Atari XL User manual

THE
ATARIXL
HANDBOOK

THE
ATARIXL
HANDBOOK
PETER LUPTON &FRAZER ROBINSON
CENTURY COMMUNICATIONS
LONDON

Copyright e Peter Lupton and Frazer Robinson 1984
All rights reserved
First published in Great Britain in 1984
by Century Communications Ltd,
12 - 13
Greek Street,
London WI V 5LE
ISBN 0 7126 02259
Reproduced, printed and bound in Great Britain by
Hazell Watson &Viney Limited,
.
Member of the BPCC Group,
Aylesbury, Bucks
Typeset by Spokesman, Bracknell

CONTENTS
Acknowledgements
Introduction
1
Computers and Programs 1
2
Setting up your XL 3
3
First Steps 8
4
Programming
18
5
Program Control
31
6
Data and Programs
45
7
Pieces of Strings 52
8
Functions 63
9
Logical Thinking
70
10
Memory Managemen t74
11
Sound and Music
77
12
Characters
105
13
Graphics 136
14
Advanced Graphics
153
15
Player-Missile Graphics
172
16
Permanent Storage 188
17
Advanced Techniques 196
APPENDICES
1
BASIC Commands 204

2 BASIC Error Codes
3
Speeding Up Programs
4N umbering Systems
5 Graphics Modes
6
Colour Codes
7
Character Codes
8
Display List Instructions
9 Useful Memory Locations
10 Music Frequencies
11 Musical Notation
12 System Memory Map
Index
215
223
225
230
231
232
234
236
238
239
243
244

ACKNOWLEDGEMENTS
Our thanks to all those who in some way made the
creation of this book possible, especially friends
and colleagues whose enthusiasm and interest was
invaluable as our stocks of midnight oil burnt low.
Special thanks to Herbert for all his contributions,
and to Richard Gollner for his continuing optimism
and sense of humour.
Once again our families have given us much
encouragement, for which we are grateful, and
sound nutritional advice, which we have ignored.

INTRODUCTION
This book is an introduction to the ATARI XL
range of computers and their facilities. It takes you
from the first steps in BASIC programming,
pointing out the pitfalls and explaining how to
make the most of the features of ATARI BASIC,
through to a detailed understanding of how to write
good, structured programs, with many illustrative
examples along the way.
A chapter is devoted to the extensive sound
capabilities of the XL, including details of the
sound generating chip itself which allow you to
create a wider range of effects than is possible
using the standard commands.
Four chapters cover the incredible graphics
facilities of the machines, including many
spectacular examples and useful programs. An
advanced chapter shows how a detailed knowledge
of the way graphics are created leads to even more
exciting effects.
A
comprehensive set of appendices ensure that the
book will remain a valuable reference work long
after you have grasped the principles of the
machine.
We hope that you will find this book both enjoyable
and instructive and that it enables you to exploit
the potential of your XL to the full.
PETER LUPTON and FRAZER ROBINSON 1984