

None.

NOCALLS, no active call frames
Explanation: The SHOW CALLS command was entered and there were
no active calls.
There are no active calls after your program
has terminated. Severity is warning.
User Action:

None.

D-10

VAX-11 SYMBOLIC DEBUGGER AND PASCAL-SPECIFIC MESSAGES

NOCNVT, incompatible types, no conversion
Explanation: A DEPOSIT command specified incompatible
the variable type. Severity is warning.

data

User Action: Reenter the command and either specify the
data type or use a type qualifier.

for

correct

NOCURLOC, current location not defined
Explanation: The current location (the last location addressed
by a SET BREAK, SET TRACE, SET WATCH, EXAMINE, or DEPOSIT
command) is not defined. Severity is warning.
User Action: Check that the current location
defined by using one of the above commands.

correctly

NODECODE, cannot decode instruction

Explanation: The address specified in the EXAMINE command is not
the beginning of a valid VAX-11 instruction. This can be caused
by specifying an address that is in the middle of an instruction
or is in a data area. Severity is warning.
User Action:
instruction.

Specify

address

that

contains

valid

NODELIMTR, missing or invalid instruction operand delimiter
Explanation: A DEPOSIT command specified an invalid
operand format. Severity is warning.
User Action:

instruction

Reenter the command with valid operands.

NODEPOSIT, cannot deposit value
Explanation: The value following the equal sign (=) in a DEPOSIT
command cannot be deposited. Severity is warning.
User Action:

Change the value to be deposited.

NOEND, string beginning with xxx is missing end delimiter y
Explanation: A DEPOSIT command specified an ASCII or INSTRUCTION
string beginning with characters xxx that did not have a
terminating apostrophe. Severity is warning.
User Action:

Reenter the command with a terminating apostrophe.

NOEXAM, value cannot be examined
Explanation: The value in an identifier cannot be referenced
the EXAMINE command. Severity is warning.

User Action Check that the symbols
contained in the symbol table.

are

D-11

being

referenced

VAX-11 SYMBOLIC DEBUGGER AND PASCAL-SPECIFIC MESSAGES
NOFIELD, xxx is not a field in this record
Explanation: An attempt was made to reference a
not defined in the record.
Severity is warning.
User Action:

field

that

debugger

Check the field specified.

NOFREE, no free storage available
Explanation: No free storage is available for
execute the command. Severity is error.

the

User Action: Free storage by using the CANCEL MODULE command and
then reenter the command.
NOGLOBALS, some or all global symbols not accessible
Explanation: The image was linked with the /NODEBUG qualifier
and there are no global symbols in the symbol table.
This
message can also be caused if the
image has too many global
symbols.
Severity is informational.
User Action: Relink the image with the /DEBUG qualifier or,
if
the message was caused by an overflow condition, remove some of
the global symbol definitions from the image (if possible).
NOINSTRAN, cannot translate opcode at location xxx
Explanation: The address specified in the EXAMINE command is not
the beginning of a v.alid VAX-11 instruction. This can be caused
by specifying an address that is in the middle of an instruction
or is in a data area.
Severity is warning.
User Action:
instruction.

Specify

address

that

contains

valid

NOINSTPRED, no valid predecessor to an instruction
Explanation: An attempt was made to reference the precedessor of
an instruction, where no such predecessor is defined.
Severity
is warning.
User Action:

None.

NOLABEL, routine xxx has no %label nnn
Explanation: The label nnn does not exist in the scope xxx
is specified in the pathname. Severity is warning.

that

User Action: Specify a valid pathname -- either change the label
or the scope.

D-12

VAX-11 SYMBOLIC DEBUGGER AND PASCAL-SPECIFIC MESSAGES
NOLASTVAL, last value not defined
Explanation: The request for information about the last value
(\) cannot be supplied because the last value is not defined.
Severity is warning.
User Action:

None.

NOLINE, routine xxx has no %line nnn
Explanation: The line nnn does not exist in the scope xxx that
is specified in the pathname. This can be caused by a source
line number that does not exist or that does not contain
executable code in the source program. Severity is warning.
User Action: Specify a valid pathname -- either change the
number or the scope.

line

NOLITERAL, no literal translation exists for xxx
Explanation: The command attempted to find a literal translation
for a value.
The debugger does not support this operation.
Severity is warning.
User Action:

None.

NOLOCALS, image does not contain local symbols
Explanation: All of the modules in the image were compiled or
assembled without traceback information.
There is no local
symbol information in the image. Severity is informational.
User Action:
them.

Recompile or reassemble the modules and then relink

NONEWCUR, cannot retain new address.

'·' lost

Explanation: The current address has been lost, the new
cannot be determined. Severity is informational.
User Action:

address

None.

NONEWVAL, cannot retain new value, '\' lost
Explanation: The current value has been lost so
value
referenced
by a backslash character
determined. Severity is informational.
User Action:

that the last
(\) cannot be

None.

NOOPRND, missing operand in expression
Explanation: One or more operands
expression. Severity is warning.
User Action:

are

missing

from

Reenter the command with a complete expression.

D-13

VAX-11 SYMBOLIC DEBUGGER AND PASCAL-SPECIFIC MESSAGES
NOOPRTR, missing operator in expression
Explanation: The expression specified
operator. Severity is warning.
User Action:

does

not

contain

Add an operator to the expression.

NOPERMSYM, permanent symbol xxx is not defined
Explanation:
is warning.

The permanent symbol xxx is not defined.

