Programmers CPM Handbook by Andy Johnson-Laird

493 Pages·2009·16.28 MB·English

THE PROGRAMMER'S
CP/M® HANDBOOK
Andy Johnson-Laird
Osborne/McGraw-Hill
Berkeley, California
Published by
Osborne/McGraw-Hill
2600Tenth Street
Berkeley, California94710
U.S.A.
Forinformationontranslations and book distributors outside ofthe U.S.A.,
please write to Osborne/McGraw-Hillat the above address.
CP/M is a registered trademark ofDigital Research, Inc.
CP/M-86, MP/M-86, and MP/M II are trademarks of
Digital Research, Inc.
Z80is a registered trademark ofZilog, Inc.
THE PROGRAMMER'S CP/M® HANDBOOK
Copyright ©1983 by Osborne/McGraw-Hill. All rights reserved. Printed in the United States of
America. ExceptaspermittedundertheCopyrightActof1976,no partofthispublicationmaybe
reproducedordistributedinanyformorbyanymeans,orstoredinadatabaseorretrievalsystem,
withoutthepriorwrittenpermissionofthepublisher,withtheexceptionthattheprogramlistingsmay
beentered,stored,andexecutedinacomputersystem,buttheymaynotbereproducedforpublication.
1234567890DODO89876543
ISBN0-88134-103-7(PaperbackEdition)
ISBN0-88134-119-3(HardcoverEdition)
MaryBprchers,AcquisitionsEditor
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THE PROGRAMMER'S
CP/M® HANDBOOK
Dedication
Several years ago I was told that "Perfection is an English education, an
American salary, and a Japanese wife."
Accordingly, I wish to thank the members of Staff at Culford School in
England, who gave me the English education, the people who work with me at
Johnson-Laird Inc. and Control-C Software and our clients, who give me my
Americansalary,and Mr.and Mrs. Kitagawa, whogaveme Kay Kitagawa(who
not only married me but took overwhere my English grammarleft off).
A.J-L.
Acknowledgments
AlthoughthisbookisnotauthorizedorendorsedbyDigitalResearch,Iwould
like to express my thanks to Gary Kildall and Kathy Strutynski of Digital
Research, and to Phil Nelson (formerlyofDigital Research, now ofVictorTech
nology)fortheirhelpinkeepingmeonthepathtotruthinthisbook. Iwouldalso
like to thank Denise Penrose, Marty McNiff, Mary Borchers, and Ralph Baum
gartnerat Osborne/McGraw-Hillfor theirapparentlyinexhaustible patience.
A.J-L.
I
Contents
1
Introduction
2
The Structure ofCP/M 5
3
The CP/M File System 17
4
The Console Command Processor (CCP) 45
5
The BASIC Disk Operating System 67
6 The BASIC Input/Output System 147
7
Buildinga New CP/M System 183
8
Writing an Enhanced BIOS 209
9 Dealing with Hardware Errors 295
10
Debugging a New CP/M System 319
11 Additional Utility Programs 371
12 Error Messages 449
A ASCII Character Set 465
B
CP/M Command Summary 469
C
Summary ofBDOS Calls 479
o
Summary ofBIOS Calls 485
Index 487
ix
Outline ofContents
Notation
Example Programs on Diskette
Iintroduction
ThisbookisasequeltotheOsborneCPjM®UserGuidebyThomHogan.Itis
atechnicalbookwrittenmainlyforprogrammerswhorequireathoroughknowl
edge ofthe internal structure ofCP/M- how the various pieces ofCP/M work,
howtouseCP/Masanoperatingsystem,andfinally,howtoimplementCP/Mon
differentcomputersystems. This bookis writtenfor peoplewho
HavebeenworkingwithmicrocomputersthatrunDigitalResearch'sCP/M
operatingsystem.
Understand the internals ofthe microprocessor world- bits, bytes, ports,
RAM, ROM, and otherjargonofthe programmer.
Know how to write in assembly language for the Intel 8080 or Zilog Z80
Central ProcessingUnit(CPU) chips.
Ifyoudon'thavethiskindofbackground,startbygettingpracticalexperience
on a system running CP/M and by reading thefollowing books from Osborne/
McGraw-Hill:
An Introduction to Microcomputers: Volume 1-Basic Concepts
This book describes the fundamental concepts and facts that you need to
1
2
The CP/M Programmer's Handbook
know about microprocessors in orderto program them. Ifyou really need
basics, there isa Volume0 called The Beginner's Book.
