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Document:	Introduction to RT-11
Order Number:	AA-5281C-TC
Revision:	0
Pages:	264
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Introduction
to RT-11
AA-5281C-TC

March 1983

This document is an introductory manual for the RT—-11 operating system. Its purpose is to acquaint new users with the RT—11 commands
that perform common system operations. This manual presents the
background material necessary to understand the system operations. It
also contains a series of command examples and demonstration exercises that complement the text.

This

manual

supersedes the Introduction to RT-11,

Order No.

AA-5281B-TC.

Operating System:

RT-11 Version 5.0

To order additional documents from within DIGITAL, contact the Software Distribution
Center, Northboro, Massachusetts 01532.

To order additional documents from outside DIGITAL, refer to the instructions at the back
of this document.

digital equipment corporation - maynard, massachusetts

First Printing, March 1980

Revised, March 1983

The information in this document is subject to change without notice and should
not
be construed as a commitment by Digital Equipment Corporation. Digital Equipmen
t
Corporation assumes no responsibility for any errors that may appear in this
docu-

ment.

The software described in this document is furnished under a license and may be
or copied only in accordance with the terms of such license.

used

No responsibility is assumed for the use or reliability of software on equipmen

t that is

not supplied by DIGITAL or its affiliated companies.

Printed in U.S.A.

A postage-paid READER’S COMMENTS form is included on the last page of this
document. Your comments will assist us in preparing future documentation.
The following are trademarks of Digital Equipment Corporation:

DEC

DECmate
DECsystem-10
DECSYSTEM-20
DECUS

DECwriter
DIBOL

clifgliltlallg

MASSBUS

PDP
P/OS

Professional
Rainbow

RSTS
RSX

M12700

UNIBUS

VAX
VMS
VT
Work Processor

CONTENTS
Page

PREFACE
INTRODUCING THE RT-11
COMPUTER SYSTEM . . . .
SYSTEM HARDWARE . . . . . . . . ..
The Computer. . . . . . . . . . . .«
The Terminal . . . . . . . . . . . . .
The Storage Medium . . . . . . . ..

CHAPTER 1

. .. . . ... ... 1-1

. . ... ... .. 1-1
o o oo 1-1
.. 1-3
. .
... .. ... ... 14

. 1-6
Optional Devices . . . . . . . . . . . .. .
SYSTEM SOFTWARE . . . . . . . . . . ... . ... ... 1-7

The RT-11 Operating System . . . . . . . . . . . ... .. 1-8
Language Processors . . . . . . . . . . . . .. ... .. 1-10
Application Packages . . . . . . . . ... ... 1-10
SYSTEM DOCUMENTATION. . . . . . . . . ... .. ... 1-10
Hardware Manuals . . . . . . . . .. ... .. .. ... 1-10
Software Manuals. . . . . . . . . ... . ... ... 1-11
Source Listings . . . . . . . . . . ..o 1-11

CHAPTER 2 STARTING THE RT-11 COMPUTER
SYSTEM. . . . . . . .

i i it it

e 2-1

oo v v 2-1
COMPUTERMEMORY . . . . . . . . . .
. ... ... .. 2-1
..
.
.
.
.
.
N
HARDWARE CONFIGURATIO
Terminal . . . . . . . .« . o 2-3
e 2-3
e
Computer . . . . . . . o .

System Volume . . . . . . . . . . . .. ... 2-3
Storage Volume . . . . . . . . . . . ... 24

Optional Devices and Supported Languages . . . . . . . . . 24

BOOTSTRAPPROCEDURE . . . . . . .. . . ... ... ... 2-4
CHAPTER 3

INTERACTING WITH THE RT-11

COMPUTER SYSTEM . . . . . .. .. ... ... 3-1
USING THE CONSOLE TERMINAL TO

... 3-1
EXCHANGE INFORMATION . . . . . . . . . . ..
USING MASS STORAGE VOLUMES . . . . . .. ... .. .. 34
FileStorage. . . . . . « o o ¢ o v v oo oo 3-7
File Protection . . . . . . . . . « .«

.« o

oo 3-7

CHAPTER 4 USING THE MONITOR COMMAND
LANGUAGE. . . . . . . . . .

ENTERING COMMAND INFORMATION .
General Command Format . . . . . .
Control Commands . . . . . . . . . .
Re-Creating the Examples. . . . . . .

iii

. v 4-1

. . . . . .. .. .. 4-1
. ... ... .. .. 4-2
. . ... 4-3
. . . . ... . ... 43

CORRECTING TYPING MISTAKES.

. . . . . ...
INITIAL MONITOR COMMAND OPERATIONS. . .
Using VT11 Display Hardware

Entering the Date and Time-of-Day . .
Assigning Logical Names to Devices. .
Listing Volume Directories . . . . . .
Initializing the Storage Volume . . . .

CHAPTER 5

..
.

...

. . . .
CREATINGATEXTFILE. .
EDITINGATEXTFILE.
. .

...

.. 4-5
.. 4-5

...

.. 4-8

...

.. 4-9

.. 4-12
. . . 4-15

CREATING AND EDITING TEXT FILES .

THE RT-11 EDITOR

...

.. 44

...

..... 5-1
...... 5-2

...

.... 54

USING UPPERCASE AND LOWERCASE CHARACTERS. .
USING A GRAPHICS DISPLAY TERMINAL
DURING EDITING

. . . . . . . . . ...
Normal Use of the Graphics Display. .
Immediate Mode . . . . . . .. ...

COMPARING TEXTFILES

PERFORMING A COMPARISON .

CHAPTER 7

. 5-12

...

.... 5-15

...

CREATING THE DEMONSTRATION PROGRAMS .
CHAPTER 6

. 5-1

...

.. 5-16

..... 5-16

. .

...

. 5-19

... 6-1

...

.... 6-1

PERFORMING FILE MAINTENANCE
OPERATIONS . . . . . . ... ... ...

.... 7-1

FILE DIRECTORY OPERATIONS.

...

FILE COPYING OPERATIONS . .
FILE RENAMING OPERATIONS .
FILE DELETION OPERATIONS .

...

.... 7-2

... 7-3

...

... 7-4

MULTIPLE FILE OPERATIONS

FILE PROTECTION OPERATIONS .
FILE LISTING OPERATIONS . . . .

CHAPTER 8

...

... 7-5

... 77

...

.... 7-8

...

... 8-1

CHOOSING A PROGRAMMING
LANGUAGE.

...

HIGH-LEVEL VS MACHINE-LEVEL LANGUAGES

RT-11 PROGRAMMING LANGUAGES . . .
CHOOSING A LANGUAGE FOR THE
DEMONSTRATION . . . . . . . . . . ...
CHAPTER 9

.. 7-1

. .. 8-1
... 8-3

...

.... 84

...

RUNNING A FORTRAN IV PROGRAM.

. .
...

. 9-1

DEVELOPING AN EXECUTABLE FORTRAN IV

PROGRAM

.. 9-1

USING LIBRARYMODULES . . . . . . . .. ... .. .... 9-2
COMPILING THE FORTRAN IV PROGRAM . . . . . .. ... 9-3
LINKING OBJECT MODULES TOGETHER. . .
RUNNING THE FORTRAN IV PROGRAM . . .
COMBINING OPERATIONS. . . . . . . .. ..
ALTERNATE FUNCTIONS . . . . . . . . . ..
FILE MAINTENANCE . . . . .. . ... ...

CHAPTER 10

. . . . . . .. 9-8
. . . . . .. 9-11
... .... 9-12
... .... 9-13
.. ..... 9-14

RUNNING A BASIC-11 PROGRAM . . . . . . 10-1

DEVELOPING A BASIC-11 PROGRAM. . . . . . . . . ... 10-1
USING THE BASIC-11 LANGUAGE PROCESSOR . . . . . . 10-1
USING THE BASIC INTERPRETER. . . . . . ... ... .. 10-2
Immediate Mode . . . . . . ... .. ... ... .... 10-3
Creating and Editing a BASIC-11 Program . . . . . . . . 104
RUNNING A BASIC-11 PROGRAM. . . . . . . ... . ... 10-8
FILE MAINTENANCE . . . . . . . . . . ... .. ..... 10-12

CHAPTER 11

RUNNING A MACRO-11 ASSEMBLY

LANGUAGE PROGRAM .

... .

.. 11-1

DEVELOPING A MACRO-11 ASSEMBLY LANGUAGE
PROGRAM . . . . . .
e s i d e e e
e 11-1
USING THE MACRO-11 LANGUAGE PROCESSOR . . . . . 11-2
The Program Counter .

. . . . . .
The Symbol Table. . . . . . . . .
Machine Language Code . . . . .

.
.

. . . .. ... .. 11-3
... ... ..... 114
. . ... ... ... 11-4

ASSEMBLING THE MACRO-11 PROGRAM . . . . . .. .. 11-6
LINKING OBJECT MODULES TOGETHER. . . . . . . . .. 11-13
RUNNING THE MACRO-11 PROGRAM . . . . . ...
... 11-15
COMBINING OPERATIONS. . . . . . . . . ... . ..... 11-16
FILE MAINTENANCE . . . . . . . . .. ... .. ..... 11-18
CHAPTER 12

LINKING OBJECT PROGRAMS . . . . . . .. 12-1

RESOLVING SYMBOLIC AND LIBRARY
REFERENCES.

. .

i 12-2

PROGRAM RELOCATION AND ADDRESS

ALIGNMENT . . . . . . .
o
o e 12-3
Absolute and Relocatable Program Sections . . . . . . . . 124
The Overlay Feature . . . . . . . . . . ... ... ... 12-6

PRODUCING A LOAD MODULE AND
ALOADMAP .

CHAPTER 13

e 127

CONSTRUCTING LIBRARY FILES

KINDS OF LIBRARY FILES.
Macro Libraries .

.
. .

. . .

. .

. 13-1

. . . . . .. .. ... .... 13-1
.

. . ..

oo 13-1

.....

13-1

CREATING AND MAINTAINING A LIBRARY FILE . . . . .
Creating Object Library Input Files . . . . . . . . . . ..
Building the Object Library . . . . . . . . .. ... ...
Updating the Object Library. . . . . . . . . .. ... ..
FILE MAINTENANCE . . . . . .. .. ... .. ......

Object Libraries.

13-2

CHAPTER 14

DEBUGGING A USER PROGRAM .

AVOIDING PROGRAMMING ERRORS .

13-2
13-5
13-6
13-7

. 14-1

...

WHEN PROGRAMMING ERRORSOCCUR .

... 14-2

USING THE ON-LINE DEBUGGING TECHNIQUE .
FILE MAINTENANCE

CHAPTER 15

...

. . .

14-1

. 14-3

....... 14-13

USING THE FOREGROUND/BACKGROUND
MONITOR .

...

...... 15-1

THE FOREGROUND/BACKGROUND

ENVIRONMENT . . . . . .. ... ...
Running the Foreground/Background
Programs .

........ 15-1

. . . . . .. .. ...
Creating the BackgrounddJdob . . . .

L 15-1
. . . . . ... ... 15-2

Editing the Background Job. .
Running the BackgrounddJob .

USING THE FBMONITOR .

.
.

. . .
...

. .. .. .. 15-2
.. .. ... 15-2
... .... 15-3

Communication in a Two-Job Environment . . . . . . . .
Creating the Foregrounddob . . . . . . . . .. ... ..
Executing the Foreground and Background Jobs. . . . . .
FILE MAINTENANCE . . . . ... .. ... ... .....

CHAPTER 16

USING INDIRECTFILES.

CREATING AN INDIRECTFILE . .

... .

...

FILE MAINTENANCE

CHAPTER 17

...

16-1

...

... 16-1

. 16-2

...

MANUAL BOOTSTRAPPING
OPERATIONS. . . . . . . ..

BOOTSTRAPPING THE SYSTEM..

15-5
15-8

..... 164
.. .... 16-8

ADVICE TONEWUSERS.

USINGTHEHELPFILE

APPENDIX A

154

... ..... 16-1

Entering Monitor Commands . . . . . . ...
Using the Editor to Create an Indirect File . .

EXECUTING AN INDIRECTFILE

15-3

... 17-1

........ 17-2

...

......

A-1

...

A-1

.......

A-3

TYPING THE BOOTSTRAP ON THE

TERMINALKEYBOARD .

. . . . . ...
USING A PUSHBUTTON CONSOLE

TO BOOTSTRAP

...

.....

USING A SWITCH REGISTER

CONSOLE TO BOOTSTRAP. . . . . . . . . . . .. .

.. A-5

APPENDIX B SELECTED SYSTEMTOPICS . . . . . . . .. B-1
STOPPING AND STARTING

THE SYSTEM . . . . . o i e e e et et e e e e e e e e s B-1
Stopping the System. . . . . . . . .. ..o B-1

Starting the System. . . . . . . . .. ... B-1

THE SYSTEM STOPS UNEXPECTEDLY . . . . . ... .. .. B-2
SUGGESTIONS FOR BOOTSTRAPPING

THE SYSTEM . . . . . o o o o e et e i e e e e e e e e B-2
BACKING UP THE SYSTEM VOLUME. . . . . ... ... .. B-3
DIRECTORY- VS NONDIRECTORY-

STRUCTURED VOLUMES . . . . . . . ... ... ... ... B4
ALTERNATE RENAME OPERATION

FORMAGTAPE USERS. . . . . . . . . .«
USING THE FORTRAN/BASIC

oo v oo B4

LANGUAGE VOLUME . . . . . . . . . .. v B-5
SUBSTITUTING VOLUMES DURING

OPERATIONS. . . . o o et e e e e e e e e e e e B-6
USING THELINK VOLUME . . . . . .. .. ... ... ... B-8
FORTRAN/LINK FILE MAINTENANCE . . . . .. .. . ... B-9

GLOSSARY . . . . & o o e e e
INDEX. . . . o o e e e e

e e e e e

e Glossary-1

e e e e e e e e e Index-1

FIGURES

FIGURE 1

1-1
1-2
1-3
1-4
1-5
1-6
1-7
2-1
3-1
3-2
3-3
4-1
5-1
5-2
9-1
9-2

Flowchart for Selective Reading. . . . . . . . . .. xii

RT-11 Computer System . . . . . . . . . . .. .. 1-2
PDP-11Computers . . . . . . . . . . . « . . .. 1-3
TerminalDevices . . . . . . . . . . . . ... ... 14
Randon-Access Storage Media and Their Devices . .1-5
Peripheral Devices . . . . . . . . .. .. ... .. 1-6
RT-11 System Software. . . . . . . . . . .. ... 1-8
RT-11 Operating System . . . . . . . . . . . ... 1-9
Bootstrap/Computer Relationship . . . . . . . . .. 2-2
LA120/VT100 Terminals . . . . . . . . . . . . .. 3-2
LA120/VT100 Keyboard Layouts . . . . . . . . .. 3-3
Mass Storage Volumes . . . . . . . . . ... ... 3-6
VT11 Display Hardware. . . . . . . . . . . . . .. 46
EditingwithRT-11. . . . . . ... ... ..... 5-2
Text WindowFormat . . . . . .. ... ... .. 5-16
Evolution of a FORTRAN IV Program. . . . . . . . 9-1
Function of a FORTRAN IV Compiler. . . . . . . . 9-2

vii

9-3

9-5
10-1
11-1

11-2
11-3

114
11-5

11-6

12-1
12-2

A-1
A-2

Dimensions of FUN(X,Y) . . . .. . ... ...
. . 9-7
The Link Operation.
. . . .. . ... . .. .. . 9-9
The Result of GRAPH.SAV . . . . . . . . .. . . 9-12
Functions of the BASIC-11 Language Processor.
. 10—2
PDP-11 Programming Card. . . . . . . . . . . . 11-1
Evolution of a MACRO-11 Program. . . . . . . . 11-2
Function of a MACRO-11 Assembler . . . . . . .
11-2
PDP-11 Computer Memory . . . . . . . .. . . .
11-3
PDP-11Word. . . . . ... ... .. ... .. .
11-5
The Link Operation.
. . . . .. ... . .. . . . 11-14

Link Functions . . . . ... ... ... ...
. 12-1
Object Module Relocation . . . . . . .. . .. .. 124
Pushbutton Console.
. . . . . .. .. . ... .
A4
Switch Register Consoles . . . . . . .. .. . .. A-5

TABLES

TABLE

2-1
22

4-1

4-2
4-3

5-1
5-2
8-1
11-1

A-1

Representative System Volumes. .
Bootstrap Prompts and Responses .

. 24

. 2-6

Keyboard Characters . . . . .. ... . .. ..
. . 3-5
Keyboard Symbols . . . . .. ... . ... . . ..
44
Physical Device
Names . . . . . . . . .. .. .. . 4-9
Special Logical Device Nmaes. . . . . . . .. . . 4-10
FileTypes. . . . . . ... ... ... ..., . . 4-13
Command Arguments.
. . . .. ... . .. ..
. 5-5
Immediate Mode Commands. . . . . . .. . . . . 5-17
Language Comparisons . . . . . . . . .. .. ... 8-2
Decimal/Octal/Binary Conversion . . . . . . . . .
11-6
Binary Conversion . . . . ... ... ... . . .
A-6

viii

PREFACE
The RT-11 (Real Time-11) computer system is a single-user
computer/operating system that serves the programming needs

of both the beginning and the advanced programmer. RT-11
supports a number of programming languages, including industry-standard FORTRAN and BASIC: and — for more advanced users — the PDP-11 assembly language, MACRO-11.
RT-11 also provides a comprehensive set of operating commands for controlling system operations.

The purpose of this introductory manual is to acquaint you with
a number of RT-11 operating commands that are used to perform common system operations. The manual first presents information that you need to understand a particular system operation; then it shows you how to apply the system operation in
a series of operating commands and exercises that you recreate; finally, it provides a list of reference materials that contain more information about the operation. This approach
makes it possible for you to learn quickly the major features of
the system; at the same time, it eliminates many of the
learning problems encountered by new users.

MANUAL INTENT

This manual describes system usage fundamentals. It is not the
intent of this manual to teach you to program the PDP-11 computer. You may already be proficient in one or more of the
available programming languages. Likewise, no attempt has
been made in this manual to cover all the possible applications
for which the RT-11 computer system is suited. You will discover many applications yourself as you continue to use the
system.

This manual is designed for three categories of RT-11 users:
e Inexperienced users: Those having little or no previous
“hands-on” computer experience (including those whose experience has been limited to batch environments)

e Experienced users: Those who are experienced users of a
computer system other than the RT-11 computer system
e Experienced RT-11 users: Those who have used previous
versions of the RT-11 computer system but wish a quick introduction to the newest features of the current system (Version 5)

The manual contains 17 chapters and 2 appendixes. The descriptions that follow and the chart at the end of this section
will help you determine your own reading path.

MANUAL DESIGN

Preface

Chapter 1, Introducing the RT-11 Computer System, discusses
general system concepts. It introduces the roles of hardware

and software in a computer system and describes the specific
hardware and software components of the RT—11 computer
system. Chapter 1 is intended for users in the first two categories.

Chapter 2, Starting the RT-11 Computer System, shows all
users how to start the system.
Chapter 3, Interacting with the RT-11 Computer System, demonstrates how you use the console terminal to control system
operations. Again, this chapter is most helpful to users in the
first two categories.
Chapters 4 through 7 describe system operations that are
useful to all categories of users. Each chapter begins with a
textual explanation of a particular system operation and expands into computer demonstrations showing the operation in
use. Topics covered are: Using the Monitor Command Language; Creating and Editing Text Files; Comparing Text Files;
and Performing File Maintenance Operations. Experienced
RT-11 users may prefer to skip the textual explanations and
review only the computer exercises.
Chapter 8, Choosing a Programming Language, helps you
which language to use.
Choose BASIC-11,
FORTRAN 1V, MACRO-11, or a combination of these three
languages to continue the exercises in this manual (BASIC-11
and FORTRAN IV are optional products).
determine

Chapters 9, 10, and 11 describe the process of running programs

written

the

FORTRAN

IV,

BASIC-11,

and

MACRO-11

languages, respectively. You should read any
chapters that apply to your choice of language.
MACRO-11 and FORTRAN IV users should continue to
Chapter 12, Linking Object Programs, and Chapter 13, Constructing Library Files.
Chapter 14, Debugging a User Program, provides some suggestions for finding and fixing errors in user programs; all users
should read this chapter.

Chapter 15, Using the Foreground/Background Monitor, is intended for users who plan to exercise the foreground/background capability of the RT-11 system.
All users should continue to Chapter 16, Using Indirect Files.

Indirect files allow the system to perform operations unat-

tended.

Preface

Chapter 17 gives some advice to new users and includes a description of the RT-11 HELP file.

Two appendixes are provided for reference. Appendix A
discusses manual bootstrapping procedures and Appendix B
provides some additional information on selected system usage.

A glossary of technical terms appears at the end of the manual

for reference purposes.

The following flowchart will help you plan your reading path

through the manual. Read the chart from top to bottom; answer
the questions and follow the direction of the arrows to see
which chapters you should read.

NOTE

The demonstration portions of this manual are for use
with Version 5 and later releases of RT-11. The exercises are quite lengthy, and you may prefer not to complete them in one sitting. You may pause at the end of
any individual chapter. It is recommended that you stop
only at the end of a chapter since you will otherwise not
complete an exercise and thus may introduce errors that
will affect later exercises. Instructions for pausing and
beginning again are given in Appendix B.

Preface

WHAT IS

Past Versions of RT-11

YOUR COMPUTER

EXPERIENCE

No Experience, or
other systems

READ
CHAPTER 2
READ CHAPTERS

1,2AND 3

READ

CHAPTERS 4
THROUGH 8

BASIC

MACRO
LANGUAGE WiLL
YOU USE

FORTRAN

READ

CHAPTER 10

READ
CHAPTER 11

CHAPTER 9

READ

CHAPTERS 12

AND 13

READ

AND 13

READ

CHAPTER 14

READ

CHAPTER 14

READ
CHAPTER 15

DO
YOU WANT

TO USE ANOTHER
PROGRAMMING

READ CHAPTERS

LANGUAGE

16 and 17

DONE

Figure 1

Flowchart for Selective Reading

CHAPTER 1

INTRODUCING THE RT-11 COMPUTER SYSTEM
A computer system is a collection of components that work together to process data. The purpose of a computer system is to
make it as easy as possible for you to use a computer to solve
problems. A functioning computer system combines hardware
elements with software elements. The hardware elements are
the mechanical devices in the system, the machinery and the
electronics that perform physical functions. The software elements are the programs written for the system; these programs
perform logical and mathematical operations and provide a
means for you to control the system. Documentation includes
the manuals and listings that tell you how to use the hardware
and software. Collectively, these components provide a complete computer system that allows both layman and expert

alike to use a computer.’

SYSTEM HARDWARE
SYSTEM SOFTWARE
+SYSTEM DOCUMENTATION
COMPUTER SYSTEM

The RT-11 computer system requires three basic hardware
items: the computer, which performs all data processing; a terminal device, used like a typewriter for two-way communication between the user and the system; and a storage medium,
for storing programs and data. Figure 1-1 illustrates the hardware components of a typical RT-11 computer system.

The computer performs all instruction decoding and data processing. The RT—-11 computer system is constructed around a
DIGITAL PDP-11 computer, several of which are shown in
Figure 1-2. Any model of PDP-11 can be used in an RT-11
system.

Notice in Figure 1-2 that the front panel, or operator’s console,
of each PDP-11 computer is slightly different. The switches,
buttons, and lights that are on the operator’s console are used
for various kinds of computer operations and applications. In
the RT-11 computer system they are used only to start the
system. Once the system has been started, your interaction
with the computer system occurs through the terminal.
UThis chapter attempts to build a working vocabulary that is both meaningful

to the new user and consistent with standard DIGITAL terminology. Some
definitions may appear inconsistent with those you have previously learned
or used.

1-1

SYSTEM
HARDWARE

The Computer

Introducing the RT-11 Computer System

Figure 1-1

1-2

RT-11 Computer System

Introducing the RT-11 Computer System

PDP11/23 PLUS

PDP11/23

PDP 11/44

Figure 1-2

PDP-11 Computers

The terminal allows two-way communication between you (the
user) and the computer system. You enter information — operating commands, for example — from the terminal keyboard,
which is operated much like a typewriter keyboard. The computer, in turn, prints information and messages on the terminal’s printer or screen. Figure 1-3 shows two terminal
devices — the VT100 video terminal and the LLA120 hardcopy
terminal — that can be used in an RT-11 computer system.

1-3

The Terminal

Introducing the RT—-11 Computer System

Figure 1-3

Terminal Devices

Generally, an RT-11 computer system has only one terminal
through which all system/user interaction takes place. This is
called the console terminal. If the system has more than one
terminal, one of them is still designated the console terminal;
others simply provide auxiliary message-printing capabilities.

The Storage
Medium

The third important hardware device in an RT-11 computer
system is the storage medium (usually a disk). It stores programs — those that make up the computer system software and
those that you create. It serves as a distribution medium;
system software is often packaged and distributed on a disk by
the system supplier. Finally, it stores other data, information
that is eventually needed for a computer operation (called
input), the results of a computer operation (called output), or

Introducing the RT-11 Computer System

textual information such as a report. Figure 1-4 shows the

.
:

random-access storage media (and their specific drive units)
that can be used in an RT-11 computer system. (Random access
means that access time for data is independent of the location of
data. Contrast this concept with sequential access.)

Figure 1-4

Random-Access Storage Media

and Their Devices

Introducing the

RT-11 Computer System

These three devices — the computer, the terminal, and the
storage medium — are the required hardware components of an

RT-11 computer system. With the exception of the computer,
all hardware devices are called peripheral devices. Peripheral
devices supplement the computer by providing external resources for operations that the computer cannot handle alone.
In addition to the terminal and storage medium (which are required peripheral devices), other peripheral devices can be used
in an RT-11 computer system.

Optional Devices

Optional peripheral devices are added to a computer system

according to the specific needs of the system users. For example, computer systems that are used primarily for program
development may have extra storage devices and a high-speed
printing device. Computer systems used in a laboratory environment may have graphics display hardware, an oscilloscope
device, and an analog-to-digital converter. Computer systems
that provide (or use) information in conjunction with another

kind of computer system usually have a magtape device, because magtape is an industry-standard storage device.
Peripheral devices are categorized as input/output (I/0) devices
since the functions they perform provide information (input) to
the computer, accept information (output) from the computer,
or do both. Line printers are output devices because they perform only output operations. Terminals and storage devices are
input/output devices because they perform both input and
output operations. Figure 1-5 shows several of the optional peripheral devices that are often added to an RT-11 computer
system.

VT11 Display

Figure 1-5

1-6

Peripheral Devices

Introducing the RT-11 Computer System

Magtape

Line Printer

Figure 1-5

Peripheral Devices (Cont.)

The hardware configuration

of your own RT-11

computer

system includes the computer, the terminal, the storage medium, and any other peripheral devices you choose to add.

System software is an organized set of supplied programs that
effectively transform the system hardware components into usable tools. These programs include operations, functions, and
routines that make it easier for vou to use the hardware to
solve problems and produce results. For example, some system
programs store and retrieve data among the various peripheral
devices. Others perform difficult or lengthy mathematical calculations. Some programs allow you to create, edit, and process
application programs of your own. Still others handle entire
applications for you.
As illustrated in Figure 1-6, system software always includes
an operating system, which is the “intelligence” of the computer system. Usually the system software includes one or several language processors; it sometimes also includes specific applications.

SYSTEM
SOFTWARE

Introducing the RT-11 Computer System

OPERATING
SYSTEM

LANGUAGE

APPLICATION

PROCESSORS

PROGRAMS

Figure 1-6

The RT-11

Operating System

System Software

An operating system is a collection of programs that provide

an environment in which you can create and run program

your own. The operating system organizes all the hardwa

s of

re and

software resources of the computer system into a workin

g unit

and gives you control.

The RT-11 operating system comprises four types of program

a monitor/executive program for system control and supervision; several device handlers (programs), one for each
of the

supported hardware devices; a variety of utility programs
for
program/data creation and manipulation; and finally, the
inter-

faces that are necessary to support several programming lan-

guage processors. The operating system is illustra

1-7.

ted in Figure

The monitor (executive) program is the link between
the
system hardware, the system software, and you. Part of the

monitor function is to accept, process, and execute your
instructions for controlling the system. A comprehensive set of
monitor
operating commands allows you to direct, from the console
terminal keyboard, those system operations that you
want to
occur.

Device handlers are routines that provide the interface

various hardware devices that are part of the computer

to the

system.

A handler exists for every peripheral device that the
system
supports.

Utility programs cover a wide range of resources; such
programs allow you to create and edit text, maintain other
pro-

Introducing the RT-11 Computer System

DEVICE
HANDLERS
UTILITIES
¢

EDITOR

FILE

DEBUGGING

MAINTENANCE

SUPPORT FOR
LANGUAGE

PROCESSORS

Figure 1-7

FILE

COMPARE
®

LIBRARIAN

The RT-11 Operating System

grams, and locate user-programming errors. Some utility pro-

grams in the RT-11 operating system are the following:
e An editor, which allows you to create and modify textual material; this material could be the statements that make up a
computer program, a memo, or any text you wish to create

¢ File maintenance utility programs, which allow you to manipulate and maintain your programs and data — to transfer
them between devices, to update them, and to delete them
when you are done with them

e A debugging program, which helps you uncover and correct
errors in your programs

e A librarian, which makes it easy for you to store and retrieve
often-used programming routines
e A linking program, which converts object modules into a
format suitable for loading and execution
e A source comparison program, which is used to compare two
ASCII files and to output any differences to a specified output
device
® A dump program, which outputs to the console or line printer
all or any part of a file in octal words, octal bytes, ASCII
characters, or Radix—50 characters
The RT-11 operating system also provides support for several
programming languages and their respective language processOrs.

Introducing the RT-11 Computer System

Language

A language processor is a translating program that you use to

Processors

process a source program you have created. A language processor exists for every programming language supported by the
system, whether it is a high-level language or a machine-level

language.'
High-level languages, such as BASIC-11 and FORTRAN 1V,
are relatively easy languages to learn and use. Since a single
language statement often performs a series of intricate computer operations, high-level languages let you direct your at-

tention to solving the problem at hand. They do not require
that you understand how the computer interprets the problem.
In addition to FORTRAN IV and BASIC-11, the RT-11 operating system supports the high-level language DIBOL, DIGITAL’s interactive commercial language.
Machine-level or assembly languages are available for users
who prefer to work at the instruction level of the computer. At

this level, you have control over such factors as program size
and speed of execution. Machine-level languages do require
that you be familiar with the computer and the hardware devices of the system. RT-11 provides the MACRO-11 assembly

language processor for those who would rather work at this
more intricate level.

Applications

The RT-11

Packages

packages. These include a laboratory applications package for

operating system supports several applications

the standard functions found in most laboratory environments.
A scientific subroutine package (for FORTRAN 1V users) provides a large selection of mathematical and statistical routines
commonly required in scientific programming. And a graphics
support package for BASIC-11 and FORTRAN IV users provides display features such as multiple intensity and blinking
vectors (lines), alphanumerics, and points. Because of the spe-

cialized nature of these applications packages, they are not described further in this manual.

SYSTEM

The third component of a computer system is documentation,

DOCUMENTATION

which includes manuals that tell you how to use the software
and hardware of the computer system. Documentation also includes any source listings of programs that make up the operating system.

Hardware Manuals

Hardware

manuals

describe

the

devices

the

computer

system. RT-11 hardware documentation includes a Processor

!Language selection is discussed in Chapter 8 of this manual.

1-10

Introducing the

RT—11 Computer System

Handbook that describes the PDP-11 computer you are using,
and a User’s Guide or Maintenance Manual for each peripheral
device in your computer system. These manuals tell you how to
operate the devices and give you special programming information that you may need if you intend to write device drivers or
special system software involving the devices.

Software manuals' describe the operating system and the language processors. RT-11 software documentation falls into
three major categories: introductory or once-only manuals (intended to be used once and then stored away); console manuals
(intended to be used at the computer); and desk/console manuals (intended to be used at your desk for reference purposes).

Software Manuals

Once-only manuals include this manual and others that are
needed only when your system is initially installed. You may
have little or no occasion to use these manuals once your computer system is in operation and you are familiar with its use.

Console manuals are those manuals that tell you how to use the
computer system. They describe in detail command usage and
syntax, list summaries of system operations, and give the
meanings of system messages. The RT—11 System User’s Guide
is an example of a console manual.

Desk/console manuals are those manuals that you continually

use for reference as you write your own application programs.
These manuals include the general language reference manuals and the advanced programming manuals that contain programming information specific to the RT-11 computer system.

The RT-11 Software Support Manual is an example of a
desk/console manual.

Source listings are actual listings of the assembly language
code that makes up the RT-11 operating system. These listings
are very detailed and are generally needed only if you intend to

modify the system software. They can be ordered on microfiche
from the DIGITAL Software Distribution Center.

This completes a general introduction to the RT-11 computer
system. Subsequent chapters of this manual describe how you

use the various system components mentioned here to perform
a series of related computer operations. You begin in Chapter 2
by learning how to start the RT-11 computer system.

1a1l RT-11-related software manuals are listed and described in the Guide to
RT-11 Documentation. Many of these manuals are provided with your system; others can be ordered from the DIGITAL Software Distribution Center.

1-11

Source Listings

Introducing the RT-11 Computer System

REFERENCES

Digital Equipment Corporation Reference Service, Volume
2: Products and
Services. Maynard, Mass.: Digital Equipment Corporation, 1982.

An overview of the PDP-11 family products and services; includes
capsule descriptions of the various PDP-11 computers, periphera
ls, and

operating systems, and describes the supportive services
provided by

DIGITAL.

Eckhouse, Richard H. and Morris, L. Robert, M inicomputer

Systems: Organi-

zation, Programming, and Applications (PDP-11). Englewoo
d Cliffs, N.J.:
Prentice-Hall, 1979.

A guide to programming fundamentals, PDP~11 organizat
ion and structure, and programming techniques. See Chapters 1, 2, and
3.

Guide to RT-11 Documentation (AA-5285G-TC
). Maynard, Mass.: Digital
Equipment Corporation, 1983.

A listing and brief summary of current RT-11-r

elated software docu-

mentation.

Katzan, Harry Jr., Information Technology, The Human
Use of Computers.
New York: Mason & Lipscomb, Petrocelli Books, 1974.
An introductory textbook covering basic computing concepts,
programming languages, and topics in computers and society. See
Chapters 1, 2,
4, 5, and 10.
PDP-11 Peripherals Handbook. Maynard, Mass.: Digital

tion, 1981-82.

Equipment Corpora-

A technical summary of the PDP-11 peripheral devices;
includes descriptions, specifications, programming, and interfacing
information for
PDP-11 peripheral devices.
PDP-11 Processor Handbook. Maynard, Mass.: Digital Equipme
nt Corporation, 1981.
A hardware manual for the owners and users of the PDP-11
computers and for those who will be using the PDP-11

guage instruction set.

family of

assembly lan-

PDP-11 Software Handbook (EB-21759-20). Maynard
, Mass.: Digital Equipment Corporation, 1982-83.
A general overview and introduction to available PDP-11
software, operating systems, and language processors.

Spencer, Donald D., Fundamentals of Digital Computer
s. Indianapolis,
Kansas City, New York: Howard W. Sams, Bobbs-Merrill, 1969.
A discussion of the history and evolution of computers, computer
applications, and fundamentals of computer use. See Chapters
1 through 12
and Chapter 20.

1-12

CHAPTER 2
STARTING THE RT-11 COMPUTER SYSTEM

Before you can use the RT-11 computer system to perform any
operations, you must start it. Starting the system involves
turning on the computer and the various hardware devices and
loading the appropriate software components into computer
memory.

Within every PDP-11 computer is a physical, designated
storage area called memory. Computer memory is where
system information and data are temporarily loaded and stored
for use during the various system operations.

COMPUTER
MEMORY

Each time you use the computer system, there may already be
information in computer memory, left by the person who used
the system last. For example, there may be the results or data
of another user’s program; there may be the results of a particular system operation; there may even be an entirely different
operating system in memory. For your purposes, computer
memory must contain the RT-11 operating system, and specifically the RT-11 monitor program. Thus, your first operation as

a system user is to transfer the monitor program from the disk
device, where it was stored during system installation, to computer memory, where you can use it. The process of transferring
the RT-11 monitor to memory is called bootstrapping the
system,; it is the only system operation that requires you to use
the operator’s console on the front panel of the computer (see
Figure 2-1).

Starting the RT-11 computer system requires that you know
how to operate your system’s hardware devices. Since you may
not have had the opportunity to use any of the devices yet, ask
an experienced user to help you the first time. Follow the instructions in the section in this chapter entitled “Bootstrap Procedure.” If necessary, refer to the RT—11 Automatic Installation
Booklet, the RT—11 Installation Guide, or the various hardware
manuals provided with your system.
First read through the following material and fill in the appropriate information where requested. You should be able to
determine all responses by checking the RT-11 Automatic Installation Booklet or the RT-11 Installation Guide.

2-1

HARDWARE

CONFIGURATION

Starting the RT-11 Computer System

RT-11

RESIDENT

;

[

E[b

Figure 2-1

BOOTSTRAP

Bootstrap/Computer Relationship

NOTE
If your system device is a diskette, you need to build four
volumes and, when running some of the demonstration
programs, limit the volumes to the components needed
to execute the programs. Also, you need to preserve the
distribution

volume

you

received

from

DIGITAL

making backup copies. The RT-11 automatic installation
procedure performs these functions for you. If you did

not use the automatic installation procedure to install
your RT-11 system, the RT-11 Installation Guide will
provide you with the commands you need to copy and
preserve the distribution volume and create the volumes
for use with this manual.

You must have the following materials to start the system and
to perform the exercises in this manual:
¢ The volume containing the RT-11 operating system (called
the system volume); refer to Section 2.3.6 of the

RT—11 Instal-

lation Guide for the list of components you will need on your
system volume to perform the exercises

¢ The volume containing the FORTRAN IV and/or BASIC-11
language processors if these languages are not stored on the
system

volume

BASIC-11 users)

(available

only

FORTRAN

and

Starting the RT-11 Computer System

e A volume for program storage (for example, magtape or another disk or diskette); this volume should contain no important information since all information on it will be erased
during a later computer exercise

e A copy of the RT—11 Automatic Installation Booklet or the
RT-11 Installation Guide

NOTE

You can find hardware configuration information in the
various hardware manuals provided with your system.
Instructions for starting (bootstrapping) your RT-11

system appear in the RT-11 Automatic Installation

Booklet and the RT—11 Installation Guide. This information should be adequate for you to answer all the questions asked here. If you have trouble, see Appendix B,
Suggestions for Bootstrapping the System. Do not continue to any other chapter in this manual until you understand the following configuration information and can
bootstrap the system yourself.

1. What kind of terminal device are you using (for example,

Terminal

2. Is your computer a PDP-11/23-PLUS, PDP-11/24, or

Computer

LA120 DECwriter III, VT100 video terminal)?

PDP-11/447

3. Does your computer operator’s console have pushbuttons or
switches?

4. How much memory does your computer have?

5. What kind of system volume are you using (for example,
RLO02 disk, RX02 diskette)?

6. What is the two-letter mnemonic for this volume (typical

mnemonics are given in Table 2-1; respond with the mnemonic for your own volume)?

System Volume

Starting the RT-11 Computer System

Table 2-1

Representative System Volumes
Volume

Mnemonic

RX01 Diskette

RXO02 Diskette

RKO05 Disk

RK*

RKO06/07 Disk

RC25/RD51 Disk, RX50 Diskette

RL01/02 Disk

* Use DK to bootstrap from an RK05 disk.

Storage Volume

What volume are you using for program storage (for example, TS11 magtape, RLO2 disk)?

In which device unit will you use this volume (choose any
available device unit — for example, 0, 1)?

Optional Devices

and Supported

What peripheral devices are part of your system (for example, line printer, magtape, VT11 display hardware; list

all devices other than the terminal and the computer)?

Languages

10. What programming languages does your system support
(MACRO-11 or BASIC-11, for example)?

BOOTSTRAP
PROCEDURE

Once you have determined your hardware configuration, you

are ready to bootstrap the system. The purpose of the bootstrap

procedure is to load and start the RT-11 monitor in computer
memory, thus activating the RT-11 computer system for your

use.

NOTE

If your answer to question 2 in the Hardware Configuration section is YES, continue to the next paragraph. Otherwise,

read

the

section

entitted

Bootstrapping

System, in Appendix A, for bootstrap instructions.

the

The bootstrapping procedure for the RT-11 computer system on

a PDP-11/23-PLUS, PDP-11/24, or PDP-11/44 processor consists of the following steps. For more detailed instructions on

Starting the RT-11 Computer System

the bootstrap operation, refer to the

RT—11 Automatic Installa-

tion Booklet.
1.
2.

Turn the terminal to an on-line condition.
Make sure that the computer power is on and that the com-

puter is not already in use.
e If your computer is a PDP-11/23-PLUS, power up the
system by lifting the AUX toggle switch to the ON posi-

tion. The red PWR OK indicator on the front panel will
light up if the system was successfully turned on.
e If your computer is a PDP-11/24 or a PDP-11/44, power

up the system by turning the status selector key to the

LOCAL position. The red DC ON indicator on the front
panel will light up if the system was successfully turned
on.

Stop the computer.
e If your computer is a PDP-11/23-PLUS, lift the HALT

toggle switch to the up position. The AUX toggle switch
that you lifted in the previous step and the HALT toggle

switch can be lifted simultaneously.
e If your computer is a PDP-11/24 or a PDP-11/44, push

the HALT/CONT/BOOT horizontal toggle switch to the
HALT position.
4.

Load the system volume in its corresponding device unit 0.
Make sure that the system volume is write-protected (for all

except RX01 or RX02 diskettes, which are always writeenabled).
5.

Load the storage volume in the device unit noted in question 8 in the Hardware Configuration section. Make sure
that this volume is write-enabled.

Boot the system.
e If your computer is a PDP-11/23-PLUS, lift the RE-

START toggle switch on the front control panel. This

switch will not remain in the up position; it will spring
back to the center position.
e If your computer is a PDP-11/24 or a PDP-11/44, push
the HALT/CONT/BOOT horizontal toggle switch to the

BOOT position. This switch will not remain in the rightmost position; it will spring back to the center position.
The red RUN indicator on the front control panel should
now be illuminated.

2-5

Starting the RT-11 Computer System

A series of self-diagnostic routines to check out the system are
then executed. The execution of these routines may take up to a
minute, depending upon how much memory is installed in your

system. A prompt appears on your console terminal when execution of the routines is completed. The prompt that appears is
dependent upon the type of processor you are using. Table 22
provides the prompts that appear and the corresponding responses

which

must

supplied

you

are

using

the

PDP-11/23-PLUS, PDP-11/24, or PDP-11/44 processor.