User Action:

None.

Severity

NOPRED, logical predecessor not defined
Explanation: The logical predecessor of the identifier
instruction referenced is not defined. Severity is warning.
User Action:

None.

NORSTBLD, cannot build symbol table
Explanation: The debugger is unable to build a symbol table
because of errors in the format of the image file. Severity is
error.
User Action: Relink the image and, if the error is reproducible,
submit a Software Performance Report (SPR) to DIGITAL, explaining
how the image file was created.
NOSTMT, routine xxx has no statement sss
Explanation: The routine xxx does not
statement sss. Severity is warning.
User Action:

contain

the

specified

Check the routine or the statement specified.

NOSUCHBPT, no such breakpoint
Explanation: The CANCEL BREAK command specified an address that
is not the address of a breakpoint. Severity is informational.
User Action: Use the SHOW BREAK command to find the location of
the current breakpoints and then cancel any of these breakpoints.
NOSUCC, logical successor not defined
Explanation: The logical successor
identifier referenced is not defined.
User Action:

None.

D-14

of the
instruction
Severity is warning.

VAX-11 SYMBOLIC DEBUGGER AND PASCAL-SPECIFIC MESSAGES

NOSUCHLAB, no scope exists to look up %label xxx

Explanation:
table.

The label xxx is not listed in the
Severity is warning.

current

symbol

User Action: Specify the routine that contains this label as the
current setting of scope.
NOSUCHLAN, language xxx is unknown

Explanation: The debugger does not recognize the
language
specified.
This message can be caused by mistyping a language
that the debugger supports or by entering a language that the
debugger does not currently support. Severity is warning.
User Action:

Specify

valid

language

the

SET

LANGUAGE

current

symbol

command.
NOSUCHLIN, no scope exists to look up %line xxx

Explanation:
table.

The line xxx is not listed in
Severity is warning.

the

User Action: Specify the routine that contains this line as
current setting of scope.

the

NOSUCHMODU, module xxx is not in module chain

Explanation: The module xxx, specified in the SET
MODULE
command, does not exist in the image. This message can be caused
when a module name has been entered incorrectly or when the image
had too many modules for the debugger to handle.
Severity is
warning.
User Action:

Specify a module that is in the image.

NOSUCHTPT, no such tracepoint

Explanation: The CANCEL TRACE command specified an address that
was not the address of a tracepoint. Severity is informational.
User Action:

Use the SHOW TRACE command to display the
tracepoints and then cancel any of these tracepoints.

current

NOSUCHWPT, no such watchpoint

Explanation: The CANCEL WATCH command specified an address that
was not the address of a watchpoint. Severity is informational.
User Action: Use the SHOW WATCH command to display the
watchpoints and then cancel any that you want to cancel.

D-15

current

VAX-11 SYMBOLIC DEBUGGER AND .PASCAL-SPECIFIC MESSAGES
NOSYMBOL, symbol xxx is not in the symbol table
Explanation: The symbol xxx cannot be located in the debugger
symbol table.
This can be caused when the module that defines
the symbol has not been added to the debugger symbol table or
when a symbol name that is not in the image has been entered.
Severity is warning.
User Action: Add the required module to the debugger symbol
table with the SET MODULE command or specify the correct symbol
name.
NOTALLSYM, cannot initialize symbols for default module
Explanation: The debugger could not put the symbol
table
information for the first module specified in the LINK command
into the symbol table. Severity is informational.
User Action: Use the SET MODULE command to add
symbol table.

modules

the

NOTARRAY, type of variable is not array
Explanation: The variable being treated as an array has not been
defined as one. Severity is warning.
User Action:
made.

Check that the correct variable reference is

being

NOTASTRUCT, xxx was not declared as a structure
Explanation: A VAX-11 BLISS-32 structure reference specified a
symbol xxx that was not declared a structure. Severity is
warning.
User Action:

Reenter the command with a valid symbol reference.

NOTCMP, incompatible types, no conversion on assignment
Explanation: The types of the data and address expression in a
DEPOSIT command are incompatible, so the bit pattern of the data
was directly assigned to the address expression.
Severity is
informational.
User Action:

None.

NOTCMPEXT, incompatible types, value zero-extended on assignment
Explanation: The types of data and address expressions specified
in a DEPOSIT command are incompatible. The bit pattern of the
data was too small; the bit pattern was zero-extended on the
left before assignment. Severity is informational.
User Action:

None.

D-16

VAX-11 SYMBOLIC DEBUGGER AND PASCAL-SPECIFIC MESSAGES
NOTCMPTRNC,
incompatible
assignment

types,

high

order

bits

truncated

Explanation: The types of data and address expressions specified
in a DEPOSIT command are incompatible. The bit pattern of the
data was too large; the bit pattern was left-truncated before
assignment.
Severity is informational.
User Action:
NOTCOMMA,

None.

' , ' expected instead of xxx

Explanation: A comma (,) was expected
found.
Severity is warning.
User Action:

but

the

value

xxx

was

Change the expression to include a comma (,).

NOTCOMPAT, operands are of incompatible types
Explanation: The operands specified in the debugger
do not conform to PASCAL's rules of compatibility.
warning.
User Action:

instruction
Severity is

None.

NOTCONTIG, value of xxx is not contiguous
Explanation: An attempt was made to reference
whose value is stored in noncontiguous storage.

