SpectrumMachineCodeMadeEasyVolume1.pdf

SPECTRUM

MACHINE CODE

MADE EASY

Volume One

For Beginners

James Walsh

Spectrum Machine Code Made Easy

Volume One—For Beginners

This book has been written to allow the user of the ZX

Spectrum computer, with any amount of BASIC

experience, to enter the wonderful world of machine

code programming. This text is aimed directly at those

who have no previous experience of machine code

programming at all.

Starting off with the basic concepts of machine code,

followed by the basics of binary maths, hexidecimal and

base conversion, leading as quickly and as painlessly as

possible on to the rules and types of addressing of the

very powerful Z80 microprocessor.

Whilst heavily laced with examples, it swiftly moves on to

the rudiments of more advanced instructions, namely

ADD, SUB, SBC, ADC, with intermittent breaks to allow

the reader to use the knowledge already gained.

Carefully and thoroughly the 'carry flag', jumping,

relative jumps, CALLs, RET and NOP commands are

explained.

Finally a section is dedicated to the theory of stacks, how

to build and manipulate them.

Another great book horn

INTERFACE PUBLICATIONS

SPECTRUM

MACHINE CODE

MADE EASY

Volume One

For Beginners

James Walsh

I MTERFdCE

PIIBLICATIONS

DEDICATION

Then at the balance let's be mute,

We never can adjust it;

What's done we partly may compute,

But know not what's resisted.

To Margy, with love

From

Robert Burns

To Charles and Emma — THANKS for all the help

THE AUTHOR

First published in the UK by:

Interface Publications,

9-11 Kensington High Street,

London W8 5NP.

James Walsh, at the time of writing this book, is sixteen years

old and attends Davenant Foundation School in Loughton,

Essex.

He has already established a reputation as a regular contributor

to several nationally distributed computer magazines, and has

previously contributed to two published books on Sinclair

computers.

in whole without the explicit prior written permission of the

publishers. The routines outlined in this book may not be used

as part of any program offered for publication nor for programs

intended to be sold as software, except as allowed by the

publisher. Permission must be sought, in advance, for all

applications of this material beyond private use by the

purchaser of this volume.

In addition to writing articles, software reviews, and books, he

finds the time to be a keen photographer, a mediocre musician

and, for the most part, a worry to his teachers.

He hopes to publish his next book in the not too far distant

future — exams permitting — although his more immediate

ambition is to travel abroad.

ISBN 0 907563 43 0

The time given to writing this book has done little for his social

life — something he now hopes to find the time to correct. In

the interim he acknowledges both the patience and support of

all his family and friends.

Cover Illustrator, Stuart Hughes

Clive C. Walsh

Typeset and Printed in England by Commercial Colour Press,

London E7.

CONTENTS

CHAPTER 1: Why Machine Code?

— machine code as the language of the computer

— 1 + 1 = 8!!!

— bi-stable states and binary introduced

CHAPTER 2: Words As Numbers.

— generalised view of how the computer works

— coming to terms with Hexadecimal and Binary

CHAPTER 3: Addresses and How To Get There.

— addresses

— RAMTOP

— entering machine code

CHAPTER 4: Working On The Registers.

— registers

machine versus assembly language

manipulating the registers

CHAPTER 5: Doing Your Sums On The Registers.

— add

— sub

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