Inside the Apple IIe

429 Pages·2011·32.79 MB·English

Inside the
Apple 1/e
Gary B. Little
Brady Communications Company, Inc.
A Prentice-Hall Publishing Company
Bowie, MD 20715
Inside the Apple //e
Copyright © 1985 by Brady Communications Company, Inc.
All rights reserved. No part of this publication may be reproduced or trans
mitted in any form or by any means, electronic or mechanical, including
photocopying and recording, or by any information storage and retrieval
system, without permission in writing from the publisher. For information,
address Brady Communications Company, Inc., Bowie, Maryland 20715.
Library of Congress Cataloging in Publication Data
Little, Gary B., 1954-
Inside the Apple lie.
Title appears on t.p. as: Inside the Apple //e.
Includes bibliographies and index.
1. Apple lie (Computer) I. Title.
QA76.8A6623L38 1984 001.64 84-12461
ISBN 0-89303-551-3
Prentice-Hall International, Inc., London
Prentice-Hall Canada, Inc., Scarborough, Ontario
Prentice-Hall of Australia, Pty., Ltd., Sydney
Prentice-Hall of India Private Limited, New Delhi
Prentice-Hall of Japan, Inc., Tokyo
Prentice-Hall of Southeast Asia Pte. Ltd., Singapore
Whitehall Books, Limited, Petone, New Zealand
Editora Prentice-Hall Do Brasil LTDA., Rio de Janeiro
Printed in the United States of America
85 86 87 88 89 90 91 92 93 94 95 345678910
Publishing Director: David Culverwell
Acquisitions Editor: Chris Williams
Production Editor/Text Designer: Michael J. Rogers
Art Director: Don Sellers
Assistant Art Director: Bernard Vervin
Cover Design: George Dodson
Manufacturing Director: John A. Komsa
Copy Editor: Keith R. Tidman
Photo of protoboard and DIP jumper cable: Tony Szary
Typesetting: Electronic Publishing Services, Baltimore, MD
Printing: Fairfield Graphics, Fairfield, PA
Typefaces: Eurostile (display), Aster (text), and Universal Monotype #3 H-P (computer programs)
To my grandfather,
Richard V. Robinson (1899-1978)
Limits of Liability and Disclaimer of Warranty
The author and publisher of this book have used their best efforts
in preparing this book and programs contained in it. These efforts
include the development, research, and testing of the programs to
determine their effectiveness. The author and the publisher make
no warranty of any kind, expressed or implied, with regard to these
programs, the text, or the documentation contained in this book.
The author and the publisher shall not be liable in any event for
claims of incidental or consequential damages in connection with,
or arising out of, the furnishing, performance, or use of the text or
the programs. The programs contained in this book are intended
for the use of the original purchaser.
Trademarks of Material Mentioned in This Text
Apple 1/e, Applesoft, Apple II, Apple II Plus, Apple //c, Apple I,
Integer BASIC, DOS 3.3, Lisa, Macintosh, and ProDOS are trade
marks of Apple Computer, Inc.
Note to Authors
Do you have a manuscript or software program related to per
sonal computers? Do you have an idea for developing such a proj
ect? If so, we would like to hear from you. The Brady Company
produces a complete range of books and applications software for
the personal computer market. We invite you to write to David
Culverwell, Publishing Director, Brady Communications Com
pany, Inc., Bowie, MD 20715.