User Action: Reference only contiguously stored values
particular context.

identifier
in

this

NOTDONE, xxx not yet a supported feature
Explanation: A DEPOSIT command specified an instruction with a
literal that the debugger does not yet support.
Severity is
warning.
User Action:
NOTDOTDOT,

None.

' •• ' expected instead of xxx

Explanation: A subrange ( •• ) was expected but the value xxx
found instead. Severity is warning.
User Action:

was

Change the expression to contain a subrange.

NOTIDENT, identifier expected instead of xxx
Explanation: An identifier was expected but the
found instead. Severity is warning.
User Action:

value

xxx

Change the expression to contain an identifier.

D-17

was

VAX-11 SYMBOLIC DEBUGGER AND PASCAL-SPECIFIC MESSAGES

NOTIMPLAN, xxx is not implemented at command level
Explanation: The SET LANGUAGE command specified a language that
the debugger recognizes but does not yet support. Severity is
warning.
User Action:

Specify a language that the debugger supports.

NOTINTID, integer or identifier expected instead of xxx
Explanation: An integer or identifier was expected,
xxx was found instead. Severity is warning.
User Action:
xxx.

the

value

Add an integer or identifier in place of or

before

NOTLABEL, 'xxx' is not a label
Explanation: The value xxx is being treated as a label.
value is not a label in the program. Severity is warning.

This

User Action: Check the value being
correct label value.

the

specified

and

specify

NOTLINBND, program is not at a line boundary
Explanation: The GO command specified an address that contains
threaded code data.
The debugger cannot execute starting from
this address. Severity is warning.
User Action: Specify
instructions.

address

that

contains

executable

NOTLINE, 'xxx' is not a line
Explanation: The value xxx is being treated as a line number.
This value is not a line in the program. Severity is warning.
User Action: Check the value being
correct line number.

specified

and

specify

the

NOTPNTR, variable is not of pointer type
Explanation: The variable being used as a pointer is not defined
as one. Severity is warning.
User Action:

Change the variable to one of pointer type.

NOTPTR, variable must be of pointer or file type
Explanation: The variable should be
Severity is warning.
User.Action:

pointer

file

Specify a variable of pointer or file type.

D-18

type.

VAX-11 SYMBOLIC DEBUGGER AND PASCAL-SPECIFIC MESSAGES

NOTRACES, no tracepoints are set, no opcode tracing
Explanation: There are no tracepoints
Severity is informational.
User Action:

opcode

tracing

set.

None.

NOTRBRACK, ']' expected instead of xxx
Explanation: A right bracket (]) was expected;
was found instead. Severity is warning.
User Action:

the

value

xxx

Include a right bracket (]) in the expression.

NOTRPAREN, ')' expected instead of xxx
Explanation: A right parenthesis ())was expected;
xxx was found instead. Severity is warning.
User Action:

the

value

Include a right parenthesis ()) in the expression.

NOUNIQUE, SYMBOL xxx IS NOT UNIQUE
Explanation: The symbol specified was not in a default scope and
was defined in more than one scope. Severity is warning.
User Action: Specify the scope of the symbol in
change the default scope.

pathname

NOVALUE, reference does not have a value
Explanation: The reference specified in
have a value. Severity is warning.
User Action:

the

command

does

not

Change the reference.

NOWATCHES, no watchpoints are set
Explanation:

No watchpoints are set.

User Action:

None.

Severity is informational.

NOWBPT, cannot insert breakpoint
Explanation:
fatal.

This is an internal debugger

User Action: Submit a Software
DIGITAL, enclosing your source
debugging session.

D-19

error.

Severity

Performance Report (SPR) to
program and a log of your

VAX-11 SYMBOLIC DEBUGGER AND PASCAL-SPECIFIC MESSAGES
NOWOPCO, cannot replace breakpoint with opcode
Explanation:
fatal.

This is an internal debugger

User Action: Submit a Software
DIGITAL, enclosing your source
debugging session.

error.

Severity

Performance Report
(SPR)
to
program and a log of your

NOWPROT, cannot set protection
Explanation:
fatal.

This is an internal debugger

User Action: Submit a Software
DIGITAL, enclosing your source
debugging session.

error.

Severity

Performance Report
(SPR)
to
program and a log of your

NULLSTRNG, null string not allowed in expression
Explanation: A null string value
expression. Severity is warning.
User Action:

cannot

used

Do not use a null string in an expression.

NUMOPRNDS, xxx instructions must have nnn operands
Explanation: A DEPOSIT command xxx instruction with an incorrect
number of operands.
This instruction requires nnn operands.
Severity is warning.
User Action: Reenter the command using
operands with the instruction.

the

correct

number

NUMTRUNC, number truncated
Explanation: The debugger truncated the numeric data because it
exceeded the length of the data type. Severity is informational.
User Action:

None.

OPSYNTAX, instruction operand syntax error
Explanation: The DEPOSIT command contained an
an operand syntax error. Severity is warning.
User Action:

instruction

with

Reenter the command with a valid instruction.

OUTPUTLOST, output being lost, both NOTERMINAL and NOLOG are in effect
Explanation: The SET OUTPUT command has
set
the
output
conditions to NOTERMINAL and NOLOG; consequently, the output is
not displayed on the terminal or written to a log file.
The
output normally displayed by the debugger will not be available.
Severity is informational.
User Action: Use the SET OUTPUT command to send
terminal or to a log file.

