Commodore VIC-20 User manual

--. - _.:-:-':~- 2'- -I
c= commodore
COMPUTER VM110

FIRST EDITION
Fourth printing-1982
Copyright C1982 by Commodore Business Machines. Inc.
All rights reseNed.
No pari of this publication may be reproduced, stored in aretrieval system, or
tfansmilled in any form Of by any means, electronic, mechanical, photocopying,
recording or otherwise without the prior wrillen permission of Commodore
Business Machines, Inc.
Ii

TABLE OF CONTENTS
INTRODUCING THE PROGRAMMER'S REFERENCE
GUIJE v
VIC 20 APPUCATIINS GUIJE vii
1 BASIC PIIOGRAPt'I'M'I REFEREM:E GUIJE....m.1
•VIC BASIC: The Language of the ViC 3
•Commands 5
•Statemer;lts 14
•ItO Statements 35
•BASIC Functions 40
•Numbers and Variables, , , _.54
•Operators 62
•Logical Operators 68
2 PIIOGRAPt'I'M'I TFS 71
•Editing Programs 73
•Using the GET Statement... 77
•How to Crunch BASIC Programs 79
•Working With Graphics 82
Character Memory 82
Programmable Characters 82
High Resolution Graphics 88
Multi-Color Mode Graphics 92
Superexpander Cartridge 94
•Sound and Music 95
3 MACIINE lANGUAGE PIIOGRAPt'I'M'I GUIJE 107
•SyStem Overview 109
•Introduction to Machine Language 123
•Writing Your First Program 132
Iii

•Special Tips for Beginners 168
•Memory Maps 170
•Useful Memory Locations 178
•The KERNAL. 182
•KERNAL Power Up Activities
211
•VIC Chips 212
6560 (Video Interiace Chip) 212
6522 (Versatile lnteriace Adapter) 218
4 INPIIT/lJUTPIJT GUlOE 227
•User Port 229
•The Serial Bus 234
•Using the VIC Graphic Printer 236
•VIC Expansion Port
241
•Game Controllers , .. 246
Joystick 246
Paddles ,
.. , , .. " .. , .. " .. , , .. , .. , , .. ,,248
Light Pen ,250
•RS-232 lnteriace Description
251
APPENDICES 261
A, Abbreviations for BASIC Keywords." "263
B, Screen &Border Color Combinations ,265
C, Table of Musical Notes 266
D. Screen Display Codes , , , .. ,.267
E. Screen Memory Maps ,270
F. ASCII and CHRS Codes 272
G. Deriving Mathematical Functions 275
H. Error Messages , , , .. , ,.276
I. Converting Programs to VIC 20 BASIC 278
J. Pinouts for Input/Output Devices " " 280
K. VIC Peripherals &Aceessories 284
INOEIL 285
SCHEMATIC 291
'v

INTRODUCING. . .
THE PROGRAMMER'S
REFERENCE GUIDEI
The Friendly Computer deserves aFriendly Reference Book.
That's
why we wrote the VIC 20 PROGRAMMER'S REFER-
ENCE GUIDE
... abook that gives you more information about
your
VIC 20 Personal Computerthan any othersource. This gUide
was compiled from the experience
of Commodore's international
programming staffs in more than half adozen countries, and
Is
designed to be used by first-time computerists as well as
experienced programmers.
To cover the areBS VIC 20 programmers are most interested in,
we divided the book into four sections: BASIC Programming,
Machine language Programming, Input'Output Interfacing and
Programming Graphics & Sound.
Here are just afew of the ways the VIC 20 Programmer's
Reference Guide helps meet your programming needs:
-Our complete "dictionary" includes not only BASIC com-
mands but also sample programs to show you how they work.
-Need an introduction to Machine Level Programming? Our
laymen's overview gets you started.
-The exclusive Kemal helps assure the programs you write
today won't be outdated tomorrow.
-The VIC's Interfacesectionlets you expand yourcomputer ...
from RS232 for telecommunications to Joysticks, game paddles
and lightpens.
-You'll have fun learning about the VIC's graphic, sound and
music capabilities
... including the unique "multicolor" mode.
-You'll discover POKEs you never knew about, and probably
PEEK into some memory locations you never knew existed.
v

There are lots of fascinating hours ahead of you. Let the
Programmer's Reference Guide be your companion as you
continue to explore your VIC 20 Personal Computer System.
And ... if you find any errors in this book, please send us a
postcard or letter in care of VIC PROGRAMMER'S REFERENCE
GUIDE, VIC Product Marketing Group, Commodore Business
Machines, Inc., 68l Moore Road,King of Prussia, PA 19406. We'd
appreciate your assistance in helping us "debug" our reference
guide for future printings.
Enjoy your new reference guide ... and happy programmingI
-The Authors
•
vi

VIC 20 APPLICATIONS GUIDE
When you first considered buying acomputer, the chances are
you said something like, "I know computers are good thingsto have
and it'snice thatthey're finally affordable, but ... what can Ido with
one?"
The great thing about acomputer is that you can tailor the
machine to do what you want it to-you can make it calculate your
home budget, play arcade-style action games-you can even
make it talk! And the bestthing is, if your VIC 20 does only ONE of
the things listed below, it's well worth the price you paid for
it.
Here then. is alist of applications for your VIC 2~n caseyou've
asked yourself, "Yes, but what else can Ido with it?"
APPLICATION
ADVENTURE
GAMES
ADVERTISING &
MERCHANDISING
ANIMATION
BABVSITIING
COMMENTS/REQUIRE-
MENTS
COMMODORE provides 5Scott
Adams Adventure games on car·
tridge, decoded to "talk" with the
VOTRAX "Type N Talk"~.
Hookthe VIC to atelevision and put
it in astorewindowwith an animated
message flashing and you've got a
great point
of purchase store dis-
play.
The VIC is well-suited to screen
animation
... aspecial aid called
THE PROGRAMMABLE CHARAC-
TER
SET & GAMEGRAPHICS
EDITOR is available from COM·
MODORE on tape cassette.
The VIC HOME BABY$ITIER car-
tridge can keep your child occupied
for hours and teach keyboard sym-
bols, special learning concepts and
relationships. A"first" from COM-
MODORE.
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