Commodore PET User manual

1

PET-CBM
Personal
Co.puter
Guide
Carroll s. Donahue
Janice K. Enger
OSBORNE/McGraw-Hill
Berkeley, California

Published by
OSBORNE/McGraw-Hill
630 Bancroft Way
Berkeley, Califomia 94710
U. S. A.
For information on translations and book distributors outside of the U. S. A. ,
please write OSBORNE/McGraw-HiII
at the above address.
PET-CBM PERSONAL COMPUTER GUIDE
1234567890 0000 89876543210
ISBN 0-931988-30-6
Copyright © 1980 McGraw-HiII, Inc. Ali rights reserved. Printed in the United States of America. No
part of this publication may be reproduced, stored in aretrieval system, or transmitted in any form or
by any means, electronic, mechanical, photocopying, recording or otherwise without the prior written
permission of the publishers.
Cartoons by Erfert Nielson.
The definitions on the back cover are adapted, with permission, from Webster's New World Oiction-
ary, Second College Edition. Copyright © 1980 by William Collins Publishers, Inc.
The programs in this book were printed on aCommodore CBM Model 2022 Tractor Printer.

Table of Contents
Preface
1. Introducing the PET
Communicating with the PET
ROM and RAM
BASIC Programming
PET Models
Features
2. Operating the PET
Unpacking
Cassette Hookup
Key top Film Covering
Startup
Keyboard
Keyboard Entry
PET Key Groups
Screen Display
Cassette Tape Drive
Cassette Operation
Cassette Tape Controls
Cleaning and Maintenance
Cleaning and Demagnetizing the Tape Head
Care of Cassette Tapes
Elementary Troubleshooting
xi
1
1
2
3
3
5
7
7
8
9
10
11
14
15
32
33
34
36
38
39
40
42
v

3. Programming the PET
47
Calculator or Immediate Mode
47
AOne-Line Program 49
Reexecuting in Immediate Mode
51
Modifying aProgram
52
Elements 53
Numbers 53
Strings 57
Variables 58
Operators
62
Arrays 69
Functions
71
File Names 74
Writing BASIC Programs 76
Line Numbers 76
BASIC Statement Groups 78
Developing aProgram 84
Modification Example Tasks 107
4. PET BASIC 111
Format Conventions 112
BASIC Commands 112
CLR
112
CO NT 112
LIST 113
LOAD 114
NEW 117
RUN
117
SAVE 119
VERIFY
120
BASIC Statements 123
CLOSE
123
CMD 124
DATA 125
DIM 126
END 127
FOR .NEXT [STEP] 127
GET 129
GET*
130
GOSUB
131
GOTO
131
IF.
.THEN
131
INPUT 133
INPUT*
134
LET =135
ON. . GOSUB 136
ON. .GOTO 136
OPEN
137
POKE
143
PRINT 143
PRINT*
145
READ 146
REM
147
RESTORE
148
VI

4. (Contlnued)
RETURN
STOP
WAIT
BASIC Arithmetic Functions
ABS
ATN
COS
EXP
INT
LOG
RND
SGN
SIN
SOR
TAN
BASIC String Functions
ASC
CHR$
LEFT$
LEN
MID$
RIGHT$
STR$
VAL
BASIC Format Functions
POS
SPC
TAB
BASIC System Functions
FRE
PEEK
ST
SYS
TI. TI$
USR
User-Defined Function
DEF FN
5. Making the Most of PET Features
Keyboard Rollover
Buffer
Two-Key Repetition
Strings
Concatenating Strings
Numeric Strings
Programmed Cursor Movement
The PRINT Statement
The CHR$ Function
Arithmetic
Addition
Subtraction
Multiplication
148
148
149
150
150
150
150
151
151
152
153
154
154
155
155
156
156
156
156
157
157
158
158
158
159
159
159
160
161
161
162
162
163
163
163
164
164
167
167
174
177
180
180
182
185
185
188
189
190
202
215
vii