D-20

output

the

VAX-11 SYMBOLIC DEBUGGER AND PASCAL-SPECIFIC MESSAGES
OUT_LMT, illegal value for parameter, maximum is xxx given
zzz
Explanation: The value specified was too large to
in the specified address.
Severity is fatal.
User Action:
maximum xxx.

value

Change the size of the value zzz to less

was

deposited
than

the

Severity

PARSEERR, internal parsing error
Explanation:
warning.

This is an internal debugger

User Action: Submit a Software
DIGITAL, enclosing your source
debugging session.

error.

Performance Report
(SPR)
to
program and a log of your

PARSTKOVR, parse stack overflow, simplify expression
Explanation: The expression was too complex for the debugger
evaluate. Severity is warning.
User Action:

Simplify the expression.

PATHLABEL, %LABEL must precede pathname when language is set to xxx
in

front

pathname.

Place the word %LABEL in
Using Action:
rather than in the pathname.

front

the

pathname

elements

pathname.

Explanation:
%LABEL
Severity is warning.

must

used

PATHTLONG, too many qualifiers on name
Explanation: There were
Severity is warning.
User Action:

too

many

Reduce the number of elements in the pathname.

PCNOTINSCP, PC is not within the scope of the routine declaring symbol
Explanation: A dynamically allocated variable was referenced and
the variable was not defined in the scope that contains the
current PC.
The value of the variable is undefined when you are
not currently executing the scope in which it is defined. The
debugger uses a value for the variable that may have no relation
to the symbol's current value. Severity is informational.
User Action: Reference only a dynamically allocated variable
when you are currently executing the scope in which it is
defined.

D-21

VAX-11 SYMBOLIC DEBUGGER AND PASCAL-SPECIFIC MESSAGES

REDEFREG, register name already defined

Explanation: The DEFINE command attempted to redefine a register
name.
The command
is ignored because you cannot redefine
register names.
Severity is warning.
User Action:

None.

RESOPCODE, opcode xxx is reserved

Explanation: Opcode
Severity is warning.
User Action:

xxx

reserved

for

use

DIGITAL.

near

None.

ROPRAND, reserved operand fault at or near xxx

Explanation:
location xxx.

User Action:
and do not
program.

A reserved operand fault occurred at
Severity is warning.

the

Do not use a reserved operand in your expression
deposit such a value into a variable used by your

RPARNFOUND, unmatched right parenthesis found

Explanation: A right parenthesis ()) was found
parenthesis ( () is missing. Severity is warning.
User Action:

but

the

left

Include the left parenthesis (().

RSTERR, error in symbol table

Explanation: There is
Severity is error.

format

error

the

symbol

table.

User Action:

If this is not caused by a user program error or a
DEPOSIT command, submit a Software Performance Report (SPR) to
DIGITAL enclosing your source program.

SETNOTCOMP, set element types not compatible

Explanation:
type of
warning.

A value was specified that is incompatible with the
elements contained in the specified set.
Severity is

User Action:

Change the value to one that is compatible.

STEPINTO, cannot step over PC = xxx

Explanation: The debugger was unable to step over the routine
Severity is
and executed a step into the routine instead.
informational.
User Action:

None.

D-22

VAX-11 SYMBOLIC DEBUGGER AND PASCAL-SPECIFIC MESSAGES
STGTRUNC, string truncated

Explanation:
exceeded
the
informational.

User Action:

The debugger truncated an ASCII string because
size of the ASCII data type.
Severity

it
is

None.

STRNGVAL, type of string character value must be integer

Explanation:
extended
warning.

The value specified inside the parentheses in the
string syntax must be of type INTEGER.
Severity is

User Action:

Change the type of the value to INTEGER.

STRVALRNG, string character value must be between 0 and 255

Explanation: The value inside the parentheses in the extended
string syntax must be between 0 and 255.
Severity is warning.
User Action:

Change the value to one between 0 and 255.

SUBOUTBNDS, subscript value zzz out of bounds at or near xxx

Explanation:
location xxx.

Subscript value zzz was out of bounds
Severity is warning.

User Action: Check the subscripts
location specified by xxx.

your

near

expression

the

SUBOUTVAL, value xxx of subscript yyy out of bounds

Explanation: An attempt to subscript out of
array was made.
Severity is warning.
User Action:

bounds

Change the value of the subscript.

SYMNOTACT, symbol xxx not active or not in active scope

Explanation: The symbol
Severity is warning.

xxx

not

active

User Action:

Check the symbol specified and, if
that you have defined the scope correctly.

call

frame.

correct,

check

syntax

error

SYNTAX, command syntax error at or near xxx

Explanation: The debugger encountered a
near element xxx. Severity is warning.
User Action:

Reenter the command.

D-23

command

VAX-11 SYMBOLIC DEBUGGER AND PASCAL-SPECIFIC MESSAGES
UNCOMP, feature not yet supported
Explanation: This feature
Severity is warning.
User Action:

not

supported

this

time.

None.

UNDEXP, undefined exponentiation at or near xxx
Explanation: An attempt was made to perform an exponentiation
operation at or near location xxx. The exponentiation operation
is undefined for the operand specified. Severity is warning.
User Action: Redefine
different operands.

exponentiation

the

operation

using

UNKNOWNTYP, type of xxx unknown to language zzz
Explanation: Type xxx is
Severity is warning.
User Action:
language.

not

used

the

current

Change to the type to one supported by the

language.
current

UNMTCHPARN, unmatched left parenthesis found
Explanation: A left parenthesis (() was found, but the
right parenthesis ()) is missing. Severity is warning.
User Action:

matching

Include the right parenthesis ()).

