Commodore 64 Programmer's Reference Manual
(It commodore
COMPUTER
==-
FIRST EDITION
THIRD PRINTING-1983
Copyright @ 1982 by Commodore Business Machines, Inc.
All rights reserved.
This manual is copyrighted and contains proprietary information. No part of this publica-
tion may be reproduced, stored in a retrieval system, or transmitted in any form or by any
means, eledronic, mechanical, photocopying, recording, or otherwise, without the prior
written permission of COMMODORE BUSINESS MACHINES, Inc.
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TABLE OF CONTENTS
INTRODUCTION. . ... . . .. . . ... . ... . . ... . . .. . . .. . . .. . .. .. ix
. What's Included? . .. . . .. . .. . . .. .. . .. . . .. . . ... . ... . . .. x
. How to Use This Reference Guide...................." xi
. Commodore 64 ApplicationsGuide. . .. . . .. . .. . . ... . . ... xii
. Commodore Information Network. . . . . . . . . . . . . . . . . . . . . .. xvii
1. BASIC PROGRAMMING RULES 1
. Introduction 2
. ScreenDisplay Codes (BASIC Character Set) ............. 2
The Operating System(OS) 2
. Programming Numbers and Variables 4
Integer, Floating-Point and String Constants.. . . . . . . . . . 4
Integer, Floating-Point and String Variables. . . . . . . . . . . 7
Integer, Floating-Point and String Arrays 8
. Expressionsand Operators... . . .. . . ... . . .. . . .. . .. . . .. . 9
Arithmetic Expressions.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Arithmetic Operations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Relational Operators 12
Logical Operators .. ... . ... . . .. . . .. . .. .. . . .. . .. . . .. ~3
Hierarchy of Operations. . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Stri ng Operations 16
String Expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 17
. Programming Techniques 18
Data Conversions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Using the INPUT Statement 18
Using the GETStatement. . . . . . . . . . . . . . . . . . . . . . . . . .. 22
How to Crunch BASIC Programs 24
2. BASIC LANGUAGE VOCABULARY... . . .. . . . .. . . .. .. 29
. Introduction 30
. BASIC Keywords,Abbreviations, and Function Types 31
. Description of BASIC Keywords (Alphabetical) 35
. The Commodore 64 Keyboard and Features 93
. Screen Editor.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 94
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3. PROGRAMMING GRAPHICS ON THE
COMMODORE64 ... 99
· Graphics Overview 100
Character Display Modes
.. ... ... .. .. . .. ... ... ... ... 100
Bit Map Modes 100
Sprites 100
· GraphicsLocations 101
VideoBankSelection... ... . .. ... ..... ... .. ... ... .. 101
Screen Memory 102
ColorMemory .1.. . ... . . .. . . .. 103
Character Memory. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 103
. Standard CharacterMode. .. . . . .. . . . . . . . . . . . . . . .. . . .. 107
Character Definitions 107
· Programmable Characters 108
. Multi-Color Mode Graphics 115
Multi-Color Mode Bit 115
. Extended Background Color Mode 120
. BitMappedGraphics... .... .... ... ..... ..... .'" .... 121
Standard High-Resolution Bit Map Mode. . ... . ... . 122
HowItWorks. . . .. .. ... ... .... .... ..... .... . .. 122
. Multi-ColorBitMap Mode. ... . .. . . . . . . . .. . .. . . .. . . ... 127
. SmoothScrolling 128
. Sprites 131
Defining a Sprite 131
Sprite Poi nters
. . . ... . . . .. . . . ... . .. .. . . . .. . . . ... . .. 133
Turning Sprites On 134
Turning Sprites Off
. . . . . . . . . .. . . . .. . . . . . . . . . . . . . . .. 135
Colors.. . . .. . . . .. .. . . . .. . . .. . . . . . . . . . . . . . . . .. . . .. 135
Multi-Color Mode 135
Setting a Sprite to Multi-ColorMode. . . . . . .. . . ... . ... 136
Expanded Sprites 136
Sprite Positioning 137
Sprite PositioningSummary.. . . . . . . . . . . . . . . . . . . .. . .. 143
SpriteDisplayPriorities.... .. ... .. . .. ... .. ... . . .... 144
Collision Detects 144
. Other Graphics Features 150
Screen Blanking 150
Raster Reg ister
..... ... ... .. ... ..... ... ... .. ... .. .. 150
Interrupt Status Register. . . . . . . . . . . . . . . . . . . . . . . . . . .. 151
Suggested Screen and Character Color Combinations... 152
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. Programming Sprites-Another Look 153
Making Sprites in BASIC-A Short Program. ... . .. . . .. 153
Crunching Your Sprite Programs 156
Positioning Sprites on the Screen 157
Sprite Priorities .. ..... . . .... . . ... . . ... . . . .. . . . .. .. 161
Drawing a Sprite 162
Creating a Sprite
. . . Step by Step 163
Moving YourSprite on the Screen. . .. . . .. . . .. . ... . . .. 165
VerticalScrolling... .. . . . . . . . . . . . . . . .. . . . .. . . . . . . .. 166
The Dancing Mouse-A Sprite Program Example. . . . . .. 166
EasySpritemakingChart.. . ... . ... .. .. . ... . . ... 176
SpritemakingNotes.. . .. . . .. . ... .. .. . ... . . .. . ... . .. 177
4. PROGRAMMING SOUND AND MUSIC
ON YOUR COMMODORE 64 183
. Introduction 184
Volume Control 186
Frequencies of Sound Waves. . . ..... ..... ..... ...... 186
. UsingMultipleVoices... . .. . . ... . ... .. ... . .. . 187
Controlling Multiple Voices 191
. Changing Waveforms . ... . . ... . . . ... . . ... . . ... . . . .. .. 192
UnderstandingWaveforms..... .... . . ... .... 194
. TheEnvelopeGenerator. . . . . .. . . . .. . . . . . .. . . .. . . . . . .. 196
. Filtering 199
. Advanced Techniques. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 202
. Synchronization and Ring Modulation 207
5. BASICTOMACHINELANGUAGE 209
. What is Machine Language? ... ... ..... .... ..... ... ... 210
What Does Machine Code Look Like? . . . ... . . ... . . . ... 211
Simple Memory Map of the Commodore 64 ...... .. .... 212
The Registers Inside the 6510 Microprocessor 213
. How Do You Write Machine Language Programs? 214
64MON 215
. HexadecimalNotation.. ... ... .... ..... .... .... .. 215
Your First Machine Language Instruction 218
Writing Your First Program 220
. Addressing Modes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 221
Zero Page 221
The Stack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 222
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