8080Aj8085 Assembly Language Programming
Thisbookcoversallaspectsofwritingprogramsin8080assemblylanguage,
giving manyexamples.
Osborne CPjM® User Guide(2nd Edition)
This book introduces the CP/M operating system. Ittells you how to use
CP/M as a tool to get things done on a computer.
ThebookyouarereadingnowdealsonlywithCP/MVersion2.2forthe8080
or Z80 chips. At the time of writing, new versions of CP/M and MP/M (the
multi-user, multi-taskingsuccessorto CP/M)werebecomingavailable. CP/M-86
andMP/M-86fortheIntel8086CPUchipandMP/M-IIforthe8080orZ80chips
hadbeenreleased,withCP/M3.0(8080orZ80)inthewings.The8086,although
related architecturally to the 8080, is different enough to make it impossible to
cover in detail in this book; and while MP/M-II and MP/M-86 are similar to
CP/M, they have many aspects that cannot be adequately discussed within the
scope ofthis book.
Outline of Contents
This bookexplains topics as ifyou were startingfrom the top ofa pyramid.
Successive"slices"downthepyramidcoverthesamematerialbutgivemoredetail.
Thefirst chapterincludesabriefoutlineofthenotationusedinthisbookfor
example programs written in Intel 8080 assembly language and in the C pro
gramminglanguage.
Chapter2deals with the structure ofCP/M, describing its major parts, their
positions in memory, and theirfunctions.
Chapter3discussesCP/M'sfile systeminasmuchdetailaspossible,givenits
proprietarynature. Thedirectoryentry,diskparameterblock,andfile organiza
tionaredescribed.
Chapter4coverstheConsoleCommandProcessor(CCP),examiningtheway
inwhichyouentercommandlines,theCP/McommandsbuiltintotheCCP,how
the CCP loads programs, and how ittransferscontrolto these programs.
Chapter5beginstheprogrammingsection.Itdealswiththesystemcallsyour
programs can make to the high-level part of CP/M, the Basic Disk Operating
System(BDOS).
Chapters6through10dealwiththeBasicInput/OutputSystem(BIOS).Thisis
thepartofCP/Mthatisuniquetoeachcomputersystem.Itisthepartthatyouasa
programmerwill write and implementfor your owncomputersystem.
Chapter6describes a standard implementation ofthe BIOS.
3
Chapter I: Introduction
Chapter 7 describes the mechanism for rebuilding CP/M for a different
configuration.
Chapter 8tells you how to write anenhanced BIOS.
Chapter9takesacloselookathowtohandlehardwareerrors-howtodetect
and deal with them, and how to make this task easier for the person using the
computer.
Chapter 10discussesthe problemsyou mayface whenyoutrytodebugyour
BIOScode. Itincludesdebuggingsubroutinesanddescribestechniquesthatwill
save you timeand suffering.
Chapter11describesseveralutilityprograms,somethatworkwiththefeatures
ofthe enhanced BIOS in Chapter 8 and some that will work with all CP/M 2
implementations.
Chapter 12concernserrormessagesandsomeodditiesthatyouwilldiscover,
sometimespainfully,inCP/M.Messagesareexplainedandsomeprobablecauses
for strange resultsaredocumented.
The appendixes contain "ready-reference" information and summaries of
information that you need at your side when designing, coding, and testing
programs to rununderCP/M oryour own BIOS routines.
Notation
Whenyouprogramyourcomputer,youwillbesittinginfrontofyourterminal
interactingwithCP/Mandtheutilityprogramsthatrununderit.Thesectionsthat
followdescribethenotationusedtorepresentthedialogthatwillappearonyour
terminaland the outputthat will appear onyour printer.
Console Dialog
This book follows the conventions used in the Osborne Cp/M User Guide,
extended slightlyto handle morecomplexdialogs. In this book
< name>meanstheASCIIcharacternamedbetweentheanglebrackets,<
and>. Forexample,< BEL>istheASCIIBellcharacter,and< HT>isthe
ASCII HorizontalTab Character. (Referto Appendix Afor the complete
ASCIIcharacterset.)
<cr> means to pressthe CARRIAGERETURN key.
123 ora number withouta suffix meansa decimal number.
100Bora numberfollowed by Bmeans a binarynumber.
OA5H ora numberfollowed by H means a hexadecimal number. A hexa
decimal number starting witha letter is usually shownwith a leading0to
avoid confusion.