Table 2-2

Bootstrap Prompts and Responses

Processor

Prompt

PDP-11/23-PLUS

TESTING MEMORY

Response
dd[n]GED

wwww. KW

START?
PDP-11/24

bbbbbbbb

<none>

PDP-11/44

>>>

B dd[n]GED

WWWW,

bbbbbbbb.

amount of memory in K-bytes (octal)

dd[n]

device mnemonic (dd) and unit number (n)

amount of memory in K-words (decimal)

Respond to the prompt that appears on your console terminal by typing the appropriate response (refer to Table
2-2) followed by a carriage return.
NOTE
Refer to question 6 in the Hardware Configuration section for the two-letter device mnemonic (dd) and refer to

question 8 for the device unit number (n).

You should now direct your attention to the console terminal,
since system interaction continues on this device,

REFERENCES

PDP-11 Processor Handbook, Maynard, Mass.: Digital Equipment Corporation, 1981.
A hardware manual for the owners and users of the PDP-11 family of
computers and for those who will be using the PDP-11 assembly language instruction set.

2-6

Starting the RT-11 Computer System

RT-11 Automatic Installation Booklet: RX02 Diskettes (AA~-M235A-TC),
RT-11 Automatic Installation Booklet: RLO2 Disk (AA-M236A-TC),
RT-11 Automatic Installation Booklet: RC25 Disk (AA-M237A-TC), and
RT-11 Automatic Installation Booklet: MICRO/PDP-11 (AA-M238A-TC).
Maynard, Mass.: Digital Equipment Corporation, 1983.

RT-11-specific software booklets which provide basic instructions for
using the automatic installation process to install and test the RT-11
monitors, system programs, and certain languages.

RT-11 Installation Guide (AA-H376B-TC) and RT-11 System Release Notes
(AA-5286E-TC). Maynard, Mass.: Digital Equipment Corporation, 1983.

Two RT-11-specific software manuals that contain instructions for installing, customizing, and starting the RT~11 computer system.

Manual
Maintenance
System
Disk
Floppy
RX8/RX11
(EK—ORX01-MM-PRE2). Maynard, Mass.: Digital Equipment Corporation,
1975.

A hardware manual for the owners and operators of RX01 diskettes and
for those who will be programming computers to interact with these

devices.

VT100 User Guide (EK-VT100-UG-002). Maynard, Mass.: Digital Equip-

ment Corporation, 1978.

A manual for the owners and operators of the VT'100 video terminal and
for those who will be programming computers to interact with these
devices.

2-7

CHAPTER 3

INTERACTING WITH THE RT-11 COMPUTER SYSTEM

Interaction with the RT-11 computer system involves an exchange of information between you (the user) and the software
operating system. The exchange may be active, with you dictating command information from the terminal keyboard and
the system responding immediately; or it may involve the
storing of information on mass storage volumes for later use.

During the bootstrap procedure you activated the RT-11 computer system by loading and starting the monitor program in
computer memory. One of the functions of the monitor program
is to provide you with the capability to use the console terminal. Since the console terminal can perform both input and
output operations, it is used to interface between the system
and the user. With it, you can:

¢ Type the commands that control system operation
¢ Receive messages and responses from the system
All console terminals have a keyboard — used to enter information — and a paper output device or video screen — used to echo
characters typed at the keyboard and to print system messages
and responses. Figure 3—1 shows two commonly used terminals,
the LA120 and the VT100.

These two terminals differ in their output mechanism. While
the LA120 terminal has a paper printer, the VI'100 has a video
screen. The paper printer and the screen serve the same purpose — they show user input and system responses; however,
paper output can be saved for later use.while screen output is
temporary. The keyboards of both terminals are shown in Figure 3-2.

3-1

USING THE
CONSOLE
TERMINAL TO

EXCHANGE
INFORMATION

Interacting with the RT-11 Computer System

LA120

VTi00

Figure 3-1

3-2

LA120/VT100 Terminals

Interacting with the

@-llflllll@m
w
LA120

%e@@lllflt

w
VT100

Figure 3-2

LA120/VT100 Keyboard Layouts

Using Figure 3-2 as a guide, study your own terminal keyboard. First, notice that the keys for the alphabetic characters
are positioned in the same way as on most standard typewriters. The SHIFT key allows you to select between numeric and
special characters and between uppercase and lowercase
characters.! The position of the numeric and special characters
varies somewhat among the different terminals, so you may
need to hunt for a particular key until you become familiar
with your own terminal.

Locate the DELETE key. This key is used to correct a typing
mistake. Pressing the key once cancels the last character typed.
Pressing it twice cancels the last two characters, and so on,
back to the beginning of the line.

1With the exception of system messages and one other exception explainedin
Chapter 5, the RT-11 computer system uses uppercase characters exclusively.

3-3

RT-11 Computer System

Interacting with the RT—11 Computer System

Locate the TAB key. Tab stops on a computer terminal are
positioned every eight spaces across the line, beginning at
column 1. Pressing the TAB key moves the character pointer

(that is, the position on the line where the next character will

be typed) to the beginning of the next tab stop.

The key marked RETURN performs a carriage return; it both

returns the character pointer to the beginning of the line and
advances it to the next line. This key is used to terminate the

line currently being typed and to terminate certain RT-11
system commands.

Locate the ESC key and the LINE FEED key. These are special
command terminators that are described in Chapters 5 and 14.
An important key is the CTRL key. It is always used with another character key to perform one of several system opera-

tions. CTRL commands are explained in detail when you begin
to use them later in the manual.

Table 3-1 reviews the console terminal keyboard characters.
Keys not mentioned are not used by the RT-11 computer
system and can be ignored.

You will have an opportunity to become familiar with your terminal keyboard as you perform the demonstrations in this
manual.

The console terminal also displays messages and responses
from the system. These messages and responses provide or request information. Error messages are an example of informa-

tional output; they help you detect typing errors, programming
errors, and system malfunctions. If an error message appears

on your console terminal while you are performing the demonstrations in this manual, refer to the RT-11 System Message

Manual for an explanation of the cause of the message and a

description of the corrective action that should be taken.

USING
MASS STORAGE

VOLUMES

Mass storage volumes provide an area (apart from computer
memory) to keep information for later use. The information

may be user application programs, data needed by a program,
the results of a program run, textual information, batch-type

programs, and so on. As an example, the RT-11 operating
system is stored on a mass storage volume called the system

volume. When information is needed, as it was during
bootstrapping, information from the storage volume is transferred into computer memory.

Interacting with the RT—11 Computer System

Before you can access the information stored on a storage
volume, however, you must first insert the volume (the medium) into its corresponding device unit (drive), the hardware
device connected to the computer. Once a volume has been in-

serted into a device unit, the device unit’s symbol identifies the

volume. There may be more than one device unit for a volume,
each individual device unit is numbered 0, 1, 2, and so on. As
you learned in the bootstrap procedure, the system volume is
inserted in device unit 0 and remains in it as long as you are
using the system. Other storage volumes can be inserted in any
available device units. Figure 3-3 illustrates several mass
storage volumes.

Table 3-1

Keyboard Characters
Function

Key

BACK SPACE

Ignored during normal system use

BREAK

Ignored during normal system use

CTRL

Control; part of several two-key command

combinations that perform specific system
functions

DELETE
ESC

LINE FEED

Erase; cancels the last character typed
Command terminator; terminates an editing

command string; transmits the command to
the computer and performs a carriage return

Command

terminator;

terminates

certain

system commands; transmits the command to
the computer and performs a carriage return

REPEAT

Ignored during normal system use

RETURN

Line terminator, command terminator; termi-

SHIFT

TAB
any other
key

nates the current line; terminates certain
system commands; transmits the command to
the computer and performs a carriage return

Selects the uppermost of two characters ap-

pearing on a key

Moves the character pointer ahead to the be-

ginning of the next tab stop

Transmits the alphanumeric or special character to the computer

Interacting with the

RT-11 Computer System

Diskette

Figure 3-3

3-6

Mass Storage Volumes

Interacting with the

RT-11 Computer System

Mass storage volumes hold large amounts of information. Most
volumes, however, are physically small enough so that you can
transport them from the system, to your desk perhaps, or to
another computer system. In addition to disks (shown earlier in
Figure 1-4), magtapes are also mass storage volumes.

You store information on a mass storage volume in the form of
files. Each file is a logical collection of data. Files may be parts
of programs or entire programs, program input data, or text,
such as a letter or report. Whatever its content, each file is
treated as a unit and occupies a fixed area of the volume.

File Storage

Every file on a mass storage volume has a unique name that is
composed of a file name and a file type. The file name and file
type identify the file and distinguish it from other files on the
volume. You can instruct the system to print on your terminal
the names of all files on a volume. The resulting list is called
the volume directory listing. By referring to the volume directory, you can find the name, size, and creation date of each file
on that volume and delete old files that you no longer need.
Whenever you perform an operation that affects the contents of
the volume, a new volume directory reflects the change.

Occasionally, after many files are added to a storage volume,
the volume has no room for new information. A storage volume
may also become damaged, lost, stolen, or worn through use.
For these reasons it is a good idea to have several extra storage
volumes on hand and to protect your more important files
against accidental erasure or loss.

One way to protect a file is to make a copy of it on a second

storage volume. The copy, called a backup file, insures you
against the loss or damage of your original file (or its respective

storage volume).

Some storage volumes provide a mechanism that protects files
against accidental erasure. This mechanism is generally a
switch on the volume itself, or on the device unit, that you can
set to a write-protect or write-enable condition (as you did
during bootstrapping). When the volume is write-protected, information can be copied only from the volume to computer
memory or to another volume that is write-enabled. A volume
that is write-enabled, on the other hand, also allows information to be copied from memory back to the volume.

3-7

File Protection

Interacting with the

RT-11 Computer System

The RT-11 operating system itself provides a protection feature. This optional feature requires that you confirm certain

system commands that might otherwise erase important information. The system also issues prompting messages so that you

provide the proper file information when it is needed by a com-

mand.

Chapter 4 and succeeding chapters require you to use the terminal to enter command information and perform file copy and

other system operations. Before you continue, make sure that
there is a backup copy of your system volume. If you cannot

locate one, read Appendix B, Backing Up the System Volume,
before going on.

REFERENCES

RT-11 System Message Manual (AA-5284D-TC). Maynard, Mass.: Digital
Equipment Corporation, 1983.
An explanation of system messages that may occur during normal
system use; includes required user actions.
VT100 User Guide (EK-VT100-UG-002). Maynard, Mass.: Digital Equipment Corporation, 1978,
A manual for the owners and operators of the VT100 video terminal and
for these who will be programming computers to interact with these
devices.

CHAPTER 4

USING THE MONITOR COMMAND LANGUAGE
During the bootstrap operation, the RT-11 monitor was copied
into computer memory and started. The RT-11 monitor is actually many different components working together to supply
basic system functions. For example, the part of the monitor
called the resident monitor (RMON) provides the console terminal service and central program code necessary for a working
environment for both system and user programs. The resident
monitor is so named because it always remains in computer
memory, regardless of other system operations that may be occurring. Other parts of the monitor are brought into memory
from the system volume as needed. These include the user service routine (USR), which provides support for the RT-11 file
system, and the keyboard monitor (KMON), which controls terminal keyboard interaction. From your standpoint, the keyboard monitor is the most visible part of the system software.
Among other services, it supplies the monitor command language that you use to control system operations.

The monitor command language is a set of English-like command words that you type on the terminal keyboard to initiate
and control system operations. You can type a command in one
of two general formats: a long format or a short format. The
long format causes the system to print prompting messages.
These messages ask you to supply specific information, such as
file names and device names. The long format is helpful until
you become familiar with the commands. You will then probably prefer to use the short format, which allows you to enter
all required information on a single command line and provides
prompts only if you do not supply necessary information. Both
formats are demonstrated throughout this manual.
You terminate all monitor commands with a carriage return.
That is, after you type the required command information, you
press the carriage return key (represented in this manual by
®D). This instructs the monitor to initiate the command and to
perform the operation.

A prompt character — a period at the left margin of the terminal printer or screen — appears whenever the RT-11 monitor is waiting for you to type a command. The period is your
cue that the system is in the monitor command mode and ready
to accept a monitor command. Check the output on your terminal printer or screen. You should see the following at the left
margin:
RT-11FB

. xx
VOS5

4-1

ENTERING
COMMAND
INFORMATION

Using the Monitor Command Language

RT-11FB

identifies

the

RT-11

monitor

called

the

foreground/background (FB) monitor. Following this is the version (and update) number of the system in use, in this case,

Version 5. The period on the next line indicates that the system
is in the monitor command mode and is waiting for you to type
a monitor command.

General Command
Format

Whenever you issue a monitor command, you must supply certain information to guide command processing. This informa-

tion includes the following (square brackets indicate optional
qualifiers and characters):

COMMAND//option]

First

you

indicate,

command,

which system operation you want initiated. Command options are available to allow you to alter the normal

(default) operation.

INPUT[/option]

You next indicate, by device and file
name, input information that is to be

used during the operation. The system
volume serves as the default input device.

You

must

explicitly

indicate

other volumes that you want used for
input, and you must usually indicate
the file names and file types of the
input files. Input file options are avail-

able to allow you to alter assumed (default) input operations.

OUTPUT{/option]*

Finally you indicate, by device and file
name, output information that is to be

created as a result of the operation.
The system volume serves as the de-

fault output device. You must explicitly indicate other volumes that you
want used for output, and you must
usually indicate the file names and
file types of the output files to be cre-

ated. Output file options are available
to allow you to alter assumed (default)
output operations.

As mentioned earlier, you can type this command information

on the terminal keyboard in one of two formats; illustrations of
both follow:
'OUTPUT(/option] is not always used; sometimes output must be specified as

COMMAND/[/option] INPUT/QUTPUT:filespec.

4-2

Using the Monitor Command Language

Long Command Format (system prompts for specific information)
+COMMANDL
/0P tionl@ED
INPUT PROMPT? INPUTL/oPtionl@D
DUTPUT PROMPT? OUTPUTL/optionl@D

Short Command Format (no prompts)
+COMMANDL/optiond

INPUTI/orptionl

DUTPUTL/crtion
]G

Notice that a slash character (/) separates an option from the
portion of the command that it qualifies, and a carriage return
@ED terminates each individual command line. When you have
supplied all the necessary information, the carriage return signals the monitor to execute the command. You can use either
format; both are demonstrated throughout this manual.

In addition to monitor commands, RT-11 has several special
function commands, called control commands, that you type by
first pressing and holding down the CTRL key on the terminal
keyboard and then typing the letter key of the command. To
execute the CTRL/C command, for example, type the letter C
while holding down the CTRL key. These control commands
require no terminator; the system performs the function as soon
as you type the command.

Control Commands

Control commands are used to interrupt program execution, to
inhibit terminal output, and to perform other similar special
system operations. They are described in the manual as you
need to use them.

During the course of this chapter, and throughout the remainder of the manual, you will use a number of monitor commands to perform some common system operations. For example, you will list the directories of device volumes, copy files
between devices, create files, and execute system and user programs. You perform these operations by re-creating on the terminal keyboard the examples already provided for you.
You should first read the entire explanation of a command to be
aware of its format, the operation it performs, and the options
that are available. Then type the command on the terminal
keyboard exactly as you see it used. Characters that you type
appear in the demonstrations in red print. Characters that are
system responses are shown in black print.
Table 4—1 lists symbols that you will see used throughout the

demonstrations. These symbols represent various keys on the

4-3

Re-Creating the
Examples

Using the Monitor Command Language

terminal keyboard. When you see one of these symbols in a
command line, type the appropriate key on the keyboard.
Table 4-1

Keyboard Symbols

Type

Symbol

®ED

carriage return key
line feed key

space bar (once for each time the symbol is shown).
Assume that you should type a single space unless
you are otherwise instructed; the space symbol is
used only if there is doubt about the number of
spaces to type.

TAB key (once for each time the symbol is shown)
DELETE key (once for each time the symbol is

shown)

ESCAPE key (once for each time the symbol is
shown)

CTRL

CORRECTING
TYPING
MISTAKES

CTRL key (hold down CTRL key while typing the
letter character [x])

All commands that you give the system are typed on the terminal keyboard. If you make a mistake while typing a command, you can correct it in one of two ways.
One way to correct a typing error is to use the DELETE key on
the keyboard. Pressing the DELETE key once cancels the character just typed; pressing it a second time cancels the next to
last character typed, and so on, from right to left, until the
beginning of the line is reached. Then additional DELETEs are
ignored.

CTRL/U

The second way to correct a typing error is to use CTRL/U, a
special control command. Typing this command once is equivalent to typing as many DELETESs as are needed to cancel every
character in the current line.
Type on the keyboard the letters DABE, followed by two DELETEs, followed by the letters TE, and notice the system’s response:

+DABE @B

The monitor echoes each deleted character and encloses them
within backslashes. As far as the monitor is concerned, the only
characters you have typed are DATE.

Using the Monitor Command Language
+DABENEBA\TE

Thus, your current line is DATE. Continue by typing a
CTRL/U. Remember to first press and hold down the CTRL key
and then type the U key; no carriage return is necessary.
€D

Notice that CTRL/U echoes on the terminal printer or screen as
“U.
+DABENEBA\TE"U

All characters on the line are canceled, and the character
pointer is moved to the beginning of a new line so that you can
enter another command. You are still in the monitor command
mode even though no prompting period appears at the left
margin.

Once the carriage return or line feed key is pressed, the previous line cannot be corrected with DELETE or CTRL/U.
These two methods are commonly used to correct typing errors
made at the keyboard. You can choose whichever method seems
most convenient.

The kinds of command operations that you usually perform immediately after the monitor is bootstrapped are those that set
up initial conditions, such as the current date and time of day,
and those that initialize and prepare the system for future operations such as file transfers. If your system has VT11 display
hardware that you want to use, you should also enable (turn on)

INITIAL MONITOR
COMMAND

Display hardware on an RT-11 computer system consists of a
cathode ray tube that allows programs to use graphics displays.

Using VT11 Display

OPERATIONS

the graphics display screen.

If your system has display hardware' (Figure 4-1), you can use
the graphics screen in place of the terminal printer or screen.
NOTE

Check question 9 in the Hardware Configuration section
of Chapter 2 to determine if your system has display
hardware. If you do not have display hardware, go on to
the next section, Entering the Date and Time-of-Day.

1yideo terminal screens are not considered graphics display hardware.

4-5

Hardware

Using the Monitor Command Language

The monitor command that enables the graphics screen is
GT command. The GT command is used to change the

of the graphics display. In this case, you will use

the

condition

it to activate

the graphics display hardware so that the VT11 display

screen
replaces the console terminal printer or screen as the termina
l

output device.

Figure 4-1

VT11 Display Hardware

Type the following on your terminal keyboard (if necessary,
refer to Table 4-1 to review the special symbols):
Long and Short Command Format
JGT

OMGEED

If your system does not have display hardware, the monitor
prints a message' on the terminal printer or screen informing
you that the command is invalid for your system configuration:
PRKMON-F-Invalid

command

Otherwise, the command is accepted. You should notice that all
character-echoing and system responses are now directed to the
graphics screen instead of to the terminal printer or screen.

After the command has been accepted, a period appears on the

graphics screen, indicating that the system is waiting for
an-

other command. The character pointer is visible as a blinking
rectangular cursor situated after the period. (In the edit mode,

the cursor is L-shaped.)

'The meanings of all system messages are listed in the RT-11 System Mes-

sage Manual.

Using the Monitor Command Language

Like output on the terminal screen, output that appears on the
graphics screen is temporary. Once the screen is filled, lines are
rolled off the top and are lost to view. However, if your terminal
has a printer, a special control command allows you to control

console terminal output so that it appears on both the graphics

screen and the terminal printer simultaneously. In this
manner, you can direct selected portions of terminal output —

directory listings, for example — to be both displayed and
printed at the same time. The advantage of this is that although the display copy is eventually lost, you have a printed
copy for later use.
The control command that provides this function is CTRL/E,
which is initiated by holding the CTRL key down while typing
the E key. No carriage return is necessary. When you type this

command, no characters echo on the graphics screen, but you
should notice that all subsequent characters (both input and
output) appear on both the graphics screen and the terminal
printer.

Thus, if your terminal has a printer and you wish to use the
printer in addition to your VT11 graphics screen, type once:
(Remember, this command does not echo.)
Now type the following and notice where the characters echo:
,WRONG

COMMAND

To disable the printer at any time so that character echoing

occurs only on the graphics screen, type another CTRL/E command:

Finally, to return terminal output control to the terminal, disabling the graphics screen, use the GT OFF command; this
changes the terminal device handler back to its original output
setting:

Long and Short Command Format
JGT

OFFG@D

Decide now whether to use the graphics screen for the remaining demonstrations. If so, use the GT ON command to enable the graphics screen, and remember that the CTRL/E command is available when you wish to produce simultaneous
output.

4-7

CTRL/E

Using the Monitor Command Language

Entering the Date
and Time-of-Day

Entering the current date and time-of-day helps in record-

keeping for system operations. Later, you can identify when
system operations were performed.

For example, by entering the current date you instruct the
system to assign this date to all files you create. The date will
also appear in volume directories and listings produced by the

various language processors and utility programs. If your

system has a clock, by specifying the current time-of-day you
instruct the system to keep track of time based on the time you
set. The current time is printed on listings when they are produced, and may also be used to control certain program operations.

DATE

Enter the date by typing the monitor DATE command with the
day, month, and year as follows (there is only one format):

Long and Short Command Format
.DATE 8-JAN-B3ED

This sets the date to January 8, 1983. Since this date is not
current, reenter the correct date using the same command
format:
JDATE

dd-mmm-vyy
@D

Typing the new date overrides the previous date.
The date that is set is temporary. You must reenter it whenever
you bootstrap the system.

TIME

The monitor TIME command is used to set the time-of-day,
specified in 24-hour notation. The system keeps track of time in
hours, minutes, and seconds, based on the initial time that you
enter in the command. Enter the time as follows (there is only
one format):

Long and Short Command Format
TIME

15:01: 0060

If your system does not have a clock, the monitor prints a message on the terminal; this message informs you that the command is not valid for your system configuration:
PKMON-W-~-No

clocK

Otherwise, the time is set to 3:01 p.m. If your system has a
clock, reenter the correct time, using the same command
format:
+TIME

hhimm:ss@D

4-8

Using the Monitor Command Language

Typing the new time overrides the previous time.
The system’s clock stops when the system stops running. If you

want the time to be kept current, you must reenter it whenever
you bootstrap the system. If your system has a clock and you do
not set the time, the TIME command will return the time
elapsed since the last hardware boot.

To check the time or date at any time while you are using the
system, simply type either the DATE command or the TIME
command, followed by a carriage return only:
Long and Short Command Format
DATEGD
8-.JAN-83

, TIMEGED
15:06:18

The system responds by printing the date or the time, based on
the information you previously entered. If the system responds
to the DATE command with the message 2KMON-W-No date,
the date has not been set since the system was last
bootstrapped.

Each hardware device in the RT-11 system is identified by a
two-letter mnemonic. The mnemonics, listed in Table 4-2, are
defined in the system software and are recognized and used by
the operating system. These are the device names that you generally use in command input and output lines. However, you
may want to change any of these device names temporarily, for
a variety of reasons. The following paragraphs describe both
using the physical device names shown in Table 4-2 and assigning logical (temporary) device names to devices.
Table 4-2

Physical Device Names

Mnemonic

Device

DUn:

RC25/RD51 Disk, RX50 Diskette

RKn:
TT:

RKO05/RK11 Disk
Console Terminal

DLn:
DMn:
DXn:
DYn:
LP:
LS:
MMn:
MSn:
MTn:

RL01/02 Disk
RKO06/07 Disk
RXO01 Diskette
RX02 Diskette
Line Printer
Serial Line Printer
TJU16 Magtape
TS11 Magtape
TM11 Magtape

4-9

Assigning Logical
Names to Devices

Using the Monitor Command Language

Two additional logical device names are used. These special
names are described in Table 4-3.

Table 4-3

Special Logical Device Names

Mnemonic

Device

SY:

The volume from which the monitor
bootstrapped; that is, the system volume.

was

DK:

The default storage volume (initially the same
as SY:; that is, the system volume).

You use device names in the input and output portions of a
command line to identify where input information can be found
and where output information will be sent. If a file is involved,
you also include its file name and file type, in the following
format:
devicename:filename.filetvre

The device name is followed by a colon and is always separated
from any file name and file type by a colon. The device name is
generally one of the mnemonics listed in Tables 4-2 and 4-3.
When you use a device name in any command, you must also
include the device unit number (represented by the letter n in
Table 4-2) unless the number is 0. The system assumes unit 0

of the device if no unit number is given. Thus, diskette unit 0 is
DY: or DYO:; diskette unit 1 is DY1:; RK: disk unit 2 is RK2;;
and so on. Note that, according to Table 4-3, you can use the
device mnemonic SY: or DK: for your system volume in addition to its standard device name. However, since the system
volume is initially the default storage volume for all operations,
you do not need to use a device name for your system volume.
The names listed in Tables 4-2 and 4-3 are the device names
defined within the system software. However, you can change
any of these name assignments temporarily, either by reassigning existing names to different devices or by assigning new
logical names of your own choosing to devices.
You might want, for many reasons, to change a device name
temporarily and assign it a logical name. You may, for example, have a program written for a device that is not available
on your system. If you assign the program name to a device that
is available, the program then uses that device instead.!
Since not all RT-11 users have access to the same kind of
storage volume, you are instructed to assign the logical name
VOL: to whatever volume you are using for storage. After you
IThis is called device independence.

4-10

Using the Monitor Command Language

make this assignment, subsequent command lines can be the
same for everyone using this manual.

Similarly, the special logical device name DK:, presently assigned to your system volume, could be assigned to any kind of
storage volume. Not only would DK: signify your storage
volume, regardless of its physical device name, but you could
also avoid typing DK: since it is the default storage volume for
most commands. (Only the R command requires that the file
specified be on the system volume SY:)

To assign a logical name to your storage volume, first determine its physical device name. Check questions 7 and 8 in the
Hardware Configuration section of Chapter 2 to see which de-

vice and which device unit you are using for your storage
volume. Translate this into the appropriate name and number
using Table 4-2 as a guide.

Use the monitor ASSIGN command to change this physical

name to a logical name. Substitute for physical-device-name in

the following command lines the physical name and device unit
number for your storage volume (for example, for RKO05 disk

ASSIGN

unit 1, substitute RK1:).

Long Command Format
+ASSIGNED

Physical device name? physical-device-name@D

Logical device name? WOL:@®ED

Short Command Format
,ASSION physical-device-name YOL @D

Once the assignment is made, the system recognizes the logical
name VOL: as the device name for your storage volume. This is

the only logical assignment you need to make. Since you are
not changing the DK: assignment, the system volume remains
the default device for all I/O operations.

As you continue to use the system, you may well make many

device assignments and deassignments. To check the status of
all assignments made during a computer session, you can use

the monitor SHOW command to print on your terminal a list of
all the logical assignments currently in effect. Use the SHOW
command now to check the status of the assignment just made:
Long and Short Command Format
+ SHOWEED

4-11

SHOW

Using the Monitor Command Language

Check the list printed on your terminal to make sure that the
code VOL: has been assigned to your storage volume. The let-

ters VOL: should follow the appropriate device name in the list,
as in the following response, in which VOL: represents disk
unit 1:
TT

(Resident)

RKO

RK1

VOL

free

slots

Logical device assignments are temporary. Thus, if you want a
logical device assignment to remain in effect, you must reassign
it each time the system is bootstrapped.

Listing Volume
Directories

Both your system volume and your storage volume have directories, which are compiled lists of all the files stored on the
volume. You can print a volume directory on your terminal,

using the monitor DIRECTORY command.' To list the direc-

DIRECTORY

tory of your system volume, type:

Long and Short Command Format
\DIRECTORY®

CTRL/O

(The system volume is the default device.)

Since the directory of the system volume may be quite long,
after approximately 10 lines have printed on the terminal, type:

This special control command, echoed as "O, inhibits the re-

mainder of the listing output from printing on the terminal,
although the information on the total number of files and
blocks is still given. When control returns to monitor command
mode, look at the directory listing. At the top of the listing is
today’s date, as you entered it earlier in the DATE command.
Following the date is a list of the files on the volume. Notice the
two-column format of each line in the directory.
'Users of VT11 display hardware may wish to use the CTRL/E command to

enable both the graphics screen and the terminal printer for the following
exercises.

4-12

Using the Monitor Command Language
08-Jan-83

.SYS
SWAP
RT11FB.SYS
RT11XM.SYS
+5YS
DT
. 8Y5
DX
«8YS
RF
«8YS
DL
+8YS
DM

26
86
94
3
3
3
4
5

2B6-Auyg-B2
26-Aug-82
26-Aug-82
26-Aug-8B2
26-Aug-B2
26-Aug-BZ
268-Aug-B82
2B-Aud-82

RT1154.8Y8
RT11BL.SYS
«8YS
T7
+SY8
Dp
+8YS
Dy
+SYS
RK
+SYS
bu
+5YS
DS

+8YS

ZB-Aug-82

73
73
2
3
4
3
4
3

26-Aud-B2
26-Ausg-B2
26-Aug-B2
26-Aug-82
26-Aug-B2
26-Aud-82
2B-Aus-82
2B6-Aug-82

170 Files s 4264 Blocks
498 Free blocks

First the file name appears, followed by a dot and a file type

that is frequently used to identify the file’s format. For exam-

ple, .SYS represents a system file; other RT-11 file types used
to represent different kinds of files are listed in Table 44. After the file type is a number that indicates the size of the file.
The size is given in blocks, a term used to designate a standard
amount of information. A file that is 1 to 10 blocks long is fairly
small, while a file over 100 blocks in length is quite large. The
date on which the file was created is shown at the right. This
space is empty if a date was not specified (with the DATE comTable 44

File Types

Meaning

File Type
.BAC
.BAK
.BAS
BAT
BUP
.COM
.CTL
.DAT
.DBL
.DIF
.DIR
.DSK
JFOR
.LOG
.LST
.MAC
.MAP
MLB
.OBJ

BASIC compiled file
Editor backup file
BASIC source file
BATCH source file
Backup/restore file

.REL
.SAV

Executable foreground program file or system job
Executable background program file

SML
SYS

Indirect command file or IND indirect control file
BATCH control file
BASIC-11 or FORTRAN 1V data file
DIBOL source file
SRCCOM output file
Directory listing file
Logical disk file
FORTRAN IV source file
Batch log file
Listing file
MACRO-11 source file
Linker map file
MACRO library file

MACRO-11, FORTRAN 1V, or DIBOL object out-

put file or library file

System MACRO library
System files and handlers

4-13

Using the Monitor Command Language

mand) on the day the file was created. At the end, you are told
how many files are on the volume, their total length, and the
number of free blocks available for your use.
NOTE

Files furnished on the distribution medium have a pro-

tected status, which means they cannot be deleted. This
is indicated by the letter P after the file size shown when
you print a directory listing. You cannot perform any operation on a protected file if the result is to delete it. You
can change the protected status of a file by using the
RENAME keyboard monitor command with the /PROTECTION or /NOPROTECTION option; you can give a

protected status to a file by using the PROTECT keyboard monitor command; and you can remove a protected status from a file by using the UNPROTECT keyboard monitor command (see the RT-11 System User’s
Guide).

DIRECTORY
/BRIEF

You can also obtain an abbreviated directory, which omits file
lengths and dates and lists only file names and file types in
five-column format. To do this, you use the DIRECTORY command with its /BRIEF option. Type the following, and after

several lines have listed, interrupt the directory by typing two
CTRL/C command characters. This double control command
echoes two "Cs and requests the running program to abort immediately, regardless of what the program is doing (one

CTRL/C CTRL/C

CTRL/C aborts an executing program waiting for input from
the console terminal). Control returns to monitor command
mode.

Long and Short Command Formats
WDIRECTORY/BRIEF®RED
08-Jan-83

SWAP

,5YS

RT11S8J.5YS5

RTILIFB.SYS

RT11BL,SBYS

RTIL1XM.8YS

+8¥85

+S¥Y8

«SYE

+8Y8

RF
DS

+8Y8
«8YS

RK
DD

«8¥S
+5¥8

DL
LP

+8YS
+SY¥S8

DU
LS

«8¥S5
«5¥YS

DM
CR

+SYS8
+8Y¥8

L CIETLC )

DIRECTORY
/PRINTER

Volume directories can be printed on a line printer if one is
available on your system. Check the answer to question 9 in the
Hardware Configuration section of Chapter 2 to determine if
your system has a line printer. Since listings print faster on a
line printer than on the console terminal, it is to your advantage to use the line printer for large amounts of output. The

/PRINTER option is used with the DIRECTORY command to
cause a directory to be printed on the line printer instead of on
the terminal. Make sure your line printer is turned on, and
then type the DIRECTORY command as shown:

4-14

Using the Monitor Command Language

Long and Short Command Format
JDIRECTORY/PRINTERGED

The listing may be quite long. When the line printer has finished printing, retrieve the listing.

Initializing a storage volume clears its directory. A new
(unused) volume should always be initialized before it is first
used. In addition, any storage volume that contains files that
are no longer needed can be initialized to recover the storage
space. Note, however, that an initialize operation is used to
remove all file names from the directory. So before you initialize a volume, make sure that it contains no files that you

Initializing the

Storage Volume

might want later.

Since you will use your storage volume to store several new
files (created as a result of the various exercises in this
manual), clear its directory using the monitor INITIALIZE
command. This operation ensures that the volume has room for
new files.

Long Command Format
VINITIALIZE®D

: @D
Device? UOL

(VOL: is the assigned logical device name for your
storage volume.)

Short Command Format
VINITIALIZE VoL 6D
RKi:/Initialize$ Are vou sure?YEJ)

The system prompt physical-device-name/Initialize; Are you
sure? gives you an opportunity to verify the command. Typing a
Y initiates the operation, while N stops the operation and returns control to the monitor command mode. Check your command line, make sure you are initializing your storage volume,
and then type a Y. Again, list the directory of the storage
volume. It should be empty.

Long and Short Command Formats
JDIRECTORY

VOL : GED

B-Jan-83

Filessy

4762

Free

Blocks
blocks

The number of blocks available for use on the volume is printed
at the end of the directory and varies depending on the type of
device you use as your storage volume.

4-15

INITIALIZE

Using the Monitor Command Language

The commands you have performed in this chapter have pre-

pared the system for major operations that will follow. In
Chapter 5 you begin by using the RT-11 editor to create text
files that you will store on your initialized storage volume.

SUMMARY:
INITIAL

MONITOR

COMMANDS

ASSIGN physical-device-name logical-device-name

Assign a logical device name to a physical device name.

DATE
Print the current date, if previously set.

DATE dd-mmm-yy

Set the current date (day-month-year).
DIRECTORY ddn:
List the volume directory on the terminal (ddn: is the mnemonic for the device name; the default storage volume, DK:,
is assumed if ddn: is not specified).

DIRECTORY/BRIEF ddn:
List a brief volume directory on the terminal, showing only

file names.

DIRECTORY/PRINTER ddn:
List the volume directory on the line printer.
DIRECTORY/PRINTER/BRIEF ddn:

List a brief volume directory on the line printer.

GT OFF
Disable the VT11 display hardware.
GT ON
Enable the VT11 display hardware so that the graphics
screen replaces the terminal printer/screen as the terminal

output device.

INITIALIZE ddn:

Clear the directory of the indicated volume (ddn: is the mnemonic for the device name and must be specified).
SHOW
Print the status of all current logical device name assignments.

TIME
Print the current time, if previously set.

TIME hh:mm:ss

Set the current time-of-day (hour:minute:second).

4-16

Using the Monitor Command Language

CTRL/C CTRL/C
Interrupt the current operation or program and return control to monitor command mode.

SUMMARY:

SPECIAL
CONTROL
COMMANDS

CTRL/E

Direct terminal output to both the graphics screen and the
terminal printer simultaneously. Type a second CTRL/E to
return output control to the graphics screen only. (Valid only
when VT11 display hardware is enabled.)
CTRL/O
Inhibit the remainder of output from printing on the terminal.

CTRL/U

Cancel every character in the current line.
DELETE

Cancel the last character typed on the current line.

LP11/LS11 Line Printer Manual (EK-LP11-TM-005). Maynard, Mass.:
Digital Equipment Corporation, 1975.

A hardware manual for the owners and operators of LP11/LS11 line

printers and for those who will be programming computers to interact
with these devices.

RT-11 Mini-Reference Manual (AA-M241A-TC). Maynard, Mass.: Digital
Equipment Corporation, 1983.

A summary of all RT-11 monitor commands, command options, system
utility program operating commands, and programmed requests.

RT-11 System User’s Guide (AA-5279C-TC). Maynard, Mass.: Digital Equipment Corporation, 1983.

A guide to the use of the RT-11 operating system.

4-17

REFERENCES

CHAPTER 5

CREATING AND EDITING TEXT FILES
The ability to create and edit text files is one of the most useful
features of the RT-11 operating system. Not only can you
create computer programs, data files, memos, and reports on
line (that is, under the control of the system), but you can alter
what you create without retyping the entire file.
You create and edit text files more often than you perform any
other system operation. Therefore it is essential that you become familiar with the editing process as quickly as possible.
Editing should become second nature to you as you learn to use
the RT-11 computer system.

Two RT-11 editor system utility programs, EDIT.SAV and
KED.SAV, are stored as part of the RT-11 operating system on
your system volume. The demonstrations in this manual illustrate EDIT, which can be used on a video terminal or a hardcopy terminal. The use of KED is restricted to video terminals.
For more information about KED, refer to the PDP-11 Keypad
Editor User’s Guide.

Text files that you create with the editor are stored in the computer in ASCII format. ASCII, which stands for the American
Standard Code for Information Interchange, is an industrystandard code that consists of a numeric representation for each
of the alphabetic characters (A to Z), the numeric characters (0
to 9), the punctuation characters, and some special communication control characters. When you type text on the terminal
keyboard, the system automatically converts the text to ASCII
codes; when you request listings on the terminal or line printer,
the system converts the ASCII code back to the text characters.
The RT-11 editor uses a specially reserved area of computer
memory to hold the text you are creating or editing. This area
of memory is called the text buffer. When you create text, the
characters that you type on the terminal keyboard are
transmitted directly into the text buffer. When you edit text,
the characters are copied from the input file into the text
buffer, where you can modify them. When you have edited the
text in the buffer to your satisfaction, the characters are moved
out of the text buffer to the output file (Figure 5-1).

5-1

THE RT-11 EDITOR

Creating and Editing Text Files
COMPUTER

OUTPUT

Figure 5-1

Editing with RT-11

Since the text buffer is a limited area of computer memory, you
may at times try to input more text than the buffer can accommodate. If this condition becomes apparent to the editor, it
prints a warning message on the terminal telling you that, before you can input any more text, you must make room in the
buffer, either by transferring text to the output file or by
erasing text already in the buffer.

You can avoid this inconvenience during editing if you make
use of a concept called paging. When you create a large text file,
instead of typing the file as one long stream of text, divide it
into individual pages of approximately 50-60 lines in length;
this corresponds roughly to the size of a line printer or terminal
listing page. You can copy the text into and out of the buffer

one page at a time. A single page of text is never too large for
the text buffer and also fits on the line printer or terminal
perforated paper when you obtain a listing.

CREATING A
TEXT FILE

EDIT/CREATE

You activate the editing capability by using the monitor EDIT
command. When creating a file, you must use the /CREATE
option followed by the file name and file type you want assigned to the new file. The default storage volume (DK:) serves
as the default device, so unless you specify a device using one of
the mnemonics in Table 4-2, the editor creates the new file on
the device DK: (which is the system volume, unless changed via
ASSIGN).
First, if you are using display hardware, disable it with the

monitor GT OFF command; the editor has a special display

capability that is not described until later in this chapter.
Long and Short Command Format
+GT

OFFGED

Creating and Editing Text Files

Next, use the editor to create a text file of five lines. Call the
file DECIND.USA, and use the default storage volume — currently the same as the system volume — for the file.
Long Command Format
JEDIT/CREATERD

File? DECIND.USAER
*

Short Command Format
JEDIT/CREATE DECIND.USAGD
#*

Once the output file is open (that is, when the appropriate file
has been established for output operations), the editor prints a
prompting asterisk at the left margin. The asterisk indicates
that the editing command mode is in control. This prompt is
your cue to enter an editing command.
The editing command used to create text is the I (Insert) com-

mand. Type:

INSERT

All subsequent characters that you type on the terminal key-

board will now be entered into the text buffer just as you type

them. Enter the following text exactly as shown, including all
spaces and errors. Before you type the RETURN key, check the
line to make sure that it matches what is shown here. Remember, if you make a typing mistake that is not intentional,

ESCAPE ESCAPE

you can use the DELETE key on the terminal keyboard to erase
individual characters and the CTRL/U command to erase all
characters on the current line. When you have finished typing
the five lines, type the ESCAPE key twice. The ESCAPE key
echoes on the terminal as a $; it is used to execute an editing
command and to return control to editing command mode.
#IWE HOLD THESE TRUTS TO BEE SELF-EVIDENT
.G

THAT ALL MEN ARE CREATED EQUAL, THAT THEYGED
HAVE UNRELIABLE TENDENCIES OF WHICH THEYGED
AR ENDOMWED BY THEIR CREATOR: THAT AMONGED
THESE ARE LIFEs LIBERTY AND HAPLENESS.EED
E0E0

Forget for the moment that this text contains several misspell-

ings and other errors, and assume instead that you are satisfied

with it and ready to transfer it from the text buffer to the
output file. The EX (Exit) editing command performs this function. This command terminates editing, transfers all text in the
text buffer to the output file, closes the currently open output
5-3

EXIT

Creating and Editing Text Files

file (making it unavailable for further output operations), and

returns control to monitor command mode, indicated by a dot at

the

left margin.

DECIND.USA:

Use the EX command to close the file

wwwwww

*EX EDED

You

now

have

file

your

system

volume

-called

DECIND.USA, consisting of the five lines of text you just created.

EDITING A

TEXT FILE

EDIT

The file DECIND.USA needs editing. To edit a file, you again
use the EDIT command to activate the editor. Next indicate in
the command line the two-letter device mnemonic for the

volume on which the file resides (the default storage volume,
DK:, is assumed). Following this, you indicate the file name
and file type of the file. The editor then opens the file, making
it available for input operations.