CONTENTS
Preface I xiii
1 Introduction to Apple and the Apple //e I 1
A Condensed History of Apple Computer, Inc. I 1
1976 I 2
1977 I 3
1978 I 4
1979 I 4
1980-1982 I 5
1983 I 6
1984 I 7
Under the Hood of the Apple lie I 7
Learning the Fundamentals I 8
Numbering Systems I 8
Bit Numbering and "Significance" I 9
Pointers and Vectors I 18
Control Characters I 11
6502 Assembly Language I 11
Running Assembly-Language Programs I 13
What Won't Be Covered I 14
Using the Optional Diskette I 14
Further Reading for Chapter 1 I 15
2 The 6512 Microprocessor I 17
Important 6502 Concepts I 17
Zero Page and the Stack I 18
6502 Instruction Set I 19
6502 Registers I 21
The Accumulator-A I 26
The Index Registers-X and Y I 27
The Processor Status Register-P I 28
Carry Flag (C) I 29
Zero Flag (Z) I 38
Interrupt Disable Flag (I) I 38
Decimal Mode Flag (D) I 38
Break Flag (B) I 31
Overflow Flag (V) I 31
Negative Flag (N) I 31
The Stack Pointer-S I 32
The Program Counter-PC I 33
6502 Addressing Modes I 33
Immediate I 34
Absolute I 35
v
vi r==llnside the Apple //e -------------------
Accumulator I 36
Implied I 36
Indexed Indirect I 36
Indirect Indexed I 37
Absolute Indexed I 37
Relative I 38
Indirect I 38
6502 Input/Output Handling I 39
6502 Interrupts I 41
Reset Interrupt I 41
Non-Maskable Interrupt (NMI) I 42
Interrupt Request (IRQ) I 43
The BRK Instruction I 44
The 6502 Memory Space on the 1/e I 45
RAM Memory I 46
Input/Output (110) Memory I 48
ROM Memory I 49
Further Reading for Chapter 2 I 51
3 The System Monitor I 53
The System Monitor Commands I 54
The DISPLAY Command: Displaying the Contents of Memory I 55
The STORE Command: Changing the Contents of Memory I 57
The MOVE Command: Copying the Contents of Memory I 61
The VERIFY Command: Comparing Ranges of Memory I 62
The EXAMINE Command: Examining the 6502's Registers I 62
The GO Command: Running a Program I 63
The LIST Command: Disassembling Assembly-Language
Programs I 64
The NORMAL and INVERSE Commands: Changing Video Display
Modes I 66
The ADD and SUBTRACT Commands: Simple Arithmetic I 66
The BASIC and CONTINUE BASIC Commands: Entering
Applesoft I 66
The USER Command: User-Defined Commands I 68
The READ and WRITE Commands: Cassette Tape 110
Commands I 69
The KEYBOARD and PRINTER Commands: Redirecting Input and
Output I 71
Multiple Commands on One Line I 71
System Monitor Subroutines I 72
Further Reading for Chapter 3 I 76
4 Applesoft BASIC I 77
Applesoft Memory Map I 78
-----------------------Contents CJ vii
Tokenization of Applesoft Programs I 83
Keyword Tokens I 84
Storage of Applesoft Variables I 88
Storage of Simple Variables I 89
The Name Header I 91
The Data Field I 91
End of Simple Variables I 93
Storage of Array Variables I 93
The Name Header I 94
Dimensioning Bytes I 95
The Data Field I 95
End of Array Variables I 96
Representation of Integer Numbers I 96
Representation of Real Numbers I 98
Number Theory I 98
Binary Floating-Point Format I 98
How an Applesoft Program Runs I 181
The CHARGET Subroutine I 182
Changing Program Flow I 184
Finding Line Numbers I 1.5
Linking Applesoft to Assembly-Language Subroutines I 185
The CALL Command I 186
The & Command I 187
The USR Function I 188
Applesoft's Built-In Subroutines I 189
Using Applesoft's Built-In Subroutines I 116
Locating Variables I 116
Evaluating Formulas I 128
Converting Numbers I 121
Further Reading for Chapter 4 I 125
5 Disk Operating System I 127
The Internal Structure of DOS 3.3 I 128
DOS 3.3 Memory Map I 128
DOS 3.3 Page 3 Vectors I 129
Volume Table of Contents (VTOC) I 129
Diskette Catalog I 133
File Types I 135
Track/Sector List (TSL) I 135
