UNDERSTANDING MICROCOMPUTERS UNDERSTANDING MICROCOMPUTERS Dennis Longley and MichaeLShain M MACMILLAN PRESS LONDON MacmillanReferenceBooks @The Macmillan Press Ltd, 1985 All rights reserved. No reproduction, copy or transmission of this publication may be made without written permission. No paragraph of this publication may be reproduced, copied or transmitted save with written permission or in accordance with the provisions of the Copyright Act 1956 (as amended). Any person who does any unauthorised act in relation to this publication may be liable to criminal prosecution and civil claims for damages. First published 1985 by THE MACMILLAN PRESS LTD London and Basingstoke Associated companies in Auckland, Delhi, Dublin, Gaborone, Hamburg, Harare, HongKong, Johannesburg, Kuala Lumpur, Lagos, Manzini, Melbourne, Mexico City, Nairobi, New York, Singapore, Tokyo. British Library Cataloguing in Publication Data Longley, Dennis Understanding microcomputers. 1. Computer networks 2. Microcomputers I. Title II. Shain, Michael 001.64'04 TK105.5 ISBN978-0-333-37573-0 ISBN 978-1-349-07553-9 (eBook) DOI 10.1007/978-1-349-07553-9 The paperback edition of this book is sold subject to the condition that it shall not, by way of trade or otherwise, be lent, resold, hired out, or otherwise circulated without the publisher's prior consent in any form of binding or cover other than that in which it is published and without a similar condition including this condition being imposed on the subsequent purchaser Contents Preface xi 1 HOW MICROCOMPUTERS WORK 1.1 INTRODUCTION 1.2 THE MICROCOMPUTER SYSTEM 1.3 THE CLERKMODEL 2 1.4 THE PROGRAM 4 1.5 BLACK BOX MODEL 6 1.6 INPUT/OUTPUT 6 1.7 CAN IT MAKE A MISTAKE? 9 1.8 CONCLUSIONS 10 2 FILESAND RECORDS 11 2.1 INTRODUCTION 11 2.2 FILESAND RECORDS:AN OVERVIEW 11 2.3 FILESAND RECORDS: A DETAILED 14 ACCOUNT 2.3.1 Introduction 14 2.3.2 File processing 15 2.3.3 Housekeeping 17 3 MICROCOMPUTER HARDWARE 19 3.1 INTRODUCTION 19 3.2 MICROCOMPUTER HARDWARE: AN 20 OVERVIEW 3.2.1 Introduction 20 3.2.2 Microcomputer building blocks 22 3.3 MICROCOMPUTER HARDWARE: A 24 DETAILED ACCOUNT 3.3.1 Introduction 24 3.3.2 CPU 26 3.3.3 Memory 27 3.3.4 Buses and interfaces 28 4 MICROCOMPUTER PERIPHERALS 32 4.1 INTRODUCTION 32 4.2 CONVENTIONAL PERIPHERALS 33 4.2.1 Introduction 33 4.2.2 Keyboards 33 4.2.3 Video monitors and terminals 35 4.2.4 Backing storage 41 4.2.5 Printers 47 4.3 SPECIALAPPLICATIONS 53 4.3.1 Communications 53 4.3.2 Input devices 55 4.3.3 Output devices 61 4.4 CONCLUSIONS 63 5 MICROCOMPUTER SOFTWARE 64 5.1 INTRODUCTION 64 5.2 MICROCOMPUTERSOFTWARE: AN 64 OVERVIEW 6 OPERATING SYSTEMS 69 6.1 INTRODUCTION 69 6.2 OPERATINGSYSTEMS: AN OVERVIEW 70 6.2.1 The operations 70 6.2.2 Operating systems and application 72 programs 6.3 MS-DOS: A MICROCOMPUTER 72 OPERATING SYSTEM 6.3.1 Introduction 72 6.3.2 What is MS-DOS? 73 6.3.3 Getting started 74 6.3.4 Housekeeping 75 6.3.5 Copying and editing 78 6.3.6 User defined routines 81 6.3.7 Programs 82 vi 6.4 CONCLUSION 82 7 HIGH LEVEL LANGUAGES 83 7.1 INTRODUCTION 83 7.2 HIGH LEVELLANGUAGES: AN 83 OVERVIEW 7.2.1 Introduction 83 7.2.2 Translation 84 7.2.3 Typical languages 85 7.3 HIGH LEVELLANGUAGES: DETAILED 86 ACCOUNT 7.3.1 Introduction 86 7.3.2 Selecting the language 87 7.3.3 Programming in BASIC 87 7.3.4 An example of a BASIC program 94 7.3.5 Learning BASIC 95 8 LOW LEVEL LANGUAGES 97 8.1 INTRODUCTION 97 8.2 LOW LEVELLANGUAGES: AN 97 OVERVIEW 8.2.1 Introduction 97 8.3 MACHINE CODEAND ASSEMBLY 98 LANGUAGE 8.3.1 Introduction 98 8.3.2 Data transfer instructions 100 8.3.3 Arithmetic instructions 101 8.3.4 Control transfer instructions 102 8.3.5 Subroutines 105 8.4 ASSEMBLING AND TESTING 105 9 COMPILERS, INTERPRETERSAND 107 ASSEMBLERS 9.1 Introduction 107 9.2 AN OVERVIEW 108 9.2.1 Interpreters 108 9.2.2 Compilers 110 9.2.3 Assemblers 110 vii 9.3 A DETAILEDACCOUNT 