Thus, to open the file DECIND.USA for editing, type:
Long Command Format
+EDITED
File? DECIND.USAGD
*

Short Command Format
+EDIT

DECIND,USAGEED

READ

The EDIT command opens the input (and output) files. Use the
R (Read) editing command to read the first page of text from the

input file into the text buffer. No output occurs to the output

file, but the file is available for output at a later time. The
input file itself is not altered in any way.
R EOED
*

BEGINNING

Whenever text is read into the text buffer, a pointer is automatically positioned at the beginning of the text. This pointer is an

invisible indicator that serves as a target for editing commands.

The pointer pinpoints the exact location in the file where the
next character will be inserted. For example, when you finished

inserting text earlier (just before using the EX command), the
pointer was positioned at the end of the file. Now that the EDIT

command has been used to read text into the text buffer, the

pointer is positioned at the beginning of the text in the text

buffer. If the pointer is not at the beginning and you want to

Creating and Editing Text Files

move it there, you can use the B (Beginning) command; this
command moves the pointer to the beginning of the text in the
text buffer, no matter where the pointer is currently positioned:
#*

With the pointer positioned at the beginning of the text buffer,

you can use the L (List) editing command to list the text cur-

rently in the text buffer on your terminal printer. The List
command lists text, starting at the pointer and continuing to
whatever place you indicate by the command argument.
A command argument is simply a prefix to an editing command
that sets limits on the command’s actions. Command arguments are used frequently and are summarized in Table 5-1.
Study this table for a moment before continuing.
Table 5-1

Meaning

Argument

Command Arguments

Represents any integer in the range -16383 to

+16383; it may be preceded by a + or —. If no
sign precedes n, it is assumed to be positive.
Whenever an argument is acceptable in a command, its absence implies an argument of 1 (or

—1 if only the — is present).

Refers to the beginning of the current line.

Refers to the end of text currently in the text
buffer.

Thus, with the pointer positioned at the beginning of the text,
use the / argument and the L command to list on the terminal
all text in the buffer. The position of the pointer does not
change. List the text and compare your output with the five
lines shown in the following example — they should match exactly.
# /1. E0E0

WE HOLD THESE TRUTS TO BEE SELF-EVIDENT,
THAT ALL MEN ARE CREATED EQUAL., THAT THEY
HAVE UNRELIABLE TENDENCIES OF WHICH THEY
AR ENNDOMWED BY THEIR CREATOR, THAT AMONG
THESE ARE LIFE. LIBERTY AND HAPLENESS.
#*

If your output and the five lines above do not match exactly,
then you probably typed some unintentional errors into
DECIND.USA.

5-5

LIST

Creating and Editing Text Files

The remaining EDIT commands in this exercise depend upon
an exact reproduction of DECIND.USA to function properly.
Therefore, since you are not yet familiar with the EDIT com-

mands necessary to correct your file, an existing copy of
DECIND.USA with intentional errors must be substituted.

Prepare the text buffer by erasing it with CTRL/CESOESD. This
unusual command combination is required by the EDIT pro-

gram when you want to exit without creating an output file.
The structure of the command prevents you from accidentally
eliminating a file with a single CTRL/C.

The monitor command mode period appears, signaling your departure from the editing command mode. Your system volume
still contains the file DECIND.USA that you created earlier.
However, it also contains the copy provided with the system,

DEMOED.TXT, which you will use for the remainder of the

exercise.
Before going any further, you must rename DEMOED.TXT to

DECIND.USA to avoid confusion.

A RENAME operation, ex-

plained fully in the File Copying Operations section of Chapter
7, is the method of choice. Type the following command:
+RENAME

DEMOED.TXT

DECIND.USAGED

The contents of DEMOED.TXT are now labeled DECIND.USA.
Note, however, that if a file labeled DECIND.USA already ex-

ists and you rename another file to DECIND.USA, the system
deletes the first file named DECIND.USA and renames the current one. Type EDIT DECIND.USA

to open the file for

input, and type the R command to read it into the text buffer.
JEDIT

DECIND.USAGD

*REDED

Since the pointer automatically returns to the beginning of the
text with an R command, you can type /L to list the entire file.
*/|. BOED
WE

HOLD

THESE

ALL

HAVE

UNRELIABLE

MEN

TRUTS

THAT

ENDOWED

THESE

ARE

5-6

BEE

SELF-EVIDENT.

EQUALs+ THAT

TENDENCIES

THEIR

LIFE:

CREATED

CREATOR»

LIBERTY

AND

WHICH
THAT

THEY
THEY

AMONG

HAPLENESS.,

Creating and Editing Text Files

The text contains errors and misspellings deliberately introduced for the purposes of the exercises in this chapter. To cor-

JUMP

rect the errors, reposition the pointer so that it is near the text

you want to change. The J (Jump) command, for instance, in
conjunction with a command argument, moves the pointer either backward or forward by the specified number of characters, including spaces. Type the J command now, using an argument of 18, to reposition the pointer 18 places ahead":
* 18 JE0ED
#

Although you cannot see it, the pointer has moved from the
beginning of the text buffer to the right of the 18th character.
You can verify this by using the List command again. The List
command with no argument prints from the pointer to the end
of the current line and thus exposes the location of the pointer:
*#L GO0

BEE

SELF-EVIDENT.

The characters in the example should match the current line on

your terminal, showing the pointer positioned at the first error
in the text where an H is missing in the word TRUTS. Since the
pointer is positioned between the second T and the S, use the
Insert command to insert an H in the proper place:
* T HEDED
*

Now use the V (Verify) command to verify the line. The V command, which does not require arguments, prints the entire line

VERIFY

containing the pointer (the current line) on the terminal. It
allows you to verify that a correction was properly made. The
pointer is not moved as a result of the V command,; its position

remains just to the right of the last inserted character (shown
here by the arrow):
#1) ESDESD
WE

HOLD

THESE

TRUTHS

BEE

SELF-EVIDENT,

! Anytime you use the Jump command to move the pointer forward (or back-

ward) by enough characters so that it moves to a new line, you must account
for two extra characters in the command argument. This is because the editor

treats the carriage return at the end of each line as two characters — a
return and a line feed.

Creating and Editing Text Files

So far you have entered and executed editing commands one at
a time. You can enter multiple commands by separating each
individual command with a single ESCAPE. Typing two ESCAPEs then executes all the commands in the entire command

string in consecutive order. For example, combine the J and L

commands as shown in the following command string:
* 7 JEDL ESDED
£

SELF-EVIDENT,

The 7J moves the pointer seven positions to the right, and L
then lists the text from the pointer to the end of the line so that
you can see the pointer’s new position.

A special CTRL command is available to erase multiple editing

CTRU/X

commands. The CTRL/X command (hold the CTRL key down

and type the X key) causes the editor to ignore an entire command string that might extend over several lines if the I command is involved. The editor echoes with "X, issues a carriage
return, and prints an asterisk indicating that you are still in

editing command mode and can enter a new command. For example, type:
*70JE0ISTART
NEW

AGED

LINE

In addition to the CTRL/X command, you may still use the
DELETE key to erase individual characters in the command
line one at a time, and the CTRL/U command to erase all char-

acters entered on the current command line.
Since you used the CTRL/X to ignore this last command string,

DELETE

the

pointer

still

positioned

the

error

the

file — just before the extra E in the word BEE. You can erase
this extra character by using the D (Delete) command.! The D
command removes one character (or space) to the right of the
pointer for every +1 in its argument and one character to the
left for every —1. Use the D command to erase the extra E and
then verify the line (+1 is assumed if no argument is used):
* DESDVESDED

HOLD

THESE

TRUTHS

SELF-EVIDENT,

'The Delete command should not be confused with the DELETE key on the

terminal keyboard. While both perform the delete function, the D command is
used to erase characters already within a text file; the DELETE key is used to
erase typed characters in a command string or during text creation.

5-8

Creating and Editing Text Files

in the example
As you can see from the position of the pointer
not actually move

(shown by the arrow), the D command doesaround the pointer.
the pointer, but simply erases characters is now positioned
Since the extra E was erased, the pointer
between the E and the space.

by
Just as you can use the Jump command to move the pointerthe
command to move
characters, you can use the A (Advance)the
command an argupointer by entire lines. Again you give
ment that indicates the number of lines, either forward or backward. The pointer is positioned at the beginning of the new

ADVANCE

line. Use the A command to move the pointer forward two lines,
and then list the current line:
* 2 A0

BOED

HAVE UNRELIABLE TENDENCIES OF WHICH THEY
*

This entire line does not belong in the text. To erase it, you

could count the number of characters in the line and use this
is
number as an argument to the D command; however, there

KILL

an easier way. The K (Kill) command erases the entire line
following the pointer and positions the pointer at the beginning
of the next line in the text. Type:
* K E501L ES0ED

AR ENDOWED BY THEIR CREATOR: THAT AMONG
*

The pointer is now at the beginning of the next line in the text.
As you can see, this line also contains an error, the word ARE is
incorrectly spelled as AR. Use the J command to jump over two
characters, and insert the E. Then verify the line:
* 2 JEE0 1 EEOVEDED

ARE ENDOKWED BY THEIR CREATOR» THAT AMONG
*

The arrow shows where the pointer is now positioned. This line

still contains an error — it is missing the words WITH CER-

TAIN INALIENABLE RIGHTS, which should follow the word
CREATOR. You can count the number of characters from the
pointer to the second R in CREATOR and then jump the pointer
by this number, or you can use the G (Get) command. The G
command searches, from the pointer, for the first occurrence of
a specified character string and leaves the pointer at the end of
that string. Use the G command to search for the string OR (in
CREATOR); then insert the missing words and list the lines
that have changed. Notice how you use the carriage return to

5-9

GET

Creating and Editing Text Files

break the line into two parts (the @ symbol is used to show
where you should insert spaces):
*CORESOIGPWI THERCERTA T NEED
INALIENABLEGRIGH
- A0 TSED
2L EDED

ARE

ENDOMWED

INALTENABLE

THEIR

RICHTS,

CREATOR

THAT

WITH

CERTAIN

AMONG

To list both lines, it was necessary to move the pointer back
to
the beginning of the first line you changed; this was done
by the
—A command. The 2L command then listed both
lines. Notice
where the pointer is; it was moved by the ~A command
and was
not repositioned by the L. command.

You must be careful when you use the Get command, becaus
e
the character string you specify must be unique if you
want the
pointer to move to the correct spot. For example, if the
characters OR had occurred anywhere after the pointer and
before the
word CREATOR, the pointer would have stopped there
instead,
and you would have inserted text in the wrong place.
The final errors in this text occur in the last line. The
words
THE PURSUIT OF are missing, and the word HAPL
ENESS is
a misspelling. Use the Get command to move the

pointer to the

word AND and insert the missing text. Move the pointer

again
with the Get command to the PLE of HAPLENESS; erase
the
LE, and insert PI. Then verify the line:
*GANDED IGPTHEBPP
TEPOF
URS
ESOED
UI
*GPLEED-2
1P ] EOVED
DED
ED
THESE

ARE

LIFE,»

} CTRLL

LIBERTY

AND

THE

PURSUIT

HAPPINESS,

Large text files — 50 lines or more — should
be delimited
into pages. To do this, insert a form feed into
the text at the
place where you want the page to end. A form
feed is typed as a
CTRL/L (hold the CTRL key down and type
the L key), which
the editor recognizes as a page break.
Since this text file is only five lines long, there is
really no need
to delimit it as a page. However, for the sake of
practice, insert
a form feed at the end of this file. Then move the
pointer to the
beginning of the text buffer and list the entire
text. Compare

your text with the following example. If

errors remain in your

file, fix them by using the commands described
%G,

016D

(CTRL/L echoes as eight line feeds.)

5-10

so far.

Creating and Editing Text Files
D
/L EDED
E0BE
TO BE SELF-EVIDENT .,
WE HOLD THESE TRUTHS TED
EQUAL» THAT THEY

THAT ALL MEN ARE CREA
WITH CERTAIN
ARE ENDOWED BY THEIR CREATOR
AMONG
INALIENABLE RIGHTS, THAT

INESS.

THESE ARE LIFEs LIBERTY AND THE PURSUIT OF HAPP
*

last two
This text is correct in spelling and content, but totheread.
The
r
lines should be justified to make them easie
G
the
pointer is currently at the beginning of the text. Usethen incommand to search for the character string AMONG,;
sert and delete text to justify the lines. Finally, list the text
again:

EOED
*GAMONGED IEPTHESESD AREEDAED!L ODEDBED /L
NT +

WE HOLD THESE TRUTHS TO BE SELF-EVIDE
THAT ALL MEN ARE CREATED EQUAL» THAT THEY
ARE ENDOWED BY THEIR CREATOR WITH CERTAIN
INALIENABLE RIGHTS, THAT AMONG THESE ARE
LIFEs LIBERTY AND THE PURSUIT OF HAPPINESS.
*

Once you are satisfied with your text, you are ready to transfer
r
it to the output file. You could use the EX command to transfe
File.
Text
a
ing
Creat
n
sectio
the
the text, as you did earlier in
However, suppose your input file has additional pages of text
that require editing. If you use the EX command, all remaining

text in the input file will be read through the text buffer into
the output file, and the files will be closed although you may
want to do more editing. To avoid this, you can use the N (Next)
command. This command transfers the text currently in the
text buffer to the output file, clears the text buffer, and reads in
the next page from the input file. The pointer is positioned at
the beginning of the text buffer.
* NEOED

2EDIT-F-End of

input file

(No text remains in the input file.)

If you use the N command when no text remains in the input
file (as just happened), the editor prints a message on the terminal telling you so. At this point, you can type the EX command to close the file.
*E X ES0ED

5-11

Creating and Editing Text Files

When you close a file after editing, the editor creates a file on
the default storage volume (or system volume). It gives this
new file the file name and file type that you indicated for input.

It then renames the input file so that the file retains its file
name but is assigned a file type of .BAK. This file type identi-

fies a backup file, here an original input file retained in case of
editing mistakes or accidental deletion of the new file. Thus you

now have two versions of the DECIND file on your system
volume:

DECIND.USA,

which

the

edited

version,

and

DECIND.BAK, which is the unedited (original) input file.

Verify this by using the monitor DIRECTORY command:

Long and Short Command Format
+DIRECTORY

DECIND.*@EED

08-Jan-83
DECIND.BAK
2

Filesy

496

Free

i
2

08-Jan-83

DECIND.USA

08-Jan-83

BlocKs

blocKs

The asterisk (*) following DECIND. is a type of shorthand notation called wildcard construction. Here it means to list all files
named DECIND, regardless of their file type. Wildcard construction is explained in detail in the Multiple File Operations

section of Chapter 7.
Whenever you edit the same file a number of times, new ver-

sions overwrite old versions. Thus only two versions of the
edited file (filnam.BAK and filnam.typ) ever reside on a volume
at one time.

USING UPPERCASE
AND LOWERCASE

CHARACTERS

Later model terminals (for example, LA120 DECwriters and
VT100 video terminals) have the capability to print in upper-

case and lowercase. Certain line printers also have this capa-

bility. You can use the uppercase/lowercase capability of these

devices if you type the EL (Edit Lower) editing command before

entering the text you want to insert in lowercase. The EL command instructs the system to accept all characters typed as

they appear on the keyboard. The monitor facility, which converts all alphabetic characters to uppercase, is disabled. In ad-

dition, the characters are echoed on the terminal printer or
screen as uppercase and lowercase characters.

Open the file DECIND.USA again, and type the EL command:

Edit Lower

Long and Short Command Format
+EDIT

DECIND.USAGD

*EL E0E0
*

5-12

Creating and Editing Text Files

Once you have typed the EL command, you can use the SHIFT
key on the terminal to designate uppercase, just as you do on a

typewriter. Editing commands may be entered as either upper-

case or lowercase characters. For example, type the following

commands, which change the characters in the first line of the

file DECIND.USA to uppercase and lowercase:
# rE50 b €0 1 ES0E0
WE

HOLD

*KEDiWe

THESE

hold

TRUTHS

these

T0O

truths

SELF-EVIDENT,

self-evident @0

€0 - 2 €50 v EOED
We

hold

these

truths

self-evident

The uppercase and lowercase capability is useful for reports,
memos,

and

other

textual

material

that

you

list

Edit Upper

uppercase/lowercase

devices. However, all characters are
printed as uppercase if you list the file on a line printer or
terminal that does not have the uppercase/lowercase capability.

If at any time you want to revert to strictly uppercase editing,

type the EU (Edit Upper) command:
#¢ uEBDED
*

Uppercase editing is a default mode. Whenever you open a file
for editing or create a new file, you must enter the EL command

if you want to use the uppercase/lowercase capability.

Close the file DECIND.USA by typing:
*EXEOE0
+

EDIT filespec
Activate the editor and open the file for editing.

SUMMARY:

EDITING

COMMANDS

EDIT/CREATE filespec

Activate the editor and create a new file.
Control Commands

CTRL/L
Insert a form feed. The form feed character is used to delimit
pages of text in a file (introduced as part of text by the Insert
command).

CTRL/X
Ignore all commands in the current editing command string.

5-13

Creating and Editing Text Files

Command Arguments
n(+ or —)
An integer value between —16383 and + 16383 that sets the
range of a command’s actions based on the pointer’s current

position.
0

Beginning of the

current

line

(the

line

pointer).

containing the

End of the text in the text buffer.

Input/Outpuf Commands (pointer is not repositioned)
(x indicates that an argument can be used)

EX
Exit; terminate editing, transfer the contents of the text
buffer and the remainder of input file to the output file; close
input and output files; return to monitor command mode.
xL,

List; list, from the pointer, x lines of text.
xN

Next; write the contents of the text buffer to the output file,
clear the text buffer, and read into it the next page from the
input file; perform this write/read sequence x times.

\Y%
Verify; list the current line (the line containing the pointer)

on the terminal.

Pointer Location Commands (pointer is repositioned)
(x indicates that an argument can be used)
xA

Advance; move the pointer to the beginning of the xth line
from the current pointer position.
B

Beginning; move the pointer to the beginning of the text

buffer.
xJ

Jump; move the pointer forward or backward by x characters.

5-14

Creating and Editing Text Files

Text Modification Commands (pointer is repositioned)
(x indicates that an argument can be used)
xD

Delete; erase x characters to the right (or left) of the pointer.

I text

Insert; insert text into the text buffer at the present pointer

position.
xK

Kill; erase x lines of text, beginning at the pointer.

Search Command (pointer is repositioned)
(x indicates that an argument can be used)
xG text

Get; search the text buffer, beginning at the pointer, for the
xth occurrence of the indicated text string and leave the
pointer at the end of the text string.

Uppercase/Lowercase Commands (pointer is not affected)
EL

Edit Lower; accept characters typed at the keyboard as
uppercase/lowercase.

Edit Upper; revert to uppercase editing (after EL).

If your system configuration includes VT11 display hardware,
there are several advantages to your using it during editing.’
First, the graphics screen becomes a window into the text
buffer, exposing twenty lines of text at a time: the current line,

the ten lines preceding it, and the nine lines following it.

Figure 5-2 illustrates this format. As you edit, the lines in view
shift to conform to the current line. In addition, the pointer is
visible and appears as a blinking, L-shaped cursor. Its position
is automatically adjusted as you execute editing commands. Finally, the four lines at the bottom of the screen display the last
three command lines plus the current command line. Horizontal dashes separate the text of the file from your commands.

1If your system does not have VT11 display hardware, skip to the next section, entitled Creating the Demonstration Programs.

5-15

USING A
GRAPHICS DISPLAY
TERMINAL

DURING EDITING

Creating and Editing Text Files

10 PRECEDING

LINES OF TEXT

CURSOR

WINDOW

(CURRENT LINE)

INTO THE
TEXT BUFFER

AND 9

FOLLOWING
LINES OF TEXT

SEPARATION

LINE

3 PRECEDING
COMMAND LINES
CURRENT

COMMAND LINE

Figure 52

Normal Use of the

Graphics Display

Text Window Format

All editing commands and functions described
so far can be
used when the graphics screen is enabled. The only
difference is
that terminal I/O is rearranged on the screen as
shown in
Figure 5-2. Note that the L and V editing comma
nds become
superfluous since the pointer is always displayed on
the screen.
Also, since twenty lines of text are always displayed,
any List

command within that range is unnecessary.

Currently, your graphics screen is not enabled. To enable
it, use
the monitor GT ON command as you did in Chapte
r 4:

Long and Short Command Format
JGT

ONGED

Now when you use the EDIT command to activate
the editor,
the graphics screen will be rearranged as shown in
Figure 5-2.
You can use the CTRL/E command, described in Chapte
r 4, to

request simultaneous I/O on the terminal printer
screen.

Immediate Mode

and graphics

In addition to the regular editing capability, a quick

and easy
method of graphics editing, called immediate
mode, is available. Immediate mode uses a simplified set of editing
commands that are limited to pointer relocation and
character deletion and insertion. Most of these commands are similar to
the
special CTRL commands because to type them you use the
CTRL key in combination with another character key. How-

5-16

Creating and Editing Text Files
ever, the use of these particular control comma
nds is mean-

ingful only in the editor immediate mode. Table 5-2

commands.

Table 5-2

Immediate Mode Commands

Command

CTRL/N

lists the

Meaning

Advance the cursor to beginning of next line
(equivalent to A).

CTRL/G

CTRL/D

Move the cursor to the beginning of the previous
line (equivalent to —A).

Move the cursor forward by one character (equiv-

alent to J).

CTRL/V

Move the cursor back by one character (equivalent to —J).

DELETE

Delete the character immediately preceding the

cursor (equivalent to -D).

ESCAPE

Return control to the editing command mode.

double
ESCAPE

Summon immediate mode.

Use the editor to open a new file called IMMODE.TXT:
Long and Short Command Format
+EDIT/CREATE

IMMODE, TXTEE

Now activate immediate mode. You do this by typing the ESCAPE key twice in response to the editing command mode
asterisk. Since there are no other commands in the command line,
the editor recognizes the double ESCAPE as an immediate
mode command.

ESCAPE ESCAPE

*EDED
i

The editor responds by printing an exclamation point in the

command portion of the screen; the exclamation point signifies

that you are using immediate mode.

Character insertion is the default operation and occurs when-

ever you type a character other than one of the immediate mode

commands listed in Table 5-2.

5-17

Character Insertion

Creating and Editing Text Files

The next several paragraphs demonstrate the use of the immediate mode commands on a selected portion of text. Remember
that all characters you type that are not immediate mode com-

mands are treated as input. Commands do not echo on the
graphics screen, so all you ever see is the current text file. Type
the following:
TO BEs+ OR NOT TO BE - THAT IS5 THE QUESTION:GD
WHETHER ‘TIS5 NOBLER IN THE MIND AND HEART TO SUFFERED
THE SLINGS OF OUTRAGEOUS FORTUNEGED
OR TO TAKE ARMS AGAINST A SEA OF TROUBLES
BB
AND BY OPPOSING END THEM?PED

CTRL/G

As you can see on the graphics screen, the cursor (pointer) is
positioned at the beginning of a new line. CTRL/G, equivalent
to —A in standard editing, moves the cursor to the beginning of
the previous line; the cursor is repositioned immediately. Type:

The cursor has moved backward three lines, one line for each
CTRL/G command, and is positioned before the line:
THE

CTRLV

SLINGS

DUTRAGECUS

FORTUNEs

CTRL/V, equivalent to —J, moves the cursor back one character.
Move the cursor back over the carriage return and line feed at
the end of the previous line by typing the CTRL/V command
eleven times (remember, the carriage return and line feed
count as two characters):
(eleven [11] times)

WHETHER

‘TIS5

NOBLER

THE

MIND

AND

HEART

SUFFER

This positions the cursor before the word TO. The command

DELETE

DELETE, equivalent to —D, deletes the character immediately

preceding the cursor. Type the DELETE key ten times:

(ten [10] times)
WHETHER

‘TIS

NOBLER

THE

MIND

SUFFER

CTRI/N, equivalent to A, advances the cursor to the beginning

CTRUN

of the next line:
CRND

THE

SLINGS

DUTRAGEOUS

5-18

FORTUNEs

Creating and Editing Text Files

CTRL/D, equivalent to J, moves the cursor forward one character; type CTRL/D ten times:

CTRL/D

(ten [10] times)
THE

SLINGS

OUTRAGEOUS

FORTUNE

Next type this text (it will be inserted immediately to the left of
the cursor):
EPANDEPARROWSE

The text on the screen should now look as follows:
TO

WHETHER
THE

NOT

‘TIS

NOBLER

SLINGS

TAKE

AND

ARMS

ARROWS

AGAINST

OPPOSING

THAT

END

OF
A

IS5

THE

MIND

QUESTION]

OUTRAGEQUS

SEA

SUFFER
FORTUNE,

TROUBLES,

THEM?

Check your results and correct any other mistakes you may
notice.

To return to the standard editing command mode, type a single

ESCAPE.

ESCAPE

This ESCAPE command does not echo on the screen. Notice

that the exclamation point immediately disappears and the text
window format returns; an asterisk appears immediately below
the exclamation point on the screen.
You use immediate mode only to create and edit text. Operations that move text in and out of the text buffer must be done
with standard editing commands.
You do not need to save the text you have just created, so use

the CTRL/C command and two ESCAPESs to return control directly to monitor command mode. As mentioned before, EDIT

CTRL/C ESCAPE
ESCAPE

requires this unusual command combination to prevent an accidental CTRL/C from killing your text.

Following are two demonstration programs. One is written in

CREATING THE

the FORTRAN IV programming language and one is written in

DEMONSTRATION

the MACRO-11 assembly language. Both programs are used in

PROGRAMS

later chapters of this manual, and both contain intentional misspellings and errors.

5-19

Creating and Editing Text Files

Use the editor to create these programs. Type them exactly ast

they are shown, including errors. Use tabs and spaces to forma
each line as shown (remember that tab stops are positioned
every eight spaces across the terminal page). Make sure that
the FORTRAN IV program is formatted properly so that a
source comparison described in the next chapter will operate
properly. Except for the comment lines (those beginning with a
C) and the lines that begin with a number, begin all lines with
a tab. Use any of the editing commands described in this

chapter. Activate the display editor and immediate mode if you
wish.

When you have finished, check each file carefully. The two files
should match those shown here exactly, including tabs and
spaces. Correct any errors that you find that are not intentional. Obtain a listing of each file by using B €O/L
before closing the file.

Create the FORTRAN 1V file first. Call it GRAPH.FOR and use
the system volume for storage. Then create the MACRO-11
program. Call it SUM.MAC and again use the system volume
for storage.

NOTE

Knowledge of the FORTRAN IV and MACRO-11 languages is not necessary to create these demonstration
programs.

The following program, GRAPH.FOR, is the FORTRAN 1V
demonstration program.

VERSION 1
C GRAPH,FOR
C THIS PROGRAM PRODUCES A PLOT ON THE TERMINAL
C OF AN EXTERNAL FUNCTION., FUN(X.Y)

C THE LIMITS OF THE PLOT ARE DETERMINED BY THE DATA STATEMENTS
¢ "STAB" IS FILLED WITH A TABLE OF WEIGHT FLAGS
C "STRING" 18 USED TO BUILD A LINE OF GRAPH FDR PRINTING
(MAXZ-1)
AX-ZMIN)
/FLOAT
SCAL (ZMIN s ZMAX sMAXZ 1K) =ZMIN+FLOAT(K-1)#(ZM
LOGICAL*#: STRING(13:3),8TAB(100)
DATA XMIN XMAX 1MAXX/-5:5:45/
DATA YMIN YMAX I MAXY/-5:5472/
DATA FMIN,FMAX/0.0+1.,0/

CALL SCOPY(‘~-

1 2 3 456 7 8 9 +',5TAB)

MAXFLEN(STAB)

IX=1.MAXX
X=BCAL (XMIN s XMAX sMAXX + IX)
MAXY)
CALL REPEAT(’#’,STRING
IF(IX.EQ.1 .OR, IX.EQ.MAXX) GOTO 20

DO 20

IY=Z,MAXY-1

Y=SCAL (YMIN YMAX /MAXY , 1Y)

IFUN=2+INT (FLOAT (MAXF-3) # (FUN(X Y)-FMIN) / (FMAX-FMIN))

1)
MAXO (1, IFUNI F
STRING(IY)=STAB(MINO(MAX

CALL PUTSTRING(7,STRING,' ")

30
CALL

EXIT

END

FUNCTION FUN(X,Y)
R=GORT(X##2+Y#%2)

FUNsX#Y#R#EXP(-R))##2
RETURN
END

5-20

Creating and Editing Text Files

The following program, SUM.MAC, is the MACRO-11 demonstration program.
+TITLE

SUM.MAC

VERSION

+MCALL

LTTYOUT

JEXIT,

JPRINT

iND.

DIGITS

‘E‘

70,

EXP:

FIRST:
SECOND:

THIRD:
FOURTH:

THE

1700

SUM

1/18

THE

1721

THE

1730

1/50

1740

«PRINT

#MEGSAG

SPRINT

MQV

#NR3

iNO.

CHARS

MOV

*#N+1 4RO

iNO.

DIGITS

MOovV

*#A,R1

$ADDRESS

ASL

BR1

500

MOV

- (SP)
BRI

iSAVE

CALCULATE
FACTORIALS
+

INTRODUCTORY

OF
OF

TYEXT

VECTOR

(DECIMAL)

POINT

NEXY

eRrt

i*d

8rt

ADD

(SPI++(R1)+

INOW

DEC

SAT

END

DIGITS?

BNE

2ZND

SBRANCH

NOT

MOV

%N RO

THRU

ALL

MOV

-(R1)R3

iBY

THE

PLACES

MOV

«-1,R2

SINIT

QUOTIENT

INC

iBUMP

QUOTIENT

suB

RO R3

SSUBTRACT

LOOP

ISN'T

BCC

FOURTH

INUMERATOR

ALWAYS

ADD

ROR3

FFIX

MOV

R3:8R1

ISAVE

#10,

PLACES:

BAD
<

10#N

REMAINDER
REMAINDER
NEXT

FGREATER

INTEGER

iTO

GIVE

DIGIT

CARRIES

$AT

END

DIGIT

THIRD

$BRANCH

NOT

Moy

-{R1) sRO

FCET

DIGIT

SUB

#10.,RO

IFIX

THE

2.7

STHAT

ONLY

scc

FIFTH

S(REALLY

ADD

®10+'0,R0O

iMAKE

VECTOR?

OUTPUT

DIVIDE

DIGIY

ASC

50
DIGIT

10)

;OUTPUT

THE

DIGITY

CLR

B8Rt

SCLEAR

DIGIYT

DEC

iMORE

DIGITS

BNE

FIRST

iBRANCH

$WE

DONE

ARE

BASIS

DIGIT

+REPT

DIVIDING

BNE

JEXIT

DIGIT

INDEX

DEC

+TTYON

ASL

R2-2(R1)

ACCURACY

DIGIT

MULTIPLY

'E’

ASL

ADD

EXP:

‘E’

RECIPROCALS

$FOR

FIFTH:

LOCATION

PRINT?

YES

N+1

+WORD

FINIT

VECTOR

ALL

ONES

+ENDR
MESSAG:

.ASCII

/THE

VALUE

€

IS:/

<183x<12>

/2.7

<2002

+EVEN

+ENDEXP

When you have created and checked these two programs, obtained listings, and stored them as files on your system volume,
go on to Chapter 6, Comparing Text Files. Chapter 6 demonstrates a proofreading aid that helps you evaluate your editing
ability.

RT-11 System User’s Guide (AA-5279C-TC). Maynard, Mass.: Digital thipment Corporation, 1983.

A guide to the use of the RT-11 operating system.

5-21

REFERENCE

CHAPTER 6
COMPARING TEXT FILES

The RT-11 operating system provides a proofreading aid, called
a source comparison, to help you quickly establish the differ-

ences between two ASCII text files. During a source comparison, the system compares the two files, character for character,

and prints on the terminal (or line printer) any lines that contain differences.
Usually, you perform a source comparison against two files that
you expect to be the same, or at least similar. For example, if an

individual has copied one of your files to make changes to it,
you can quickly scan the changes by performing a source comparison between the new version and your original. Another
use of a source comparison is to check edits you have made to a
file yourself. By comparing the backup file against the edited
version, you can proofread the changes since only the portions

of text that are different are printed.
In this chapter, you will use source comparisons to find editing
errors

that

may

exist

the

demonstration

programs

(GRAPH.FOR and SUM.MAC) that you created in Chapter 5.
These demonstration programs contain intentional misspellings and misplaced text that you must correct before the programs can be used in later demonstrations. On your system
volume is a counterpart of each file. These counterparts are
provided as part of the RT-11 operating system so that you can

use them to perform a source comparison against your own versions. Essentially, the counterpart programs have been carried
one step further in the editing process than your own; they

contain no editing errors. Therefore, when you compare them
against your versions, the printed list of differences will reflect

the typing errors that still exist in your versions
— some of
these errors are intentional; others you may have inadvertently
introduced during editing. All must be corrected before you can
use the programs.

The monitor command used to compare two text files is the
DIFFERENCES command. When you type this command on
the terminal, it activates the RT-11 utility program called
SRCCOM.SAV, which is part of the RT-11 operating system
stored on the system volume. The system prompts you for the
input file names. Respond to the input prompts with the names
of the files you want to compare; the default storage volume is
the system volume. The output will be sent to the terminal,
which is the default device for output.

6-1

PERFORMING A

COMPARISON

Comparing Text Files

The programs that you created in Chapter 5, SUM.MAC and
DIFFERENCES

GRAPH.FOR,

have

their

respective

counterparts,

DEMOX1.MAC and DEMOF1.FOR, on the system volume. Use
the DIFFERENCES command to compare the MACRO-11
(.MAQ) files first. The /MATCH option indicates the number of

lines that determine a “match”, explained in a moment.’

Long Command Format
[DIFFERENCES/MATCH:
1 @D
File 17 DEMOX1.MACEED
File 27 SUM,MACED

Short Command Format
DIFFERENCES/MATCH:1

DEMOX1.MAC

SUM,MACGED

The list of differences printed on your console terminal should
be similar to the following example. It will show all the differences listed here, plus any others that you may have introduced
yourself during editing.
Notice the format of the list. Individual sections are marked
with the letters A, B, C, and D to help you become acquainted
with the format. A description follows the list, and you should
refer to it as you study the list.
A

A 2)

DK:DEMOX1.MAC

DK:BUM.MAC

EERXERRRER

+TITLE

EXAMP.MAC

(VERSION

+MCALL

JTTYOUT,»

JEXITs

+TITLE

SUM.,MAC

VERSION

JMCALL

TTYOUT,

(EXIT,

PROVIDED)

D
B

#%xx

2)1

D 2»

ERREEEKERS

11t

BNE

SECOND

iBRANCH

MOy

#N RO

iGO

ALL

THRU

NOT
PLACES.

iDIVIDING
B

x#xx

D 2

BNE

2ND

$BRANCH

MOV

#N RO

iGO

THRU

NOT

ALL

PLACES,

iDIVIDING
R

1)1

D1
B

ADD

%10+ 04RO

+TTYON

iMAKE

DIGIT

F0UTPUT

THE

ASCII
DIGIT

#%%%

C 21

ADD

D 2)

+TTYON

#10+'0,R0O

IMAKE DIGIT ASC
iOUTPUT

THE

DIGIT

ERERERRERS

#xxx

EXP

+END

+ENDEXP

EEERERRRNER

?SRCCOM-W-Files

are

different

1Users of display hardware may wish to enable both the graphics screen and

the terminal printer by first typing the CTRL/E command.

6-2

Comparing Text Files

comThe first two lines identify the two files that are being
s
reside
file
pared. The file name and the device on which the
are printed. Also, the numbers 1) and 2) are assigned to the
files (see lines labeled A in the example list above).

The first difference that is listed occurs in the title line of the
program. Usually differences that occur in these two lines are
intentional and reflect information that is unique to each file,
such as name and file type, version or edit number, and perhaps
date of creation.

The numbers that appear at the left margin of the list further
identify the files. For example, 1)1 indicates the first page of
the first file and 2)1 indicates the first page of the second file.
The lines of both files are compared character for character.
Blank lines are ignored, but all other characters, including tabs
and spaces, are compared. When two lines are found to be different, the system prepares a difference section, which it subsequently prints (see lines labeled B).

The system prepares the difference section as follows. When it
finds two lines that are different, it notes the page number and
records the lines (see lines labeled C). Next it searches for a
match. A match is a certain number of lines in each file that
are exactly the same. Since you specified a match of 1 in the
/MATCH:n option (MATCH:1), the system in this case searches
for a single line in each file that is exactly the same. When the
system finds a match, it records the last line of the match for
identification purposes (see lines labeled D). Then it prints the
difference section and repeats the process, preparing a subsequent difference section if more differences exist. Individual difference sections are separated from each other by a long row of
asterisks, while the short rows of asterisks separate the lines of
the first file from those of the second.

A message is printed following the comparison. Files are different is printed if differences exist; No differences found is
printed if the files are the same.

Check the list printed on your terminal to find the errors the
system detected. Mark each error on the listing of SUM.MAC
that you obtained in Chapter 5.

Now perform a source comparison between the FORTRAN IV
files, DEMOF1.FOR and GRAPH.FOR.
Long Command Format
WDIFFERENCES/MATCH: 1EED
File 1? DEMOF!.FORGD
File 27 GRAPH,FORGE

6-3

DIFFERENCES/
MATCH:n

Comparing Text Files

Short Command Format
'DIFFERENCES/MATCH:1
1)

DK:DEMOF1.FOR

DK:GRAPH.FOR

DEMOF1.FOR

GRAPH,FORGED

HRERARRRHA

1)1

EXAMP,FOR

THIS

2)1

GRAPH.FOR

€

THIS

(VERGION

PROGRAM

PRODUCES

PROVIDED)

PLOT

THE

TERMINAL

THE

TERMINAL

EREH

PROGRAM

VERSION

PRODUCES

PLOT

TABLE

HREREEERRH

€

"STAB"

"STRING"

2)1

"STAB"

"STRING"

FILLED

USED

WITH

BUILD

LINE

HEIGHT

FLAGS

GRAPH

FOR

PRINTING

(222

IS5

FILLED

USED

WITH

TABLE

BUILD

LINE

WEIGHT

FLAGS

GRAPH

FOR

PRINTING

HEREREERES

MAXF=LEN(STAB)

| )

IX=1:MAXX

*EEE

MAXFLEN(STAB)

IX=1,MAXX

HREH KRN KN

CALL

PUTSTR(7,STRING,’

EXIT

231

CALL

PUTSTRING(7.:STRING,’

)

EXIT

HEERREEARN

?BRCCOM-W-Files

are

different

Similarly, mark the errors on the listing of GRAPH.FOR that
you obtained in Chapter 5.

Now return to the section entitled Editing a Text File in
Chapter 5. Review the editing commands described there and
the summary at the end of the section. Use the appropriate

commands to correct the files SUM.MAC and GRAPH.FOR.
When you have finished editing, perform the source comparisons again against DEMOX1.MAC and DEMOF1.FOR. If you

have edited the files correctly, the comparison finds differences

only between the first lines of each program. The following

messages should print on your console:
+DIFFERENCES/MATCH
1B
:

File

17?7

DEMOF1.FORED

File

GRAPH.FORGD

DK:DEMOF1.FOR

DK:GRAPH,FOR

LRI

EXAMP.FOR

THIS

(VERSION

PROGRAM

PRODUCES

* KR

GRAPH.FOR

THIS

PROGRAM

PROVIDED)

VERSION

PRODUCES

HEEEEEEERSE

PBRCCOM-W-Files

are

different

and

PLOT

THE

TERMINAL

PLOT

THE

TERMINAL

Comparing Text Files
.DIFFERENCES/MATCH:l@@

File 17 DEMOX1.MACED
File 27 SUM,MACED
1)

DK:DEMOX1.MAC
DK:5UM,MAC

(VERSION PROVIDED)

KK
FEEEHHEK

1)1

LTITLE EXAMP.MAC

]

JMCALL TTYOUT,» (EXIT, .PRINT

* % %%

231

,TITLE SUM.MAC VERSION 1

JMCALL JTTYOUT» JEXIT. LPRINT

EEERREERER

PGRECOM-W-Files are different

These messages indicate that a difference exists in the first line
of each program. However, no other differences were found in
the programs during the comparison. Thus, your programs are

ready for use in later demonstrations, and you know how to
create and edit programs.

If differences still exist in your files and you cannot resolve
them by editing, you may continue to the next chapter if you
wish. However, you need practice editing, and it is to your advantage to rework the examples in both Chapter 5 and this
chapter.

DIFFERENCES

List the differences between two ASCII text files.

SUMMARY:
COMPARISON
COMMAND

DIFFERENCES/MATCH:n

Indicate the number of lines (n) to determine a match; the
default number is 3.

RT-11 System User’s Guide (AA-5279C-TC). Maynard, Mass.: Digital Equipment Corporation, 1983.

A guide to the use of the RT-11 operating system.

RT-11 System Utilities Manual (AA-M239A-TC). Maynard, Mass.: Digital
Equipment Corporation, 1983.

A guide to the use of the RT-11 system utilities.

6-5

REFERENCES

CHAPTER 7

PERFORMING FILE MAINTENANCE OPERATIONS
The system volume, as it is initially supplied, contains only the
files of the RT-11 operating system
-— the monitor files, the
system device handlers, the system utility programs, and perhaps the language processors. Since the system volume serves
as the default storage volume for all system operations (unless
DK: was assigned to another volume), you will discover that it
acquires many additional files during normal use. For example,
files that you create with the editor are written on the system
volume; edited files automatically create backup versions on
the system volume; many utility programs create output and
listing files on the system volume as part of their normal processing operations. By the time you finish an average session of
computer operations, several new file names have been added
to the directory of your system volume. Eventually your system
volume may become full and its directory cluttered with the
names of files for which you have no use. To avoid this you
should perform regular housekeeping, or file maintenance, operations as you use the system. You should update and transfer
copies of your important files to other storage volumes for safekeeping and later use, and you should delete from your system
and storage volume directories the names of files you no longer
need.

The RT-11 operating system provides a number of monitor
commands for this purpose. These commands activate the
RT-11 utility programs called PIP.SAV, DUP.SAV, and
DIR.SAV, which are part of the RT-11 operating system stored
on your system volume. These utility programs allow you to
transfer and erase files. The commands used in this chapter
show one way to maintain your system and storage volume.
When you become more familiar with system operations and
learn some of the commands not described here, you may prefer
other methods.

Before you perform operations that might move or erase files on
a volume, list a directory of the volume involved. The directory
tells you the full names of files, their sizes, and whether backup
copies exist. A directory of your system volume shows the files
that have been added to it through normal use.