Storing File Data I 136
RWTS-Accessing the Diskette Directly I 137
DOS 3.3 READ SECTOR Program I 147
The Internal Structure of ProDOS I 148
ProDOS Memory Map I 158
ProDOS Page 3 Vectors I 151
viii c::::::J Inside the Apple //e -------------------
Volume Bit Map I 152
Diskette Directory I 153
"Protecting" Files I 157
Storing File Data I 158
MLI...,..-Accessing the Diskette Directly I 168
ProDOS READ.BLOCK Program I 162
Further Reading for Chapter 5 I 166
6 Character Input and the Keyboard I 169
Standard Character Input Subroutines I 173
Reading One Character I 174
RDKEY ($FD0C) I 174
Keyboard Input (80-Column Firmware Off) I 177
Keyboard Input (80-Column Firmware On) I 177
Escape Sequences I 178
RDCHAR ($FD35) I 188
Reading a Line of Characters I 188
Changing Input Devices: The Input Link I 182
How About Output? I 183
Designing a KSW Input Subroutine I 184
Replacing the Keyboard Input Subroutine I 184
DOS 3.3, ProDOS, and the Input Link I 187
The K,eyboard I 191
:gncoding of Keyboard Characters I 191
Special Keys I 192
The "Apple" Keys I 192
Keyboard I/0 Locations I 193
Modifying the Keyboard Input Subroutine I 195
Keyboard Auto-Repeat I 212
Keyboard Type-Ahead I 285
Potential Problems with SOFTWARE TYFE-AHEAD I 217
Resetting the Apple lie I 218
Special RESET Procedures I 218
Trapping "Soft" RESETs I 218
Trapping RESET from Assembly Language I 228
Trapping RESET from Applesoft I 221
Further Reading for Chapter 6 I 226
7 Character and Graphic Output and Video Display Modes I 227
Text Mode I 228
Turning on the Text Display I 229
Text Mode Memory Mapping I 232
40-Column Text Mode I 233
80-Column Text Mode I 236
Using Page2 of Text I 237
Video Display Attributes: Normal, Inverse, Flash I 239
------------------~----Contents c=::J ix
Standard Character Output Subroutines I 241
Video Output (80-Column Firmware Off) I 245
Video Output (80-Column Firmware On) I 245
Video Screen Windowing I 246
How COUTl and BASICOUT Set the Video Attribute I 248
Changing Output Devices: The OUTPUT Link I 249
Designing a CSW Output Subroutine I 258
Replacing the Video Output Subroutine I 251
DOS 303, ProDOS, and the Output Link I 252
Low-Resolution Graphics Mode I 253
Turning on the Low-Resolution Graphics Display I 253
Low-Resolution Graphics Screen Memory Mapping I 255
Low-Resolution Graphics Colors I 256
Double-Width Low-Resolution Graphics I 256
Turning on Double-Width Low-Resolution Graphics I 257
Double-Width Low-Resolution Graphics Screen Memory
Mapping I 258
Double-Width Low-Resolution Graphics Colors I 259
Built-In Support for Low-Resolution Graphics I 268
High-Resolution Graphics Mode I 268
Turning on the High-Resolution Graphics Display I 261
High-Resolution Graphics Screen Memory Mapping I 263
High-Resolution Graphics Colors I 266
Animation with High-Resolution Graphics I 267
Double-Width High-Resolution Graphics I 269
Turning on Double-Width High-Resolution Graphics I 272
Double-Width High-Resolution Graphics Screen Memory
Mapping I 273
Double-Width High-Resolution Graphics Colors I 273
Built-In Support for High-Resolution Graphics I 275
Further Reading for Chapter 7 I 277
8 Memory Management I 279
Bank-Switched ROM Areas I 288
The INTCXROM Switches: Switching the $C100 $CFFF Memory
o o o
Space I 288
The SLOTC3ROM Switches: Switching the $C300 0 0 0 $C3FF Memory
Space I 283
16K Bank-Switched RAM Areas I 284
Using Bank-Switched RAM I 285
Reading the Status of the Bank-Switched RAM Soft Switches I 286
Auxiliary Bank-Switched RAM I 288
Using Bank-Switched RAM I 289
Bank-Switched RAM and ProDOS I 291
Auxiliary RAM Memory Area I 291
Using Auxiliary Memory I 292