VALOUTBNDS, value assigned is out of bounds
Explanation: The value assigned to a variable of a subrange type
is out of bounds. Severity is informational.
User Action:

None.

VERIFYICF, xxx indirect command file yyy
Explanation: The debugger is verifying an indirect command file.
This message is displayed before the command file is executed and
after all the commands have been displayed.
Severity
is
informational.
User Action:

None.

WRONGLANG, language is not xxx
Explanation:
or variable
warning.

The language used to evaluate the last expression
reference is not the current language. Severity is

User Action: Do not change languages between the definitions of
last value
(\), logical predecessor (A), current location (.),
logical successor (RET), and their use.

D-24

VAX-11 SYMBOLIC DEBUGGER AND PASCAL-SPECIFIC MESSAGES
WRONGVAR, field xxx is not in current variant yyy associated with
field xxx

tag

Explanation:

Field xxx is not in the current variant.

User Action:

Check your program to verify the expected results.

D-25

INDEX

A
Access,
direct (random), 6-3, 6-4
remote, 6-7
sequential, 6-3, 6-5
Actual parameter list, 7-2, 7-3
Addresses, debugger, 5-3
data location, 5-4
symbolic, 5-3
program, 5-5
Address parameters--see By-reference mechanism
Argument count, 7-1
Argument list, 7-1, 7-6
Arguments to PASCAL subprograms,
7-6
Array descriptor, 7-4, 7-6
Assigning logical names, 6-2
Attributes, program section, 9-1
@file-spec command, debugger, 5-71

B
Binary numbers, debugger, 5-5
Bound procedure value, 7-6
Bounds checking, 2-2
BRIEF qualifier, 3-1, 3-3
By-descriptor mechanism, 7-2,
7-4
By-immediate-value mechanism,
7-2' 7-9
By-reference mechanism, 7-2, 7-6,
7-9
By-reference semantics, 7-2, 7-3
By-value semantics, 7-2

c
CALL instruction, 7-1
Calling conventions, PASCAL, 7-1
Calling Run-Time Library procedures, 7-12
Calling standard, procedure, 7-1
Calling system services, 7-6
Calls, procedure, 7-1
CALLS instruction, 7-1, B-2
CANCEL ALL command, debugger, 5-16
CANCEL BREAK command, debugger,
5-11, 5-1 7
CANCEL EXCEPTION BREAK command,
debugger, 5-11, 5-18
CANCEL MODE command, debugger,
5-10, 5-19

CANCEL MODULE command, debugger,
5-10, 5-20
CANCEL SCOPE command, debugger,
5-13, 5-21
CANCEL TRACE command, debugger,
5-11, 5-22
CANCEL TYPE/OVERRIDE command,
debugger, 5-10, 5-23
CANCEL WATCH command, debugger,
5-11, 5-24
CARRIAGE attribute, 6-6
Carriage control, 6-5
Character parameters, passing, 7-11
CHECK qualifier, 2-2, 2-6
Checking, bounds, 2-2
Commands,
ASSIGN, 6-2
EDIT, 1-1, 4-4
LINK, 1-1, 3-1
PASCAL, 1-1, 2-1
RUN, 1-1, 4-1
Debugger - see Debugger Commands
Command line qualifiers, 2-4
Communication,
DECnet, 6-8
interprocess, 6-6
network, 6-7
task-to-task, 6-7
Compiler error messages, A-1
Compiler listing, 2-3, 2-8, 2-15
Compiler qualifiers, 2-1
Compiling a program, 2-1
Concatenating source files, 2-7
Condition handler, 8-1
data accessible to, 8-4
default, 8-2
establishing, 8-5
example of, 8-10
function return values, 8-7
parameters for, 8-5
removing, 8-5
request of stack unwind by, 8-7
responses, 8-4
system-defined, 8-2
user written, 8-2, 8-3
Condition handling, 8-1
Condition signal, 8-3
Condition symbol, 8-3, 8-8
Condition symbol definition
files, 7-6
Condition value, 7-7, 8-2
format, 8-8
Creating and executing a program,
1-1
Cross-reference listing, 2-3,
2-11, 2-1 7

Index-!

INDEX
CROSS REFERENCE qualifier
(compiler) , 2-2, 2-3, 2-6,
2-11, 2-17
CROSS REFERENCE qualifier
(linker), 3-2, 3-3
CTRL/Y Command, debugger, 5-12,
5-25