First obtain a directory of your system volume (as you learned
in Chapter 4), using the appropriate command to list it on either the terminal or the line printer. The directory is relatively
long; let it list to completion.

FILE DIRECTORY
OPERATIONS

Performing File Maintenance Operations

Long and Short Command Format
(Line printer)
,DIRECTORY/PRINTERGED

(Terminal)
,DIRECTORYGE

At the end of the system volume directory you should see several additional entries. These files are the result of the system
operations you have performed so far:
DECIND.USA

DECIND.BAK
GRAPH .FOR
GRAPH .BAK
+MAC
SUM
+BAK
SUM

1
2
2
3
3

8-JAN-B3

B8-JAN-B3
B8-JAN-83
B-JAN-83
B-JAN-B83
B8-JAN-83

Next list a brief directory of your storage volume. This directory should be empty (void of any file names or file types) because you initialized it in Chapter 4.

Long and Short Command Format
(Line printer)
L,DIRECTORY/BRIEF/PRINTER VOL:@D

(Terminal)
,DIRECTORY/BRIEF VOL: G

These directories give you the information you need for erasing

and copying files. For example, you know the additional files

that are now on your system volume, and you know that since
the directory of the storage volume is empty, there is ample
room on it for new files.

MULTIPLE FILE
OPERATIONS

You often have occasion to perform the same utility operation
on several files. For example, you may copy from one volume to
another all files with the file type .MAC, or you may erase from

a volume all files with the name TEST. Rather than perform
the required operation on the files one at a time, it is easier to

use the wildcard construction, a shorthand method provided by
the RT-11 operating system. Wildcard construction allows you
to substitute an asterisk (*) or percent sign (%) for a portion of
the file name that is variable among all the files you want used

Performing File Maintenance Operations

a comin the operation. For example, specifying DECIND.* in
name
file
the
mand causes the operation to act on all files with
em
syst
es the
DECIND, regardless of their file type; * BAK caus
their file
to act on files with the file type BAK, regardless of
act on all
to
tion
name. Specifying TEST%.FOR causes the opera
files having a type of FOR, starting with the four characters
TEST, and having any fifth character (for example,
TESTA.FOR, TEST1.FOR, etc.).

A special use of the wildcard construction involves substitution
of an asterisk for both file name and file type. *.* implies that

all files, regardless of the file name or file type, are to be used
in the operation.

Exercises in this chapter and throughout the remainder of the
manual demonstrate various uses of the wildcard construction.
Storage volumes provide an area where you can store important

files. Since most files are originally created on the default system volume, you must copy them from the system volume to the
storage volume. The following exercises show you how to make
backup copies on your storage volume of the two provided demonstration programs (DEMOF1.FOR and DEMOX1.MAC), and

FILE COPYING

OPERATIONS

how to copy to the storage volume the two programs you created (GRAPH.FOR and SUM.MAC).

The monitor command that copies files between volumes is the
COPY command. This command instructs the system to duplicate the file that you indicate as input, and then gives the new
file the name and file type that you specify as output. The original version of the file is unaffected; that is, a copy of the original version is made and moved to the new volume.
To copy GRAPH.FOR to your storage volume under the new
name GRAPH.TWO, type:

Long Command Format
,COPYED

From? GRAPH.FORGD
To

7 WOL:GRAPH,TWOGED

(System volume is

for input.)
assumed

Short Command Format

,COPY GRAPH.FOR VOL:GRAPH.,TWOEED

The system makes a copy of the file GRAPH.FOR on the storage volume and gives the copy the name GRAPH.TWO. When
the operation is complete, the monitor prints a period at the left

margin and waits for you to enter the next command. This

time, copy SUM.MAC to the storage volume.

7-3

COPY

Performing File Maintenance Operations

Long Command Format
, COPY@ED
From?

SUM.MADEET

WOL:SUM.MACER

Short Command Format
¢ COPY

SUM.MAC

vOL:SUM. MACED

The system copies the file SUM.MAC to your storage volume

and gives the copy the name SUM.MAC.

Now,
copy the two provided demonstration
programs,
DEMOF1.FOR and DEMOX1.MAC, to the storage volume.
Long Command Format
+ COPYEED
From?

DEMOFL.FORGD

UOL:DEMOF1.,FOREED

, COPY @D
From?

DEMOX1.MACED

VOL:DEMOXI,MACED

Short Command Format
COPY

DEMOFL.FOR

VOL:DE
. MOF
.FORGD

»COPY

DEMOXI
. MAL

VOL:DEMOXD
. MACED

A directory of your storage volume should verify that it now
contains these four files.'

Long and Short Command Format
«DIRECTORY

YOL @D

0B-Jan-83

GRAPH

THD

08-Jan-83

DEMOFL.FOR

5UM

+MAC

Z26-Aug-8BZ

0B-Jan-83

DEMOXI

MAC

2B-Aug-87

Filess

4732

FILE RENAMING
OPERATIONS

Free

Blocks

blocks

The directory you just listed shows that you copied the GRAPH
demonstration file to your storage volume under a new file
type, TWO. Assume you did not intend to copy it using a new

file type and now wish that it were assigned its original file

'If you are using magtape as your storage volume, read the section entitled

Directory vs Nondirectory-Structured Volumes in Appendix B.

Performing File Maintenance Operations

type, .FOR. Use the monitor RENAME command to rename the
file already on the storage volume.’

RENAME

Long Command Format
E
. RENAMRED

From? YOL:GRAPH.TWOGD
To

7 VOL:GRAPH.FORGD

Short Command Format
, RENAME UOL:GRAPH,TWO VOL:GRAPH.FORGD

The RENAME command simply changes the file name or file

type of a file in the volume directory without altering or moving the file itself. When you perform a rename operation, the
volume indicated in the input and output portions of the command must be the same; otherwise a system message is printed.

Rename the file copies DEMOX1.MAC and DEMOF1.FOR
presently on your storage volume to EXAMP.MAC and EXAMP.FOR respectively.

, RENAME UOL:DEMOX1.,MAC VOL:EXAMP,MACEED

, RENAME UOL:DEMOF1.,FOR VOL:EXAMP,FORGED

Again list a directory of your storage volume to verify that the

renaming operation occurred.

Long and Short Command Format
., DIRECTORY VOL:@D
08-Jan-83

GRAPH.FOR
EXAMP.FOR

2
2

08-Jan-B3
26-Aug-BZ

4 Filess» 10 Blocks
4752 Free blocks

JMAC
SUM
EXAMP . MAC

3
3

08-Jan-83
26-Aug-B2

Once copies of your important files are stored on a storage volume, you can delete from the system volume — or any other
volume — those files that you no longer need. The file deletion
operation removes information about the file from the volume’s
directory; the space that the file occupies on the volume becomes available for reuse. Files that you want to delete generally include .BAK files created during editing, temporary files
created by utility programs, or any other unnecessary files.
1Magtape users cannot use the RENAME command and should read the section entitled Alternate Rename Operation for Magtape Users in Appendix B.

7-5

FILE DELETION
OPERATIONS

Performing File Maintenance Operations

Now that you have copies of your important files, you can de-

lete several files from your system volume. For example, you

can delete all files with a .BAK file type created as a result
of
editing. You can delete the file DECIND.USA, since this was

created only for editing practice. Finally, you can delete the
files GRAPH.FOR and SUUM.MAC, since copies of these arc now
on VOL..

Do not delete DEMOF1.FOR and DEMOX1.MAC from your

system volume, even though copies of these are also on VOL:.

You should consider these two files as part of the RT-11 opera-

ting system, and therefore should not erase them from the Sys-

tem volume. These copies can serve as additional backups for

the files on the storage volume.

DELETE

The monitor DELETE command is used to delete file names
from a volume. You can specify as many as six input files for

deletion.

Long Command Format
Files?

DECIND . UBAGRAPH,FOR,SUM,
MOCED

Short Command Format
JDELETE

DECIND,USAGRAPH,FORSUM.
MACED

If wildcard construction is used or if the /QUERY option is specified, the DELETE command requests confirmation from you by

printing each file name on the terminal before it deletes it.
If
you type a Y response, the system deletes the file, while
an N
response instructs the system to ignore that file and go on to

the next. Notice how you use the wildcard construction in the
input file to delete all files with a .BAK file type.

Long Command Format
Files?

#.,BAnRD

Files?

Files

deleted:

Files

DEK:DECIND.BAK

DK:8UM,BAK

DK:GRAPH
. BAK

GRAPH
. BAK SUM, BAK DECING , BAKHET
deletved:

DK:DECIND,BAK

DK :SUM (BOK

vin

DK:GRAPH.BAK

YED

Short Command Format
VOELETE
Files

#.BoKGED

JOELETE/GUERY

deleted:

Files

GRAPH, BAK BUM, BAK ,DECIN
. BAK D
6T

deleted:

DK:DECIND,.BAK

DK:DECIND.BAK

DK :SUM, BAK

OVED

DK :8UM. BAK

DE:GRAPH.BAK

DEK:GRAPH,.BAK

7—6

Performing File Maintenance Operations

You can give a file a protected status to prevent it from being
deleted from the volume it resides on. A file that has a protected status cannot be deleted until that status is removed.
The files DEMOF1.FOR and DEMOX1.MAC should still be on
your system volume. These files must not be deleted because

FILE PROTECTION
OPERATIONS

they are part of your RT-11 operating system. You can give
these two files a protected status to ensure that they are not
accidentally deleted.

The monitor PROTECT command is used to give files a protected status. You can specify up to six input files (separated
with commas) with this command. As with the DELETE command, if you use the wildcard construction or specify the
/QUERY option, the RT-11 system requests confirmation be-

PROTECT

fore protecting each file.

Use the PROTECT command to give the files DEMOF1.FOR
and DEMOX1.MAC a protected status.
Long Command Format
+ PROTECTGEED

Files? DEMOF1.FOR,DEMOX1.MACGD

Short Command Format
.PROTECT DEMOF1.FORDEMOX1.MACGRED

List a directory of these two files and notice the “P” next to the
number of blocks in the second column.
Long and Short Command Format
+DIRECTORY DEMOF1.FOR,DEMOX1.MACGE
08-Jan-83

DEMOX1 .MAC
2

Filesy

921

Free

3P 2B-Aug-82
D

DEMOF1.FOR

2P 26-Aug-82

BlocKks

blocks

The UNPROTECT command removes a file’s protected status
so that the file can be deleted. You can determine whether a file
is protected or not by listing the directory. If a file is protected,
a “P” will appear next to the block size number of the file’s
directory entry. You can specify up to six input files (separated
with commas) with this command. As with the DELETE command, if wildcard construction is used or if the /QUERY option
is specified the UNPROTECT command requests confirmation
for each file.

Remove the protected status from the files DEMOF1.FOR and
DEMOX1.MAC.

7-7

UNPROTECT

Performing File Maintenance Operations

Long Command Format
JINPROTECTED
Files? DEMOF1.FORVDEMONL

MACHED

Short Command Format
JINPROTEDT

DEMOFILLFORDEMONT
. MACHED

Again list a directory of the two files DEMOF1.FOR and DEMOX1.MAC. The “P”’s are removed from the listing, signifying
that the files are no longer protected.

Long and Short Command Formats
OIRECTORY

DEMOFLL.FORDEMOXL,
MACHED

0g-Jan-83

DEMOX1 .MAC
3
Z2B-Aug-82
Z Filess 5 Blocks
821 Free blockKs

FILE LISTING
OPERATIONS

DEMOF1,FOR

26-Aug-B82

You sometimes need a listing of a file before you can decide
whether or not to delete it. In Chapter 5, you used the RT-11
editor to get listings of the files you created. You can also use
monitor commands to obtain listings of files. One command
lists a file on the conseole terminal; another lists a file on the

line printer.' The system volume is the assumed storage volume
for the input file.

Type one of the following sets of commands to obtain listings of
EXAMP.MAC and EXAMP.FOR.
Long Command Format
PRINT

TYPE

{Line Printer)

(Terminal)

PRINTED

Files? UOL:EXAMP. MACKD

Files?

Files? VOL:EXAMP.FORGED

Files? UDLsEXaMP, FOREE

wOL:ExAMP, MADET

Short Command Format
{Line Printer)

{Terminal)

UOL

tEXAMP . MACEDD

fTYFE

UOL s EXAMP, MADET

sPRINT

UOLsEXAMP
., FORGED

STYPE

VDL rEXA

1f a line printer is available on your system, you should always use it for

listings because of its high speed of printing.

Performing File Maintenance Operations

You should perform file maintenance operations periodically as
you use the system. File maintenance keeps your system and
storage volumes up-to-date and provides maximum free space
on volumes for new files.

COPY
Copy the specified file from one volume to another.
DELETE
Delete the specified file(s) from the volume’s directory. Confirmation is required before deleting the file if wildcard construction or the /QUERY option is used.

SUMMARY:
FILE MAINTENANCE

COMMANDS

DIRECTORY
List the volume directory on the terminal.

DIRECTORY/PRINTER
List the volume directory on the line printer.
PRINT
List the contents of the specified file on the line printer.

PROTECT
Give the specified file protected status so it cannot be deleted
until that status is removed. Confirmation is required before

protecting the file if wildcard construction or the /QUERY
option is used.
RENAME
Give a new name to the specified file.
TYPE
List the contents of the specified file on the terminal.
UNPROTECT
Remove the protected status of the specified file so that the
file can be deleted. Confirmation is required before removing
each file’s protection if wildcard construction or the / QUERY
option is used.

RT-11 System User’s Guide (AA-5279C-TC). Maynard, Mass.: Digital Equipment Corporation, 1983.

A guide to the use of the RT-11 operating system.

7-9

REFERENCE

CHAPTER 8

CHOOSING A PROGRAMMING LANGUAGE
Programming languages and language processors are aids provided by the operating system to help you develop programs of
your own. Whenever you plan to write a program, you must
first decide on the programming language that you will use,
since most computer systems support several. After you have
chosen the language, you must design and code your program
using appropriate language statements and being careful to
follow formatting rules and restrictions. Finally, you must use
the corresponding language processor, which is stored on the
system volume or on a volume of its own, to convert your program statements into a format suitable for execution.

Hundreds of programming languages have been developed for
computer systems. Some languages can be used only for specific
applications or with a particular computer system. Other languages are general purpose; they are suitable for a variety of
problem-solving situations and, in addition, are easy to learn
and use. The languages demonstrated in this manual include
two well-known and widely used high-level programming languages (BASIC-11 and FORTRAN IV) and one RT-11 systemspecific machine-level programming language (MACRO-11).
High-level languages, like BASIC-11 and FORTRAN 1V, are
usually easy to learn and use. You write programs using language statements that need not deal with the specifics of the
computer system. The language processor — and perhaps
other utility programs as well — handles all conversions that
are necessary for program execution. Since a single high-level
language statement may perform several computer operations,
and since you need not be concerned or familiar with the structure of the computer and peripheral devices, you can concen-

trate solely on solving the problem at hand. The language processor takes care of translating the statements into computer
information.

Thus,

high-level

languages

are

considered

machine-inde-

pendent languages because language statements are such that
any program written in the language can usually be executed
on an entirely different computer system (that supports the language) with few, if any, modifications.
Machine-level languages, on the other hand, such as the assembly language MACRO-11, require that you know about the
computer and the peripheral devices and how they work together. You write programs in formats that are closer to those

8-1

HIGH-LEVEL VS
MACHINE-LEVEL

LANGUAGES

Choosing a Programming Language

required for execution. Since a single machine-level language
statement usually performs only one computer operation, you
must account in your program for each computer operation that
will be required.
For this reason, machine-level languages are machinedependent languages. The program is coded in a format that is
not usually interchangeable among systems. Machine-level language programs can be efficient because the knowledgeable
programmer will choose the fastest and most precise instructions for getting a job done.
Table 8-1 lists a comparison of high-level vs machine-level languages.

Table 8-1

Language Comparisons

High-Level
Easy to learn and use; no
experience required

Machine-Level

difficult

learn

and

use; familiarity with the computer system required

Machine-independent

Machine-dependent

Many hidden conversions
necessary for program exe-

Only direct translation is necessary for program execution;
less computer memory is used

cution;

computer

memory is used

Slower execution time

Faster execution time

Less

the system

More efficient; the program-

makes decisions concerning
computer operations

mer makes decisions concern-

Easier to debug (find and fix

Harder to debug (find and fix
errors)

efficient;

errors)

ing computer operations

Easier to understand programs; functions added with

grams; functions added with

less difficulty

greater difficulty

Harder

wunderstand

pro-

Beginning programmers, students, commercial applications
programmers, and the casual computer user prefer high-level
languages because they are less difficult to learn and to use,
and they produce fast results. System programmers, on the
other hand, may prefer machine-level languages for writing
programs (those that make up an operating system, for example) that must often be as fast, efficient, and concise as possible.

8-2

Choosing a Programming Language

The designers of a computer system generally select programming languages that will satisfy and suit the current (or perhaps potential) system user environment. The RT-11 computer
system is designed for use in many environments: education,
business, laboratory, etc. Some of its applications include data
acquisition and analysis, record keeping, control systems, and
learning through computer simulation. RT-11 programmers
and users include both the very knowledgeable and the
student/beginner.

To satisfy the varied requirements of these environments,
RT-11 supports several programming languages:
High-Level

Machine-Level

BASIC-11
FORTRAN IV

MACRO-11

DIBOL

Whenever you choose one or more of these programming languages for your own use, consider the following criteria:
e What is your programming experience? What languages do
you already know?

¢ How much time do you have to learn a new language?

¢ For what applications will you use the language? How important are program speed and efficiency?
¢ Will you use your program on any other computer systems?
If you are already familiar with a language supported by the
system, you may prefer to continue using that language rather
than spend time learning a new one. However, if you want to
learn a language, consider your application. High-level languages handle most programming jobs. Unless you plan to
write extremely detailed or time-critical programs, you should
select a high-level language.

If you are a beginning programmer, you may prefer to start
with a language like BASIC-11, which is a conversational, interactive language. Language statements use simple, Englishlike words and common mathematical expressions. You can request immediate answers to problems by using the immediate
modes of the language, or you can create detailed programs by
combining single language statements into larger segments.
BASIC-11 is a superset of the industry-standard BASIC developed at Dartmouth College. Chapter 10 of this manual describes BASIC—-11 in more detail.

8-3

RT-11

PROGRAMMING
LANGUAGES

Choosing a Programming Language

RT-11 FORTRAN 1V is a superset of the industry-standard
FORTRAN 1V. This language has long been recognized for its

use in the scientific field; in addition, it is one of the most commonly supported languages across systems. You may decide to
choose FORTRAN IV because it is a more powerful language
than BASIC-11 or because you plan to use your programs on
more than one system. Chapter 9 of this manual describes FORTRAN IV in more detail.

Finally, if you are an experienced user, you may select the machine-level programming language MACRO-11. This is a powerful language that allows user programs to access and utilize
every possible feature available on the RT—-11 computer system.
The language requires a considerable amount of computer experience and knowledge to be used effectively, however. The
MACRO-11 language is best for you if you are a system programmer or an experienced high-level language programmer.
It is described in more detail in Chapter 11 of this manual.

CHOOSING
A LANGUAGE

FOR THE

DEMONSTRATION

Three RT-11 programming languages are demonstrated in the
next several chapters of this manual;, FORTRAN 1V,
BASIC-11, and MACRO-11. Consider your ability as a pro-

grammer. If you are a beginner, BASIC-11 is probably the best
language for you to start with; FORTRAN 1V is also a good
choice. However, you need not be proficient in any of these
programming languages to perform the exercises provided in
this manual.
Your particular RT-11 computer system may not provide all
three languages. First check question 10 in the Hardware Configuration section of Chapter 2 to find out which languages are
available on your system.
Then select a language to continue the demonstration. If you
choose FORTRAN 1V, continue to Chapter 9. If you choose
BASIC-11, go on to Chapter 10. If you choose MACRO-11, go
to Chapter 11.

REFERENCES

Digital Equipment Corporation Reference Service, Volume 2: Software and
Services. Maynard, Mass.: Digital Equipment Corporation, 1982.
An overview of the available PDP-11 family products and services.
Katzan, Harry Jr., Information Technology, The Human Use of Computers.
New York: Mason & Lipscomb Publishers Petrocelli Books, 1974.
A textbook covering basic computing concepts, programming languages,
and topics in computers and society. See Part II, Chapters, 7, 8, and 9.
PDP-11 Software Handbook (EB—-21759-20). Maynard, Mass.: Digital Equipment Corporation, 1982-83.

A general overview and introduction to available PDP-11 software, operating systems, and language processors.

CHAPTER 9

RUNNING A FORTRAN IV PROGRAM
The FORTRAN IV programming language' is a machine-independent programming language that was originally designed
as a quick and easy aid for solving mathematical equations and
formulas. However, FORTRAN 1V is a powerful language and
not difficult to learn or use, and is also well suited to many
other kinds of applications.

FORTRAN (FORmula TRANSslation) IV is an algebraically oriented language. You write a FORTRAN IV program as a sequence of language statements that combine common English
words with quasi-algebraic formulas. You then arrange groups
of the language statements into logical units called program
units. One or more program units make up an entire executable

DEVELOPING AN
EXECUTABLE
FORTRAN IV
PROGRAM

FORTRAN 1V source program.

When you are satisfied with the logic of your FORTRAN IV
source program, you use the RT-11 editor to create it as a file
(see Chapter 5). You use tabs and spaces to format each line

properly, and you may choose to insert comment statements

throughout the source code to explain what various parts of the
program are doing. When you have finished creating the program as a complete, edited file, you next enter it as input to the
FORTRAN IV language processor, which is stored on your system volume or on a separate volume of its own. The FORTRAN
IV language processor processes (compiles) the language statements, converting them into internal machine-language code
called object code. This code is next processed by the system
linker, which combines your program units and necessary system-supplied routines to make your program suitable for execution. The development of an executable FORTRAN IV program
is represented in Figure 9-1.

CREATE

Figure 9-1

EDIT

COMPILE

LINK

RUN

Evolution of a FORTRAN IV Program

The FORTRAN IV language processor is a compiler that translates your source program into a machine language program.
IThe PDP-11 FORTRAN IV programming language conforms to the specifi-

cations for American National Standard FORTRAN X3.9-1966.

9-1

USING THE
FORTRAN IV
LANGUAGE

PROCESSOR

Running a FORTRAN IV Program

Since you create a FORTRAN IV source program in ASCII for-

mat, you must next translate the program into a machine for-

mat that the computer can use. The FORTRAN IV compiler
performs the translation, producing as output a new version of

the program, called an object module. You may instruct the
FORTRAN IV compiler to produce a listing of the source pro-

gram at the same time. Figure 9-2 is a diagram of the compiler’s function.

SOURCE

COMPILE

PROGRAM

OBJECT

MODULE

LISTING

{OPTIONAL)

Figure 9-2

USING LIBRARY
MODULES

Function of a FORTRAN IV Compiler

Typical FORTRAN IV programs often require similar operations. Most programs, for example, use routines and instruc-

tions that calculate square roots, exponentials, and other arithmetic functions; handle input and output operations; detect cer-

tain kinds of error conditions; test values; calculate subscripts;
and perform conversions. These commonly used operations
have been gathered into a special file called SYSLIB.OBJ (de-

fault System Library), which is provided with the RT-11 operating system and is stored on your system volume.

During the processing of your source program, the FORTRAN

IV compiler examines each language statement in the program.
If you use operations that are provided in SYSLIB, the compiler

notes them and makes references to SYSLIB. The compiler
translates all the information gathered during processing (your

converted language statements and the references to SYSLIB)

into numerical data called object code that the system linker
can use. The result of the compilation, therefore, is an object
format file, called an object module, which is automatically
joined with SYSLIB (containing many object modules) and with

any other required object modules at link time. Linking all the

necessary object modules together produces a complete, workable FORTRAN IV program.

The FORTRAN IV object time system (OTS) is also needed to

successfully compile a FORTRAN IV program,; this system is in

9-2

Running a FORTRAN IV Program

file is included in SYSLIB
the file FORLIB.OBJ. Whether this
em was built.
or not depends on how your syst

program, you must either
To link the example FORTRAN IV or
fy SYSLIB before
include FORLIB.OBJ in SYSLIB, speci
ructions on how to inFORLIB in the link command. For inst
clude FORLIB in SYSLIB, refer to Section 3.4 in the RT-11
FORTRAN IV Installation Guide.

TRAN
In Chapter 5 you used the RT-11 editor to create a FORge
volstora
your
on
IV source program, which you then stored
step
next
ume. Since a source program is in ASCII format, the
is to use the FORTRAN IV compiler to convert it to object code.

Some RT-11 systems store the FORTRAN IV compiler on a
volume apart from the system volume.! You can quickly deter-m
mine whether the FORTRAN IV compiler is on your syste
volume by using the DIRECTORY command.
,DIRECTORY SY:FORTRA.SAVED

In the directory listing that results, if the directory entry for
FORTRA.SAV is included, then the required FORTRAN 1V
files are on your system volume. If, however, FORTRA.SAV did

not appear in the directory listing, then the required files are
not part of your system volume. Before you can use the compiler, you must make a volume substitution. Read the section in
Appendix B entitled Using the FORTRAN/BASIC Language
Volume.

The next step involves using the monitor COPY command to
copy the FORTRAN IV source program from the storage volume (where you stored it in Chapter 7) back to the system

volume, which serves as the default volume for input/output
operations.

Remember that on your storage volume are two FORTRAN v
source programs, the one you created (GRAPH.FOR) and the
one provided as part of the system (EXAMP.FOR). Which of
these you should use depends on the results of the source com-

parison you performed in Chapter 6. If the comparison resulted
in no differences except for the title lines, copy your own program (GRAPH.FOR) as follows:
Long Command Format
JLCOPYED

From? VOL:GRAPH,FORGED
To 7 GRAPH.FORED

not have enough free
1This is true for any RT-11 system volume that does
RX01 diskette is an
files.
system
IV
AN
blocks to accommodate the FORTR
example.

COMPILING THE

FORTRAN IV
PROGRAM

Running a

FORTRAN IV Program

Short Command Format
LOPY

UOL:GRAPH.FOR

GRAPH.FORGD

However, if differences were printed in addition to the title
lines, use the provided program (EXAMP.FOR) instead, copying it under the new name GRAPH.FOR:

Long Command Format
LOPY R
From?

UOL::EXAMP
. FORED

GRAPH,FORED

Short Command Format
LCOPY

VOL:EXAMPL.FOR

GRAPH.FORGD

The FORTRAN IV source file now resides on your system volume under the name GRAPH.FOR and is the file that you will
process with the FORTRAN IV compiler. The command used to
compile a FORTRAN IV source program is the monitor
FOR-

TRAN command.

FORTRAN

Use the FORTRAN command with its /LIST option to compile
your program and produce a listing. The system prompt asks

you to supply the input file name. You can omit typing the
FOR file type since the FORTRAN command assumes this file
type unless you indicate otherwise. The system will assign the

name GRAPH.OBJ to the object module and GRAPH.LST to
the listing file and store both newly created files on your system volume, which is the default storage volume for input/output operations.

Long Command Format
JFORTRANEED
Files? GRAPH/LIGTHLD

Short Command Format
JFORTRAN

GRAPH/LISTHY

Compilation begins. If the compiler discovers an error during
processing, it prints a message. In this particular case, you

should see the following on your terminal printer or screen:
CHMATN,

PFORTRAN-I-L

MAIN,]

Errors:

Warningds:

Errors:

Warninds:

FUN
PFORTRAN-T-[FUN

This indicates that, during processing, the FORTRAN IV compiler found six errors in the source program. It helps at this

Running a

point to look at the listing produced by the compiler, because

more information is shown there. Print the listing on either the
line printer or terminal, using one of the following commands:
Long Command Format

(Terminal)

(Line printer)

TYPE

Files? GRAPH . LSTHD

Short Command Format

(Line printer)

(Terminal)

JPRINT

+JTYPE

GRAPH.LET

Your listing should look like the following example.
NOTE

You do not need to understand the FORTRAN [V language or the way this program works to successfully
complete the exercises in this chapter.
FORTRAN

YOILE

S8at

UB-Jan-83

10:52:04

VERSION

GRAPH.FOR

£
£

THIS PROGRAM PRODUCES A PLOT ON THE
OF AN EXTERNAL FUNCTION. FUN(XLY)

THE

"GTABY

U"STRINGTM

LIMITS

o001

THE

FILLED

USED

PAGE

001

PLOT

ARE

TERMINAL

DETERMINED BY THE DATA
OF HEIGHT FLAGS

STATEMENTS

TABLE

WITH A

TO BUILD

FRINTING

GRAPH FOR

LINE

SEAL

000z

(ZMINZMAX MBXZ +K) =ZMINGFLOAT (K- 1)1 # (ZMAN-ZMIN) /FLOAT (MAXZ-1)
LOGICAL®1 STRING(LI3:3):8TAB(L10O)

jeledine]
[elers

DATA AMINAMAX MAKX/-5,3.:45/
DATA YMIN YMAX (MAXY/-5,5.72/

0005

DATA

FRINFMAX/O. 010/

000E

CALL

SCOPY(’'~

Qo077

MAXF=LEN(GTAR)

aoog

+/,8T4AB)

IX=1MAXX

0008

H=GUAL (XMIN XMAX S MAXN 1)

0010

CALL

o011

IF(INGEQ.1

0013

"+ STRING MAXY)
REPEAT({
10

GOTO

IXLEQ.MAXX)

OR.

IY=2:MAXY-1

(1Y)
MAXY AN
Y=S0RLIYPINYM

o014

Q013

®
) -FMIN)Y Z (FMAX-FMIN)
LOAT(MAKF-3)
IFUN=Z+INT(F(FUNIXHY

0016 10

STRINGOIY)=5TAB(MING
(MAXF (MAXO(L IFUNI )

CaLL

0017 30

cabl

ool
0018

.
PUTSTRO7,8TRING

EXIT

END

FORTRAN

Diasnostics

for

Program

Unit

JMAIN,

line

0003,

Error:

Modes

variable

“MMIN"

and

data

item

differ

line

0004,

Errors

Modes

variable

“YMIN®

and

data

item

differ

tine

0008,

Error:

Reference

undefinegd

statement

label

line

0012,

Errors

Reference

undefined

statement

label

line

Q016,

Error:

Wrond

FORTRAN

Storade

Mar

PSECT

number

for

subscriets

Unit

Prosram

%DATA.

Size

for

array

"BTRING"

LHMAIN.

Local

Mariabless

000334

(

110,

words)

Name

Trvee

Gffset

Name

Trre

Offset

MName

Trvee

Offser

FHAX

Red

0o0230

FMIN

R#d

000224

IFUN

000312

1#2

Q0260

MAXX

T#2

I#2

Cou300

Quoz272

Qoaese

MAXF

T#2

000274

MAaXe

1#2

000254

MAKD

GO0316

MING

GO0314

Maxy

1#2

GO0Z76

FORTRAN IV Program

Running a FORTRAN IV Program
X

Red

0002682

XMAX

R*g

000266

XMIN

R#4

000214

R*4

000302

YMAX

R#q

000308

YMIN

R*q

000220

ZMAX

Req

00025¢

ZMIN

R#4

000244

Local

and

Name

COMMON

Trre

8748

L*1

STRING

L#)

Vec

Subroutines:

Arravs:

Section

Offset

----Size----

$DATA

000047

000144

(

30.)

(100)

$DATA

000000

000047

(

20.)

(13,3)

Functions,

Statement

and

Dimensions

Processor-Defined

Functians:

Name

Trre

Name

Tyre

Name

Trre

Name

Trre

Name

Tree

EXIT

R*4

FLOAT

R*4

FUN

R*4

INT

I#2

LEN

I»x2

PUTSTR

R*4

REPEAT

Re4

SCAL

Scory

Red

15:52:07

PAGE

FORTRAN

v02.95

Sat

0001

FUNCTION

FUN(X.Y)

0002

R=GQRT(X%%2+Y482)

0003
#xees

FUN=X®YHR®EXP(-R)
) %22

0004

RETURN

0005

END
1V

Diagnostics

0003,

Error:

(See

Storage

Map

line

FORTRAN

Name

001

FORTRAN

Local

08-Jan-83

Variables,

Trre

FUN

R#*4

R#4

.PSECT

Offset

000004
B

Subroutiness

Name

Trre

SQRT

Rad

Eav

for

Prosram

scurce
for

$DATA,

Unit

FUN

listinsg)

Prosram

Size

Unit

FUN

000020

(

words)

Name

Trree

Offset

Name

Tyre

R*4

¢G00010

R#g

Statement

and

Processor-Defined

Oftset

000000

000002

Functions,

Name

Trre

Name

Tree

Name

Functions:

Trre

Name

Tyre

The first part of the listing shows the main program unit and
consists of the language statements up to, but not including,

the function. This is followed by a diagnostics list, then by a
storage map. Next the language statements composing the
function program unit are listed, again followed by a diagnos-

tics list and a storage map.

Before considering the individual sections of the program list-

ing, first examine the program logic to determine what this
program should do. The first few lines of this program are user

comment lines that briefly describe the program. Essentially,
this program produces on the terminal a graph of a “threedimensional” function, FUN(X, Y). The graph is plotted using

45 lines down and 72 characters across the terminal page. The
limits of the X and Y axes are +5 and —5. The third dimension,

height, is a real number within the range 0 to 1 and is represented in the listing as a number within a scale of 1 to 9. These

dimensions are illustrated in Figure 9-3.

The SCAL function determines the value of the next coordinate

on the graph. The statements within the DO loops calculate the
coordinates using the SCAL function and determine the height

value. This is done for an entire line of coordinates across the
terminal page. The entire line is then printed on the terminal,

using the CALL PUTSTR statement; the number 7 in this
statement is the FORTRAN IV method of naming the terminal

Running a FORTRAN IV Program

-5

Figure 9-3

s 72 ChBracters —————————et

- +5 45 Lines

Dimensions of FUN(X,Y)

as the output device. This procedure is repeated until all 45
lines of the graph have been printed.
The function to be plotted is shown in the last few lines of the
program. It is compiled as a separate program unit and you can
edit these lines to plot any function of your choice (several alternate functions are suggested later in the chapter).
This program as it stands contains errors. The compiler detected certain error conditions during processing that prevent
the program from working properly. The compiler printed appropriate messages in the diagnostics sections of the program
listing.! Look first at the messages following the main program
unit. Errors were discovered in lines 3, 4, 8, 12, and 16.
The messages for lines 3 and 4 indicate that the floating-point
variables “XMIN” and “YMIN” are assigned integer values.
The DATA statements must be changed. (The same error exists
for “XMAX” and “YMAX”; the compiler, however, lists only the
first error that it discovers in a line. Both "MAXX” and
“MAXY” are integer variable names, so no error exists for
them.) You must correct the DATA statements (lines 3 and 4),
then, as follows:
DATA
DATA

XMIN XMAX sMAXX/-5.0:5.0,45/
YMIN,YMAX MAXY/-5.0,:5.0.,72/

The next two messages in the diagnostics section show that
reference has been made from both lines 8 and 12 to an undefined label. (Line 12 is actually the second portion of line 11,
the GO TO statement.) Statement label 20 is referenced in each
case, but only labels 10 and 30 are shown in the program. This
indicates either that a statement is missing or that a typing
1Refer to the RT-11 System Message Manual for greater detail about any

system messages printed.

9-7

Running a FORTRAN IV Program

error exists. Examination of the program logic shows a typing
error in line 17. Label 30 should actually be 20. Correct line 17

as follows:
20

CALL

PUTSTR(7,:STRING,"

The last message in this diagnostics section states that an in-

correct number of subscripts was given for the array “STRING”.
Again, examination of program logic shows that the error is
actually in line 1. “STRING” is really a vector (a one-dimension
array), not a matrix (a two-dimension array). Thus the comma
is a typing error and line 2 should be changed as follows:
LOGICAL*1

STRING(133),5TAB(100)

Skip next to the diagnostics section for the FUN program unit.
The message printed there refers you to the source listing, to

line 3. A letter “P” appears next to this line. The RT-11 System
Message Manual describes a P error as an indication of unbal-

anced parentheses. Notice that the parentheses are not properly matched in this line. Thus, line 3 should be corrected as
follows:

FUN=(X*Y*R*#EXP(-R)
) #%2

This explains the errors flagged by the compiler in the diagnos-

tics sections. Other sections of the program listing (storage
map, for example) simply provide additional information that is

helpful to programmers who wish to check the data types of
various symbols and later make sure that object modules have

been appropriately linked.

Before you can continue the exercises in this chapter, you must
edit, in the source program, those statements that contain er-

-rors. If necessary, review the editing commands in Chapter 5.

Then use the RT-11 editor to edit the file GRAPH.FOR on your
system volume so that the five lines are error-free. Do not re-

name the file. When you are ready, recompile the program,
using the FORTRAN command, and obtain a new object module

and a new listing. This time the program should compile without error (that is, no diagnostics should list). The compiler will

indicate two warnings, but you can ignore them. If diagnostics

occur, you have not edited the program correctly. Compare list-

ings and try to correct your errors, or go back to the beginning
of this chapter and repeat the demonstration.

LINKING OBJECT
MODULES TOGETHER

The object module produced by the FORTRAN command is in
itself incomplete. As mentioned earlier, it needs parts of the

9-8

Running a

FORTRAN IV Program

system library, SYSLIB, and perhaps other object modules and

libraries as well, to form a complete functioning program.' All

required object modules must be joined, or linked together, before the program can work.
Even if your program does not require any other object modules, you must still link it. In addition to joining object modules
together, the link operation adjusts the object code to account
for many program units being placed one after the other. The
result of the link operation is a memory image load module,
which is actually a picture of what computer memory looks like
just before program execution. Figure 9—4 is a diagram of the
link operation.

sYSLIB
Other OBJ's

OBJECT

LINK

MODULE

Figure 94

LOAD
MODULE

The Link Operation

To link the object modules, use the monitor LINK command.
The system prompts you to enter the names of the input modules and any libraries other than the system library to be joined

together. You can omit typing the .OBJ file types in the command line, since the LINK command assumes this file type for
input. The system automatically assigns the file name of the
first input file and a file type of .SAV to the output file. The
linker will scan the SYSLIB library if it is present on the system volume.

Some RT-11 systems store the linker (LINK.SAV) and the default system library (SYSLIB.OBJ) on a volume apart from the

!For more information on linking files and using library files, see Chapters 12

and 13, respectively.

9-9

LINK

Running a

FORTRAN IV Program

system volume or the FORTRAN/BASIC language volume.'
You can quickly determine whether the system library is on

your system volume by using the DIRECTORY command.
VDIRECTORY

SY:8YSLIB,OBJED

If SYSLIB.OBJ did not appear in the directory listing on your
terminal, the required files are not part of your system volume.

Before you can link GRAPH.OBJ, you must make a volume

substitution. Read the section entitled Using the LINK Volume
in Appendix B.

If you have not included the FORTRAN IV library FORLIB.OBJ in SYSLIB, use the DIRECTORY command to see if

the library is on your system volume. Type:
JDIRECTORY

SY:FORLIB.OBJEED

If FORLIB.OBJ did not appear in the directory, the required
files are not part of your system volume. Before you can link

GRAPH.OBJ, you must make a volume substitution. Read the

section entitled Using the LINK Volume in Appendix B.

Long Command Format
FORLIB not included in SYSLIB:
@
NKI
o L
Files?

GRAPH,SYSLIB,FORLIBG&D

FORLIB included in SYSLIB:

Files?

LRAPHED

Short Command Format
FORLIB not included in SYSLIB:
JLINK

GRAPH ,SYSLIB
. FORLIBED

FORLIB included in SYSLIB:

Any messages printed on the terminal identify error conditions

discovered by the system during the link operation (for exam-

'This is true for any RT-11 system volume that does not have enough free

blocks to accommodate the files required for linking. The RX01 diskette is an
example.

9-10

Running a

FORTRAN IV Program

ple, you may not have specified all the object modules that are
needed as input). However, assuming that you edited your
source program correctly and that it compiled without error, it
should also now link without error.
A load module is one that you can run on the system. Unless

your program contains logic errors that prevent it from running
properly (errors that the system cannot always detect), running

the .SAV version of your file should produce the results you
intended. However, if logic errors exist within your program,
running the program will produce either erroneous results or

none at all. If this is the case, you must study the source program, rework it, reedit it, and perform the compile and link
operations again.

If your FORTRAN IV program is error-free, running the .SAV
version should produce the expected results. In this demonstration, running the GRAPH.SAYV file should produce a graph on
the terminal printer or screen.

RUNNING THE
FORTRAN IV
PROGRAM

Before you run GRAPH.SAV, you have the option of changing

the output device from the terminal printer or screen to the line
printer by using the monitor ASSIGN command to assign device names (see Chapter 4, Assigning Logical Names to Devices). If you prefer to print the graph on the line printer, sim-

ply assign the logical device name 7 (which is the FORTRAN
IV code for the terminal) to the line printer code (LP:). You
have designated a new output device without altering the

source program. To change the device assignment to the line
printer, type:

Long Command Format
+ ASSIGNED
Physical device
Logical
device

name?
name?

LP:@ED
7@D

Short Command Format
+ASSIGN

LP:

This assignment remains in effect until you deassign the names

or reboot the monitor.

Now, to execute the FORTRAN IV demonstration program, use
the monitor RUN command. You can omit typing the .SAV file

type since it is assumed within the RUN command.

Long and Short Command Format
+RUN

GRAPHED

9-11

RUN

Running a FORTRAN 1V Program

After a brief pause, the graph begins to print on the terminal

(or line printer) and should look like the graph shown in Figure

9-5.