5. (Continued)
Graphies
Graphies in Calculator Mode
Programming Graphies
Summary
Animation
Time Delay
Programming Character Placement
Summary
Files
Program Files
Data Files
File Handling
Writing aData File
Reading aData File
Alternate Character Set
Features of the Alternate Character Set
BASIC
Word Abbreviations
Setting the Clock
Digital Display Clock
POKE to the Screen
Calculating the Screen Address
Generating Random Numbers
6. System Information
Organization of the PET System
Memory Map
PET BASIC Interpreter
BASIC Statement Storage
User Program Area Initialization
Data Formats
Array Header
Assembly Language Programming
Appendices
A. PET ASCII Codes
B. PET Error Messages
Operating System Error Messages
C. Program Examples Solved
D. BASIC Bibliography
E. PET Newsletters and References
F. Conversion Tables
Hexadecimal-Decimal Integer Conversion
Powers of
Two
Mathematical Constants
Powers
of Sixteen
Powers
of T en
G. Variations for Original ROMs (Revision Level 2)
H. PET Features
Index
viii
225
225
229
231
232
232
233
237
237
239
239
240
242
255
273
277
278
281
285
288
288
291
303
303
308
310
312
315
317
322
329
347
361
366
369
387
389
393
394
400
400
401
401
403
425
427

FIGURES
1-1 Three Models of the Commodore PET
4
2-la
Front View of Compact Keyboard PET
8
2-lb
Front View of Full Size Keyboard PET
9
2-2 Back
View of PET
10
2-3 Full Size
PET Keyboard 12
2-4 Compact
PET Keyboard 13
2-5 The
PET Video Screen 32
2-6 The
8x8 Dot Matrix
33
2-7
PET Cassette Tape Drive 34
2-8 Inserting aTape Cassette 35
2-9
PET Cassette Tape Head 39
2-10 ATypical Tape Head Demagnetizer
40
2-11
Write Protect Notches
41
2-12 PET Internai View
43
2-13 Memory Deviee Unconnected
44
2-14 Extractor Tooi
45
2-15 RAM Numbering
46
4-1
Logical Files 139
5-1 Odd/Even Division of PET Keyboard 170
5-2 Odd/Even Three-key Rollover
171
5-3 Draw the Square
228
5-4 Make Program Statement from Graphies 230
5-5 Using PRINT:#:
244
5-6 MAIL. PRINT:#: 252
5-7
Read aData File 256
5-8 MAIL. INPUT:#:
264
5-9 Format Printing Using GET:#:
272
5-10
Standard/ Alternate Character Set Decision 274
5-11 Standard to Alternate Character Set
276
6-1
PET Block Diagram 304
6-2 Principal Pointers in User Program Area
311
6-3 BASIC Statement Storage 312
6-4 User Program Area on Power-up
316
lx

TABLES
2-1 Special Symbols as Program Operators 19
2-2 Graphie Character
Keys
21
3-1
Special String Symbols 58
3-2 Reserved Words 62
3-3 Boolean Truth Table 67
3-4 Operators 69
4-1 Physical Deviee Numbers 140
4-2 Secondary Address Codes
141
4-3
ST Values for Tape 1/0 162
5-1 Addition Operations
181
5-2 Keyword Abbreviations 280
6-1 PET Memory Allocation by 4K Blocks 304
6-2
PET Memory Map (Rev. 3 ROMs) 334
6-3
PET BASIC Keyword Codes 313
6-4 ASCII Standard 7-Bit Codes 327
6-5
PET Screen Memory 7-Bit Codes 328
G-l PET Memory Map (Rev. 2 ROMs)
41L1
x

Preface
The personal computer field was already brimming with excitement when
the Commodore
PET@ entered the scene in late 1977. A minimum PET system,
housed in aself-contained
unit with custom keyboard, video display, and tape
cassette, cost
just $595.
The
PET was an immediate sales success. Many thousands of units have
been sold, and
PET user groups are springing up ail over.
The
PET has surely become famous as one of the first popular personal com-
puters.
It has also become widely known -indeed infamous -as having the
most meager literature auser
has ever had to face. That is why this book has been
written.
After reading this book vou will have agood understanding of what aper-
sonal computer -especially the
PET -can be expected to do for vou. Certainly
as important as knowing what vou can do with apersonal computer is knowing
what vou can't do. Sy examining the capabilities and limitations of the PET. vou
will have agrasp of what vou can realistically expect apersonal computer to do
for
Vou - which is important ifvou have apersonal computer, or Vou are thinking
of getting one.
There are numerous programming examples throughout this book; by
reproducing these examples vou
will quickly get your PET working. These exam-
pies are thoroughly described and documented so vou can leam
how and why the
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