D
Data representation,
floating-point, 9-8
DEBUG qualifier (compiler), 2-2,
2-3' 2-6
DEBUG qualifier (execution), 4-1
DEBUG qualifier (linker), 3-1,
3-4' 4-1, 4-2
Debugger, 2-3, 3-4, 4-1, 4-2,
4-3, 5-1 to 5-6
Debugger Commands,
@file-spec, 5-71
CANCEL ALL, 5-lo
CANCEL BREAK, 5-11, 5-17
CANCEL EXCEPTION BREAK, 5-11,
5-18
CANCEL MODE, 5-10, 5-20
CANCEL MODULE, 5-10, 5-20
CANCEL SCOPE, 5-13, 5-21
CANCEL TRACE, 5-11, 5-22
CANCEL TYPE/OVERRIDE, 5-10,
5-23
CANCEL WATCH, 5-11, 5-24
CTRLY/Y, 5-12, 5-25
DEPOSIT, 5-12, 5-26
EVALUATE, 5-12, 5-29
EXAMINE, 5-3, 5-12, 5-31
EXIT, 5-12, 5-34
Format, 5-2
GO, 5-12, 5-35
HELP, 5-36
SET BREAK, 5-11, 5-38
SET EXCEPTION BREAK, 5-11, 5-40
SET LANGUAGE, 5-9, 5-41
SET LOG, 5-9, 5-42
SET MODE, 5-10, 5-43
SET MODULE, 5-10, 5-45
SET OUTPUT, 5-10, 5-46
SET SCOPE, 5-14, 5-48
SET STEP, 5-12, 5-50
SET TRACE, 5-11, 5-52
SET TYPE, 5-10, 5-54
SET WATCH, 5-12, 5-56
SHOW BREAK, 5-11, 5-57
SHOW CALLS, 5-12, 5-58
SHOW LANGUAGE, 5-9, 5-59
SHOW LOG, 5-9, 5-60
SHOW MODE, 5-10, 5-61
SHOW MODULE, 5-10, 5-62
SHOW OUTPUT, 5-10, 5-63
SHOW SCOPE, 5-14, 5-64

Debugger Commands, (Cont.),
SHOW STEP, 5-12, 5-65
SHOW TRACE, 5-11, 5-66
SHOW TYPE, 5-10, 5-67
SHOW WATCH, 5-11, 5-68
STEP, 5-14, 5-65
Declaring Run-Time Library procedures, 7-12
Declaring system services, 7-6,
7-7, 7-9
DECnet communications, 6-8
DEPOSIT command, debugger, 5-12,
5-26
Descriptor, 7-2, 7-4, 7-6
Device, 1-2
Diagnostic messages,
compiler, A-1 to A-19
format of compiler, A-1
format of run-time, A-19
run time, A-19 to A-22
Direct access, 6-3, 6-5
DIRECT attribute, 6-4, 6-5
Directory, 1-3
Divide by zero, 8-9
Double-precision format, 9-9

E
EDIT command, 1-1
Entry mask, 7-6
Environment, PASCAL system, 9-1
Environment pointer, 7-6
Error,
compiler, A-1
correction, 4-1
default processing, 8-2
messages, A-1 through A-22
numbers, A-1
processing, 8-2, A-1
run time, 8-2, A-19
severity code, 8-8
ERROR LIMIT qualifier, 2-2, 2-3
Establish a condition handler,
8-5
EVALUATE command, debugger, 5-12,
5-29
EXAMINE command, debugger, 5-12,
5-31
Examining locations, debugger,
5-12, 5-29, 5-31
Example,
listing format, 2-16 to 2-20
debugger, 5-6, 5-72 to 5-81
Executable image, 3-2, 3-3
EXECUTABLE qualifier, 3-2, 3-3
Executing a program, l~l, 4-1
EXIT command, debugger, 5-12, 5-34
Extensions to standard PASCAL,
2-4
External subprograms, 7-2

Index-2

INDEX

Fault, reserved operand, 8-9, 9-9
File,
attributes, 6-4
characteristics, 6-2
image, 3-3
LIBDEF.PAS, 7-7
library, 3-5
listing, 2-2, 2-8
map, 3-4
MTHDEF.PAS, 7-7
object, 2-2, 2-4, 2-5
organization, 6-3
parameter, 7-3, 7-6
sequential, 6-3
SIGDEF.PAS, 7-7
specification, 1-2
status, 6-4
File specification defaults, 1-3
Filename, 1-3
Files,
concatenating source, 2-7
condition symbol definition,
7-6, 7-7
Fi 1 etype, 1-3
FIND procedure, 6-3, 6-5
FIXED attribute, 6-5
Fixed-length records, 6-3, 6-5
Floating-point data,
errors involving, 9-7, 9-8
representation of, 9-8
Floating-point operation, 8-9
Formal parameter,
function, 7-5, 7-6
list, 7-2, 7-3
procedure, 7-5, 7-6
Format,
carriage control, 6-4
compiler listing, 2-8
condition value, 8-8
double-precision data, 9-9
file specification, 1-2
floating point, 9-8
listing file, 2-8
OPEN procedure, 6-4
record, 6-3, 6-4
single-precision data, 9-8
FORTRAN attribute, 6-5
FULL qualifier, 3-2, 3-3
Function,
arguments to, 7-6
as parameters, 7-5
declaring system service as,
7-7
external, 7-2
MTH$RANDOM, 7-12
MTH$TANH, 7-2
return status, 7-8
return values, 7-5
Run-Time Library, 7-1, 7-12

GO command, debugger, 5-12, 5-35

H
HELP command, debugger, 5-36
HISTORY attribute, 6-3, 6-4

Image,
executable, 1-2, 3-3
shareable, 3-3
%IMMED FUNCTION specifier, 7-5
%IMMED mechanism specifier, 7-3,
7-9
%IMMED PROCEDURE specifier, 7-5
Immediate value, 7-2, 7-3, 7-9
· procedure and function names,
7-5
%INCLUDE directive, 7-7
INCLUDE qualifier, 3-2, 3-5
Input by-reference parameters,
7-9
Input/output, 6-1
Interprocess communication, 6-6