KKK IOKKSAIOIOK KK AKARAOK N

*
x
X

*x
X

IKRK FHAAR I

1111111113111111111
11111131131123111211111131

11111111

1111111

11111

1111
22222222222

22222
2222

x1111

222

*111

333333333

333

111
11

333

*111

222

333

4444

332

%111

*¥111

222

4444444

*111

222

x1111

222

11111

1111

11111

22
2

22222
2222

333333333

333

33 2

2 33 444

4444

444

4444

44444444

211

444

3333

333

22
Q22222222

11111141

4444444

111

1111

4444

111

1111%

1itx

222

111x

111x%

111x

222

111x%

222

1111%

222

3333

11i11x

1111

222

11111

222222222

1111

11111x%
1111%

333

444

333

X
X

1111

3
X

x
x

11111
222

1111

X111

222

444

44444444

4444

*1111

444

444
4444444

444

4444

333

33 2
333

333333333

2222

11111

22222

111111

22
2222

22222222222

11111111

11
111

1111

11111

HRAOKHK KR IOKH A KK A

Figure 9-5

1111

1111%

1i1x

111x

111%

4444

333

111x%

333

111x%

3333333332
3

1111%
22

1111%

22222

11111x%

23222222222

111111
1111111

11111

11111111

1111111111131 11111111

IO KK KKK KIK K IR

11111%

4444

2222

1111

4444
4444444

111

11111

333

111

1111111111213141111
KA

233
22

111

11111111131 3133111411

FRAK KA

COMBINING
OPERATIONS

1111111

3333

222

333

*1111

211
2

222

333

11111
222

222

2222223222
22

222

444

*111

111

11111111

44444444

*111

*1i11

111

333

111t

22
3333

222

*ii11

1111

222222222

11111

*11111%

1111

11111111

1111

11111

11113111

1111

%
%

222

333

4444

222

2222
22

1111111
111111

22222222222

11111

113
i1

%
*

11111111

4444

222

1111
111

111

2222
22

KK KK KKK KKK KKK KK

111111111113111311
11111444211121311211112

11111

111111

*x11111
*x1111

IORK AR KKK F ORI AR

111311211111111112
IR F KK KA

IR AR NOK K KKK

%
%
%

*
K KK KK KKK

The Result of GRAPH.SAV

To produce these results, you first compiled the FORTRAN IV
source program (GRAPH.FOR), then linked it with the default

library (SYSLIB.OBJ), and finally ran the resulting .SAV file
(GRAPH.SAV). You can combine these three operations using

EXECUTE

one monitor command, the EXECUTE command.
NOTE

The use of the EXECUTE command requires the following files on your system volume:

FORTRA.SAV
SYSLIB.OBJ

LINK.SAV
GRAPH.FOR
FORLIB.OBJ (if not included in SYSLIB)

If you have substituted the special LINK volume for your
system volume, you do not have the necessary files to

use the EXECUTE command. Proceed to the next section, entitled Alternate Functions.
9-12

Running a FORTRAN 1V Program

The EXECUTE command instructs the system to select the language processor, then process, link, and run the program. There
are several ways to establish which language processor the EXECUTE command invokes. One way is to specify a language-

name option, such as /MACROQO, which invokes the MACRO as-

sembler. Another way is to omit the language-name option and
specify the file type for the source files. The EXECUTE com-

mand then invokes the language processor that corresponds to
that file type. Specifying the file GRAPH.FOR, for example,

invokes the FORTRAN IV compiler. A third way to establish
the language processor is to let the system choose a file type of

.MAC, .DBL, or .FOR for the source file you name. If, for example, you specify the file GRAPH, the monitor searches device
SY:

(your

system

device)

for the files GRAPH.MAC,
GRAPH.DBL, and GRAPH.FOR, in that order. If the monitor

finds neither GRAPH.MAC nor GRAPH.DBL, it invokes the
FORTRAN IV language processor to compile GRAPH.FOR. For
example, to combine the compile-link-run operations that you

performed in this chapter, you would use the following command (do not actually type this command until you have read

the next section, Alternate Functions):
Long and Short Command Format

FORLIB not included in SYSLIB:
+EXECUTE

GRAPH/FORTRAN/LIST/LINKLIB:SYSLIB/LINKLIB:FORLIBED

FORLIB included in SYSLIB:
JEXECUTE

GRAPH/FORTRAN/LISTED

The following are some alternate functions that you can substitute in your FORTRAN IV source program to produce different

graphs. Simply reedit the program (GRAPH.FOR) so that lines

1-5 in the function portion at the end contain one of the following alternate functions. Then compile, link, and run the programs as described in the previous sections. If the necessary
files are available on your system volume (see the previous sec-

tion, Combining Operations), use the EXECUTE command to
run the program. The source program compiles, links, and runs,

and the new graph prints on the terminal (or line printer).
Function

FUNCTION

FUN(X.Y)

FUN=EXP{-SQRT(X##2+Y%%2)}
RETURN

END

Function 2
FUNCTION

FUN(X.Y)

R=CRORT(X#*2+Y*%2)
FUN=X#Y*#(R-3.)/
(1. +EXP(3.,#(R-3.5)))
RETURN
END

9-13

ALTERNATE
FUNCTIONS

Running a

FORTRAN IV Program

Function 3
FUNCTION FUN(X.:Y)
FUN=EXP(+SQRT(X*%2+Y*%2))/1177.4
RETURN
END

SUMMARY:
COMMANDS TO
RUN FORTRAN
PROGRAMS

EXECUTE
Combine the compile-link-run operations into one command.
EXECUTE file

Combine the compile-link-run operations into one command.
Specify the libraries to be used during linking.
EXECUTE file/FORTRAN

Combine the compile-link-run operations into one command,
and specify the input file to be a FORTRAN file.
EXECUTE/LIST
Combine the compile-link-run operations into one command.
Obtain a listing file of the source program and print on line
printer.

FORTRAN

Compile the FORTRAN 1V source program and produce an
object module.
FORTRAN/LIST
Compile the FORTRAN IV source program and produce both
an object module and a listing file.
LINK
Link individual object modules together to form a complete
program and produce a load module.
RUN
Run the indicated load module.

FILE MAINTENANCE

Before continuing further you should perform the necessary file
maintenance operations.
NOTE
If you used a special LINK volume to perform this demonstration, turn now to the section entited FORTRAN/LINK File Maintenance in Appendix B.

Obtain a directory of all files on your system volume that have
the name GRAPH regardless of file type; these files were created as a result of the exercises in this chapter.

9-14

Running a FORTRAN IV Program

Long and Short Command Format
+DIRECTORY
08-Jan-83

GRAPH,
@D

GRAPH

.5AV

08-Jan-83

GRAPH

,LST

08-Jan-83

GRAPH

BAK

0B-Jan-83

GRAPH

FOR

0B-Jan-83

GRAPH

,0BJ

168

08-Jan-83

Filess

447

Free

Blocks

blocKs

The fact that you have corrected errors in the source file
GRAPH.FOR makes the version of that file on your storage

volume obsolete. Therefore, transfer the updated copy from

your system volume to VOL: replacing the copy
GRAPH.FOR on the storage volume with the new version.

Long Command Format
+COPYEED
From?

GRAPH.FOREED

YOL:GRAPH,FORGED

Short Command Format
+COPY

GRAPH,FOR

VOL:GRAPH,FORGED

Similarly,
transfer GRAPH.LST,
GRAPH.OBJ,
and
GRAPH.SAYV to your storage volume. This allows you to examine a listing or rerun the FORTRAN IV program without re-

compiling and relinking the source.
Long Command Format
YCOPY®ED

From? GRAPH.LST GRAPH.OB.JGRAPH, SAVED
To
? ugL:@D
Files

coried:

DK:GRAPH.LST

VYOL:GRAPH.LST

DK:GRAPH.0BJ

VOL:GRAPH.0BJ

DK:GRAPH,.SAY

VYOL:GRAPH,SAV

Short Cofilmand Format
+COPY
Files

GRAPHLLSTGRAPH.OBJ

GRAPH.5AY

VOL:ED

coried:

DK:GRAPH.LST

VOL:GRAPH.LST

DK:GRAPH.DBJ

VYOL:GRAPH.OBJ

DK:GRAPH,.BAY

VOL:GRAPH,SAV

Once you have transferred all files of value to your storage
volume, delete the useless files — that is, all the GRAPH
files — from the system volume.

9-15

Running a FORTRAN IV Program

Long Command Format
+DELETEGRED
Files?

GRAPH.*@ED

Files

deleted:
DK:GRAPH.BAK
?

YGED

DK:GRAPH.S5AYV

Y@ED

DK:GRAPH,FOR

DK:GRAPH.LST

YGD

DK:GRAPH,0BJ

YG@ED

Short Command Format
+DELETE
Files

GRAPH.*GD
deleted:

DK:GRAPH.BAK

YGD

DK:GRAPH.S5AV

YG@D

DK:GRAPH.FOR

DK:GRAPH.LST

YG&D

DK:GRAPH.O0BJ

YGD

Finally, obtain an up-to-date directory listing of your storage
volume so that you can see its current status.
Long and Short Command Format
+DIRECTORY

VOL
: @D

08-Jan-83
SUM

+MAC

08-Jan-83

EXAMP

.MAC

,FOR

ZB6-Aug-82

GRAPH

,LST

,FOR

08-Jan-83

0B-Jan-83

GRAPH

.S5AY

GRAPH

08-Jan-83

.0BJ

08-Jan-83

Filess

4707

Free

26-Aug-82

blocks

This completes the FORTRAN IV demonstration. Continue to

Chapter 12 to read about the linking process. If you followed
the special instructions in Appendix B to load the language
volume, leave this volume in device unit 0 until you have finished Chapter 12.

REFERENCES

McCracken, Daniel D., A Simplified Guide to FORTRAN Programming. New
York: Wiley, 1974.
An introduction to programming in the FORTRAN language.

PDP-11 FORTRAN Language Reference Manual (AA-1855D-TC). Maynard,
Mass.: Digital Equipment Corporation, 1980.
A reference manual and guide to programming in the PDP-11 FORTRAN IV language.

RT-11 FORTRAN 1V Installation Guide (AA-5240E~TC). Maynard,
Mass.:
Digital Equipment Corporation, 1980.
An RT-11-specific manual that contains instructions for installing

the

RT-11 FORTRAN IV language processor, and describes known problems and differences between versions.
RT-11 RSTS-E FORTRAN IV User's Guide (AA-5749B-TC). Maynard,
Mass.: Digital Equipment Corporation, 1980.
An RT-11-specific manual that contains information necessary to
compile, link, run, and debug a FORTRAN IV program.

9-16

CHAPTER 10
RUNNING A BASIC-11 PROGRAM

The BASIC-11 program language' is a machine-independent

programming language that is one of the easiest languages for
the beginning programmer to learn. It has both elementary language features that you use to write simple programs, and more
advanced operations that allow you to produce complex and efficient programs. In addition, a special “immediate mode” lets
you use BASIC-11 like a calculator to obtain instant answers
to mathematical problems.

BASIC (Beginner’s All-purpose Symbolic Instruction Code) —11
is conversational in nature. It uses simple English keywords
and common mathematical expressions to form easily under-

DEVELOPING
A BASIC-11
PROGRAM

stood language statements.

You write a BASIC-11 program as a series of one or more program lines. You begin each program line with a number that
both identifies the line and indicates the order in which the line
will be processed. Individual program lines contain one or more
BASIC-11 language statements that define the operations to be
performed.

When you are satisfied with the logic of your BASIC-11 source
program, you create it as a file. However, unlike your methods
under other programming languages, you create the file under
the control of the BASIC~11 language processor, which is part
of the RT-11 operating system and is stored on your system
volume or on a separate volume of its own. Thus, you use commands that are part of the BASIC-11 language processor to
create and edit the program, list it, run it, and save it for later
use.

The BASIC-11 language processor is an interactive interpreter.
It allows you to create and execute a program in its entirety or
a few lines at a time. The interpreter examines each program
language statement, interprets it, and executes it before going
on to the next. If it discovers an error that prevents further
processing, it prints on the terminal a message informing you of
the error condition and stops. You correct the error so that execution can continue past that point, and then rerun the program.

IBASIC-11 is a superset of the standard BASIC language developed at Dart-

mouth College.

10-1

USING THE
BASIC-11

LANGUAGE
PROCESSOR

Running a BASIC-11 Program

|
l

|
|
CREATE

EDIT

RUN

Figure 10-1

Functions of the BASIC-11
Language Processor

USING THE
BASIC-11
INTERPRETER

The functions of program creation, editing, processing, and execution are all handled by the BASIC-11 language processor.
Some RT-11 systems store the BASIC-11 interpreter (language
processor) on a volume apart from the system volume.' You can
quickly determine whether the BASIC-11 interpreter is on
your system volume by typing the monitor DIRECTORY com-

mand and specifying the BASIC.SAV program.
J,DIRECTORY

BASIC,SAVEED

In the directory listing that results, if the directory entry for

BASIC.SAV is listed on your terminal, then the required
BASIC-11 files are on your system volume and you are ready to

use the interpreter. However, if BASIC.SAV did not appear in
your listing, then the required files are not part of your system
volume. Before you can use the interpreter, you must make a
volume substitution. Read the section in Appendix B entitled

Using the FORTRAN/BASIC Language Volume.

Now

BASIC

use

the

monitor

BASIC

command

activate

BASIC-11 interpreter:

the

Long and Short Command Format
L BASICED
BAGIC-11/RT-11
OPTIONAL

V2.1

FUNCTIONS

(ALLs

NONE:

INDIVIDUALS?

A prompting message is printed by BASIC-11. You must respond with an A, N, or I and a carriage return to indicate
whether you want to preserve all, none, or some of the arithmetic functions initially provided by BASIC-11. BASIC-11’s func-

tions include operations that calculate random numbers, deterYThis is true for any RT-11 system volume that does not have enough free
blocks to accommodate the BASIC-11 system files. RX01 diskette is an
example.

Running a BASIC-11 Program

mine absolute values, convert octal and binary numbers to deci-

mal, and so on. You can conserve memory space by saving only
those functions that your program needs. For now, however,
instruct BASIC-11 to save all the functions.
ARED
READY

BASIC-11 prints the READY message to indicate that it is
ready to accept a BASIC-11 command. Any text that you type
that is not preceded by a BASIC-11 command is accepted as
program (or immediate mode) input. If at any time you wish to
return to the monitor command mode, simply type the BYE
command following the READY message. READY appears
after any BASIC-11 execution that is completed or interrupted
by a double CTRL/C, or after any BASIC-11 wait condition that
is terminated by a single CTRL/C.

BYE

NOTE

You do not need to understand the BASIC—-11 language
or the way the examples work to perform successfully
the exercises in this chapter.

Immediate mode allows you to use the BASIC-11 interpreter
like a calculator to obtain immediate answers to arithmetic
problems. You enter the appropriate BASIC-11 statement keyword and any necessary mathematical formula. When you
press the carriage return key, BASIC-11 immediately calculates and prints the results. (Use the terminal DELETE key
and the CTRL/U command to correct any typing errors.)
PRINT

immediate Mode

(128+75)%3ED

608

BASIC-11 adds the two numbers in parentheses, multiplies
them by 3, and prints the answer. The PRINT statement causes

the answer to be printed on the terminal. The following command provides another example:
PRINT

INT(34.67)ED

34
READY

The greatest integer less than or equal to 34.67 is printed.
You can combine several statements on a single line, or on
several lines, including variable names, arithmetic equations,
and data. Individual statements are separated from one another by a backslash (\) character. BASIC-11 considers all the

10-3

Running a BASIC-11 Program

information, calculates the answer and prints it on the ter-

minal, as illustrated in the following example:
A=5\B=14\C=,37296D
READY

PRINT
THE

"THE

HEIGHT

HEIGHT
IS

IS"3A¥SIN{(C)+B3"METERS"@D

15.8216

METERS

READY

The first statement equates variable names with values; the
second statement introduces a formula for calculating a result
and prints it.

You can use immediate mode to solve fairly lengthy and complicated mathematical problems by combining statements and
printing identifying messages. However, immediate mode infor-

mation is temporary. You cannot save it, and you can change it

only by retyping every statement line. If your needs are more
complex, or if you want to save your statements, you should
create a BASIC-11 program.

Creating and Editing
a BASIC-11 Program

To create a BASIC~11 program, assign line numbers to language statements and then type the numbered statements on

the terminal keyboard.

Now your program lines are saved in memory and you can
transfer program control to specific lines within the program,
repeat parts of the program any number of times, store the
entire program for later use, and perform other similar operations that are not possible in immediate mode.

SuB

Once you have created the program, you use BASIC-11 editing

commands to list lines, change lines, add and erase lines, and
correct typing errors. In addition to the DELETE key and the

CTRL/U command, BASIC-11 provides a SUB command (SUB-

STITUTE) for correcting typing errors. This command allows
you to substitute new characters for existing ones in a line. For

example, type:
10

SUB

"THIS

BADIC

PROGRAM"GE

BASIC

PROGRAM"

BBADBBASRRD
"THIS

READY

The SUB command substitutes the letters BAS for BAD in line

10. Use a delimiting character (shown here as @) to separate
the old text from the new. The delimiter can be any character

as long as it is unique in the line. The corrected line is automatically printed by BASIC-11 after you use the command. As
another example, type:

104

Running a BASIC-11 Program
15 B=10\C=5GD
20 LET A-B+CA\PRINT CED

There are two typing errors in line 20; the — should be an =
and the C at the end of the line should be A. These errors can be
corrected with the SUB command, as follows:
SUB 20 B-B=RED
20 LET A=B+C \ PRINT C
READY

SUB 20 BCEARZEED
20 LET A=B+C \ PRINT A
READY

The second SUB command changes the second occurrence (specified by the 2 after the last @) of C to A.

You can erase an entire line by typing the line number followed

by a carriage return:
1 0@ED

You can also use BASIC-11’s DEL command'. Use the DEL

command (DELETE) to erase a single line or several:
DEL

DEL

15-2060

This erases all statements with line numbers between and including 15 and 20.

To list lines of a program, BASIC-11 provides the LIST com-

mand. First, create a few program lines:
5 FOR I=1 TO 10GE
20 INPUT JED
2% LET T=T+JED
50 NEXT G

55 PRINT
88

“THE TOTAL

18" iT@ED

ENDED

List individual lines by specifying the line number. For example, type:
LIST

0B-JAN-83

NONAME
S

FOR

I=1

70O

00:18:49

READY

Do not confuse the BASIC~11 DEL command with the DELETE key on the

terminal keyboard.

10-5

LIST

Running a BASIC-11 Program

LISTNH

Notice that BASIC-11 prints a header line. Since you have not

as yet assigned a name to your program, BASIC-11 assigns it

the name
NONAME and prints this name, along with the date
(which is only correct if previously entered via the DATE monitor command) and the time when you use the LIST command.

You can omit the header line by using the LISTNH command
instead of the LIST command.
LISTNH

50-8BED

END

"THE

TOTAL

IS"ST

READY

By typing the LIST or LISTNH commands without indicating

any line numbers, you can print on the terminal a listing of
your entire program. Terminate the command with a carriage
return.
LISTNHED
S

FOR

I=1

INPUT

LET

END

T=T+J
I
"THE

TOTAL

IS"ST

READY

SCR

Finally, to erase the entire program, which you must do before
typing a new program, use the SCR (SCRATCH) command.
SCRED
READY

All program lines are erased from memory.

SUMMARY:
BASIC-11 EDITING
COMMANDS

line #
Erase the indicated program lines.

DEL line #
Erase the indicated program lines.

LIST
List the entire program and print a header that includes the
program name, date, and time.

LIST line #
List the indicated lines and print a header that includes the
program name, date, and time.

10-6

Running a BASIC-11 Program

LISTNH

List the entire program but do not print a header.

LISTNH line #

List the indicated lines but do not print a header.

SCR

Erase all program lines from memory and change the name

to NONAME.

SUB line #@FIRST@SECOND@n
Replace the nth occurrence of the FIRST character(s) with
the SECOND character(s) in the indicated line (default is
n=1).

Create the following demonstration program’, using the appro-

priate BASIC—11 editing commands, exactly as it appears here.
If you forget to insert a line, type it at the end or when you
notice the omission; BASIC-11 sorts and arranges lines by
number before execution, regardless of the order in which they
are typed. When you have finished, list the entire program and
make a final check for typing errors.
100 REM THE
101

REM

110 PRINT
115 PRINT
120 PRINT

PROGRAM Z3 MATCHES

“WE BEGIN WITH 23 MATCHES., YOU MOVE FIRST., YOU"
“MAY TAKE 1, 2, OR 3 MATCHES., TYPE YOUR CHOICE"
"FOLLOWED BY A CARRIAGE RETURN. THEN THE COM-"

125 PRINT "PUTER CHOOSES 1+ 2+ OR 3 MATCHES. YOU CHOOSE"
130 PRINT "AGAIN, AND S0 ON, WHOEVER MUST TAKE THE LAST®

135
140
200

PRINT "MATCH: LOSES.”
PRINT \ LET M=23
REM THE HUMAN MOVES

201

REM

210
215

PRINT
PRINT

230

240
250
260
270

INPUT H
1F H>M THEN 510
IF H<SINT(H THEN
IF H<{=0 THEN 510
IF H»=4 THEN 510

280

LET

\
\

PRINT
PRINT

“THERE ARE NOW"iM3i"MATCHES."
"HOW MANY DO YOU TAKE"j

510

M=M-H

290
300

IF M=0 THEN 410
REM THE COMPUTER

301

REM

305
310
320
330
350

IF M=1 THEN 440
LET R=M-4%INT{(M/4)
IF R<>»1 THEN 350
LET C=INT(3#RND)+1 \ GO TO
LET C=(R+3)-4*INT((R+3)/4)

360

LET

370

380

400

REM

401

REM

410

THEN

988

END

440

SOMEBODY

510 PRINT

"3
"THE COMPUTER TOOK"3C3i"..s.

310

500 REM BAD
REM

380

M=M-C

M=0

440 PRINT
501

MOVES

WON

"THE

COMPUTER

"YOU WON,"

WON."”

\ GO TO 998

988

INPUT

"ENTER ONLY

OR 3."

GO TO 215

193 Matches, 101 BASIC Computer Games, Maynard, Mass.: Digital Equip-

ment Corporation, 1975.

10-7

Running a BASIC-11 Program

As you can see from the first few lines of the listing, this pro-

gram is a mathematical game where you match your logic

against the program logic. The PRINT statements in the program print messages, game instructions, results, and so forth,
on the terminal. The REM statements identify comment

lines — remarks that provide general information about the

program, but that are ignored by BASIC-11 during processing.
The INPUT statement in line 230 allows you to supply data
from the terminal. Depending on the value you enter, program
control transfers to various other parts of the program. For example, if you type an invalid value, program control skips
ahead to a PRINT statement in line 510 informing you of your
mistake and then returns to line 215 to ask for a value again.
The mathematical algorithms of this program are in lines 310
through 350, which determine the number of matches the computer will select based on your choice.

RUNNING A

BASIC-11 PROGRAM

RUN

Once you have typed the program and checked the listing to be
sure that it corresponds to the example, you are ready to run it.
The BASIC-11 RUN command initiates program execution.
This command prints a header that includes the program name,
date, and time. If you want to omit the header line, type the
RUNNH command instead.
RUNNHG®ED

If you typed the program correctly, you will see this text print
on your terminal:
WE BEGIN WITH 23 MATCHES. YOU MOVE FIRST., YOU
MAY TAKE 1: 2, OR 3 MATCHES. TYPE YOUR CHOICE
FOLLOWED BY A CARRIAGE RETURN., THEN THE COMPUTER CHOOSES 1, 2, OR 3 MATCHES. YOU CHOOSE
AGAIN,s

AND

MATCH,

LOSES.

THERE
HOW

ARE

MANY

NOW
DO

ON.,

WHOEVER

MATCHES.

YOU

MUST

TAKE

THE

LAST

TAKE?

NOTE
If this response does not appear, you have not entered

the program correctly. Compare your listing very carefully against the one provided earlier. Spacing does not

matter, but all other characters must match. To correct

your errors type CTRL/C, which, under control of
BASIC-11 only, returns you to BASIC-11 command
mode, indicated by the READY message. Correct the
program and then rerun it.

10-8

Running a BASIC-11 Program

When the program pauses and asks you a question, you must
supply data, in this case a 1, 2, or 3. Type your choice (represented here by n), followed by a carriage return:
n&ED
?SYNTAX

ERROR

LINE

250

READY

BASIC-11 discovered an error' in line 250 that prevents further processing. Check line 250 in your listing or list it on the
terminal:
LISTNH

25060

250

H<>INT(H

THEN

510

READY

Note that a right parenthesis is missing after the second H in

this line. Correct the line using the SUBSTITUTE command:
SUB

250

B(HE(H)RED
H<>INT(H)

THEN

510

READY

You are ready to run the program again.
RUNNHGEED

BASIC-11 begins processing at the start of the program.
WE

BEGIN

MAY

TAKE

FOLLOWED

PUTER

WITH

CHOOSES

AGAIN,»

AND

MATCH
.

LOSES.

THERE
HOW

ARE

MANY

NOW
DO

MATCHES.

YOU

MATCHES.

MOVE
TYPE

CARRIAGE

RETURN.,

ON.,

WHOEVER

MATCHES.

YOU

THEN

MATCHES.
MUST

FIRST.
YOUR
THE

YOU

TAKE

YOU

CHOICE
COM-

CHOOSE

THE

LAST

TAKE®?

Type your choice again. But notice this time that a different

kind of error is detected. The BASIC-11 interpreter has entered
an infinite loop, a series of commands that it repeats endlessly.

After several lines have printed, type a double CTRL/C; this
interrupts execution and returns control to BASIC-11 command mode.

Refer to the RT-11 System Message Manual for greater detail about any

messages printed during normal system use.

10-9

CTRL/C CTRL/C

Running a BASIC-11 Program
n@

THE
THE

COMPUTER
COMPUTER

TOOK
TOOK

THE COMPUTER TOOK
THE COMPUTER TOOK
THE
THE

COMPUTER
COMPUTER

ETRLC)
STOP

LINE

TOOK
TOOK

e
LI
[N

L)oo

THE COMPUTER TOOK
THE COMPUTER TOOK

A
LRI

WM W

THE COMPUTER TOOK
THE COMPUTER TOOK
THE COMPUTER TOOK

LR
2N

L
2
L

380

READY

An infinite loop is a programming logic error. However, since
the error does not prevent processing, BASIC-11 does not print
an error message. Instead BASIC-11 is caught in a loop of instructions and executes them endlessly. This particular loop is
obvious because it prints a line of text; other kinds of loops may
not be so evident. At this point you must examine the program
logic to determine why these instructions are being repeated.
Look at your listing of this program. The problem in this case is
in line 390. This line instructs program control to return to line
310; therefore lines 310 through 390 are repeated endlessly
without ever obtaining your next value choice. Program control
should really return to line 210. Correct line 390 as follows:
SUB 390 E310B210RED
390

210

READY

Now you are ready to run the program again. This time the
entire program should execute without error. Enter your value
choices when requested. (A hint to playing the game: your first
value choice determines whether you can win; if your first
choice is wrong, the program has the advantage throughout.) A
sample run follows.
RUNNHGEED

WE BEGIN

WITH 23 MATCHES.

YOU

MOVE

FIRST.

YOU

MAY TAKE 1, 2, OR 3 MATCHES., TYPE YOUR CHOICE
FOLLOWED BY A CARRIAGE RETURN. THEN THE COMPUTER CHOOSES 1, 2, OR 3 MATCHES. YOU CHDOSE

AGAIN,

AND SO ON.,

MATCH,

LOSES.

THERE ARE NOW

WHOEVER MUST

TAKE

THE LAST

MATCHES.

10-10

Running a BASIC-11 Program
HOW MANY DO YOU TAKE? 1@&D
THE COMPUTER TOOK 1 444
THERE ARE NOW 21 MATCHES.,

HOW MANY DO YOU TAKE?

1@ED

THE COMPUTER TOOK 3 444
THERE ARE NOW 17 MATCHES.

HOW MANY DO YOU TAKE? Z2ED
THE

TOOK

COMPUTER

THERE

ARE

HOW MANY

NOW

DO YOU

MATCHES.

TAKE?

160

THE COMPUTER TOODK 3 444
THERE ARE NOW 9 MATCHES.,

HOW

MANY

YOU

TAKE?

1GED

THE COMPUTER TOOK 3 ++4.
THERE ARE NOW 5 MATCHES.

HOW

MANY

YOU

TAKE? 36D

THE

COMPUTER TOOK 1 4440
THERE ARE NOW 1 MATCHES.

HOW MANY DO YOU TAKE? 0@
ENTER ONLY 1,y 2,y DR 3.
HOW

MANY

THE

COMPUTER

YOU

TAKE?

WON.

READY

RUN

Execute the BASIC-11 program currently in memory; print a
header line including the program name, date, and version
number.

SUMMARY:
BASIC-11
EXECUTION

COMMANDS

RUNNH
Execute the BASIC-11 program currently in memory; omit
the header line.

CTRL/C

Under control of BASIC-11 only, interrupt execution of the
BASIC-11 program and return control to BASIC-11 command mode.

BYE
Return control to monitor command mode (only when using
BASIC-11).

10-11

Running a BASIC-11 Program

FILE MAINTENANCE

You can transfer the BASIC-11 program currently in memory
to a storage volume by using the SAVE command of BASIC.
The SAVE command copies the program to the storage volume
and gives the program the file name and file type that you
indicate in the command line. A file type of .BAS is assigned
automatically unless you indicate otherwise.

SAVE

Use the SAVE command to store this BASIC-11 program as
MATCH.BAS on the storage volume (VOL:) as follows:
SAVE VOL:MATCHED
READY

NEW

After you save a BASIC-11 program on a storage volume, you
can create a new program in memory by typing the BASIC-11
NEW command. This command erases the current memory contents and asks you for a new program name:
NE WEED
NEW FILE

NAME--

You can type any file name you wish and BASIC-11 assigns it
to the file you create. Or you can respond by typing only a
carriage return; BASIC-11 then assigns the file name NONAME.

Another way to create a new program in memory is to type the

BASIC-11 SCR command. This command simply erases the
current memory contents. It assigns the name NONAME:
SCRED
READY

OoLD

To use an existing BASIC-11 program, one that you have previously stored on a storage volume, type the BASIC-11 OLD
command:
OLDED
OLD FILE

NAME--

Reply by typing the device name, file name, and file type of the
file that you want to use. If you omit an explicit device name,
BASIC-11 assumes DK: (the default volume); if you omit an
explicit file type, BASIC-11 assumes .BAS. BASIC-11 erases
memory and then copies the program from the volume into
memory. For example, type:
YOL t MATCHED
READY

This copies VOL:MATCH.BAS back into memory.

Assume that you have edited or changed the MATCH.BAS file
and now want to transfer it back to VOL:. Since the file already

10-12

Running a BASIC-11 Program

exists as MATCH.BAS on that volume, you must use the
BASIC-11 REPLACE command:
REPLACE VOL:MATCHED
READY

The REPLACE command replaces an existing file with a new
version.

REPLACE

The SAVE and REPLACE commands copy a BASIC-11 program from computer memory to a storage volume. As these
commands copy the program, they convert it from the internal
format used by BASIC-11 to ASCII format. Thus, you can, if
you prefer, use the RT-11 editor to create and edit BASIC-11
programs, since the editor also uses ASCII format. However,
many users would rather use BASIC-11 to create and edit a
BASIC-11 program, since they can then run the program,
reedit it, rerun it, and save the new version — all in BASIC-11 command mode — rather than perform the several corresponding monitor commands.
The last file maintenance operation that you should perform is
to obtain an up-to-date directory of your storage volume so that
you can see its current status; however, you must return to
monitor command mode to do this. Type the BYE command,;
this BASIC-11 command (rather than CTRL/C) returns control
to monitor command mode. Next use the DIRECTORY monitor
command to check the status of your storage volume.
BYE®ED
+DIRECTORY/BRIEF

VOL:

08-Jan-83
SUM
+MAC

EXAMP

FOR

EXAMP

.MAC

GRAPH

5AV

MATCH

.BAS

.0BJ

Filess

4704

Free

GRAPH

,FOR

GRAPH

,LGT

Blocks

blocKs

NEW

Create a new BASIC-11 program, assigning the file name
indicated.

SUMMARY:
BASIC-11 FILE
MAINTENANCE

COMMANDS

OLD

Copy into memory an existing BASIC-11 program (for use
under BASIC-11).
REPLACE
Copy the BASIC-11 program currently in memory to the in-

dicated storage volume, replacing the version that already
exists on that volume.
SAVE

Copy the BASIC-11 program currently in memory to the indicated storage volume.

10-13

Running a BASIC-11 Program

This completes the BASIC-11 demonstration. Before you con-

tinue to Chapter 14 to learn about program debugging, make

sure that the main system volume is loaded in device unit 0. If
you followed the special instructions in Appendix B to load the

language volume, you should now stop the system, unload that
volume, load the main system volume, and rebootstrap the
system.

REFERENCES

BASIC-11 Language Reference Manual (AA—1908A-TC). Maynard, Mass.:
Digital Equipment Corporation, 1976.
A reference manual and guide to programming in the BASIC-11 language.

BASIC-11/RT-11 Installation Guide and Release Notes (AA-K724B-TC).
Maynard, Mass.: Digital Equipment Corporation, 1983.

An RT-11-specific manual that contains instructions for installing the
RT-11 BASIC-11 language processor and lists known problems and
differences between versions.
BASIC-11/RT-11 User's Guide (AA-5071B-TC). Maynard, Mass.: Digital
Equipment Corporation, 1983.

An RT-11-specific manual that contains information necessary to
create, edit, run, and debug a BASIC-11 program.

10-14

CHAPTER 11

RUNNING A MACRO-11 ASSEMBLY LANGUAGE PROGRAM
The MACRO-11 programming language is a machine-dependent programming language developed for the PDP-11 programmer, or for the FORTRAN IV programmer who intends to combine assembly language routines and FORTRAN IV routines.
The MACRO-11 language enables the knowledgeable programmer to access all the features of the RT-11 computer system
using a precise and efficient programming code.

The MACRO-11 assembly language uses the PDP-11 instruc-

tion set, a list of mnemonic instructions that correspond to various PDP-11 computer operations. These instructions allow you
to add, compare, increment, complement, and perform many
other manipulations on numerical data. The instructions are
summarized in a pocket-sized folding card, called the PDP-11
Programming Card (Figure 11-1), and are described in detail
in the PDP—11 Processor Handbook. By choosing the appropriate instructions and by providing any additional data needed,
you can create a complete program.

Figure 11-1

PDP-11 Programming Card

You write the MACRO-11 program as a sequence of lines, each
a single assembly language statement in the following format:
LABEL:

OPERATOR OPERAND(S)

COMMENTS

The operator and/or operand are instructions selected from the
PDP-11 instruction set, data needed by the instructions, or assembler directives (instructions to the assembler to guide the
assembly process). The optional statement label identifies the
statement line so that you can refer to the instructions or data
on that line from other parts of the program. Optional comments describe generally what operations are being done.
Sequences of language statements constitute a routine (to perform a specific function); groups of routines and data compose
the entire executable program.
11-1

DEVELOPING
A MACRO-11
ASSEMBLY
LANGUAGE
PROGRAM

Running a MACRO-11 Assembly Language Program

When you are satisfied with the logic of your MACRO-11
source program, you use the RT-11 editor to create it as a file

(see Chapter 5). You use tabs and spaces to make the program

more readable. When you have finished creating the program
as a complete, edited file, you next enter it as input to the
MACRO-11 language processor, which is part of the RT-11
operating system and is stored on your system volume. The

MACRO-11 language processor processes (assembles) the lan-

guage statements, converting them into an internal machine

language code called object code. This code is next processed by
the system linker, which combines your program units and

makes the program suitable for execution. Figure 11-2 repre-

sents the development of an executable MACRO-11 program.

CREATE

EDIT

Figure 11-2

USING THE

MACRO-11
LANGUAGE
PROCESSOR

ASSEMBLE

LINK

RUN

Evolution of a MACRO-11 Program

The MACRO-11 language processor is an assembler that accepts information in one format (that is, your source program)
and translates it into another format (that is, a machine lan-

guage program). The assembler interprets and processes the
assembly language statements, one at a time, and generates

one or more computer instructions or data items. Since you
originally use the editor to create a MACRO-11 program in

ASCII format, you must next translate it into a machine format
that the computer can use. The MACRO-11 assembler performs this conversion, producing as output a new version of the

program, in object format, called an object module. You may
request the MACRO assembler to produce a listing of the
source program at the same time. The role of the assembler is

represented below in Figure 11-3.

SOURCE

PROGRAM

ASSEMBLE

OBJECT
MODULE

LISTING

(OPTIONAL)

Figure 11-3

Function of a MACRO-11 Assembler

11-2

Running a MACRO-11 Assembly Language Program

During assembly processing, the MACRO-11 assembler:
e Accounts for all instructions used within the source program
and determines their relative positions in computer memory;
it does this by means of a storage location (program) counter.

o Keeps track of all user-defined symbols and their respective
values in a symbol table.

¢ Converts assembly language mnemonics, user-defined symbols, and data values into their respective machine language
(object code) equivalents.

The program counter keeps track of addresses in computer
memory where instructions and data will be stored.

PDP-11 computer memories are composed of physical storage
locations that can hold numerical data. These locations are
numbered consecutively from 0 up to the highest memory location, which varies according to the amount of memory acquired
with the computer system (Figure 11—4). PDP-11 computers
used in an RT-11 system have at least 32,768 bytes (16,384
words).

CONVERTED INSTRUCTION

Figure 11-4

PDP-11 Computer Memory

11-3

The Program
Counter

Running a MACRO-11 Assembly Language Program

During processing, the assembler converts each program language statement into numerical data (the object code) and as-

signs the data a relative storage location. The system linker
will convert the relative storage locations assigned by the as-

sembler to absolute storage locations in the computer memory.!
The location’s associated number is called its address. As the
assembler translates and assigns each statement, it updates the

value of the program counter accordingly.

The Symbol Table

Since you may not know which locations, or how many locations, the program needs, you use symbolic names (variables,
constants, and labels) to represent individual locations and

their contents. As the assembler processes the source program,

it constructs a symbol table, which is a compiled list of all the
symbolic names and labels that you have used within the pro-

gram. The MACRO-11 assembler defines each symbolic name
by assigning an address or data value, as appropriate, and adds

the symbol definition to the symbol table. After assembly, you
can refer to the symbol table, which is printed at the end of the

assembly listing, to find all symbol definitions.

Machine Language
Code

The

third function of the assembler is to convert your
MACRO-11 source language statements into machine language code (the object module).
NOTE
The following information will help you understand the
assembly listing used later in this chapter.

Machine language code is numerical data in the form of binary

numbers (numbers composed of only the digits 0 and 1). Binary
numbers are appropriate because the digits 0 and 1 can be easily manipulated by the two-state electronic logic of the computer.

For example, a typical assembled instruction in PDP-11 com-

puter memory looks like this:

location

address

contents

01000

11000000

01001

11100101

"The system linker is discussed in Chapter 12.

114

Running a MACRO-11 Assembly Language Program

Since a single instruction requires two (or more) consecutive
memory locations, the instruction is actually put together in
memory in the following manner:

01001

high-order byte

low-order byte

11100101

11000000

01000

Each individual digit of the instruction is called a bit (binary
digit). A single memory location, called a byte, contains 8 bits;
two memory locations, called a PDP-11 word, contain 16 bits.

The byte in the even-numbered memory address is called the
low-order byte and is stored first; the byte in the odd-numbered
memory address is called the high-order byte and is stored next.
Both bytes together form one PDP-11 16-bit word (Figure
11-5).
PDP-11 Word

gioorf 11+

t}1

0] 01000

\\T etc.
bit

—" -

Low-order byte

High-order byte

Figure 11-5

PDP-11 Word

The computer works in terms of 8-bit bytes and 16-bit words of
binary data. However, binary numbers are generally too long
and cumbersome to be used effectively by a programmer. But
binary numbers can be easily represented as octal numbers
(numbers composed of digits within the range 0 to 7). Since
octal numbers are closer to the familiar decimal number system
and are much more readable than binary numbers, the programmer more often uses octal numbers than binary numbers.
Table 11-1 shows the decimal numbers 0 through 10 and their
respective octal and binary equivalents. Tables and formulas
are available to calculate higher conversions.

Thus, you can think of the binary instruction shown earlier in
terms of its octal equivalent as follows (conversion is done from
low-order to high-order byte in groups of three bits):

01001

high-order byte

low-order byte

11100101

11000000

01000
= 162700(8)

11-5

Running a MACRO-11 Assembly Language Program
A MACRO-11 assembly listing shows the addresses of memory
locations and their contents as octal numbers. The octal numbers represent the respective binary machine language code
that makes up the object module.
Table 11-1

Decimal/Octal/Binary Conversion

—

QWX TITDHOp
WN
O

Decimal

ASSEMBLING
THE MACRO-11
PROGRAM

Octal

Binary

000

001

010

011

100

101

110

111

1 000

1 001

1 010

In Chapter 5 you used the RT-11 editor to create a MACRO-11
source program; you then stored it on your storage volume.

Since a source program is in ASCII format, the next step is to
use the MACRO-11 assembler to convert the source program to
object code.

Copy the MACRO-11 source program from the storage volume
back to the system volume (which is the default volume for
input/output operations).

On your storage volume are two MACRO-11 source programs,
the one you created, SUM.MAC, and the one provided for you,
DEMOX1.MAC, which was renamed to EXAMP.MAC in Chap-

ter 7. Which of these you should copy depends on the results of
the source comparison you performed in Chapter 6. If the comparison resulted in no differences except for the title lines, copy

your own program (SUM.MAC) as follows:
Long Command Format
.COPYGED
From? VOL:SUM.MACGEED
To
7 SUM,MACGED

Short Command Format
,COPY

VOL:SUM.MAC

SUM.MACED

However, if differences were listed in addition to the title lines,

substitute the program EXAMP.MAC:

11-6

Running a MACRO-11 Assembly Language Program
Long Command Format
+COPYGED

From? VOL:EXAMP.MACED
? SUM,MACGEED
To

Short Command Format
,COPY VOL:EXAMP,.MAC SUM.MACED

Whichever source file you copied now resides on your system
volume under the name SUM.MAC and is the file that you will
process with the MACRO-11 assembler. The command used to
assemble a MACRO-11 source program is the monitor MACRO
command.

Use the MACRO command with its /LIST and /CROSSREFER-

ENCE options to assemble your source program and produce a

cross-referenced assembly listing. The system prompt asks you
to supply the input file name. You can omit typing the .MAC
file type, since the MACRO command assumes this file type
unless you indicate otherwise. The system will automatically
assign the name SUM.OBJ to the object module and SUM.LST
to the listing file, and store both newly created files on the

system volume. (The system volume is the default storage volume for input/output operations.)
Long Command Format
+ MACROGED

Files? SUM/LIST/CROSSREFERENCEGE

Short Command Format
+MACRD SUM/LIST/CROSSREFERENCEGED

Assembly begins. When it is finished, a message similar to the
following prints on the terminal printer or screen:
?MACRO-W-Errors detected:- B
DK:SUMDK:SUM/C=DK:5UM

This message indicates that the assembler detected errors in six
lines of the source program during processing. It helps at this
point to look at the listing produced by the assembler for information.

