Table Of ContentInside the IBM PC
Revised and Enlarged
Peter Norton
BRADY
New York
Inside the IBM PC, Revised and Enlarged
Copyright © 1986 by Brady Books, a division
of Simon & Schuster, Inc.
All rights reserved
including the right of reproduction
in whole or in part in any form
BRADY
Simon & Schuster, Inc.
Gulf+ Western Building
One Gulf+ Western Plaza
New York, NY 10023
DISTRIBUTED BY PRENTICE HALL TRADE
Manufactured in the United States of America
8 9 10
Library of Congress Cataloging in Publication Data
Norton, Peter, 1943
Inside the IBM PC.
Bibliography: p. 361
Includes index.
1. IBM microcomputers. I. Title.
QA76.8.I2594N67 1985 004.165 85-25562
ISBN 0-89303-583-1 (paper edition)
ISBN 0-13-467325-5 (book/disk)
Printed in the United States of America
Contents
Introduction I viii
A Maze to Think About I x
Some Things To Try I xi
1 A Family Tree I 1
1.1 Some Family History I 1
1.2 The PC Family I 4
1.3 The 8086 Family I 8
Some Things To Try I 11
2 Fundamentals: What a Computer Is I 13
2.1 My Computer, the Model I 13
2.2 An Outline of the Computer I 15
Some Things To Try I 20
3 Data! I 23
3.1 Bits, Bytes, and Characters I 23
3.2 Learning About Hexadecimal I 27
3.3 Standard Numbers I 31
3.4 Hot Numbers I 34
3.5 Stringing Along / 37
Some Things To Try / 39
4 The PC Character Set / 41
4.1 A Character Set Overview / 41
4.2 The Ordinary ASCII Characters I 43
4.3 The ASCII Control Characters / 48
4.4 A Cast of Odd Characters / 52
Some Things To Try / 56
5 Hardware: The Parts of the PCs / 57
5.1 The Breakdown / 57
5.2 Options and Adapters / 63
5.3 Key Chips / 67
Some Things To Try I 71
6 Brains: Our Microprocessors / 73
6.1 What the Microprocessor Can Do I 73
6.2 Math Auxiliary: the 87s / 78
6.3 Tools at Hand: Memory and Ports, Registers and Stacks I 82
6.4 Interrupts: The Driving Force / 87
iii
6.5 Special Features about the 286 / 94
Some Things To Try / 96
7 The Memory Workbench / 99
7.1 Memory Overview / 99
7.2 Getting Into Memory / 102
7.3 The PC's Memory Organization / 105
7.4 Into Extended Memory / 114
7.5 Memory Banks and Expanded Memory / 117
Some Things To Try / 120
8 Disks: The Basic Story / 121
8.1 Basic Disk Ideas / 121
8.2 Varieties of Disks / 126
Some Things To Try / 132
9 Disks: The DOS Perspective / 133
9.1 DOS Disk Overview / 133
9.2 The Structure of a DOS Disk / 138
9.3 Learning About File Formats / 142
9.4 ASCII Text Files / 144
Some Things To Try / 148
10 Disks: Deeper Details / 149
10.1 Hard Disk Features and Partitions / 149
10.2 Detailed Disk Structure / 154
10.3 Nonstandard Formats and Copy Protection / 161
Some Things To Try / 163
11 Video: An On-Screen Overview / 165
11.1 How the Screen Works / 165
11.2 Video Mode Overview / 168
11.3 Exploring Video Modes / 177
Some Things To Try / 179
12 Video: Text Fundamentals / 181
12.1 Text Mode Outline / 181
12.2 Details of the Text Mode / 185
12.3 Text Mode Tricks / 193
Some Things To Try / 197
13 Video: Graphics Fundamentals / 199
13.1 Graphics Mode Outline / 199
13.2 A Tour of the Graphics Modes / 204
iv
13.3 Graphics Details / 211
Some Things To Try / 215
14 Keyboard Magic / 217
14.1 Basic Keyboard Operation / 217
14.2 Keyboard Tricks / 226
Some Things To Try / 229
15 Other Parts: Communication, Printers and More / 231
15.1 Printers: The Parallel Port / 231
15.2 Communication Lines: The Serial Port / 233
15.3 Sound / 236
15.4 Miscellaneous Parts / 240
Some Things To Try / 245
16 Built-In BIOS: The Basic Ideas / 247
16.1 The Ideas Behind the BIOS / 247
16.2 How the ROM-BIOS Works / 249
Some Things To Try / 254
17 Built-In BIOS: Digging In / 255
17.1 Working Principles and Machine Problems / 255
17.2 The BIOS Services / 257
Some Things To Try / 264
18 The Role of DOS / 267
18.1 What Any DOS is About / 267
18.2 History and Concepts of Our DOS / 269
18.3 Installable Drivers and Flexible Facilities / 272
18.4 Visual Shells: TopView and Others / 274
Some Things To Try / 276
19 DOS Serving Us / 277
19.1 Command Processing / 277
19.2 Batch Processing / 281
Some Things To Try / 282
20 DOS Serving Our Programs / 285
20.1 DOS Services and Philosophy / 285
20.2 All the DOS Services / 287
21 How Programs Are Built / 293
21.1 A Little Talk About Programming Languages / 293
21.2 Translating Programs / 303
v
21.3 Putting Programs Together / 309
Some Things To Try / 312
22 Exploring and Tinkering / 315
22.1 The Point of Exploring and Tinkering / 315
22.2 Working with DEBUG / 317
22.3 Working with NU / 320
Some Things To Try / 326
A Program Listings / 327
MAZE / 327
HEXTABLE / 330
ALL-CHAR / 331
REF-CHAR / 332
BOXES / 333
MSG-HUNT / 337
VID-MODE / 338
COLORTEXT / 340
GRAPHTXT / 342
COLOR-4 / 343
KEY-BITS / 346
B Narrative Glossary I 349
C Products and Trademarks I 359
D Other Sources of Information I 361
Index I 363
User's Manual for the Optional Diskette I 373
vi
About the Author
Peter Norton was born in Seattle, Washington, and educated at Reed
College in Portland, Oregon. During the past 20 years, he has worked with
a wide variety of computer equipment from personal computers to the larg
est main-frames, and he has worked on every kind of software from the
most intricate system programming to thoroughly mundane commercial
applications.