L
LIB$ESTABLISH, 8-2, 8-5
LIB $REVERT I 8-5
LIB$SIGNAL, 8-2, 8-3
LIB$STOP, 8-2, 8-3, 8-4
LIBDEF.PAS file, 7-7
Library files, 3-5
LIBRARY qualifier, 3-2, 3-5
Library, object-module, 3-5
Line length, maximum (record
length), 6-4, 6-5
LINK command, 1-1, 3-1, 9-2
LINK command qualifiers, 3-2, 4-2
Linker input file qualifiers, 3-5
Linking the object modules, 3-1
List, argument, 7-1
LIST carriage control format, 6-5
LIST qualifier, 2-2, 2-3
command line, 2-5
file specification for, 2-3, 2-6
files produced by, 2-3, 2-6
specified in source code, 2-6
Li sting,
cross reference, 2-3, 2-11, 2-17
machine code, 2-12 to 2-15,
2-18 to 2-20
source code, 2-9, 2-10, 2-11,
2-16
traceback, 4-1

Index-3

INDEX
Listing file, 2-2
format of, 2-8, 2-9, 2-10, 2-11
when produced, 2-3, 2-6, 2-7
Locations, debugger
Examining, 5-12, 5-29, 5-31
Modifying, 5-12, 5-26
Logical names, 6-1, 6-2

M
Machine code listing, 2-12 to
2-15, 2-18 to 2-20
MACHINE CODE qualifier, 2-2,
2-3; 2-6, 2-12
Mailbox, 6-6
Map f i l e , 3-4
MAP qualifier, 3-2, 3-3, 3-4
Mechanism arrays, 8-5
Mechanism specifier,
default, 7-2
%DESCR, 7-4
%IMMED, 7-3
%IMMED FUNCTION, 7-5
%IMMED PROCEDURE, 7-5
%STDESCR, 7-4
VAR, 7-2
Messages,
compiler, A-1
run-time, A-19
Modifying locations, debugger,
5-12, 5-26
MTHDEF.PAS file, 7-7

N
Names,
logical, 6-1, 6-2
program section, 9-2
Network communications, 6-7
Node, 1-2
NEW file attribute, 6-4
NOCARRIAGE attribute, 6-5
NONE attribute, 6-5
Nonstandard features, 2-4

0
Object code, 2-4
Object code listing, 2-12 to 2-15,
2-18 to 2-20
Object file, 2-2, 2-4, 2-6
OBJECT qualifier, 2-2, 2-4, 2-6
Octal numbers, debugger, 5-5
OLD file attribute, 6-5
OPEN procedure parameters, 6-4
Optional parameters, 7-11
Options--see qualifiers
Output by-reference parameters, 7-9
Overflow, floating, 8-9

p
Parameter lists, 7-2, 7-3
Parameters,
character, 7-11
condition handler, 8-5, 8-6
formal function, 7-5, 7-6
formal procedure, 7-5, 7-6
input and output by-reference,
7-9
OPEN procedure, 6-4
optional, 7-11
PASCAL subprogram, 7-5, 7-6
passing mechanisms, 7-2
signal, 8-6, 8-7
VAR, 7-2, 7-6, 8-5
PAS$INPUT, 6-1
PAS$0UTPUT, 6-1
PASCAL command, 1-1, 2-1
PASCAL command qualifiers, 2-2
PASCAL subprograms,
arguments passed to, 7-6
Passing mechanisms,
by-descriptor, 7-2, 7-4
by-immediate-value, 7-2, 7-3
by-reference, 7-2, 7-9
default, 7-2
Passing parameters,
by default mechanism, 7-2
by-descriptor, 7-2, 7-4
by-immediate value, 7-2, 7-3
by-reference, 7-2, 7-9
to PASCAL subprograms, 7-5
to Run-Time Library procedures,
7-12
to system services, 7-9
Pathnames, debugger, 5-14
Procedure calling standard, 7-1
Procedure calls,
contents of run-time stack,
B-1, B-2
Procedures, 7-1
arguments to, 7-6
as parameters, 7-5
declaring system service, 7-9
external, 7-2
Run-Time Library, 7-1, 7-12
system service, 7-1, 7-9
Program development process, 1-1,
1-2
Program sections, 9-1
attributes, 9-1
names, 9-2

Q
Qualifiers, compiler, 2-1
CHECK, 2-2, 2-6
CROSS REFERENCE, 2-2, 2-3, 2-6
DEBUG7 2-2, 2-3, 2-6
ERROR_LIMIT, 2-2, 2-3

Index-4

INDEX
Qualifiers, compiler, (Cont.),
LIST, 2-2, 2-3, 2-6
MACHINE CODE, 2-2, 2-3, 2-6
OBJECT, 2-2,2-4
STANDARD, 2-2, 2-4, 2-6
WARNINGS, 2-2, 2-4, 2-6
Qualifiers, debugger, 5-2
/ADDRESS, 5-3
/ASCII I 5-3
/BYTE, 5-3
/HEXADECIMAL, 5-3
/LONG, 5-3
/OCTAL, 5-3
/WORD, 5-3
Qualifiers, linker, 3-1
BRIEF, 3-1, 3-3, 3-4
CROSS REFERENCE, 3-1, 3-3
DEBUG7 3-1, 3-4, 4-1
EXECUTABLE, 3-1, 3-3
FULL, 3-2, 3-3, 3-4
INCLUDE, 3-2, 3-5
LIBRARY, 3-2, 3-5
MAP, 3-2, 3-3
SHAREABLE, 3-2, 3-3
TRACEBACK, 3-2, 3-5, 4-1
Qualifiers, PASCAL command, 2-4, 2-5
Qualifiers, source code, 2-6