Long Command Format

(Line Printer)

L PRINTED

Files? SUM.LSTGD

(Terminal)

, TYPEGD

Files? SUM,LSTED

11-7

MACRO

Running a MACRO-11 Assembly Language Program

Short Command Format
(Line Printer)

(Terminal)

+PRINT

+TYPE

SUM.LSTEED

SUM,LETRD

Your listing should look like the following example. An explanation of this listing follows. You should refer to the listing as

you read the accompanying explanation.
NOTE
You do not need to understand the MACRO-11 language or the way this program works to successfully

complete the exercises in this chapter.
BUM.MAC

VERSION

MACRD

V05,00

Ssturdaw

08-Jan-83

093121

~TITLE

SUM.MAC

VERSION

JHMCALL

JTTYOUT,

JEXIT,

#NO.

DIGITS

Fage

2
3
4

5
6

000106

8
9

70,
=

THE

1701

SFRINT

SMESSAG

$PRINT

MOV

#NsRS

$NG.

CHARS

MOV

#NHLPRO

#NO.

DIGITS OF

MOV

#A,R1

3$ADDRESS

1720

RECIFROCALS

THE

1738

1/50

CALCULATE

THE

'E‘

EXF!

1710

‘E’

SUM

1/40

FACTORIALS
4

...

000000

000006

012705

000104

000012

012700

000107

000014

012701

000000

000024

011146

MoV

BR1y—(SF)

18AVE

000026

006311

ASL

ar1

ka4

000030

004311

ASL

eRt

ADL

(SF) 4y (R1D+

FNOW

DEC

END

BIGITS?

BNE

SECOND

PBRANCH

NOT

MOV

#NsRO

THRU

ALL

=(R1)+R3

$BY

THE

FLACES

15 000022

006311

000032

082621

000034

005300

000038

001371

000040

012700

000044

014103

Q00046

012702

000052

005202

FIRST:

SECOND?

0001046
THIRD:

ASL

MOV

177777

@rR1

INTROBUCTORY

ACCURACY

00 MULTIPLY BY 10

VECTOR

(DECIMAL)

%10,

POINT

PLACES,

MOV

#-1,R2

FINIT

QUOTIENT

INC

i BUMF

QUOTIENT

160003

SUB

ROsR3

$SUBTRALT LOOP

103375

BCC

FOURTH

FNUMERATOR

$FOR NEXT
$BREATEST

FOURTH?:

TEXT

‘E’

DIGIT

LDIVIDING

INDEX
REGISTER

27 000054
28

0000546

29 000060
30 000062

080003
010311

31
32 000064

046167

ADT
MOV
000000

000000

ROYR3
R3IsBR1

DIGIT
INTEGER

ADD

R2-2(R1)

#70

GIVE

000072

005300

DEC

#AT

END

DIGIT

000074

001363

BNE

THIRD

PBRANCH

NOT

346

000076

014100

000100

1482700

000104

103375

40 000106
41 000112
42 000114

062700
000000
003011

000116

000120

000122

MOV

~(R1)sRO

¥GET

BIGIT

#10.,R0

JFIX

THE

FTHAT

BEC

FIFTH

# (REALLY

ADD
STTYON
CLR

#10,1/0sRO
2Rt

#MAKE DIGIT
JOUTPUT THE
FCLEAR NEXT

003305

DEC

#MORE

001334

BNE

FIRST

FBRANCH

$WE

DONE

FIFTH!

000072

BAD
<

10%N

CEXIT

CARRIES
VECTOR?

OQUTPUT

2.7

ONLY

DIVIDE

DIGIT

ASCII
DIGIT
DIGIT

DIGITS

ARE

~—

DIGIT

8SUB

000012

ISN'T

IS ALWAYS

$FIX REMAINDER
FSAVE REMAINDER AS BASIS

10)

LOCATION

PRINT?

YES

47 000124
48

000107

EXP?

+REFT
+WORD

49
50
51

000342

124

110

105

000345

040

126

101

000353

040

117

104

000354

040

105

040

000361

111

123

072

114

000344

0135

VERSION

128

012
MACRO

0003467

056

Swmbol
A

TO ALL

ONES

MESSAG:

(ASCIT

/THE

VALUE

OF £

IS3/

<1%5>412:

/2./

<200>

062

V05,00

Saturdaw

08-Jan-83

Q%9i21

Fade

1~1

Fagde

1-2

200

000000
VERSION

SJEND
MACRO

V05.00

Saturdaw

08-Jan-83

EXF
09121

table
=

KXKRKK

FIFTH

0001 00R

FOURTH

Q00052R

000000R

FIRST

000012R

MESSAG

000342R

SECOND

000000

ABS,

000372

Errors

Kork
Work

detected!

Assembler

file
file
of

vreads!
writes!

core

Operating

000

(RWrI,GBLyARS,OVR)

001

(RW>TsLCL+REL
s CONY

000106

THIRD

Q00044R

000022R

STTYON=

RRXARK

statistics

Size of work file!
Size

EXP

*k¥

JEVEN

BUMMAC

VECTOR

105

)

FINIT

+JENDR

0006350

SUM.HAC

N+1
1

O
Q

8222 Words

rooll

15872

swystem!

RT-11

UWords

(

33 Fasmes)
(

62 Pasges)

—”

11-8

Running a MACRO-11 Assembly Language Program
Elarsed
DK

time!

00:0C104.34

SUMy DK I SUM/C=DK! 5UN

SUM.MAC
Cross

VERSION

reference

«TTYON

HACRO

table

(CREF

1-11%

1-47%

FIFTH
FIRST

1-37%
1-13¢

1-29
1-44

MESSAG

1-11

1-51%

N
SECOND

1-7%
1-15¢

1-12
1-21

THIRED

1-23%

1-35

FOURTH

1-25¢

SUM.MAC

0%:21

Page

5-1

VERSION

reference

MACRO

1-3¢

1-45

1-38

i-11

LTTYDU

1-38

VERSION

reference

1-13

1
table

+PRINT

SUM.HAC

1-54

1-28

JEXIT

STIP
D>

08-Jan~-83

1-14

EXP

Cross

Saturdaw

1-41

Cross

V05.00

V05.00)

(CREF

V05,00

1-47

Saturdaw

08-Jan-83

09i21

Fase

M-1

Saturdaw

08~Jan-83

09121

Fase

E-i

VQ5.00)

HACROQ

table

1-22

V05,00

V05,00)

1-32
1-54

31-~311

1~47

1-32
1-14

t~41

The first part of the listing has four logical sections, as follows:

line
number

octal
memory

octal
instruction

address

value(s)

statement line

The assembler assigns consecutive decimal line numbers to
each line of the source program, including blank lines and comment lines. These numbers are used for reference purposes. The

next column to the right shows the relative' even-numbered
octal memory (byte) addresses of storage locations assigned by
the program counter to each instruction in the program. This
has been assigned relative memory addresses 0
through 370. The third column (and possibly fourth and fifth)
program

shows the octal equivalent of the assembled instruction or data
value. An apostrophe following an octal value indicates a relative value that must be modified before it can be used (the
actual value is determined during linking). Finally, the source
program as you created it appears in the right-hand portion of
the listing.
For example, look at line 18 of the listing:
18

000030

0086311

ASL

@r1

The instruction ASL @R1 is stored in relative memory locations 30 and 31 as binary data (the comment, ;*8, is ignored):
31

00001100
0

11001001
3

30
1

!The assembler assigns relative memory addresses to instructions. Actual

addresses are not determined until the link operation is performed. Linking
and address relocation are discussed in Chapter 12.

11-9

Running a MACRO-11 Assembly Language Program

Some instructions require more than two memory locations; for
example, those at lines 13 and 14. The number of memory locations required depends upon the operation.
Following the assembled code in the listing is the symbol table,
an alphabetical listing of user-defined symbols and labels in the
program and their respective definitions. Symbols are defined

as values. For example, the symbolic variable name N is de-

fined (in line 7) as 000106(octal) or 70(decimal), an absolute
value. Labels are defined as addresses. The symbolic label
FIRST is defined (in line 14) as 000012, a relocatable address
(the R following 000012 in the symbol table indicates that the
address will be relocated or modified during linking). A row of
asterisks next to any symbolic name in the table indicates that

for some reason — possibly a programming error — the assembler could not define the symbol.
At the very end of the symbol table (where the . ABS. occurs) is
the program’s size information (or synopsis) in terms of the to-

tal number of octal storage locations it requires (in this case,
372). Following is the number of errors detected, and the
amount of free and used memory pages (statistics provided by

the assembler).
Following the symbol table is the cross reference (CREF) listing.

The

CREF

listing

optional — as

the

assembly

listing — but provides you with useful reference and debugging information, especially if the program is large. The CREF

listing can contain several kinds of tables of reference information, each beginning on a new page. The default tables are the

three shown here.
Every reference in a CREF table shows the page number of the
listing (in the preceding example, all references are on page 1),
followed by the appropriate line number. A number sign following a line number indicates that this line is where a label or
symbol definition occurs.
The first CREF table shown here lists alphabetically all userdefined symbol and label references.
The second CREF table lists alphabetically all macro symbol
references.

(Macro

symbols

are

special

feature

of the

MACRO-11 assembly language; they are described shortly.)
The third CREF table lists alphabetically the codes of the er-

rors detected during assembly. These errors must be corrected

before you can run the program.
Now that you are familiar with the format of an assembly listing, go back to the beginning of the example listing to determine what this program should do.

11-10

Running a MACRO-11 Assembly Language Program

The first two comment lines (preceded by semicolons) indicate
that the program calculates the value of ‘E’, which is the sum of
the inverse of the factorials between 1 and infinity. The algorithm used in this program is somewhat complicated (this was
necessary to keep the program reasonably short). ‘E’ is calculated one digit at a time by using a difference function between
its actual value and the current approximation for each new

digit. The program forms:
1+

+0+.. .+ 1+ 1+ 1/N)/N-1)/(N-2))/.../2)/1)

and is 2.11111... in the inverse factorial base system, which is

the first sum shown in the program listing.
The statements between lines 1 through 7 define initial states
to the assemblers, such as the value of N, and designate the
macros that will be used throughout the program.

Macros, from which the MACRO-11 language processor derives
its name, are a useful feature of the MACRO-11 assembly lan-

guage. You can define as a macro any recurring sequence of

coding instructions. By giving the macro a name, you can thereafter call it from any other part of the program by using a
single language statement.
In addition to the macros you define yourself, the RT-11 system
provides system macros that your programs can access. System
macros are defined in a special system library file called SYSMAC.SML (SML stands

for System Macro Library).

SYS-

MAC.SML is part of the RT-11 operating system and is stored

on the system volume. If you request a system macro from your
source program, the MACRO-11 assembler automatically
searches SYSMAC.SML for the required information.
The system macros defined in SYSMAC.SML are calls to certain services performed by the RT—11 monitor, such as terminal
handling, input and output operations, program termination,
file capabilities, and so on. The portion of the monitor that performs these services, or that is capable of getting the necessary
program code to perform these services, is always in memory
and is therefore called the resident monitor. Thus, whenever
your source program is in memory and is to be executed, the

resident monitor is also there with its services.
You communicate the need for a monitor service by issuing a
programmed request in your source program. A programmed

request consists simply of a macro call to a specific macro defined in SYSMAC.SML. The macro expands into the appropri-

ate machine language code, which, during program execution,
makes a request to the resident monitor to supply the desired
service.

11-11

Running a MACRO-11 Assembly Language Program

You specify all programmed requests that you intend to use in
your source program in an .MCALL statement, like the one

shown at line 3 in the listing. For example, the programmed
request .TTYOUT requests the monitor to print an ASCII char-

acter on the console terminal. During assembly, the .TTYOUT
macro in SYSMAC.SML is expanded into machine language
code. During program execution this code requests the resident
monitor to take the indicated ASCII character and send it to

the console terminal.
Line 12 in the program uses another programmed request,
PRINT, to print a message on the terminal.
Lines 13 through 15 are initialization instructions: they set initial values in three of the special registers. Lines 16 through 22
represent a routine that does a multiplication by 10. Lines 23
and 24 are setup instructions for the division routine of lines 25
through 28. Lines 29 through 35 save the quotient and remain-

der. Lines 36 through 40 print the digits of E. Lines 43 and 44
count the number of digits.
The statements at lines 47 through 49 reserve a buffer area (a
series of locations in memory) to be used by the program and
therefore not to be assigned to other instructions. The statement at line 51 provides the data for printing the ASCII text
message THE VALUE OF E IS: 2.
This program, however, contains errors. The assembler discov-

ered six lines with errors that prevent the program from assembling properly. The assembler flags (points out) errors by printing a code letter in the assembly listing or on the terminal if no

listing is requested.’
The first error occurs at line 12 and is an M error. This means a

label was defined more than once. You can refer to a label any
number of times, but you may define it only once. By looking at
the CREF user symbol table, you can see that the label is defined at line 12 and again at line 47; one of these definitions is
wrong. Examination of the program logic reveals that the definition at line 12 is correct. Before deciding how to change line
47, though, check the other errors to see if one of them indicates
what should be done. In fact, the next error encountered (line
15) shows what is wrong. A U error identifies an undefined
symbol. The label A is referenced in line 15, but is never defined within the program. It should be defined logically at line
47. Therefore, line 47 should be changed to read:
A:

+REPT

N+1

1Refer to the RT—11 System Message Manual for greater detail about any
system messages printed during normal system use.

11-12

Running a MACRO-11 Assembly Language Program

Thus, this one change eliminates three errors flagged by the
assembler; those at lines 12, 15, and 47.

The next error occurs at line 32. Actually, the assembler
flagged two errors here. An A error indicates an addressing
problem and an R error indicates a register error (invalid use of
a register, a special PDP-11 storage feature). If you look at the
language statement in line 32, you can see that the ADD operator is followed by one operand. However, ADD is an instruction
that requires two operands (two values to be added together)
separated by a comma. This statement simply contains a typing
error, which can be corrected by inserting a comma between the
R2 and the —2(R1). Thus, changing the line as follows both
corrects the addressing problem and eliminates the invalid register expression:
ADD

R24+-2(R1)

At line 41 is another undefined symbol, the macro symbol
.TTYON. Since the program designated the macro symbol
TTYOUT in line 3, this error indicates a misspelling. Correct
line 41 to read:
JTTYOUT

Finally, a D error occurs in line 54. This indicates that refer-

ence was made to a symbol that is defined more than once. This
error has already been eliminated as a result of the correction

made to line 47.
Thus, by changing the three lines indicated, you can correct all

the errors flagged during assembly. So the next step is to edit
the appropriate lines in the source program. If necessary, re-

view the editing commands in Chapter 5, and then edit the file
SUM.MAC on your system volume so that the three lines indicated are error-free. Do not rename the file. When you are
ready, reassemble the program, using the MACRO command,
and obtain a new object module and a new listing. This time the
program should assemble without error. If errors occur, you

have not edited the program correctly. Compare listings and try
to correct your errors, or go back to the beginning of this chap-

ter and repeat the demonstration.

The object module produced by the MACRO command may in
itself be incomplete. It may need to be joined with other object
modules or library files to form a complete functioning
program,’ since all required object modules must be joined before the program can work.
!Chapters 12 and 13 give more information on linking files and using library

files, respectively.

11-13

LINKING OBJECT
MODULES
TOGETHER

Running a MACRO-11 Assembly Language Program

Thus, you must next link the SUM object module with any

other object modules it requires. However, the only file used by
this program was the macro library file SYSMAC.SML, and it
was used during assembly. So in this case, you do not need to
join the SUM object module with any other modules.
NOTE

Some other MACRO-11 programs that you write later
may reference system subroutines supplied in the sys-

tem subroutine library, SYSLIB.OBJ. Programs that reference these routines must be linked with the system

subroutine library to satisfy external references. If SYSLIB.OBJ is not present on your system volume, follow

the guidelines in the section of Appendix B entitled Using
the LINK Volume.

Even though SYSLIB is not required for SUM.OBJ, you must
still link the file. The link operation, in addition to joining object modules together, also assigns absolute memory addresses
to the relative addresses calculated by the MACRO-11 assembler. Since the memory addresses of one object module must be
relocated to accommodate addresses used in another object
module, the link operation serves to resolve all address
changes. The result of the link is a memory image load module,
with all module links resolved and all absolute memory addresses and storage information assigned (Figure 11-6). The
memory image module, then, is actually a picture of what computer memory looks like just before program execution.

OTHER

OBJECTS

OBJECT

MODULE

Figure 11-6

LINK

LOAD

MODULE

The Link Operation

To link the object modules, use the LINK command. The system

LINK

prompts you to enter the names of the input object modules to

be linked together. You can omit typing the .OBJ file type in
the command line since the LINK command assumes this file
type for input. After you have entered the input information,
the system begins linking the object module. You do not have to

11-14

Running a MACRO-11 Assembly Language Program

specify an output file, since the system automatically assigns
the file name of the first input file and a file type of .SAV to the

output file.
Long Command Format
+LINKGED
Files?

SUMED

Short Command Format
+LINK

SUMED

Any messages printed inform you of error conditions discovered

during the link operation (for example, if you fail to specify all
the necessary input object modules). However, assuming you
edited your source program correctly and that it assembled
without error, it should also now link without error.
A load module is one that you can run on the system. Unless
your program contains logic errors that prevent it from running

properly (errors that the system cannot always detect), running

the .SAV version of your program should produce the results
you intended. However, if logic errors exist within your program, running the program will produce either erroneous re-

sults or none at all. If this is the case, you must study the
source program, rework it, reedit it, then perform the assembly
and link operations again.

If your MACRO-11 program is error-free, running the .SAV
version should produce the expected results. In this demonstra-

tion, running the SUM.SAV file should produce a value on the
terminal that is the constant E (2 followed by 70 digits).

To execute the MACRO-11 demonstration program, use the
monitor RUN command. You can omit typing the .SAV file
type, since the RUN command assumes this file type. Type the
following, and note the results printed on the terminal:

Long and Short Command Format
+RUN
THE

SUMGED
VALUE

IS:

2.3/606/806237.2301314,065253/130440275535025,71477737352744745405502.,544
+

You can see that something is wrong. Slashes and periods appear in the result, indicating that an error still exists somewhere in the program.
Programming errors, called “bugs,” can be difficult to find and

fix.

A debugging aid called ODT (On-line Debugging Tech-

nique) is described in Chapter 14. You will use it to correct the

program’s final error and to rerun the program. For now, however, the error will be pointed out and explained.

11-15

RUNNING THE
MACRO-11
PROGRAM

Running a MACRO-11 Assembly Language Program

Look at line 40 in the assembly listing. Notice that the instruction in this line converts a digit into the appropriate ASCII code
before printing it on the terminal. To do this, the constant 10 is
added into the value of the digit already stored in memory, and
then the value is converted — via ’0, the ASCII code for
0 — to an ASCII code that can be printed. Unless you ex-

plicitly designate a value as decimal, however, the assembler
assumes all values used in the program are octal. Therefore, it
interprets the constant as 10(octal) or 8(decimal), and adds the

wrong value every time. The conversion consequently causes
the codes of the ASCII characters / and . to be used as results in

some cases. The codes of other digits, while representing numeric values, are also off by two. To correct this error, you must
insert a period after the 10 in line 40. The period instructs the

assembler to accept the constant value 10 as a decimal value.

COMBINING
OPERATIONS

EXECUTE

produce

program

results,

you

first

assembled

the

MACRO-11 source program, SUM.MAC, then linked it, and
finally ran the resulting .SAV file, SUM.SAV. You can combine
these three operations using one monitor command, the EXECUTE command.
NOTE

In order to use the EXECUTE command, the following
files must be present on your system volume:

SUM.MAC
MACRO.SAV
LINK.SAV
SYSLIB.OBJ
The last file, SYSLIB.OBJ, is required only if the
MACRO-11 program you need to link refers to routines
that are contained in the system library. The program

used in this demonstration, SUM.MAC, does not require
SYSLIB.OBJ.
The EXECUTE command instructs the system to select the appropriate language processor, then process, link, and run the
program. There are several ways to establish which language

processor the EXECUTE command invokes. One way is to specify a language-name option, such as /MACRO, which invokes
the MACRO-11 assembler. Another way is to omit the language-name option and explicitly specify the file type for the

source file’ The EXECUTE command then invokes the language processor that corresponds to that file type. Specifying
the file SUM.MAC, for example, invokes the MACRO-11 as-

sembler. A third way to establish the language processor is to
let the system choose a file type of MAC, .DBL, or .FOR for the
source file you name. If, for example, you specify the file SUM,

11-16

Running a MACRO-11 Assembly Language Program

the monitor searches device SY: (your system device) for the
files SUM.MAC, SUM.DBL, and SUM.FOR, in that order. If it
finds a file named SUM.MAC, it invokes the MACRO-11 assembler to process the file. For example, to combine the assemble-link-run operations you performedin this chapter, you use
the following command:
Long Command Format
+» EXECUTE®ED
Files? SUM/LIST/CROSSREFERENCEGE

Short Command Format
+EXECUTE SUM/LIST/CROSSREFERENCEGD
THE

VALUE

IS:

2.5/608/606237,2301314.,06525/130440275535025,71477737352744745405502,544

Notice how you use the /LIST and /CROSSREFERENCE options following the file name to request both an assembly and a
cross-referenced listing.

EXECUTE

Combine the assemble-link-run operations into one command.
EXECUTE file/eMACRO
Combine the process-link-run operations into one command,
and specify the input file to be a MACRO-11 file.
EXECUTE/CROSSREFERENCE
Produce a cross-referenced listing file.

EXECUTE/LIST
Produce a listing file of the source program.
LINK

Link individual object modules together to form a complete
program and produce a load module.

MACRO
Assemble the MACRO-11 source program, and produce an
object module.
MACRO/CROSSREFERENCE
Assemble the MACRO-11 source program, and produce both

an object module and a cross-referenced listing file.

MACRO/LIST
Assemble the MACRO-11 source program, and produce both
a listing on the line printer and an object module.
RUN

Run the indicated load module.

11-17

SUMMARY:
COMMANDS TO
RUN MACRO-11
PROGRAMS

Running a MACRO-11 Assembly Language Program

FILE MAINTENANCE

Before continuing, you should perform the necessary file maintenance operations. Obtain a directory of all files on your system volume that have the name SUM, regardless of file type;
these files were created as a result of the exercises in this chapter.

Long and Short Command Format
,DIRECTORY SUM,*ED
08-Jan-83

SUM
SUM

.BAK
.L8T

3
9

0B-Jan-83
08-Jan-83

0B-Jan-83
t
.0BJ
SUM
S Filess 18 Blocks
480 Free blockKs

SUM
SUM

+SAV
+MAC

2
3

08-Jan-B3
08-Jan-B83

The fact that you have corrected errors in the source file of

SUM.MAC makes the version of that file on your storage volume obsolete. Therefore, transfer the updated copy from your
system volume back to VOL:, replacing the copy of SUM.MAC
on the storage volume with the new version.
Long Command Format
+COPYGED
From? SUM.MACGED
To
? VOL:5UM.MACGD

Short Command Format
\COPY

SUM.MAC

VOL:SUM.MACEED

Similarly, transfer SUM.SAV and SUM.OBJ to your storage
volume. This allows you to rerun the MACRO-11 program
without reassembling and relinking the source.
Long Command Format
+COPYERED
From? SUM.SAV,SUM.0BJGD
To
7 VOL:ED
Files

coried:

DK:SUM,.5AV

YOL:SUM,.8AV

DK:SUM,0BJ

YOL:SUM.0BJ

Short Command Format
+COPY
Files

SUM.SAV,S5UM.DBJ

VOL:ED

copied:

DK:5UM,5AV

VOL:8UM.SAV

DK:SUM.0BJ

VOL:SUM.0BJ

Once you have transferred to your storage volume the files you
want saved, delete from the system volume those you no longer
need (that is, all the SUM files).
o

11-18

Running a MACRO-11 Assembly Language Program

Long Command Format
+DELETE/NDQUERYGED
Files? SUM,»ED

Short Command Format
+DELETE/NOQUERY SUM, @D

Notice that the /NOQUERY option suppresses confirmation

when wildcard construction is used.

Finally, obtain an up-to-date directory listing of your storage
volume so that you can see its current status.

Long and Short Command Formats
,DIRECTORY VOL:@D
08-Jan-83

+5AV
SUM
EXAMP FOR
GRAPH .FOR
GRAPH
SUM

,0BJ
+MAC

4701

Free

Filess

2
2
2
18
3

08-Jan-B3
26-Aud-82
08B-Jan-83
08-Jan-83
08-Jan-83

BlocKs

+0BJ
SUM
EXAMP .MAC
GRAPH .LST
GRAPH
MATCH

,8AV
.BAS

1
3
8
21
3

08-Jan-B83
26-Aug-82
08-Jan-83

08-Jan-83
08-Jan-83

blockKs

This completes the MACRO-11 demonstration. Continue now

to Chapter 12 to learn more about the link operation.

PDP-11 MACRO-11 Language Reference Manual (AA-5075C-TC). Maynard,
Mass.: Digital Equipment Corporation, 1983.
A reference manual for the PDP-11 programmer using the MACRO-11

assembly language.

PDP-11 Peripherals Handbook. Maynard, Mass.: Digital Equipment Corporation, 1981-82.

A technical description of the PDP-11 peripheral devices, including nec-

essary programming information.

PDP-11 Processor Handbook. Maynard, Mass.: Digital Equipment Corporation, 1981.

A technical description of the various PDP-11 processors, including
complete information concerning the PDP-11 instruction set.
PDP-11 Programming Card. Maynard, Mass.: Digital Equipment Corporation, 1975.

A pocket-sized folding card summary of PDP-11 machine instructions
used by the various PDP-11 assembly language processors.
PDP-11 Software Handbook (EB~21759-20). Maynard, Mass.: Digital Equipment Corporation, 1982-83.

A general overview and introduction to available PDP-11 software, operation systems, and language processors.

11-19

REFERENCES

Running a MACRO-11 Assembly Language Program
RT-11 Programmer’s Reference Manual (AA-H378B-TC). Maynard, Mass.:
Digital Equipment Corporation, 1983.
An RT-11 system-specific programming manual for the MACRO-11
programmer.

RT-11 System User’s Guide (AA-5279C-TC). Maynard, Mass.: Digital Equipment Corporation, 1983.
A guide to the use of the RT-11 operating system.

RT-11 System Utilities Manual (AA-M239A-TC). Maynard, Mass.: Digital
Equipment Corporation, 1983.
A guide to the use of the RT-11 System Utilities.

11-20

CHAPTER 12
LINKING OBJECT PROGRAMS
Programs that you write in the MACRO-11 and FORTRAN IV
programming languages require additional processing after
their conversion to object format. Before you can run these programs on the system, you must link them. The link operation:

¢ Joins together the object modules that use a symbol with the
object module that defines it.
¢ Relocates individual object modules as necessary and assigns
absolute (permanent) memory addresses; it can also define an
overlay structure.

® Produces a load module and an optional load map (Figure
12-1).

OBJECT

MODULE(S)

LINK

LOAD

—"1 MODULE

LOAD MAP

(OPTIONAL)

Figure 12-1

Link Functions

Program linking gives you the advantage of a modular approach to programming. You can create an entire program as a
series of smaller, independent subprograms. One of these is
written as the main, or controlling, program, and the rest as
subordinate subprograms and subroutines. You use a language
processor to translate each part of the program into an object
module. Then you use the linker to join all the object modules
together into a complete, functioning unit.
Modular programming makes program creation and debugging
easier. For example, several programmers can simultaneously
work on a single program, each creating a portion of it. The
individual portions, or subprograms, can be processed and
linked with test programs and debugged for logic errors separately. Then all the object modules can be joined together to
form a complete program that can be tested as a whole. If errors
occur at this stage, only those object modules with errors need
be debugged and changed.

12-1

Linking Object Programs

In addition, modular programming allows you to make use of
library files. These are files containing subprograms and subroutines that have been debugged. After you join library files
with your program at link-time, their routines can be used by
your program as needed.

RESOLVING
SYMBOLIC AND
LIBRARY

The linker reads through all the object modules that you indicate as input to the LINK command. It gathers and evaluates

REFERENCES

essor) that is necessary for program linking. For each input

information (provided to the modules by the language procmodule, this information includes the object code, information

needed for relocation, the relative address of the first instruction, the global symbols used, and the absolute length of each
program and program section.
One of the linker’s first functions is to resolve all user-defined
symbolic

references

and

library

references

the

joined

routines. There are two types of user-defined symbols — internal symbols and global symbols.
Internal symbols are limited to the object module in which they
appear; thus, they cannot be referenced from or defined in any
other module. A program containing only internal symbolic
references — like

those

the

demonstration

program

Chapter 11 — is complete in itself and does not need to be
joined with any other object programs at link-time. Thus, in-

ternal symbols are not resolved at link-time because they have

already been resolved by the language processor.
Global symbols, on the other hand, are the key to modular programming. Global symbols provide the communication between

object modules. Such symbols may be symbolic labels to instructions, symbolic labels to data, or symbols that are equated to a

value or constant. Global symbols are defined in one object
module and referenced from other object modules that have

been separately assembled or compiled. Such symbols must be
designated as global in the source code. The following segment

of MACRO-11 assembly language code illustrates the use of
global symbols:

MACRO

VO5.00

SATURDAY

CB-JAN-83

0B8:42

PAGE

SGLOBL

AC/VALUE

MOU

B(RS}I+.RO

SDECLARE
iAS

060000

000002

013500

016701

Q00016

Mav

LOCAL 4RI

GLOBAL

3CLOBAL

AND
A

iHERE

AND

IFROM

OTHER

iBY

SUBROUTINE

FLDCAL

CAN

IHITHIN THIS ®ODULE
Q00000

000007

©Q0000G

00014

013501

000016

005003

000020

000207

000022

000011

VALUE

oodoza

177777

LOCAL:

usR

PC.C

L1019

(RS} +,R1

CLR

RYS

«WORD

WORD

177777

000001

+END

12-2

FGLOBAL

SYMBOL

REFERENCED

GLOBAL

iDEFINEQ

18
17

$CALL

ANGC

PROBABLY

CALL

INTERNAL

IDEFINED

000006

DEFINED

REFERENCED

MODULES.

a8
10

VALUE

SYMBOLS

SYMBOL

DAD
W N -

+MAIN.

ROUTINE

ANOTHER

SYMBOL

THIS

FINTERNAL

SYMBOL

C»

MODULE

VRLUE

FREFERENCE

ONLY

DATA
USED

USED

LOCATION
FOR

DATA

Linking Object Programs

While internal symbolic references, such as LOCAL in the example, can be resolved by the assembler or compiler within the
single program unit, global references, such as C, cannot. They
require other object modules. During translation, the language
processor notes in the object module those symbols that are
global. During linking, the linker keeps track of the global references and definitions found in all the object modules. As
linking proceeds, it makes the appropriate correlations and
modifies instructions or data as necessary. After linking, the
linker prints on the terminal a list of all symbolic references
that were not resolved (undefined globals), either because of a
programming error or because all necessary object modules
were not included in the linking process.
References to library files also involve the use of global symbols. You access the routines in a library by naming a routine
as a global symbol in the source code of your program. You then
link your program with the appropriate library file, and the
linker resolves the library references just as it does any global
symbol. Library usage is discussed in greater detail in Chapter
13.

A second important function of the linker is to “fix” the relative

memory addresses so that they are absolute.' The object module

represents translated source instructions that have been assigned memory addresses relative to a base address of 0.
Look back at the assembly listing in Chapter 11. Note the
second column; these addresses are relative to a base address of
0. Thus the first instruction is assembled at relative address 0,
the second at relative address 6, and so on. A program cannot
actually be stored and run in memory using locations relative
to address 0, however, because system information is already
stored in some of these locations. For example, the RT-11 operating system uses byte addresses 40 through 57 to store information about the program currently executing. In addition, the
RT-11 operating system uses locations in the upper range of
memory for storing the resident monitor. Thus, the linker must
assign memory addresses to your program that are not already
in use or that will not be used during program execution. It
must, therefore, assign absolute memory addresses to the relative addresses assigned by the language processor.
The linker normally starts assigning memory addresses at address 1000, since this begins a large section of free memory
IFORTRAN IV and BASIC-11 users who have not performed the demonstra-

tion in Chapter 11 may wish to read the section in that chapter entitled The
MACRO-11 Language Processor. That section explains the concept of converting and storing instructions in computer memory.

12-3

PROGRAM
RELOCATION
AND ADDRESS
ASSIGNMENT

Linking Object Programs

space. So, to obtain the actual addresses used for program
loading, you must add the relocation constant 1000 to each relative address shown in the assembly listing.

A conflict arises when several individually processed object
modules are linked together. The linker cannot assign memory

addresses starting at 1000 to every module, since address assignments of one would then override those of another. However, part of the information that the language processor calcu-

lates and passes to the linker is the size of each program section
in each module. So the linker simply adds this size into the

relocation constant for each module and assigns higher addresses, appropriately modifying the relative location of all instructions and data as necessary to account for the relocation of
each individual module. Figure 12-2 illustrates the relocation
that

must

occur

together.!

accommodate

object

modules

linked

372 {octal)
PROG

bytes

370

RESERVED

1000

I
SUBONE

42 (octal)
bytes

PROG
1370
1372

SUBONE
1432

1434

SUBTWO

170 {octal)

bytes

SUBTWO

assembied/compiled programs

1624

Relative addresses of three

Absolute addresses of three

linked programs

Figure 12-2

ABSOLUTE AND
RELOCATABLE
PROGRAM SECTIONS

Object Module Relocation

Just as global symbols allow you to create an entire program,
using several individual object modules, program sections allow
you to create an object module as a series of individual sections.

The advantages gained through the sectioning of programs relate primarily to control of memory allocation, program modu1A load map for this relocation example is shown later in the chapter.

124

Linking Object Programs

larity, and more effective partitioning of memory. The linker
processes the program section information in the object modules as directions on how to create the executable program
image.

The FORTRAN IV and MACRO-11 language processors insert
program sectioning information into the object module. The
FORTRAN IV language processor does this automatically when
program sectioning is implied by the source language statements in a user program. For example, FUNCTION, SUBROUTINE, and COMMON statements result in the production of
program section directives. In MACRO-11 assembly language,
you are responsible for explicitly directing the assembler to
output program section information for the linker. You do this
through the .PSECT (or .CSECT and .ASECT) MACRO-11 assembly language statement.

Some of the basic functions associated with program sections
are:

Instructions or data can be placed in absolute locations in
memory. The named absolute program section (. ABS.) allows you to instruct the linker as to exactly where to place
program code or data. Declaring a section as part of the
absolute program section instructs the assembler or compiler to use the internal value of the program counter as the
physical memory address to be assigned after linking. This
section is processed relative to absolute memory address 0
and is not relocated at link time.

Named relocatable program sections are used to group data
or instructions into logical portions of memory. The FORTRAN IV COMMON statement invokes this construct to
allow access to named data areas from many separate
routines. Declaring a section as part of a named relocatable
program section causes the section to be processed at relocatable address 0. Such sections are relocated by the linker.

If you do not care about having exact control over where a
portion (section) of a program will be placed in memory, use
the blank program section — a special program section that
the linker treats as relocatable. The linker decides where to
place this program section in the loadable memory image.
The blank program section is the default for a MACRO-11
source program and remains in effect until an explicit program section is identified (the program example in Chapter
11 used the blank program section).

A program section can be identified as an instruction section. The linker, using this information, can provide automatic loading of declared overlay code when needed by the
executing program (this will be discussed in more detail).

12-5

Linking Object Programs

The language processor, then, actually maintains several program counters — one for the absolute program section, one for

the unnamed relocatable program section, and as many as
needed (maximum is 254) for named relocatable program sections. The assembled example that follows helps explain this
concept.
+MAIN,

NMACRO

V05.00

SATURDAY

OB-JAN-B3

08:04

PAGE

iUNNAMED

RELDCATABLE

PROGRAM

iSECYION

{BY

F(".PSECT"

000000

005000

000002

012701

000006

0B2100

000010

022701

000014

100374

BTARY:

000034
LOOP:

naov

#BEG /R1

ADD

000044

SBEG+10,RI

BPL

Loop

nov

*2000.A00R

CLR

«FSECT

000018

012767

000024

605003

000000

CLEAR

INAMED

000000

012703

000100

nov

#100+R3

FSECTION

000004

012701

©o000aa

noy

#RADDR R}

000010

005021

CLR

{(RL)+

000012

005303

DEC

000014

001278

BNE

AGRIN

000000

60004z

000020

AGAIN:

+ASECTY
000042

001000

+®ORD

1000

000026

+PBECT

000026

008267

000032

000000

000034

000001

000042

000004

000044

000000

000012

INC

PROGRAM
(VIA

VALUE

(VIA

“.PSECT

NAME")

SECTION

“.ABECT")

1000

PROUGRAM

DECLARED

MILL

ABSOLUTE

iWHEN

THE

3IBACK

UNNAMED

iPROGRAM

SECTION

PROCRANM

MEMORY

LOCATIN

EXECHTED

RELOCATABLE

HALT
000002

000002

BEG:

<WORD

ADDR:
SNOTE

SCONTIGUOUSLY

FIN

0006001

1:243.4

+HORD

ADDR

IDECLARED

ISTORED

RELOCATABLE

FABSOLUTE
3THE

DEFALLT)

ASSUMED}

(R1)}+ RO

cne

002000

CLR

DECLARED

THAT

THE

YOU

CAN

SOURCE

WRITE

MEMDRY
.,

PROGRAM

LANGUAGE

BUT

(1.E,,»

STATEMENTS

MOY

THE

THAT

NEEESSARILY

CODE

LINES

+END

WILL

DCCUR
1-10

LOADED

CONTIGUOUSLY
AND

22-29)

Since the system does not know at assembly (or compile) time
into which actual memory locations each relocatable section
goes, all references among sections (see line 18) are relative to

the base of the section. This information is then passed to the

linker so that it can make the appropriate adjustments at link-

time.

The Overlay Feature

The RT-11 linker is also capable of handling the special relocation and address assignments that are required whenever you

indicate that an overlay structure is needed. An overlay structure is necessary when you write a program that is too large to

fit in the available memory of your system. You write the program in discrete parts (some programming restrictions must be
observed) so that your program can subsequently be executed in
parts. Some of these parts, or segments, are allowed to share
memory

with

other

segments,

thus

reducing

the

overall

memory requirements of the program. One segment of the pro-

gram is called the root segment and must remain in memory at
all times. The root segment contains the necessary information
for use by the other segments of the program, called overlay
segments. Overlay segments are stored on storage volumes and
brought into memory as needed. The purpose of the overlay
structure is for parts of the program to share the available
memory in such a way that when one part is complete, it is
overlaid (and therefore erased) by another.
You indicate how to plan to overlay your program by using the

/PROMPT option in the LINK command line. The linker then

12-6

Linking Object Programs

creates a load module that contains the necessary information
for loading the appropriate segments as needed during execution. The RT-11 System Ultilities Manual explains the overlay
feature in more detail. You need not specify an overlay structure for the examples demonstrated in this chapter.

The load module is the result of the linking processes described
so far: joining object modules, resolving symbolic and library
references, relocating object modules, assigning absolute addresses, and creating an overlay structure if required. The load
map is essentially a synopsis of the load module — that is, what
memory looks like when the program is loaded and ready to be

PRODUCING
A LOAD MODULE
AND A LOAD MAP

executed.

In Chapters 9 and 11, you produced load modules, but you did
not request load maps. You obtain a load map by using the
/MAP option with the LINK (or EXECUTE) command. At this
time, relink the FORTRAN IV or MACRO-11 object module
that you stored on VOL: and use the /MAP option to produce a

load map.! The load map is created as a file on the system
volume, which is the default storage volume for input/output

operations. The load map has the name of the first input
module and a file type of MAP.

Long Command Format
MACRO-11 object module:
+ L INKGED

Files? VOL:SUM/MAPGRD

FORTRAN IV object module, if FORLIB is not included in
SYSLIB:
+LINKG@ED
Files? SYSLIB.FORLIB VOL:GRAPH/MAPGEED

‘FORTRAN IV object module, if FORLIB is included in SYSLIB:
+LINKGEED
Files? VOL:GRAPH/MAPEED

Short Command Format
MACRO-11 object module:
+LINK VOL:SUM/MAPED

1FORTRAN IV users who followed the special instructions in Appendix B for
loading the LINK volume should check that this volume is loaded in device
unit 0. FORTRAN IV users who have a special FORTRAN IV language volume, but not a LINK volume, should make sure that the FORTRAN IV volume is now loaded in device unit 0.

12-7

/MAP

Linking Object Programs

FORTRAN IV object module, if FORLIB is not included in
SYSLIB:
+LINK

SYSLIB,FORLIB,VOL:GRAPH/MAPEED

FORTRAN IV object module, if FORLIB is included in SYSLIB:
+LINK

VOL:GRAPH/MAPGRED

Now list the .MAP file on either the line printer or terminal,

choosing the appropriate command:

Long Command Format
(Line printer)

(Terminal)

MACRO-11 object module:
+PRINTED

Files?

» TYPEGED

SUM.MAPED

Files?

—

SUM.MAPED

FORTRAN IV object module:
+PRINTGEED

+ TYPEGRED

Files?

GRAPH.MAPED

Short Command Format
e’

(Line printer)

(Terminal)

MACRO-11 object module:
+PRINT

SUM.MAPGD

+TYPE

SUM.MAPGE)

+TYPE

GRAPH.MAPGEE

FORTRAN IV object module:
+PRINT

GRAPH.MAPGD

For your convenience, both maps are provided here. In addition,
a load map of the relocation example used in Figure 12-2 is also
provided.
RT-11

LINK

SUM

+ 8AV

Section
«

ARS,

)
Transfer

+«

ABS.,

toad Mar

Saturdaw 08-Jan-83

Title!

SUM.MA

Ident!