110 9.3.1 Introduction 110 9.3.2 Interpreters 111 9.3.3 Compilers 112 9.3.4 Assemblers 114 10 WRITING YOUR OWN APPLICATIONS 115 10.1 INTRODUCTION 115 10.2 WRITING YOUR OWN APPLICATION:AN 116 OVERVIEW 10.3 WRITING YOUR OWN APPLICATIONS: 117 DETAILEDACCOUNT 10.3.1 Introduction 117 10.3.2 Defining the problem in outline 117 10.3.3 Seeking available software packages and 118 estimating computing costs 10.3.4 Defining the problem in detail 120 10.3.5 Selecting the language 121 10.3.6 Estimating the system requirement 122 10.3.7 Specifying file formats, data input and 124 output formats, operator actions 10.3.8 Programming 126 10.3.9 Debugging 126 10.3.10 Testing 128 10.3.11 Setting up the system 128 10.3.12 Trial running 129 10.3.13 Documentation 130 10.3.14 Conclusion 131 11 SELECTING A PACKAGE 132 11.1 INTRODUCTION 132 11.2 SOFTWARECAPABILITIES 132 11.3 HARDWARE COMPATIBILITY 133 11.4 PACKAGEPERFORMANCE 134 11.5 DOCUMENTATION 136 11.6 BUYING A PACKAGE 136 11.7 CONCLUSIONS 138 viii 12 AN INTEGRATEDSPREADSHEET 139 PACKAGE 12.1 INTRODUCTION 139 12.2 SPREADSHEET 140 12.3 GRAPHICS 142 12.4 DATABASE 143 12.5 PROGRAMMING 143 12.6 CONCLUSIONS 144 GLOSSARY 146 ix PREFACE The contents of this book are derived from the Understanding Microcomputers section of the Microcomputer Users Handbook by Longley and Shain. It is written primarily for the business microcomputer user who may wish to obtain an overall view of the topic in one reading or to dip into particular sections to uncover the meaning behind a particular piece of jargon. The development of microcomputers over the past decade commenced with video games, moved through hobbyist computers with audio cassette players and quickly established an entirely new market in business computer systems. The success of the microcomputer market, coupled with the rapid developments in microelectronics and software, has resulted in the development of small businesscomputing systems which rival the powerof earlydata processing mainframe installations. The business microcomputer has revolutionized the data processingindustry; small businesses and professional users have computerized their operations whilst large companies have completely restructured their data processing operations. The computing industry is now poised to enter the fifth generation era in which computers will exploit the potential of artificial intelligence and herald in the powerful user-friendly executive workstation. The successful exploitation of computers has always depended upon the optimum combination of human and computer resources. In the business world the user should undertake a fundamental reappraisal of his modus operandi inthe light of the facilities offered by the computer system. Ideally the businessman would be able to exploit the power of the business system with a minimal knowledge of the internal hardware and software functions. However, the ultimate user friendly computer system is still a goal for the future rather than a current reality. The computer user who holds his system at arms length, relegating its role to a particular operation, is unlikely to obtain the maximum benefit from its full potential. Moreover the microcomputer market continues to produce new hardware components, peripherals and software which can substantially improve the performance of the basic system. The selection of the worthwhile enhancements, from the myriad on offer, demands some degree of familiarity with the system. On the other hand any attempt to develop a mastery of computing opens up a Pandora's Box of technology and jargon. The problem for the average user is to predetermine the relevance and the necessary depth of knowledge in the various aspects of hardware and software. This book addresses itself to the problem of the average business microcomputer user. In each chapter the reader is xi