R
Random (direct) access, 6-3, 6-4
Record access mode, 6-3, 6-4
Record formats, 6-3, 6-4
Record length, 6-4, 6-5
Record Management Services, 6-4,
6-6
Record size, maximum, 6-5
Record type, 6-4, 6-5
Records,
fixed-length, 6-4, 6-5
variable-length, 6-4, 6-5
Reference, pass by, 7-2, 7-6,
7-9
Remote access, 6-6, 6-7
Remove a condition handler, 8-5
Reserved operand fault, 8-9, 9-9
Resignal, 8-2, 8-4
RMS, 6-4, 6-6
Routines, 7-1
RUN command, 1-1, 4-1
Run-time error messages, A-19
through A-22
Run-Time Library procedure, 7-1
declaring, 7-12
LIB$ESTABLISH, 8-2, 8-5
LIB$FIXUP FLT, 8-9
LIB$REVERT, 8-5
MTH$RANDOM, 7-12
MTH$TANH, 7-2
optional parameters, 7-11

s
Scope, debugger, 5-13, 5-21, 5-48,
5-64
Default, 5-13
Defining, 5-14
Setting, 5-14, 5-48
Sequential access, 6-3, 6-5
SEQUENTIAL attribute, 6-5
Sequential files, 6-3
SET BREAK command, debugger, 5-11,
5-38
SET EXCEPTION BREAK command,
debugger, 5-11, 5-40
SET LANGUAGE command, debugger,
5-9, 5-41
SET LOG command, debugger, 5-9,
5-42
SET MODE command, debugger, 5-10,
5-43
SET MODULE command, debugger, 5-10,
5-45
SET OUTPUT command, debugger, 5-10,
5-46
SET SCOPE command, debugger, 5-14,
5-48
SET STEP command, debugger, 5-12,
5-50
SET TRACE command, debugger,5-11,
5-52
SET TYPE command, debugger, 5-10,
5-54
SET WATCH command, debugger, 5-12,
5-56
Shareable image, 3-3
SHAREABLE qualifier, 3-2, 3-3
SHOW BREAK command, debugger, 5-11,
5-57
SHOW CALLS command, debugger, 5-12,
5-58
SHOW LANGUAGE command, debugger,
5-9, 5-59
SHOW LOG command, debugger, 5-9,
5-60
SHOW MODE command, debugger, 5-10,
5-61
SHOW MODULE command, debugger,
5-10, 5-62
SHOW OUTPUT command, debugger,
5-10, 5-63
SHOW SCOPE command, debugger, 5-14,
5-64
SHOW STEP command, debugger, 5-12,
5-65
SHOW TRACE command, debugger,
5-11, 5-66
SHOW TYPE command, debugger, 5-10,
5-67
SHOW WATCH command, debugger, 5-11,
5-68
SIGDEF.PAS file, 7-7
Signal parameters, 7-4, 7-5

Index-5

INDEX
Signal procedure,
LIB$SIGNAL, 8-2, 8-3, 8-5
LIB$STOP, 8-2, 8-3, 8-5
Signals,
condition, 8-2
Single-precision data representation, 9-8, 9-9
Source code listing, 2-9 to 2-11,
2-16
Source code qualifiers, 2-6
Source files, concatenating, 2-7
STANDARD qualifier, 2-2, 2-4,
2-5,2-6
STEP Command, debugger, 5-14, 5-65
Storage allocation,
packed arrays, 9-4
packed sets, 9-4
packed records, 9-4, 9-6
pointer types, 9-2
scalar types, 9-2
unpacked arrays, 9-3
unpacked records, 9-3
unpacked sets, 9-3
String descriptor, 7-4
Subprograms, 7-1
arguments to, 7-6
external, 7-2
Subprograms as parameters, 7-5
Symbol, condition, 8-3, 8-8
Symbol, special, debugger, 5-5
Symbolic names, debugger, 5-3
Symbolic references, debugger,
5-13
System services,
Broadcast (SYS$BRDCST), 7-4
Create Mailbox (SYS$CREMBX),
6-6, 7-7, 7-9, 7-10
declaring as functions, 7-7
declaring as procedures, 7-9
Get Job/Process Information
(SYS$GETJPI), 7-13
Get Time (SYS$GETTIM), 7-3,
7-11
naming, 7-6
optional parameters, 7-11
output from, 7-10
parameters to, 7-9
Translate Logical Name
(SYS$TRNLOG), 7-11
unwind (SYS$UNWIND), 8-2, 8-4,
8-7

System services, (Cont.)
Wait for Single Event Flag
(SYS$WAITFR), 7-3

T
Task-to-task communication, 6-7
Terminal session, 4-4
Text file,
carriage control, 6-5
maximum line length, 6-5
Traceback information, 3-4, 4-1
Traceback list, 4-2, 4-3
TRACEBACK qualifier, 3-2, 3-5,
4-1

u
Unwind, 8-2, 8-4, 8-7
User-written condition handler,
7-2, 7-3

v
Value semantics, 7-2
Values,
condition, 8-8
function return, 7-5
signal procedure, 8-8
VAR parameters, 7-2, 7-3, 7-6,
8-5
VARIABLE attribute, 6-5
Variable-length records, 6-3,
6-4, 6-5
Version, 1-3

w
Warning messages, 2-2, 2-4, A-1,
A-17
WARNINGS qualifier, 2-2, 2-4,
2-6
Writing a condition handler, 8-4

z
Zero divide, 8-9

Index-6

VAX-11 PASCAL
User's Guide
AA-H485B-TE

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