Addr

Size

Global

Value

Global

000000

001000

204,

words

(RW»IsGBL,ARS,OVUR)

001000 000372

125,

words

(RWrsI/LCLsRELCON)

address

RT~11 LINK
SYSLIR,SAV
Section

408,00

001000,

V08.00
Titlet

Addr

Size

000000

001000

12-8

High

limit

Load Mar
Ident!
MAIN.,

001370

Value

380,

Global

Value

Pade

Value

words

Saturdaw 08-Jan-83
FORVO2
Global

10100

10111

Global

Pade

Global

Value

236,
$USRSW

words
000000

VIR

000000

$NLCHN

000004

$8YSV$s

000012

$WASIZ

000152

$LRECL

000210

$TRACE

004737

(RWsIsGBLARSyQUR)
$RF2A1
000000
$HRIWR

Value

000000
e

Linking Object Programs
[228-1 39

RT-11

001000 017722 = 4073,

LINK

SYSLIB.SAV

V08.00
Title!

words

(RWsIs{.CLYRELsCON)

$$0TSI

001000

S$CUTIF

001000

$CVUTIC

001014

$CVUTID

001014

(CCIS

001026

CDI$

001026

$IC

001024

$ID

001026

CFI¢

001042

$IR

001042

EXF

0011246

ADFSIS

001466

ADF$PS

001474

SUF$FS

001500

SUF$MS

001504

ADF$MS

0015186

SUF$IS

001526

$ADDF

001534

$SUBF

001550

SUF$SS

001542

$SER

001562

ARF$58

00135446

$ADR

001566

ALE

001602

DIFSFS

002226

DIFSMS

002232

DIF$IS

002242

$DIVF

002250

DIF$SS

002262

$DOVR

002262

MUF$FS
SMULF

002550
002572

MUF$SMS
MUF$SS

002554
002604

MUF$IS
$MLR

002564
0024604

$0TI

003142

$3%0TI

003144

$SETOF

003354

$$SET

005026

SQRT

005322

STR$L

Q05516

STK¢1

005522

STK$F

0055246

IOR$

Q05536

ANDS

005542

EQVS

005550

XOR$

005552

NMI$iM
BEQS

000546
005612

NMIS1II
BGTS

005600
005620

ELES$
ERGE$

005610
Q05622

BRAS

005424

BNES

0054630

BLTS

Q05632

CAls

005642

CALS

005650

END$

005700

ERR$

005712

$END

005724

$ERR

Q05742

SOPNER

005764

$CHKER

004022

$I0EXI

006046

$EOL

006114

EOLS

006116

EXIT

006232

MOF$SS

0062346

MOFSMS

006250

MOF$FS

0046262

MOF$SM

004266

MOF$SF

006276

MOF$MM

006302

MOF$MA

006314

MOF$SMF

006322

MOFSFM

006330

MOF$FPA

006334

MOF$FF

006340

HMOF$SRS

006344

MOF$RM
NGD$S

006352
006372

MOF$RA
NGF$S

006342
006372

MOFSRF
NGDSM

006386
0046404

NGF $M

006404

NGDOSF

006420

NGFS$F

006420

NGD$A
ADI$SA

006424
006434

NGF$A
ADISSM

006424
006440

ALI$SS
ADRISIS

006430
0046444

ADISIA

006450

ADISIM

006454

ADISMS

006440

ADI$MA

008464

ADISMM

008470

CMI$SS

006474

CMI$SI
CHMI$II

006500
006514

CMI$SM
CMI$IM

008504
004520

CMI$IS
CMISMS

006510
006524

CMISMI
$IFW
MOI$SRS

006530
006544
006656

CMISMM
$$IFW
MOLSRS

006534
006550
006656

IFW$
IFWSS
HMOISRM

006540
Q06606
006662

MOISRF
MOL$SS

006866
006674

HMHOISRA
MOISSM

006670
004700

MOISSS
MOISSA

0084674
006704

MOIS$IS

0046710

MOL$IS

006710

RELS

006710

HOISIM
MOISMM

006714
006730

MOISIA
MOISMA

004720
0046734

MOISMS
MOIS0S

008724
006740

MOISOM

004744

MOISOA

006750

MOI$1S

006754

MOI$1M

006762

HOIS1A

006770

ICISS

006776

ICIsH
DCIsS

007002
007014

ICISP
DCISM

007006
007020

ICISA
DCISF

007010
007024

DCISA

007026

IDINT

007032

INT

007032

MOISIF

007060

MOISSP

007042

MOISFF

007070

Load

Mar

Saturdaw 08-Jan-83

10:11

Fade

JHMAIN.

Ident!

FORVO2

MOISMP
MOISPA
ISNS

007074
007120
007144

MOISFS
MOISOP
SISNTR

007104
007126
007150

MOISPFM
MOI$iP
LSNS$

007112
007134
007164

SLSNTR
SUISSM
SUIS$IM

007170
007334
007350

SUI$SS
SUISIS
SUISMS

007324
007340
007354

SUIs$SA
SUISIA
SUISMA

007330
007344
007360

SUIsMM
MOLS$MS
MOL$SF

007364
007400
007420

MOLSSM
MOLSMM
MOLSFF

007370
007410
007424

MOL$SA
MOLSMA
MOLSMF

007374
007414
007432

HMOLSFM

007442

HMOLS$FS

007450

MOLSPA

007454

MOLSIM
LLES

007462
007506

MOLSIA
LEQS

007470
007510

MOL$IF
LGTS

007476
007516

LGES

007520

LNES

007530

LLTS

007532

TSL$S

0075386

TSLM

007542

TSL$I1

007546

TSLSP

007554

MAXO

007562

MINO

007606

RETSL

007632

RETSF

007636

RET$I

007644

RETS
TVLS

0076446
010024

$OTIS
$TUL

007702
010024

$$0TIS
TUF$

007704
010032

$TVUF
TGRS
$TUP

010032
010046

TVD$
$TVUR

010040
0100446

$TVD
TUFPS$

010040
010054

010054

TVI$

010042

$TVI

Q10062

SALSIM

010216

SAL$SSM

010220

SVLSIM

0103224

SUL$SM
SALS$IF

010226
010244

SALs$MM
SALSSF

010234
010244

SULSMM
SULSIF

010240
010252

SVULS$SF

010254

SALSHP

0102462

SUVLSMF

0102646

$CUTFB

010272

$CVUTFI

010272

$CYTCB

$CVUTCI

010306

$CVUTDE

010306

$CVYTDI

010306

cIics

010320

CIDs

010320

CLCs

010320

CLD$

010320

CIFs

010330

CLFs

010330

$RI

010330

CILs

010442

CLIs

0104446

SINITI

010450

SCLOSE

010566

$ERRTE

011344

$ERRS

011451

S$FCHNL

015212

12-9

010306

Linking Object Programs
$FI0

016054

$$FI0

0160460

$FUTRE

017224

$FUTBL.

0178532

$GETBL

017742

$EOFIL

020124

$EOF2

020142

SAVRGS

0201462

THRID$

020340

020342

STF$

020350

4STF

020350

020354

$EXIT

020374

$UWAIT

020520

SURINT
22,

020562
SDUMFL
020574
words (RWsDyGELYREL yQUR)

0TS ¢F

020722

Q00054

SYS$I

020776

000244

LEN

020776

USER$I

021242

000000

words

(RWsI
LCL RELyCON)

$CODE

021242

0013146

359.

words

(RWsT«LCL,REL,CONY

0TS$0

022560

001036

$$0TSC

021242

$8TES
FOOs

271,

words

SYS$0
sDATAF

023616
0234616

000000
0001046

=
=

0TSsn

023724

000006

82,

words

023732 000002 =

REFEAT

RELCON)
021014

FUN

022120

SCOFY

FPUTSTR

022560

0,
35,

words
words

(RWsI+LCL REL,CON)
(RUsDeLCL
REL CON)

$OFEN

words

(RW-DyLCL,REL
yCON)

023730

words

$A0TS

Q23732

words

(RWsDyLCL,RELyCON)

023734

000004

$SYSLE

023734

$DATA

023740

000536

175,

words

(RWsIyLCLyREL yCON)

USERSD

024476

000000

words

(RWsDeLCLREL,CTOND

«$4%%,

0244746

000000

words

(RWsDyGRLyREL yOVR)

LINK

SYSLIB.S5AV

Transfer

RT-11
TEST

ABS.,

Load

Title:

address

LINK
.54V

Section

v08,00

Mas

MAIN.,

021242y

VO08.00
Title:

Hiagh

Transfer

(RUsDLCLRELsCON)
$LOCK

Ident!

limit

023734

08-Jarn-83

024474

%5278,

FORVO2

$CRASH

Saturdaw

Load Mar
MAIN.
Ident:

Saturday

Global

Value

Global

Sire

000000

001000

2564.

words

(RWy I»GELARS»OVUR)

001000

000626

203,

words

(RWsIsLCLsRELYCON)

address

001000,

High

001000

limit

Vaslue

SUBONE

001624

10111

023737

Fadge

Fade

words

08-Jan-83

Addr

FROG

022264

022560

SYS$S

RT-11

021146

(RWsIyLCLYyRELyCON)

$30TSO

NHCLN$

aT15%S

(RWsI.LCL

1016

Glohal

001372

SUBTWO

458,

worids

Value

001434

The second line has the name and file type of the load module

created. Next, the absolute section and each named and unnamed section are listed under the SECTION column. To the
right are abbreviated codes designating whether the section
contains Instructions or Data, is Read/Write or Read Only, is a
Local or Global section, is Relocatable or Absolute, is Concatenated or Overlaid. Below this falls a listing of all the global
symbols (GLOBAL) and their values (VALUE). Finally, at the
end of the map is the transfer address where the program actually starts when executed, followed by the high limit — the
total number of bytes used by all the individual program sections.

Look first at the MACRO-11 load map. The default absolute
section starts at absolute location 0; its size is 1000 bytes. Thus,

it extends from absolute memory location 0 through absolute
memory location 777. The unnamed program section (there
were no named program sections in this program) starts at absolute 1000; its size is 372 bytes. Thus it extends from absolute

location 1000 to absolute location 1370. The high limit of this
program (total bytes) is therefore 1370. Since this program is
not linked to any other object modules, there are no global sym-

bols and the rest of the map is blank.
Look now at the FORTRAN IV load map, remembering that it
reflects the appropriate expansions into machine language code
provided by the FORTRAN IV compiler. Again, the absolute

12-10

Linking Object Programs

section extends from absolute 0 through absolute 777. Globals
listed in the absolute section show the global variable names
that the program uses as constants throughout the program.
The unnamed relocatable program section begins at absolute
location 1000. Some of the named relocatable sections that are
declared are OTS$P, SYS$I, and $CODE. Global symbols and
their respective addresses appear to the right of all sections.
The total number of bytes used is 24474, or 5278(decimal)
words.
The third load map is for the program illustrated in Figure
12-2. First, the map shows the absolute program section, labeled .ABS. It extends from location 0 through location 777.
Next, the map shows the unnamed program section, which begins at location 1000 and is 1624 bytes long. This program section consists of a main program, called PROG, and the subroutines SUBONE and SUBTWO that were linked with PROG.
Look again at Figure 12-2 to see how these routines fit into
memory. The transfer, or starting, address is 1000, and the
total number of bytes the program occupies is 1624, or 458(decimal) words.

Load maps are most helpful when used in debugging to locate
and correct assembly language programming errors. Load maps
are not generally obtained or used for FORTRAN IV programs,
except to determine program size. In Chapter 14 you will see
how a load map is used to debug the one remaining error in the
MACRO-11 demonstration program.

LINK

Link individual object modules together to form a complete

program and to produce a load module.

SUMMARY:
COMMANDS
FOR LINKING
PROGRAMS

LINK/MAP

Link individual object modules, and produce a load map
showing all address assignments made during linking.
NOTE

FORTRAN |V users who followed the special instructions in Appendix B to load the language or LINK volume
should now stop the system, unioad that volume, load
the main system volume, and rebootstrap the system
before going on to Chapter 13.

RT-11 System Utilities Manual (AA-M239A~TC). Maynard, Mass.: Digital
Equipment Corporation, 1983.

A guide to the use of the RT-11 system utilities.

12-11

REFERENCE

CHAPTER 13

CONSTRUCTING LIBRARY FILES
A library is a specially constructed file consisting of one or
more programming routines. Generally, these routines provide

services that you are apt to need repeatedly, or services that are
related and so have been gathered together for ease in use and
storage. You use the routines in a library by joining the library
file with your source program. Usually this occurs at link-time:
but in the case of assembly language programs, it may also
occur at assembly-time.
The RT-11 operating system provides several library files;

SYSLIB and VTLIB for example. These libraries supply the

monitor services, input and output routines, conversion
routines, and other programming services that user programs
may need. You can create other library files yourself. Thus you
can construct libraries that contain routines specific to your
programming needs or to the combined needs of those using
your RT-11 system.

There are two kinds of library files — macro libraries and object libraries.

KINDS OF
LIBRARY FILES

Macro libraries, such as SYSMAC.SML, are used by
MACRO-11 source programs at assembly-time and consist entirely of macros. A macro is described in Chapter 11 as a recurring sequence of coding instructions, which, when defined in a
.MACRO statement, can then be called and used anywhere in
your program. A macro library is merely several macro definitions gathered together into a single file. To use the macros in a
macro library, you simply name those macros you plan to use in
a .MCALL statement. When the assembler encounters the
.MCALL statement during processing, it searches the appropriate macro library (SYSMAC.SML is default) for the definitions.
It takes the definitions from the library and inserts them in a
special table called the macro symbol table where they become
available for use during assembly.

Macro Libraries

Object libraries, such as SYSLIB, are used by assembled

Object Libraries

MACRO-11 source programs and/or by compiled FORTRAN IV

source programs at link-time. These libraries consist of object
modules that contain global routines; such routines have been
defined with global entry points and then named as global symbols in the source program. During the link operation, the
linker searches the object libraries to determine if they provide

13-1

Constructing Library Files

definitions for any undefined globals. If the linker finds defini-

tions, it takes those object modules containing the definition
from the library and includes them in the link.
A special table, called the global symbol table, lists each global
in a given object library. You can print this list on the terminal

or the line printer and thus keep track of an object library’s

current contents.

CREATING AND
MAINTAINING

A LIBRARY FILE

You create a library file by combining several macro routines,
or several object modules, into a single larger file using the

monitor LIBRARY command.

To build a macro library, first use the editor to create an ASCII

text file that contains all the macro definitions. Then process

this file using the LIBRARY command in combination with its
/MACRO option. To update a macro library (that is, to add or

delete macro definitions), simply edit the ASCII text file and
then reprocess the file with the LIBRARY command.

To build an object library, use the editor to create an ASCII text
file. The file contains the routines and functions written as
complete program segments in either the MACRO-11 assembly

language or the FORTRAN IV programming language. Then

process the file, producing an object module. Next, use the LI-

BRARY command in combination with its /CREATE option.
Once the library file is created, update it (add and delete
routines) by means of various other options to the LIBRARY

command.

In the following exercises, you create an object library that con-

tains three input object modules. The routines in two of these
modules can be used by both MACRO-11 and FORTRAN IV

programs; the routine in the third module can be used only by
FORTRAN 1V programs.

To build the library file, first use the editor to create the three

ASCII text files. Then convert the ASCII text files to object
format. Finally, process the object files with the LIBRARY com-

mand. Once you create the library files, use LIBRARY command operations and options to add and delete modules and
globals and to obtain a listing of the library file contents.

Creating Object
Library Input Files

The first step in building an object library is to prepare the
source code of the routines and functions that you choose to
include in the library. Use the editor to create the following
three text files, calling them FIRST.MAC, SECOND.MAC, and
THIRD.FOR, respectively. FORTRAN IV users should create
all three files; MACRO-11 users (who do not use FORTRAN
IV) should create only the first two files.

13-2

Constructing Library Files

FIRST.MAC
«TITLE

comMp

+MCALL

+PRINT

I=LEN(A)}

LEN:

TST

(R3)+

iGKIP

MOV

BRS5,RO

SGET

STRING

TSTB

(RO} +

§FIND

END

BNE

iLOOP

UNTIL

DEC

iBACK

suB

EBRS RO

SCALC

RTS

+GLOBL

1%:

PRINT:

LEN

CALL

PRINTC(ISTRNG)

+GLOBL

MOV
+«PRINT

Z2(R3) sRO

RTS

ARGS
POINTER

STRING
NULL

BYTE

CHARS

$ADDR

STRING

ISTRNG

3 PRINT
$AND

RETURN

+END

SECOND.MAC
+TITLE

ITTOUR

I=ITTOUR(CICHAR)

I=0

CHARACTER
RING

+MCALL

+TTOUTR

+GLOBL

ITTOUR

ITTOUR:MOUB

BZ(RS5) RO

+TTOUTR

HAS

BUFFER

BEEN

OUTPUT

FULL

iGET CHARACTER
i.TTOUTR

BIC

ADC

RTS

sCLEAR

ERROR

FLAG

iRETURN

+END

THIRD.FOR
C

CALL PUTSTR(LUNAREA,CC)
SUBROUTINE PUTSTR(LUNAREA,CC)
LOGICAL#*1 AREA(230)
.CC
IF(CC) GOTO 1
WRITE

(LUN.99)(AREA(I) »I=1,LEN(AREA))

RETURN

WRITE

FORMAT (250A1)

(LUN,S9)CC,(AREA(I) »I=1+LENC(AREA))

END

The routines in these files are representative of the kinds of
services generally provided in a library file. They are, in fact,
taken from the RT-11 system subroutine library, SYSLIB.

13-3

Constructing Library Files

FIRST.MAC contains two global routines, LEN and PRINT.

The LEN routine returns the number of characters in a string.

PRINT outputs an ASCII string terminated with a zero byte to
the terminal (it is the FORTRAN IV equivalent of the system
macro .PRINT, used in the demonstration program in Chapter

11). SECOND.MAC contains one global routine, ITTOUR,

which

transfers

character

the

console

terminal.

THIRD.FOR also contains one global routine, PUTSTR. This

routine can be used only by FORTRAN IV programs and writes

a variable-length character string on a specified FORTRAN IV
logical unit (see GRAPH example).

Once you create these text files, the next step is to convert them
from ASCII format to object format. Assemble or compile the
text files as appropriate, first assembling FIRST.MAC and ob-

taining an object module (a listing is not necessary). FORTRAN

IV users who are not familiar with the assembly process simply
type the MACRO commands as shown.
Long Command Format
+ MACROGED
Files? FIRSTEED

Short Command Format
.MACRO

FIRST®D
e

The command creates an object module called FIRST.OBJ on
the system volume. If errors occur, the assembler prints a message on the terminal, indicating the number of errors encountered during assembly. No errors should occur.

In the same way, assemble SECOND.MAC. Again, no errors

should occur.

Long Command Format
+ MACROGED
Files? SECONDGED

Short Command Format
+MACRO

SECONDGE

If any errors occur during the assembly operations, you have

typed the source files incorrectly. Find and correct the typing

errors, and reassemble.

If you are a FORTRAN IV user,
THIRD.FOR.

13-4

continue by compiling

Constructing Library Files

NOTE

Chapter 9 you

needed to

load the special

FORTRAN/BASIC language volume, you must again

load that volume before you can compile THIRD.FOR.
Read Appendix B, Substituting Volumes During Operations, before continuing.
Long Command Format
+FORTRANGD
Files? THIRDGD
PUTSTR

Short Command Format
+FORTRAN

THIRDGD

PUTSTR

Notice that the compiler prints the name of the global
(PUTSTR) generated. If any errors occur during the compile
operation, you have typed the source file incorrectly. Find and
correct the typing errrors, and recompile.
Once you have produced the object modules, you are ready to
build the object library file.
Use the LIBRARY command in combination with its /CREATE
option to construct a library file. You must indicate in the command the name of the library file and the names of the input

Building the

Object Library

object modules. Call the library file LIBRA and specify as input
the two object modules, FIRST and SECOND. The LIBRARY
command assumes that the input modules have the .OBJ file
type (unless you indicate otherwise) and automatically assigns
.OBJ to the library file.
Long Command Format
LIBRARY/

+LIBRARY/CREATEGD

CREATE

Library? LIBRAGD
Files
? FIRST,SECONDGD

Short Command Format
LLIBRARY/CREATE LIBRA

FIRST ,SECONDED

Once the CREATE operation is complete, obtain a listing of the
library file’s contents, using the LIBRARY command with its
LIST operation. The line printer is the assumed output device
for the list file, although you may indicate a different output
device by adding the two-letter device mnemonic to the LIST
option that follows.

13-5

Constructing Library Files

Long Command Format

LIBRARY/LIST

(Line printer)

(Terminal)

+LIBRARY/LISTED

Library?

+LIBRARY/LIST:TT
6D
:

LIBRAGD

Library?

LIBRAGD

Short Command Format

(Line printer)

(Terminal)

+LIBRARY/LIST

LIBRAGD

+LIBRARY/LIST:TT:

LIBRAGD

The listing produced shows the library file’s current contents.

This library has three entry points: LEN and PRINT in the first

module, and ITTOUR in the second module.
RT-11

LIBRARIAN

V03,00

DK:LIBRA.OBJ

MODULE

SAT

B8-JAN-B83

11:03:28

SAT

B8-JAN-B83

10:59:43

GLOBALS

LEN

GLOBALS

ITTOUR

Updating the

Object Library

LIBRARY/
INSERT

Once you have created an object library, you use various LIBRARY command operations to update and maintain it by
adding and deleting modules and globals.
If you created the THIRD.OBJ object module, you can add it to
the library file using the INSERT option. If you did not create

this module, read through this section anyway; the command
steps apply to any object module you wish to insert.

Long Command Format
+LIBRARY/INSERTGEED

Librarvy?
Files
7

LIBRAGD
THIRDGE

Short Command Format
+LIBRARY/INSERT

LIBRA

THIRDGD

This operation inserts the object module contained in the file
THIRD.OBJ, including all its globals, into the library file
LIBRA. Obtain a listing of the library contents, using the LIST
option, to verify that the new globals have been added. The
listing should look like this:
RT-11

LIBRARIAN

V05.00

DK:LIBRA.OBJ

MODULE

SAT

B8-JAN-B83

11:05:1

SAT

B8-JAN-83

11:04:21

GLOBALS

LEN

ITTOUR
PUTSTR

13-6

GLOBALS

Constructing Library Files

This listing shows the complete library file containing the globals from all three modules.

You can remove individual globals by using the REMOVE option. For example, to remove the global ITTOUR, type:

Long Command Format

LIBRARY/
REMOVE

. LIBRARY/REMOVEGE

Library? LIBRAGD

Global? ITTOURGH
Global?
@D

Short Command Format
+LIBRARY/REMOVE LIBRAGD

Global?

ITTOURGED

Global?@D

The library file’s contents now look like this:
RT-11 LIBRARIAN
DK:LIBRA.0BJ
MODULE

V05,00

SAT
SAT

B-JAN-B3
B-JAN-B3

GLOBALS

LEN

11:10:22
11:10:05
GLOBALS

PUTSTR

These are some of the library maintenance operations that you
can perform by using the LIBRARY command. Other library
operations are available and are explained in the RT-11
System Utilities Manual.

SUMMARY:

LIBRARY/MACRO

Create a macro library.

COMMANDS FOR

LIBRARY/CREATE
Create an object library.

LIBRARY FILES

MAINTAINING

LIBRARY/INSERT
Insert object modules into the object library.
LIBRARY/LISTI:filespec]
List the current contents of an object library on the line
printer; [:filespec] is an optional output file and/or device.

LIBRARY/REMOVE

Remove globals from the object library.

Since all the object modules used in this chapter already exist
as modules within the provided system library SYSLIB, there is

no need to save them or the LIBRA library file. You can delete
these object modules and their source files from your system

13-7

FILE MAINTENANCE

Constructing Library Files

volume by using the DELETE command as follows (exclude
THIRD.* from the command line if you did not create this file):
Long Command Format
+DELETE/NOQUERYED
Files?

FIRST.%*,SECOND,*,THIRD.* ,LIBRA.0BJED

Short Command Format
+DELETE/NOQUERY

FIRST.*,8ECOND.#,THIRD.*,LIBRA.OBJED

FORTRAN IV users who performed the special instructions
given in Appendix B should also delete the THIRD files from

the storage volume.

Long Command Format
+DELETE/NOQUERYGE
Files?

VUDL:THIRD.*RED

Short Command Format
+DELETE/NOOUERY

REFERENCE

VYOL:THIRD
. *@D

RT-11 System Utilities Manual (AA-M239A~TC). Maynard, Mass.: Digital
Equipment Corporation, 1983.
A guide to the use of the RT-11 system utilities.

—

13-8

CHAPTER 14
DEBUGGING A USER PROGRAM
Debugging is the process of finding and fixing the programming
errors that almost every user program initially contains. From
your experience in Chapters 9, 10, and 11, you already know

about some of the kinds of programming errors that can prevent a program from working properly when you run it on the
system.

Frequently, debugging a program requires more time and persistence than writing the program code requires. Therefore, you
should anticipate the debugging process throughout the entire
program development cycle. That is, you should follow some
common programming practices that help you first to make as

few programming errors as possible. When errors become apparent during the various phases of development, correct them
immediately. Test the validity of any algorithms used within
your program. Finally, even though the program appears to be
working properly, check it thoroughly with test data.

You can take several steps to decrease the likelihood of intro-

AVOIDING

ducing errors into your program and to make debugging easier.

PROGRAMMING

First, always use a high-level language if one will suit your
programming needs. High-level language programs tend to use
fewer statements. English-like words and phrases in the lan-

ERRORS

guage statements make the program logic easier to follow.
Design the program. The technique of flowcharting the program and then correlating it with the program coding simplifies tracking the program logic and module interrelationships.
Use modular programming. Create the program as a series of

smaller, self-contained subprograms. Debug the program in
parts.

For frequently used functions, maximize the use of subroutines,

subprograms, and — in the case of assembly language programs — macros. These help to structure the program and
make it easier to alter or to add features that may be required
in the future.
Make use of any software provided by the system, such as library routines and functions. System software has already been

debugged and can save you the trouble of re-creating the services.

Make the general flow of a program proceed down the page.
Avoid nonstructured branching and convoluted logic, as these

14-1

Debugging a User Program

tend to produce programs that are difficult to debug. Finally,
use comments liberally throughout the program to show what
individual statements or groups of statements do. Use spaces
and tabs in the program code to make it easier to read.

Following these preventative steps eliminates many common
programming errors and helps to create a programming style.

However, even the most careful programmer may overlook a
small detail: a typing error during program creation, an unde-

fined label in the code, or some other programming bug. When

something is overlooked, debugging becomes necessary.

WHEN
PROGRAMMING
ERRORS OCCUR

There are three general types of programming errors — syntax,
clerical, and logical.
Syntax errors are errors in the physical coding, such as omit-

ting necessary portions of the statement (delimiters for example), reversing the order of information within the statement, or misspelling keywords or instructions.

Clerical errors are non-syntax errors in the physical coding,
such as mistyped letters or digits in data. Clerical errors may

result in valid statements that do not reflect correct programming logic.

Logical errors are errors made in program development.
The translating program (compiler/assembler/interpreter) gen-

erally catches syntax errors and flags them as such in the pro-

gram listing or on the terminal. On the other hand, you must
locate clerical and logical errors by reexamining the program
code and logic, using one or more debugging techniques.
Some debugging techniques involve insertion of special debugging code within the program. For example, one way to locate

logical errors is to write out intermediate results of a program.
You can insert WRITE or PRINT statements at strategic points

in the program logic to show the intermediate state of values
being calculated. When debugging is complete, you can remove
these statements or change them to comments.

You may also find it useful to write a special debugging subroutine that writes out values, particularly if the same variables

must be examined in several places or many times.

Another method for finding logic errors — unit testing — is to
break the program into smaller parts and test each part separately with artificial data. After you test all parts individually,
you can test routine and module linkage — system testing — to

see that all related code fits together properly.

Check the program with test data. A standard method for
checking out modules is to write a test program that calls the

14-2

Debugging a User Program

program with possible options. The test should cause the pro-

gram to execute all steps in all algorithms. Check programs
first with representative data, then with improper data (data

that is not in the correct range or size). You should also do
volume testing to see that the program works successfully with
a representative amount of data.

Each programming language has special debugging aids for examining immediate states.

For example,

BASIC-11

has a

STOP statement that you can insert at strategic points in the

program. When the program arrives at a STOP statement, it
pauses so that you can use BASIC-11’s immediate mode to ex-

amine variables, values, and so on. Use an immediate mode GO

TO statement pointing to the appropriate line number to continue execution.

FORTRAN 1V has a special DEBUG statement indicator, a D

in the first column of a statement line. Operations in statements marked with a D can perform useful debugging func-

tions, such as printing intermediate results. You can treat such
statements as source text (and thus execute them) or as com-

ments (and thus ignore them), depending on whether you use a
special compiler command option. In addition, FORTRAN IV
has a traceback feature that locates the actual program unit
and line number of a run-time error. If the program unit is a
subroutine or function subprogram, the error handler traces

back to the calling program unit and displays the name of that
program unit and the line number where the call occurred. This

process continues until the calling sequence has been traced

back to a specific line number in the main program unit. Finally, FORTRAN IV has an optional interactive debugger

called FDT (FORTRAN DEBUGGING TECHNIQUE) that can
be linked with a user program.
For MACRO-11 users, RT-11 provides a special on-line debugging tool called ODT (On-line Debugging Technique). This is

provided as part of the RT-11 operating system and is an object
program on your system volume. It is used exclusively for de-

bugging assembled MACRO-11 programs.

The use of ODT is described next for MACRO-11 users and for
those FORTRAN IV users who will be combining MACRO-11
and FORTRAN IV program code. Other users can continue to
Chapter 15, or go back and perform one of the other language
demonstrations. Refer to the reading path outlined in the
Preface.

ODT is an interactive debugging tool that allows you to monitor program execution from the console terminal. ODT is provided as the object module ODT.OBJ on your system volume.
To use it, you link ODT.OBJ with the assembled MACRO-11

14-3

USING THE ON-LINE
DEBUGGING
TECHNIQUE

Debugging a User Program
program that needs debugging. You then start execution of the

resulting load module, not at the transfer address of your program, but at the entry point of the ODT module (shown on the
linker load map as the global symbol O.0DT). Once ODT is

started, you can use its special debugging commands to control

the execution of your assembled machine language program
from the console terminal, to examine memory locations, to
change their contents, and to stop and continue program execution.

The MACRO demonstration program in Chapter 11 still contains one error, which you can locate and correct using ODT.

Several ODT debugging commands are demonstrated in the

process.

Throughout the examples in this chapter you need to refer to
the program assembly listing of SUM.MAC. The listing that
was produced in Chapter 11 was deleted, so you must create a
new program assembly listing. Assemble your source program

and produce a cross-referenced assembly listing as you did in
Chapter 11. (Remember that SUM.MAC is now on your storage
volume.)

Long Command Format
+MACROGED
Files?

VOL:SUM/LIST/CROSSREFERENCEGE

Short Command Format
+MACRO

VOL:SUM/LIST/CROSSREFERENCEGRED

Print the listing on either the terminal or the line printer:
Long Command Format
(Line printer)

(Terminal)

+ PRINTGEED
Files?

SUM,LSTED

+TYPEGED
Files?

SUM.LSTED

Short Command Format
(Line printer)
+PRINT

SUM,LSTGED

VERSION

OB G

SUMMAC

(Terminal)

MACRD

V05,00

000000

SUM,LSTGEED

08-Jan-83

09:38

«TITLE

SUM,MAC

VERSION

«MCALL

LTTYOUT,

.EXITy

JPRINT

#NO.

DIBITS

THE

RECIPROCALS

000106

+TYPE
Saturdas

‘€’

Page

70,

1700

EXP?

«FRINT

THE

SUM

4+ 1780

4 1/20

#MESSAB

1/30

1/4)

PPRINT

'E‘

THE

% 1/50

CALECULATE

FACTORIALS

INTRODUCTORY

TEXT

144

Debugging a User Program
12 000004
13 000012

012705
012700

000104
000107

14 000016
13 000022

012701
004311

000124

FIRST!

MOV
MOV

WNSRG
#N+1 RO

$ND.
#NO.

SECOND?!

Moy
ASL

$4,R1
@R1

JADDRESS OF DIGIT VECTOR
B0 MULTIFLY BY 10 (DECIMAL)

ié

000024

011144

000026

004311

000030

006313

Hov

BRLy~(8F)

TSAVE

ASL

2R1

ixa

ASL

2Rl

122

19 000032
20 000034

042421
005300

ADD

(SPY44+ (R1) %

INOW

21 0000346
22 000040

001371
012700

BEC

BNE
MOV

#AT END

23 000044

014103

000046

012702

000052

005202

000106
THIRL!
177777
FOURTHT

MOV

SECOND
4NIRO

OF CHARS OF ‘E‘ TD FRINT
OF DIGITS OF ACCURACY

%10,

POINT

DIGIT

DIGITS?

$BRANCH IF NOT
360 THRU ALL PLACES,

-(R1},R3

$BY

MOV

$-1sR2

FPINIT

QUOTIENT

INC

$BUMP

THE PLACES
QUOTIENT

UIVIDING

INDEX
REGISTER

28 000054

103375

140003

|UB

ROLRY

$QUBTRACT LOOP

29 000040
30 000062

27 0000%4

040003
010311

apn
MOV

ROsR3
R35@R1

$FIX REMAINDER
JBAVE REMAINDER AS BASIS
JFOR NEXT

DIGIT

060261

R2s~2(R1)

FOREATEST

INTEGER CARRIES

000084

BCC

177776

FOURTH

INUMERATOR

33
34 000070

005300

000072

001344

36 000074
37 000076
38
39 000102
A0 000104

014100
142700

000012

103375
062700

000072

FIFTH:

DEC

$AT

END OF

DIGIT

VECTOR?

BNE

THIRD

$BRANCH

- (R13 rRO
#10. RO

BCC
ADD

FIFTH
#10.4°0sR0

SBET DIGIT TO DUTPUT
SFIX THE 2.7 TO .7 SO
JTHAY IT IS ONLY 1 DIGIT
3} (REALLY DIVIDE BY 10)
PMAKE DIGIT ASCI

NOT

JOUTPUT

THE

DIGIT

000114

005011

CLR

@R1

SCLEAR

DIGIT

43
44

000114
000120

00530S
001334

bee
BNE

RS
FIRST

IMORE DIGITS TO PRINT?
#BRANCH IF YES

43
48

000122

000124

STTYOUT

000110

A9
50
31 000342

SEXIT
Q00107

124

110

105

000343

040

126

101

114
040
040

125
117
105

1035
106
040

000341
000344

111

123

072

015

012

062

52
53
54

Swabol

N+1

JWORD

ARE

SINIT

MESSAS!

MACRO V05,00 Saturdau

056

JASCII

08~Jan-83

/THE VALUE OF E

ALL

ONES

09:38

Fage

1-1

FPage

1-2

/2./

200>

200
+EVEN

000000
VERSION

+END

HACRO

VO03.00

Ssturdaw

0B-Jan—-83

EXF
09:38

table
000124R

FIFTH

000076R

FOURTH

0Q00%2R

EXP

000000R

FIRST

000012R

MESSAG

0003AZR

SECOND

ABS.

000000

000

{RW:X,GBL7ABSYOVR)

000372

001

{RW» I+LCLsREL,CON)

Errors detected:
A% Assembler

Wark

DONE

VECTOR

I8!/ <13><12>

Work

LOCATION

000350
000353
000356

VERSION

SJWE

REPT

JENDR

000347

BUM.HAC

10%N

Hov
SUB

SUM.MAC

Size

ISN’T BAD

ALWAYS <

3TO GIVE DIGIT

+«

THIRD

000044R

statistics

reads:

file

writes?

work

000106

QO0022R

file
of

file!

O
B222

Words

8ize of core rool!

15872

Orerating

RT-11

sustem!

(

Words

(

Pases)

&2 Fases)

Elarsed time: 00100:04,31
DBK$8UM
DK SUM/C=DR $ SUM

BUM.MAC VERSION i
Cross refarence table

MACRO V05.00
(CREF V05.00)

1-14

1-474

EXp

1-11%

1-54

FIFTH
FIRST
FOURTH

1-37¢
1-138
1-2G#

1-39
1-44
1~28

MESSAG

N
SECOND

1~-11

1-51¢

1-74
1-158

1-12
1-21

THIRD

1-23¢

1-35

BUM.MAC VERSION

Cross

1-13

MACRO

reference table

SEXIT

1-3¢

1-45

+PRINT
LTTYOU

1-3%
1-3%

1-11
1-41

Saturday 08-Jan-B3

1-22

093138 fase S-1

1-47

V05.00 Saturdaw 08-Jan-83 09338 Pase N-1

(CREF V05.00)

Now link the MACRO-11 program object module (SUM.OBJ)

stored on the storage volume (VOL:) with ODT.OBJ by using
the /DEBUG option, and print a load map directly on the terminal or the line printer, choosing one of the following com-

mands:

Long Command Format
(Line printer)

(Terminal)

+LINK/MAP/DEBUGHED
Files? VOL:SUMGED

+LINK/MAP:TT:/DEBUGED
Files? V0L :SUMGEED

14-5

LINK/DEBUG

Debugging a User Program

Short Command Format
(Terminal)

(Line printer)
JLINK/MAP/DEBUG VOL:SUMED
RT-11
SUM

LINK
+BAY

Section
+

ABS.

$0DTS

Transfer

V08,00
Titles

Addr

Size

000000
001000
001372

001000
000372
006152

address

JLINK/MAP:TT:/DEBUG VOL :SUMED

l.oad Map
Saturday 08-Jan-83
Ident: VO05.00
ODT
Global
256,
125,
1589,

001824,

High

Value

Global

words
words
words

(RW,I,GBL,ABS,0UR)
(RW,I,LCL,REL,CON)
(RW,I.LCL,REL,CON)

0.0DT

001624

limit

VYalue

10:08

007342

Pagde

Global

1969,

Value

words

Look at the load map, and note that ODT starts at address
1372. The two modules together, ODT and SUM, reside in
memory up to location 7542, the high limit. Look at the symbol
table listing for the MACRO-11 program. This shows that the
program is 372(octal) bytes long and starts at location 1000.
To load and start execution of the load module, use the monitor
RUN command. The RUN command brings the entire load
module, called SUM.SAYV, into the absolute (physical) memory
locations shown in the load map and begins execution automatically at the starting, or transfer, address of the first module in
memory, which is ODT. Type:

Long and Short Command Format
+RUN SUMGEED
oDT

V05,00

ODT prints an identifying message on the terminal and an asterisk indicating that you are in ODT command mode and can
enter an ODT command. You are now using ODT to control the

execution of your program.' ODT commands let you execute the
entire program or just portions of it, examine individual locations, examine the contents of the PDP-11 general registers,
and change the contents of any locations in your program you
wish. If you make a mistake while you are typing any commands, type the DELETE key; ODT responds with a question
mark (?) and an asterisk (¥), allowing you to enter another
command.

1Be sure to read the chapter on ODT in the RT—-11 System Ultilities Manual

before you use ODT with any of your own programs. You must observe certain
precautions when you write your program and when you load it with ODT.
For example, you should make sure that ODT is not loaded into memory
locations used by your program. Follow the precautions described in the
RT-11 System Utilities Manual.

14-6

Debugging a User Program

Look at locations 6 through 16 in the assembly listing. With
ODT, you can examine these locations in memory as follows (all
ODT commands use octal numbers, as does the assembly

listing):
*#1006/0127030

001010

/0001060

001012

/0127000

001014

/000107

001016

/01270160

By typing a location address and a slash, you open that location
for examination and possible modification. A line feed closes
that location and opens the next sequential location for examination. A carriage return simply closes the currently open location.

Note that since the MACRO-11 program was linked to begin at

address 1000, you must add the constant 1000 to each address
shown in the assembly listing to obtain the actual address used
during loading. ODT can do this for you by using special internal locations called relocation registers. Each register can be
set to a relocation constant. Thus, if you have linked several
modules together, you can set various relocation registers to the
corresponding relocation constants of the individual modules.

You then indicate in your command which register to use, and
ODT automatically adds the constant in that register to the
address specified in your command. For example, set relocation
register 0 to 1000:
*100030R

Now, to examine locations 0 through 10 in the assembly listing,
type:
*0,0/01270008
0:+000002

/0013420

0000004

/1043531

0+000006
0:000010

/012705@
/000106GD

In your commands, indicate the number of the relocation register (followed by a comma), since generally you will have more
than one register set at a time.
Execute the MACRO-11 program now, using the ODT ;G command, indicating in the command where you wish execution to

start. In this case, the program’s start (transfer) address is
1000, so type:
*040iG

THE

VALUE

IS:

2,5/6806/606237,2301314.,06525/130440275535025.,71477737352744745405502,544

14-7

Debugging a User Program

As you discovered in Chapter 11, these program results are
incorrect. Note that a period has printed, indicating that you

are

back

monitor

command

mode.

This

particular

MACRO-11 program returns to the monitor after execution.