Shortly after he began working with microcomputers, he created, for
the IBM PC family of computers, the now-legendary Norton Utilities soft
ware package.
Although Mr. Norton continues to develop software for small com
puters, his work now concentrates on writing about the use of personal
computing.
Limits of Liability and Disclaimer of Warranty
The author and publisher of this book have used their best efforts in prepar
ing this book and the programs contained in it. These efforts include the
development, research, and testing of the theories and programs to deter
mine their effectiveness. The author and publisher make no warrantyof any
kind, expressed or implied, with regard to these programs or the documen
tation contained in this book. The author and publisher shall not be liable in
any event for incidental or consequential damages in connection with, or
arising out of, the furnishing, performance, or use of these programs.
Note to Authors
Have you written a book related to personal computers? Do you have
an idea for developing such a project? If so, we would like to hear
from you. Brady produces a complete tange of books for the per
sonal computer market. We invite you to write to Editorial Depart
ment, Brady Books, Prentice Hall Press, One Gulf+ Western Plaza,
New York, NY 10023.
vii
ITntroduction
his is the beginning of a marvelous voyage of discovery into
the secrets, wonders, and mysteries of the IBM Personal
Computer and the family of computers that has grown up
around it.
From the day it first appeared, the IBM Personal Computer has been
stirring up excitement and fascination, because the PC-as everyone calls
it-marked the coming of age of personal computing. Today, the PC is
solidly established as the power tool without equal for helping business and
professional people improve their performance and the quality of their
work. The PC has also spawned a great many other computers-some from
IBM, and some from the makers of "PC compatible" computers-that
have become what we call "the PC family."
This book is designed to help you understand the remarkable PC and
its entire family. In this book, we-you and I-will set off to discover the
mysteries and wonders of what the PC is and what marvels it can perform. I
am excited and enthused about the PC and the PC family, and I want to lead
you into understanding the workings of this marvel and sharing with me the
excitement of knowing what it is, how it works, and what it can do.
As you must have already realized, this isn't a book for people who
are having trouble finding the On/Off switch on their computers. Instead,
it's for people like you who have both the intelligence and the curiosity to
comprehend this wonderful family of machines. My goal is to make under
standing the PC easy for you and fun as well.
This is, more than anything else, a book of understanding, written to
help you learn what you really need to know about the PC. You can very
successfully use a PC without really understanding it. However, the better
you understand your PC, the better equipped you are to realize the potential
in the machine, to recognize the best software and hardware for your
machine, and-let's not forget this-to deal with emergencies that might
arise when working with a PC. After all, when something goes wrong in
your PC, the better you understand the machine the more likely you are to
make the right moves to fix the problem, rather than goof up and make
things worse.
There are a lot of reasons why we might want to understand the inner
workings of our pes. One reason, a really good one, is simply for the
intellectual satisfaction and sense of mastery that comes with understanding
the tools that you work with. Another reason is to open up new realms for
yourself. After all, there is plenty of demand these days for people who
Vlll
have PC savvy. But perhaps the most practical reason is the one that I
suggested above. By analogy, we might think back to the early days of the
automobile, when you had to be an amateur mechanic to safely set out on a
journey by car. It doesn't take the skills of a mechanic to drive a car today,
because cars have been tamed for everyday use. We'd like it to be that way
with computers, but frankly computing hasn't progressed that far yet.
Today, to safely and successfully use a personal computer you need some
degree of expertise-and the more expert you are, the better you can deal
with the practical crises that sometimes arise.
This book is here to help you, to take you as far as possible into the
realm of expertise, to help you join that select band of wizards who really
know how to make the PC perform its magic.
If you know anything about me, Peter Norton, or about the first edi
tion of this book, you know that I made my reputation, and this book
became a best-seller, by explaining the technical wizardry of the PC. In the
early days of the PC, that was what PC users needed most-an inside
technical explanation of how the PC worked. The world of the PC has
matured and changed since then, and so have the needs of the mainstream
of PC users. Today people still need to understand their machines, how
they work, and what it takes to make them sing, but the focus of people's
needs has changed, so this new edition of Inside the IBM PC has changed
as well.
You will still find in here lots and lots of interesting and useful techni
cal information that will help you understand what makes the PC tick. But
now, I'm drawing a dividing line between two kinds of material that you'll
be seeing here. The first and main part of this book explains the basic
principles of the PC and the PC family covering all those elements that you
need to comprehend the PC without having to plow through a great deal of
technical information; that part of the book is for all readers, and you can
easily identify it because it appears as normal text.
For readers who want to go further, dig deeper, and understand more
technical details, the second phase of the book, identified by this head:
TECHNICAL BACKGROUND I I I ••• __________
will cover the heavier stuff. In these sections, we'll go into the hardware
and programming details that show the underlying engineering that gets
things done in the PC family. These more advanced sections are for anyone
who wants to have more than simply a practical understanding of the PC
this part is for anyone who wants to actually wear the wizard's cap and
ix