Therefore, to continue using ODT, you must RUN the load

module again:

Long and Short Command Format
+RUN

SUMED

goT

Y05.00

Changes that you make to a program while using ODT, and

ODT register assignments that you make, are temporary. Thus,
when you restart ODT, you must reenter any commands, such
as relocation register commands, that you want to remain in
effect. Reset relocation register 0:
*100030R

To help you find programming errors, ODT provides a break-

point feature. Setting one or more breakpoints in a program

causes program control to pause at those locations during execution. When control pauses, ODT prints a short message on
the terminal, informing you that a breakpoint has occurred and
showing the location at which execution has stopped. This

pause returns control to ODT and gives you the opportunity to
examine and possibly modify variables or data. Breakpoints are
numbered from 0 to 7, so that you can have a total of eight

breakpoints set at various instructions in the program at one
time.
For example, set breakpoint 0 at location 22 (line 16 in the

assembly listing) and breakpoint 1 at location 40 (line 23):
*0,2250B
*¥0.,404%1B

Now when you run the program, control pauses first at location
22. Since the breakpoint was set at the instruction at location
22, that instruction has not yet been executed, but all preceding
instructions have:
*0,035G

TB0i0,000022

Note the message that ODT prints when execution reaches the
breakpoint. Normally when execution encounters a breakpoint,

only the breakpoint number and location are printed on the

14-8

Debugging a User Program

terminal. In this case, the letter T precedes the breakpoint message. This happens because of the way the ODT program uses
the console terminal. The assembly instruction .PRINT at line
12 of the assembly listing requests the monitor to print a program message at the same time that ODT needs to print the
breakpoint message. ODT, however, has higher priority. By the
time the .PRINT request starts to print the program message,

execution reaches the breakpoint and gives control to ODT. The
.PRINT request has time to print only one character of its message before ODT takes over and prints the breakpoint message.
When the program regains control, its message will continue
printing from the second character.
Program control has paused at location 22 in the MACRO-11
program. Look in the assembly listing at the instructions that
occur there. The instruction at location 16 (line 15) stores the
address of the digit vector (at label A) in register 1 (R1). Examine the contents of register 1 to discover what this address is;
then open the address and examine its contents and the contents of several addresses following it by using two new ODT
commands, $ and @:
¥$1/001124

0,000124

/0000010

0:000126
04000130

/0000010
/000001

0:000132

/000001GD

The $ command opens for examination the contents of one of
the general PDP-11 registers 0 through 7. The @ command
uses the contents of the currently open location as an address
and opens that location for examination. Notice that the digit
vector A, which begins at location 124, has been initialized to
the value 1, the precise value indicated by the comments at line
48 of the program listing.
If you were to continue program execution now, the branch in-

struction at line 22 of the assembly listing would cause program control to loop back to the instruction at line 16 where
breakpoint O is set, again causing execution to pause. Since you
wanted to continue to the next breakpoint (set at location 40),
you must first cancel the breakpoint at location 22. To do this,
type:
*308B

This removes the breakpoint at location 22. The number (in
this case 0) indicates which breakpoint is to be removed. Now

continue program execution using the ;P command (proceed
from breakpoint). Execution progresses through the loop and
continues until it reaches the breakpoint set at location 40:

14-9

Debugging a User Program
*iP

HB13i0,000040

(Note that the monitor has time to print the second character,
and perhaps additional characters, of the program message be-

fore ODT gains control.) Now examine the contents of several of
the program vector locations beginning at location 124:
*0:124/0000120
0,000126

/000012010

0,000130
0+000132

/0000120
/00001260

The instructions prior to the breakpoint at location 40 constitute a multiplication routine. This routine multiplies the vector
contents by 10 (12 octal), as you have just verified.
You can see how the breakpoint feature is a very useful debugging aid. It allows you to execute selected portions of a program

and verify that data and variables are being used correctly
during execution. You can use the breakpoint feature to locate

the error that is in this program.
First, clear all previously set breakpoints (in this case, there is
only the one at location 40) by typing the ;B command with no
argument.
*iB

Now set a breakpoint at location 110 (line 41 of the assembly
listing). You want to verify the data that is being passed to the

monitor in register 0 in the ADD instruction in line 40.
*0,110508B
*3P

EB0O30,000110

Now examine the contents of register 0.
*$0/000065

\0BS

=5@D

At this point in execution, register 0 contains 000065. The
backslash (\) command prints the low-order byte of the opened
location on the console terminal and also converts this to an
ASCII character (if it is a valid ASCII code) and prints the
character. In this case, the number 5 prints. If you look back at

the program results printed earlier in this chapter, you can see

that 5 is the first digit of the tabulated result (following the
message THE VALUE OF E IS 2). If you are experienced in
mathematics, you know this result is incorrect because the ap-

proximate value of E is 2.718. And you now also know that the

14-10

Debugging a User Program

program error is not in the interface to the monitor service used
to print the result (TTYOUT), but that it occurs somewhere

before location 110. So the next step in debugging this program
is to set a breakpoint at some earlier point in the program logic
and to rerun the program. You must restart ODT to do this.
Return to monitor mode by typing CTRL/C. The remainder of
the program message prints on the terminal; then the monitor
period appears, indicating that you are in monitor mode.
*CTRLC)
VALUE

IS:

Restart ODT and reset relocation register 0.
RUN SUMED
oDy

vo5.00

*100030R

Set a breakpoint at location 76 (line 37 in the assembly listing),
and start program execution at its beginning.
*04+7684508B
*01035G

TB0O30 000076

Again, examine register 0 to verify its contents.
#$0/0000336D

By following the program logic in the assembly listing, you
know that the value in register 0 should at this point be
33(octal) (2.7, previously multiplied by 10, = 27[decimal] =
33[octal]). So the value in register 0 is correct. From this, you
can deduce that the error must occur somewhere between locations 76 and 110. The proper step now is to check the assembly
listing, where you find the error at line 40. The decimal point
that should follow the 10, identifying it as a decimal 10, is
missing. Therefore the program treats the 10 as an octal 10, or
8(decimal), making each digit in the result off by an additive
factor of 2. The data in location 106, then, should be 72, not 70.
Since this data has not yet been used, you can change it now
with ODT and continue program execution; if it had been used,
you would need to restart ODT and then change the data. To
change the contents of a location, simply open the location, type
in the new contents, and close the location, using a carriage
return.
*#0,106/000070 726D

14-11

- Debugging a User Program

Now eliminate all breakpoints.
*3B

Continue program execution; the correct results should print.
*iP

THE

VALUE

I8:

2,71828182845904523536028747135266249775724709389899505749668676277240766
+

SUMMARY:
COMMANDS FOR

DEBUGGING

To Start ODT

LINK/DEBUG

Link the assembled program (the program to be debugged)

PROGRAMS

with the ODT object module.
To Use ODT!

Close the currently open location and open the next sequential location for examination and possible modification.

EED
Close the currently open location.
addr/
Open the location indicated (addr) for examination and pos-

sible modification.

addr;G
:
Begin program execution at the indicated address (addr).
P
Continue program execution from a previous breakpoint.

addr;nB
Set one of the eight available breakpoints (n) at the indicated

address (addr).
;nB

Cancel the indicated breakpoint (n).
;B

Cancel all breakpoints.
addr;nR

Set one of the eight available relocation registers (n) to the
relocation constant value indicated by addr.
!Only a very few of the available debugging commands have been demon-

strated in this chapter. Consult the RT-11 System Utilities Manual for all
ODT commands.

14-12

Debugging a User Program

Open one of the eight general registers (n) for examination
and possible modification.

Use the contents of the currently open location as an address;
close the currently open location; go to the new address, and
open it for examination and possible modification.

Print on the console terminal the low-order byte of the currently open location; if possible, convert the value to an
ASCII code and print the corresponding character on the ter-

minal.

Changes you make with ODT are temporary. Therefore you
should now use the editor to correct the source program

FILE MAINTENANCE

SUM.MAC. You should edit line 40 so that it reads:
ADD

#10.,+'0:RO

iMAKE

DIGIT

ASCII

The file SUM.MAC is currently stored on the storage volume
VOL:. Edit this file, then reassemble, relink, and rerun it to
verify that it is correct. When you have done this, store the
updated version of the source file on the storage volume under
the same name (SUM.MAC), including the files SUM.OBJ and
SUM.SAV.
After you have corrected and rerun the program, continue on to
Chapter 15, or go back and perform one of the other language
demonstrations. Refer to the reading path outlined in the
Preface.

RT-11 System Utilities Manual (AA-M239A-TC). Maynard, Mass.: Digital
Equipment Corporation, 1983.
A guide to the use of the RT-11 system utilities.

14-13

REFERENCE

CHAPTER 15

USING THE FOREGROUND/BACKGROUND MONITOR
A special feature of the RT-11 operating system is that it provides a choice of operating environments. You are using its
foreground/background environment. This environment allows
two independent programs to reside in memory at the same
time and to execute concurrently.

You have used the foreground/background (FB) monitor to control the system and to perform the various exercises in this
manual.

The foreground/background environment is designed so that
two programs can — but need not — share memory and run
concurrently. One of these programs you designate as the foreground program. The system gives priority to the foreground
program (or job, as it is usually called) and allows it to run until
some condition, perhaps waiting for an I/O completion, causes it
to relinquish control to the other program (the background job).
The system then allows the background job to run until the
foreground job again requires control, and so on. In this way,
the two programs share system resources. Whenever the foreground program is idle, the background program runms. Yet
whenever the foreground program requires service, its requests
are immediately satisfied. To the user at the terminal, the two
programs appear to run simultaneously.

THE
FOREGROUND/
BACKGROUND
ENVIRONMENT

Foreground priority programs are generally time-critical. For
example, you may want to designate as the foreground job a
program that collects and analyzes data. Background programs
are usually non-time-critical. Thus, you can continue to do program development as the background job by using monitor commands to run the editor, the FORTRAN IV compiler, the linker,
and so forth.

In order to perform the following exercises your system must

have a clock. Verify whether your system has a clock by entering the TIME command twice. If the time displayed changes,
your system has a clock. If your system does not have a clock
you should skip ahead to Chapter 16.

Two programs are provided for you to run a foreground/background demonstration. These programs reside on your system
volume. The background job is called DEMOBG, and the foreground job DEMOFG. The function of the foreground job is to
send messages every two seconds to the background job, telling
it to ring the terminal bell. The background job recognizes

15-1

RUNNING THE
FOREGROUND/
BACKGROUND
PROGRAMS

Using the Foreground/Background Monitor

these messages and rings the bell once for each message sent by

the foreground job.
Although the foreground job is always active, sending messages

to the background job every two seconds, other programs be-

sides DEMOBG can be executed in the background. Only when
DEMOBG is active, however, is the circuit complete so that
messages can be successfully received and honored. During the

periods when DEMOBG is not running, the foreground program enters the messages in the monitor message queue. Once
you restart DEMOBG in the background, the system immedi-

ately dequeues all the messages since the last exit of DEMOBG,
resulting in many successive bell rings. When the queue is
empty, the normal send/receive cycle resumes, and the bell
rings every two seconds as each current message is sent and

honored.

Creating the
Background Job

The background program DEMOBG.MAC is an assembly lan-

guage source file and must be assembled and linked before you
can use it. When you execute DEMOBG, it displays a message
on the terminal. It is assumed that you have set the date.

Editing the
Background Job

Use the text editor to modify the background job,
DEMOBG.MAC. One of the lines of the message that is output

by the program has a semicolon character preceding it, which

makes the line a comment field. This will prevent the line from
being printed as part of the message. Thus, the semicolon must
be deleted from that line.
Change the line
i

WASCII

/WELL

DONE./

to
+ASCITI

/KWELL

DONE./

Running the

If you performed the demonstration in Chapter 11, you are al-

Background Job

ready familiar with assembly/link operations, and the following

command explanations can serve as a review. If you did not
read Chapter 11, simply type the command lines as shown.
Assemble the background job.

Long Command Format
+ MACROGE
Files? DEMOBG/LISTED

15-2

e’

Using the Foreground/Background Monitor

Short Command Format
+MACRD DEMOBG/LISTED

Link the .OBJ file produced by the assembler to create a runnable job.

Long Command Format
+LINKEED
Files? DEMOBGGEE

Short Command Format
LINK DEMOBGGED

Now run the background job and check the results.
+RUN DEMOBGED

RT-11 DEMONSTRATION PROGRAM
1F INCORRECTLY EDITED, THIS
WELL DONE.

THE

LAST

LINE,

If you did not delete the semicolon character, the last line will
not be output. Return to the monitor by typing two successive
CTRL/Cs.
€RI/C)
€mUC)
“C
"C

The FB monitor provides you with commands that allow you to
control the two-job environment. They let you interact with the
two jobs and let the two jobs interact with one another.

USING THE
FB MONITOR

When two jobs run simultaneously, you must have some means
of indicating the job to which you are directing commands.

Communication
in a Two-Job

Likewise, the two jobs must have the means to identify themselves when they have messages to print. The following are
some conventions that apply to system communication in a twojob environment.

Environment

The foreground job has priority. If both the foreground and
the background job are ready to print output at the same
time, the foreground job prints first. The foreground job

prints a complete line, then the background job prints a
complete line, and so on.

15-3

Using the Foreground/Background Monitor

Either job can interrupt your input at the terminal if it has
a message to print.

3.
4.

Messages printed by the background job are preceded by the
characters B>.
Messages printed by the foreground job are preceded by the
characters F>.

Typed commands are initially directed to the background
job. You can redirect control alternately to the foreground
and background jobs by using the CTRL/F and CTRL/B
commands.

To direct typed input to the foreground job, type CTRL/F.
This command instructs the monitor that all subsequent
terminal input — commands and text — is directed to the

foreground job. Typing this command causes the system to
print an F> on the terminal, unless output is already
coming from the foreground job. Command input remains
directed to the foreground job until the foreground job terminates, or until it is redirected to the background job

through CTRL/B.
To direct typed input to the background job, type CTRL/B.

This command instructs the monitor that all subsequent
terminal input — commands and text — is directed to the
background job. Typing this command causes the system to
print a B> on the terminal, unless output is already coming
from the background job. Command input remains directed

to the background job until redirected to the foreground job
through CTRL/F.

Creating the

The foreground program DEMOFG is an assembly language

Foreground Job

source file; it must be assembled and linked before you can use
it.
Long Command Format
+MACROGED
Files? DEMOFG/LISTGED

Short Command Format
MACRO

DEMOFG/LISTED

The output resulting from this MACRO command includes an

LINK/

object file

FOREGROUND

DEMOFG.LST. The command creates both files on your system
volume. You must link the .OBJ file to produce a runnable
foreground program. You use the LINK command, just as you

called

DEMOFG.OBJ

and a

listing file

called

have in earlier chapters, but you also use the /FOREGROUND

154

Using the Foreground/Background Monitor

option.' This option produces a load module with a .REL file
type which signifies to the system that the file is a foreground
program and is to be run as the priority job.
Long Command Format
WLINK/FOREGROUNDGRED

Files?

DEMOFGGD

Short Command Format
+LINK/FOREGROUND DEMOFGGEED

Now you are ready to operate the two-job environment. Many
times, you have to consider the devices that are used for output
in a foreground/background environment. For example, if your
program assumes that the output device is a line printer, and
you do not have a line printer or you want to output to another
device, use the ASSIGN command. Type this command in the
following way, substituting the two-letter mnemonic from

Executing the

Foreground and
Background Jobs

Table 4-2 for the storage volume in place of dd.

Long Command Format
+ ASSIGNGED

Physical device name? dd:@D
Lodical device name? LP:GD

Short Command Format
+ASSIGN

dd:

LP:@D

You do not have to consider the above information for the demonstration programs that are provided, since the foreground job
communicates with the background job, and both jobs send
their output to the terminal.
When you use the FB monitor, you must always load into
memory the peripheral device handlers needed by the foreground job. You use the monitor LOAD command to make a
device handler permanently resident in memory. For example,
if your foreground job requires the use of the line printer, you
must load the LP device handler. You must specify the jobtype
with the command. For a foreground job, the jobtype is F; for a
background job, the jobtype is B. If you have assigned the code
LP: to another device, the system automatically loads the as-

signed handler and you need not enter a LOAD command. If

you are using the line printer, type:

1This command option also applies to compiled FORTRAN IV programs that

are to be linked as a foreground job.

15-5

LOAD

Using the Foreground/Background Monitor

Long Command Format
LDADED
Device?

LP:=F&D

Short Command Format
+LOAD

LP:=FGED

The command to load and start execution of the foreground job

FRUN

is FRUN, which is similar to the RUN command except that
the system automatically loads and starts the execution of the
foreground .REL program. (To execute a FORTRAN IV foreground job, you must use the /BUFFER:n option with the
FRUN command. The argument n represents, in octal, the

number of words of memory to allocate.) Use this command to
start the execution of DEMOFG.REL.
Long and Short Command Format
+FRUN

DEMOFGEED

F>
FOREGROUND

DEMONSTRATION

SENDS

MESSAGE

EVERY

SECONDSs

THE

PROGRAM

BACKGROUND

TELLING

PROGRAM

RING

THE

"DEMOBG"

BELL.

The foreground program DEMOFG is now running and
queuing the message for the background program every two
seconds. You now execute the background program DEMOBG

to allow it to receive the messages that were queued and to ring

the bell.
+RUN
RT-11
IF

DEMOBGGED
DEMONSTRATION

INCORRECTLY

WELL

PROGRAM

EDITEDs

THIS

THE

LAST

LINE,

DONE.

The bell rings several times in rapid succession as the monitor

dequeues the messages, and then every two seconds as the foreground job sends its message to the background job.
You can run other jobs in the background. First, terminate the
background job DEMOBG, using the double CTRL/C command.
€RUC)

EmRi/C)
+

Execute a DIRECTORY command in the background to get a
listing of all the .OBJ files on the system volume by typing:
+DIRECTORY

*,0BJGEED

15-6

Using the Foreground/Background Monitor

The foreground job is still running and queuing its messages to
the monitor. Rerun the background program to collect all the
foreground messages while the background job was stopped and
the directory was printing.
+RUN DEMOBGRED
RT-11 DEMONSTRATION PROGRAM
IF INCORRECTLY EDITED» THIS
WELL DONE.

THE

LAST

LINE,.

The bell again rings several times in succession and then rings
once every two seconds. Stop the background job by using the
double CTRL/C command.

Now stop the foreground job and remove it from memory. To do
this, you must first use the CTRL/F command to direct terminal
input to the foreground. Type:
+ CRLE)

The system prints the characters F> to remind you that you
are now directing command input to the foreground job. Use the
double CTRL/C command to interrupt and terminate the execution of the foreground job, and return control to the background
job.
CIRL/C)
CRL/C)
B>

You should unload the foreground job to reclaim memory space
for background use. Use the monitor UNLOAD command as
follows:

Long and Short Command Format
UNLOAD FEGED
+

F represents the foreground job; you should use this code whenever you want to unload the foreground job. To unload any
loaded device handlers, you must use their two-letter device
mnemonics.

Check to see if the' .LST files were produced as a result of this
demonstration.

15-7

UNLOAD

Using the Foreground/Background Monitor

Long and Short Command Format
+DIRECTORY #,L8T
08-Jan-83
DEMOBG.LST
4
0B-Jan-83
2 Filesy 10 Blocks
406 Free blocks

DEMOFG,LST

08-dan-83

The foreground program has access to all the system features
available to a background program — opening and closing
files, reading and writing data, and so on. However, before you
begin to write and use programs in the foreground, read the
RT-11 Software Support Manual for coding restrictions.

SUMMARY:

COMMANDS USED
IN AN FB

ENVIRONMENT

CTRL/B
Direct all keyboard input to the background job (until
CTRL/F).
CTRL/F
Direct all
CTRL/B).

keyboard input to the foreground job

(until

FRUN

Load and start execution of the foreground job.
LOAD dd

Bring the indicated device handler into memory; the handler
becomes resident in memory.
UNLOAD dd
Take the indicated device handler out of memory, reclaiming

its memory space; the handler becomes nonresident in
memory.

UNLOAD FG
Reclaim the memory space used by the foreground job.

FILE MAINTENANCE

You assembled the source file DEMOFG.MAC and produced an
.OBJ file, linking it to produce DEMOFG.REL. You also created a .LST file named DEMOFG.LST on your system volume.
You should save on your storage volume the files
DEMOFG.REL and DEMOFG.MAC, and delete from your
system volume the files DEMOFG.OBJ and DEMOFG.LST. Do
not delete DEMOFG.MAC, since this file was distributed as
part of the RT-11 operating system. Do the same for the file
DEMOBG, which you created as a .SAV file instead of a .REL

file.

’

15-8

Using the Foreground/Background Monitor

Long Command Format
, COPYGED
From? DEMOFG.MAC,DEMOFG.RELGEED
To
% YOL:*,*ED
Files

copied:

DK :DEMOFGMAC
DK : DEMOFG.REL

to YOL:DEMOFG.MAC
to YOL:DEMOFG.REL

DELETEGD

Files? DEMOFG.0BJ:DEMOFG.LSTEE

Short Command Format
,COPY DEMOFG.MAC,DEMOFG.REL VYDL:*,*ED
Files

coried:

DK :DEMOFG.MAC
DK :DEMOFG.REL

to
to

VOL:DEMOFG.MAC
VOL:DEMOFG.REL

,DELETE DEMOFG.OBJ.DEMOFG.LSTGED

Finally, obtain a brief directory listing of your storage volume
so that you can see its current status:

Long and Short Command Format
,DIRECTORY/BRIEF VOL:GD

RT-11 Software Support Manual (AA-H379B-TC). Maynard, Mass.: Digital
Equipment Corporation, 1983.

A technical manual providing RT-11 programming concepts.

RT-11 System User’s Guide (AA-5279C-TC). Maynard, Mass.: Digital Equipment Corporation, 1983.

A guide to the use of the RT-11 operating system.

15-9

REFERENCES

CHAPTER 16

USING INDIRECT FILES
The RT-11 system provides an operational aid called an indirect file, which allows the system to run unattended. An indirect file is a file composed entirely of monitor operating commands. When you start the execution of the indirect file, the
monitor processes these commands in consecutive order. So
once you have created an indirect file and started its execution,
you can direct your attention to other tasks or even physically
leave the system, since the monitor executes the commands au-

tomatically and consecutively.'

The kinds of operations that RT-11 can best perform in an
indirect file are those that involve much computer processing
but that do not require your supervision or intervention. For
example, multiple assemblies, compilations, and data transfer
operations are ideal operations for indirect file processing. Also,
any series of commands that you are likely to type often can
easily run as an indirect file.

Use the editor to create an indirect file as a text file. You can
call the file by any file name you wish, but you should give it a
file type of .COM, since this file type is the default used by the
monitor to locate the file.

CREATING AN
INDIRECT FILE

You structure the lines of text that make up an indirect file just
like keyboard input. Thus, if you were to list the indirect file it
would look like terminal keyboard text without any monitor
prompts.

You enter monitor commands into the indirect file as you would
on the terminal. As an example, both of the following accomplish the same operation when executed as part of an indirect
file:
COPYRD
INFIL.MACGE
QUTFIL . MACED

COPY

INFIL.MAC OUTFIL.MACGE

Since monitor prompts are not included in the indirect file,
using the long command format requires that you anticipate
IThe indirect file concept is similar to BATCH processing. Although indirect
files lack many of the BATCH capabilities, they are easier to use than
BATCH. (The RT-11 computer system also supports a BATCH processor, as
described in the RT—11 System Ultilities Manual.)

16-1

Entering Monitor
Commands

Using Indirect Files

each prompt and its proper response. It is suggested that you
use the short command format and enter the command as a
single line of text. Terminate each command line with a carriage return.

Using the Editor
to Create an
Indirect File

The indirect file that you will now create incorporates several

of the commands previously demonstrated in this manual. Thus
it serves both as an example of the format of indirect file input
and as a brief review of the monitor commands used to copy,
process, and delete files. In addition, one new command, DEASSIGN, is demonstrated.
List a directory of your storage volume. The only files that
should appear in the listing are GRAPH.FOR, SUM.MAC, and
MATCH.BAS. All three files will be in the directory only if you
performed the exercises for all three languages (FORTRAN IV,
MACRO-11, and BASIC-11).
Long and Short Command Format
,DIRECTORY vOL:G68
08-JAN-83
SUM

+MAC

08-JAN-B3

GRAPH

FOR

0B-JAN-B3

Filess

4754

Free

MATCH

.BAS

0B-JAN-83

Blocks
blocks

If any other files are listed, delete them using the DELETE
command before you create the indirect file.

Use the EDIT/CREATE monitor command to create a file called
INDCT.COM, inserting the commands according to the directions in the right-hand column. When you have finished cre-

ating the file, list it and check for typing errors. Correct any
errors you find, and then close the file, using the EX editing
command.

Long and Short Command Format
JEDIT/CREATE

*IDATE

INDCT.COM@

8-JAN %3@

TIME B:00:00

Enter

hypothetical

date

and time (if your system has
a clock).

DATEGD

Print the date.

DEASSIGNED

Deassign all previous device

assignments

and

set

new

ones as follows:
ASSIGN TT: LP:E

Assign the logical name LP:

to the terminal.
ASSIGN ddn VOL:@D

Assign

the

logical

name

VOL: to the storage volume

(dd).
16-2

Using Indirect Files

DIRECTORY/BRIEF VOL:@
COPY YOL:GRAPH.FOR GRAPH,FOREE

List an abbreviated direc-

tory of VOL.:.

FORTRAN IV users insert

this command to copy the
FORTRAN

pro-

demo

gram to the system volume.

COPY UOL:SUM.MAC SUM.MACED

MACRO-11

users

insert

this command to copy the

MACRO-11 demo program
to the system volume.

COPY VOL:MATCH.BAS MATCH.BASED

BASIC-11 users insert this

command to copy the BASIC-11 demo program to
the system volume.

FORTRAN/LIST GRAPHED

LINK/MAP GRAPH:SYSLIB FORLIBGEED

FORTRAN 1V users who do

not

need

load the

lan-

guage volume include these

commands to compile and
link the FORTRAN
demo program.

MACRO/LIST/CROSSREFERENCE sum@

All users assemble and link

RENAME MATCH.BAS MATCH.MAPED

BASIC-11 users simply re-

LINK/MAP SUMED

the demo program.

name the demo program.

MACRO/LIST/CROSSREFERENCE DEMOFGED

LINK/FOREGROUND/MAP

All users assemble and link

DEMOFGEED

the DEMOFG file.

DIRECTORY *.0BJED

List a directory of object

DELETE/NOQUERY GRAPH.*ED

FORTRAN IV users delete

DELETE/NDOUERY SUM, »@D

MACRO-11

DELETE MATCH.MAPE®

BASIC-11 users delete the

DEASSIGNGED

files.

the GRAPH files.

the SUM files.

users

delete

MATCH file.

Deassign all device assignments.

TIMEE

If your system has a clock,

print the time to show how
long total processing took.

EED
*B /L BOED

Terminate the insert command and list the indirect

TIME 8:00:00

file to check for errors. (Ex-

DATE

B-JAN-83

ample input is shown here.)
16-3

Using Indirect Files

DATE

DEASSIGN
ASSIGN

TT:

ASSIGN

RK1i:

LP:
VOL:

DIRECTORY/BRIEF

VOL:
VOL:GRAPH.FOR GRAPH.FOR
VOL:SUM.MAC SUM.MAC
VOL:MATCH.BAS MATCH.BAS

COPY
COPY
COPY

FORTRAN/LIST
LINK/MAP

GRAPH

GRAPH,SYSLIB,,FORLIB

MACRO/LIST/CROSSREFERENCE

LINK/MAP SUM
RENAME MATCH.BAS

MATCH.MAP

MACRO/LIST/CROSSREFERENCE

LINK/FOREGRODUND/MAP
DIRECTORY

DEMOFG

#.0BJ

DELETE/NOQUERY

GRAPH.#*

DELETE/NOQUERY

SUM.*

DELETE

SUM

MATCH.MAP

DEASSIGN
TIME

*EXEDED

EXECUTING AN

INDIRECT FILE

Close the file INDCT.COM.

Once you have created an indirect file and checked it for errors,
you are ready to start its execution. The command to start execution of an indirect file is the at sign (@) followed by the
appropriate file name (the file type .COM is assumed unless

you indicate otherwise). Execution starts immediately, and the
system processes commands in the indirect file in consecutive
order. Each command is echoed on the terminal as it is pro-

cessed. If an error within the indirect file affects the processing
of a command, the system prints a system message on the terminal and stops execution of the entire file. Therefore, it is
particularly important that you check your indirect file for errors before you start it and then leave the area. You can stop

execution of an indirect file at any time by typing two
CTRL/Cs.
Run the indirect file that you have just created by typing:
+BINDCTRED

It takes a minute or two for the commands in this file to be
processed and for the listings to print. If your system has a
clock, the time printed at the end of execution tells you exactly
how long command processing has taken. Following is an example run.

+RINDCT
<DATE

8-JAN-83

.TIME

8:00100

+DBATE
#-Jan-83
SDEASSIGN
+ASSIGN

YTt

«ABSIGN

RK1!

VOL?Y

SDIRECTORY/BRIEF

GRAPH
3

.FOR

Filesr

4754

Free

VOL:

SUM
8

LMAC

MATCH

. BAS

Rlocks
blocks

«COPY

V0L :BRAFH.FOR

LCOPY

VOL:SUM.MAC

GRAPH.FOR

SUM,MAT

164

Using Indirect Files
JCOPY VOLIMATCH.BAS MATCH.BAS

SFORTRAN/LIST GRAPH

)

PAGE 001

VERSION 1

GRAPH . FOR

Sat 08~Jan-83 08100116

v02.5

FORTRAN 1y

f””‘

€ THIS PROGRAM PRODUCES & FLOT ON THE TERNINAL
FUN(XsV)

C OF AN EXTERNAL FUNCYIONs

€ THE LIMITS OF THE PLOT ARE DETERWMINED BY THE DATA STATEMENTS

0001
0002

€
€

*STABR' IS FILLED WITH A YARLE DV NEIENT FLAGS
*STRING* 1S USED VO BUILD A LIi
GRAPH FOR PRINTIA

SCAL(ZNIN-ZN‘X-MXZvK)IZN!NGFLOAY(K'U'(INM( ZH]N)/FLMT(Nth 13
LOGICALE] BYRINGC133).STABL100)

0003

DATA XMIN» XMAX s HAXX/~5.0¢5.0045/

0004

DATA YHIN: YRAX s HAXY/~5.015,0072/
DATA FAINsFHMAX/0.0s1.0/

0005

CALL SCOFY(’~ § 23 458 7 8 9 +,5TaB)

G004
0007
6008

HAXF=LEN(BTAB)
DO 20 IX=1yMAXX

X=SCAL (XMIN XHAX e HAXX» IX)

0009

0010

CALL

DO 10

0013

0016

0017

0018

JOR.

INT CFLOAT CRAXF -3 KEFUN(X 0 Y3 -FNIND / (FMAX-FNINDY
IFUNe2+

yMAXO 1y IFUKY ) )
STRING(IY)=STAB(NINOUNAXF

CALL PUTSTR(ZySTRING»

CALL EXIT

001%

END

JHAIN,

Storage Mar for Promram Unit .MAIN.

.PSECT $DATAs Size = 000476 (156, words?

Local Variabless

Hame
FNAX

Ture
REA

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122
%2

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Qs Warninas!

TFORTRAN-1-C.MAIN.] Errors!

FORTRAN [V

Local

IX,E@.MAXX) BOTQ 20

IY=2sHAXY-1

Y=GCAL (YMING YMAXs MAXYS 1Y)

0014

0015

REPEAT(“%°
. STRING»NAXY)

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152

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and COMMON Arraws:

Section Offset

Twee

Neme

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000000

$DATA
SDATA

LAt
STAB
SYRING LEL

==~ Size---~- Dimensions

000144 ¢
000205 ¢

50.) (100}
&7.) (13%)

Subroutiness Functions: Statessnt and Processor-Detined Functionsi

Nemy

Ture
I$2

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Nase

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LEN

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Locel Varisbles:s

INT

FUNCTION FUN(X)Y)
ReSORT (XN2+Y2E2)
C-R) ) 482
FUl=(XEYSREEXP
RETURN
€MD

0003
0002
0003
2064
0008

Fun

Bat 0B-Jan~83 08101144

voz.5

FORTRAN IV

Naaw

R¥4

Ture

RE4

10, words)

PSECT 8DATA, Size = 000024 ¢

UOffset

Name

000004 Eav R

RE4 @ 000002

Twrs

R&4

Offset

000010

Name

Tere

Offset

RE4 & 000000

Subroutinese Functionsr Statement and Processor-Defined Functions!

Naae

Ture

EXP
#

Nane

SGRT

Ture
Rx4

Name

Ture

<LINK/MAP BRAPH,SYSLIB»FORLIP

lY-ll LINK

Section

08,00

Title:

Addr

Bize

Load Mar
Global

000000 001000 = 256,
SUSRSM

arse1

001000 017722 = 4073,

SVIR

FORVO2

Value

Global

000000

000008

$SYSUS

000210

STRACE

$$0TSI

001000

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001000

SCUTIC

001014

SCUTID

001014

CCI

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e IC
1R
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001514

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wards

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Value

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Saturdaw 08-Jen-83 08102

Ident!

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ABS.

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NOX.!P

007014
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007040

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007074

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007144

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MOLISPA
SLENTR

007120

001362

002232

SSBR

DIFSIS

002554
002404
003144
005322
005524

MUFSIS
SMLR
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004737

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007470

NOLSPA
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007454
007476

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007334

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007330

007344

16-5

Using Indirect Files
LiLES

007506

LBEY
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007520
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007534

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CALCULATE

REE IPROCALS
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OF THE FACTORIALS
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EXPY

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000124
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011144

Page

STITLE

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INTRODUCTORY

CHARS

TEXT

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ik
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177777

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Page

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000038

08102

0B-Jan-83 08107

012705
012700

5278,

023737

SUM

HACRO

000012

OB-Jan-83

FORYOQ

000108

006000

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(RW»IrLCLeREL+CONY

words
words
words

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021144

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010246

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= 0.
= 35,
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010040

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023416 000000
023414 000106
023724 000004

GRAFH

007606

007432

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RT-11

007532
007546

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LEGS

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2.7

IS ONLY 1
DIVIDE BY

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10)

ASCII

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DONE

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VECTOR?

QuTPyY
TO

YES

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1

<ENDR

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ALL

ONES

50
51

000345

040

105

136

114

000353

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117

105
106

000356

040

105

040

000341

111

123

125

01%

VERSION

012

MACRO

000347

(&2

MESSAG:

Ssturdaw

OH-Jan-B83

V05.00

Saturday

0B-Jan-83

Exr

0000COR

000000

000372

Errors

detected:

Assembier

wark

work

HACKD

08:07

Pase

1-2

EXF

file

reads:

file

urites:

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00GOIZK

MESSAG

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SECOND

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file!

core

rool!

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swustem!

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time!

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(

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table

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1-14

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1-114

1-54

FIFTH

1-37%

1-3%

FIRST

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1-44

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1-518

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1-12

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1-21

23¢

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statistics

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table

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VALUE

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54

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SUM.MAC

110

V05,00

Saturday

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V05.00)

1-478

1-13

1-22

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1-a7

081

Page

S-1

000106

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THIRD

000GR4R

Using Indirect Files
HACRO V05.00
1
Cross reference table (CREF v03.00)

Ssturdaw 08-Jan-83 08307 Pase N-1

SUM.MAC VERSION

<EXET

<PRINT

1-38

143

136

1-41

1-30

JTTYOU

1-31

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Losd Mar

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284,

words

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125,

words

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1 CORY

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RENAME

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addrass = 001000y
MATCH.BAS

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Bsturdaw 08-Jan-83 08t11

Global

Vaslue

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Value

wards

HATCH.HAP

«MACRO/LIST/CROSSREFERENCE DENOFG

DEMOFS

MACRD V0S.00

Saturdes 08-Jan-83 08:11

Fese 1

STITLE

DENOFG

<IDENT

/V05.00/

+ FOREGROUND DEMONSTRATION PROGRAM TO PRINT MESSAGE YO BACKGROUND: THEN

4 GUEUE A MESSAGE EVERY 2 SECONDS FOR THE BACKGROUND TO RING
MCALL

STARTI!

000000

.PRINT

«QSET

Q00006
10 000020
11

JMRKT

15 000062

026727

000070

003020

000126

005267

20 000146
21

000207

24 000170
35 000174

005367
000207

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000132

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27
28
29

30 000174

106

31 000240
32 000324

117

123
105

33
34

35 000402

122

105
126

MKTEM COMPLETION ROUTINE

CMP

MSGCNT» $90.

INC

MSGONT

BST
+SDATC

JHMRKT

RETURN

MKTCL
$AREA-PBUFFER #1,#SDATC

SAREASBTIMEr 8NKTC, 41

SDAT

SDATCT

DEC
RETURN

ASCII MESSAGES
(NLIET BEX

MSG!

116
105

SPRINT

SOUEUE»$100,

MKTC?

MKTCL1:

@MSG

#AREAr$TINE) SHKTCy 81

<SPND

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38 000404
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48
DEROFG
MACRO V05.00
Saturdaw 08-Jan-83 08111
Swmbol

TBUNP MESSAGE COUNTER

JSET UP aNOTHER MKTIM FOR 2 SECONDS

4RETURN FROM COMPLETION ROUTINE

000410R
000424R

MKTC

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000000
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ABS.

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253 Assesbler
file

000
001

FHESSAGE COUNTER
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160 TICKS A SECONDs2 SECONDS
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100.%10.

710, WORDS FER QUEUE ELEMENT FOR THE XM AONITOR

START
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1-19

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statistics

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Ssturdaw 08-Jan-83 0BI1Y
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refarence table

1~9

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1-17
1-10

1~17
1-17

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1-17
1-10

1-438
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119

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1-48
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1-35¢

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Saturdaw 08-Jan-83 08111

table

Pase S-1

Fase

M-t

(CREF V05.00)

1-9
1-17

1-10

1-17
1-9

1-10

1-17

1-10

1-17

1-19

1-19
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1-64

1-6%
1-64

1-8
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1-68

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1-11

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Addr

Size

000000 001000 =
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address

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1-17

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Value

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1-17

001000,

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0B-Jan-83

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Value

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limit

006342

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uords

22-Cct-82

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22-0ct-82

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22-0ct-82

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141

12-Naw-80

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0B-Jan-83

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1
245

08-Jan-83

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OB

22-Dct-82
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08-Jan-83

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SUM,
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0§-Jan-83

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1-1%

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Title:

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apT

BEEN RECIEVED

table

AREA
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Work

SYES~ND SENSE OUEUEING ANOTHER
ISEND MESSAGE TO 80

IONE OF THE MESSAGES HAS
SRETURN(RTS PC)

190 MESSAGES QUEUED YET?

/FOREGROUND DEMONSTRATIDN PROGRAN/<I$><12>

MSGCNT:

$SUSPEND THE FG TILL MKYIN SATISFIED

/SENDS A MESSABE TO THE BACKGROUND PROGRAM *DEMOBG*/<1S>:12
/EVERY 2 SECONDS, TELLING LT TD RING THE BELL..

000000

41 000410

$SET UP HKTIM FOR 2 SECONDS FROM NOW

LASCII
.ASCIZ

<EVEN

INTROBUCTORY MESSAGE

3SET ASIPE 100 0 ELEMENTS fOR MESSAGES

CONPLETION ROUTINE

THE BELL.

JSDATC, .PRINT:.MRKT» . GSET) .SFND

MATCH.MAP

16-7

Using Indirect Files
«DEASSIGN

0at1x;as

SUMMARY:

COMMANDS TO
START AN
INDIRECT FILE

@filnam.COM

Start the execution
(filnam.COM).

the

specified

indirect

file

CTRL/C CTRL/C
Halt execution of the indirect command file (use with caution).

DEASSIGN

Remove logical device assignments.

FILE MAINTENANCE

Indirect file INDCT.COM contains commands that perform the

appropriate copy and delete file maintenance operations. If the

commands were not already part of the file, you would need to

perform the appropriate file maintenance commands, in monitor command mode, after execution.

REFERENCE

RT-11 System User’s Guide (AA-5279C-TC). Maynard, Mass.: Digital Equipment Corporation, 1983.

A guide to the use of the RT-11 operating system.

16-8

CHAPTER 17

ADVICE TO NEW USERS
This manual introduces several common RT-11 functions but is
neither exhaustive nor comprehensive in its treatment of
system features, commands, or their options. For many users,
this manual’s description of these fundamental system operations is sufficient; other users, however, may need or want further description of a programming language, extended system
features, or the internal workings of the RT-11 system. These
people should consult the references at the end of each chapter,
RT-11 System User’s
the Guide to RT-11 Documentation,
Guide, or the RT-11 System Ultilities Manual. The Guide to
RT-11 Documentation lists all RT-11-related material available from DIGITAL; the RT—11 System User’s Guide explains
in detail monitor commands and command options; the RT-11
System Utilities Manual describes the use of the RT-11 system
utilities to develop programs, execute programs, and maintain
files and storage media.

The Introduction to RT-11 has shown you the right way to use
some important system features and their associated monitor
commands. This information, combined with the following basic
guidelines for using the system, can help you to avoid pitfalls
common to new users:

e Do not become dependent on a single copy of a file. Always
make a backup copy of any useful file.
e When using the editor, close files periodically to preserve
edits. Divide long editing sessions into short ones so that
user — or hardware — errors do not lose the efforts of long
hours of editing. Close the file with the EX command and
begin editing again from where you left off.

e Avoid careless use of wildcard operations that manipulate
multiple files. Use the /QUERY option to verify the operation
to be performed.

e When using indirect files or BATCH streams, avoid operations that manipulate any of the system (.SYS) files or the
indirect file in use. Check the indirect file carefully for errors
before you use it. Once the command stream is initiated, you
may be unable to detect and prevent possibly serious errors.
e If you run two jobs under the control of the foreground/background monitor, be sure there is no conflict of nondirectorystructured devices (LP:, MT:, TT:) used by the two jobs.

17-1

Adpvice to New Users

USING THE

A HELP file containing information about the keyboard mon-

HELP FILE

itor commands and how to use them is distributed with the
RT-11 system. A list of keyboard monitor commands and a description of their functions can be displayed at the terminal by
typing:

HELP
+HELP

»@D

To get a detailed description of the use of the HELP command
itself, type only HELP.
+HEL PEED

The following information is displayed on your terminal.

HELP

Lists

SYNTAX
HELPL/opPptions]Il
or

HELP

helpful

torpicl

information

subtopicliitemsss
eyl

S
:

SEMANTICS

HELP

lists

the

items

for

which

help

available.

HELP

lists

the

HELP

text

(of

which

this

Part).

HELP toric lists information on the srpecific
toric onlvy.
HELP topic subtorpic lists information on the
specific subtoric only (for example,
HELP HELP SEMANTICS lists the paradgrarh of
which this text is a part),
HELP torpic subtopiciitem lists only the text
associated

HELP
the

with

the

specific

S’

item.

topic/item lists the text associated with
specific item under the subtoric QOPTIONS,

Valid torpics are the Kevboard monitor commands.
Subtorics are "SYNTAX", "SEMANTICS", "OPTIONS",

and

"EXAMPLES".

Items

are

specific

command

orPtions,

OPTIONS

PRINTER
Prints
TERMINAL
Tyrpes

the

HELP

text

(default)
the HELP text

the

line

Printer
B

the

terminal

EXAMPLES
HELP

COPY

'Lists
'COPY

HELP/PRINTER

EXECUTE

'Prints
tabout

HELP

OPTION:COPIES

HELP

COPY/BOOT/DEVICE

information

about

command

information
EXECUTE

command

'Describes the COPIES
tortion for PRINT

!Describes
loptions

the

for

listed

COPY

In the command syntax shown above, topic represents a specific

keyboard monitor command about which you need information.
The subtopic represents a specific category within a topic; the
subtopics are syntax, semantics, options, and examples. The

17-2

Advice to New Users

item represents one of the members within the subtopic group.
You can specify more than one item in the command line if you
separate the items with a colon (2).

The only two options you can use with the HELP command are
/PRINTER and /TERMINAL. The option /PRINTER sends the
help information to a printer if one is available. The option
/TERMINAL (the default mode) sends the information to the

terminal.
To get all the information in the help file about the keyboard
monitor command ASSIGN, type the following command:
JHELP

ASSIGNGED

You have used this command in examples in the other chapters.
The following information is displayed at your terminal:
ASSIGN

Associates
physical

logdical

device

name

with

device

SYNTAX
ASSIGN

physical-device-name

SEMANTICS
Phrsical-device-name
rermanent

name

for

{ogical-device-name
characters

long

The phrvysical
separated by

the

one

name and
a space.

RT-11

standard

device.

with

logical-device-name

three

alphanumeric

intervenind

logical

name

srpaces

must

tabs.,

OPTIONS

None
EXAMPLES
ASSIGN

DK:

RK1:

When you want specific information for a keyboard monitor
command, such as the syntax, semantics, options, or examples,
include that subtopic in the command. For example, the following command lists all the options that are available for use

with the DIRECTORY keyboard monitor command:
+HELP DIRECTORY

OPTIONSEED

If you need information only about a specific item in a list of
options, type the item in the command line.
+HELP