100
PROGRAMS
FOR THE
ACORN ELECTRON

   ELECTRON

BASIC PROGRAMMING ON THE ACORN ELECTRON,
Neil Cryer and Andrew Cryer
(book and cassette)

   BBC MICROCOMPUTER

BASIC PROGRAMMING ON THE BBC MICROCOMPUTER,
Neil Cryer and Pat Cryer

GRAPHICS ON THE BBC MICROCOMPUTER,
Neil Cryer, Pat Cryer and Andrew Cryer
(book and cassette)

BBC MICROCOMPUTER FOR BEGINNERS,
Seamus Dunn and Valerie Morgan

100 PROGRAMS FOR THE BBC MICROCOMPUTER,
John Gordon
(book and cassette)

THE BBC MICROCOMPUTER DISK COMPANION,
Tony Latham

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100
PROGRAMS
FOR THE
ACORN ELECTRON

Englewood Cliffs, NJ London New Delhi Rio de Janeiro
Singapore Sydney Tokyo Toronto Wellington

British Library Cataloguing in Publication Data

Gordon, John
   100 programs for the Acorn Electron
   1. Electron (Computer) - Programming
   I. Title
   001 64'25 QA76.8.A
   ISBN 0-13-634858-0

Electron and Acorn are trademarks of Acorn Computers Ltd

© 1984 by JOHN GORDON

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmited in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior permission of the author.
For permission within the United States contact Prentice-Hall Inc., Englewood Cliffs, NJ 07632.

ISBN 0-13-634858 0
ISBN 0-13-634866 1 {CASSETTE}

Prentice-Hall International, Inc., London
Prentice-Hall of Australia Pty Ltd, Sydney
Prentice-Hall Canada, Inc., Toronto
Prentice-Hall of India, Private Ltd, New Delhi
Prentice-Hall of Japan, Inc., Tokyo
Prentice-Hall of Southeast Asia Pte Ltd, Singapore
Prentice-Hall, Inc., Englewood Cliffs, New Jersey
Prentice-Hall do Brasil Ltda, Rio de Janeiro
Whitehall Books Ltd, Wellington, New Zealand

10 9 8 7 6 5 4 3 2

Printed in Great Britain by A. Wheaton & Co., Ltd., Exeter

To Teresa and Jayne for putting up with me.

SECTION 1	INTRODUCTION
	P1	Nitemare	6
	P2	Musak	8
	P3	Tunes	10
	P4	Pattern	12
	P5	Graph Plotting	14
	P6	Bouncing Ball 1	17
	P7	Bouncing Ball 2	18
	P8	Jimmy	19
	P9	Clock	21
SECTION 2	GAMES
	P10	Wheel of Fortune	25
	P11	Mastermind	26
	P12	Guess the Number	28
	P13	Reaction Test	30
	P14	Gobble	31
	P15	Tennis	33
	P16	Bombs	35
	P17	Bat'n'Moths	38
	P18	Monster Island	41
	P19	Battleships	44
SECTION 3	BUSINESS
	P20	Loan Repayment Period	48
	P21	Depreciation	50
	P22	Four-weekly Moving Average	52
	P23, P24, P25	Stock Control	55
		P23 Stock File Creation
		P24 Transaction File Creation
		P25 Stock File Update and Report
	P26	VAT Calculator	58
	P27	True Rate of Interest	59
SECTION 4	AT HOME
	P28	Simple Tax Calculator	60
	P29	Loan Repayments	62
	P30	Monthly Accounts	66
	P31	Conversion	66
	P32	Birthday Lists	68
	P33	Diary	70
	P34	Calendar	72
	P35	Telephone List	74
	P36	Investments	76
SECTION 5	MATHEMATICS
	P37	Quadratic Equations	78
	P38	Factorization	80
	P39	Factorial	83
	P40	Greatest Common Divisor	85
	P41	Secant Method	86
	P42	Method of Bisections	88
	P43	Trapezoidal Rule	90
	P44	Simpson's Rule	92
SECTION 6	PAINTING ON THE SCREEN
	P45	Circles	93
	P46	Interference	95
	P47	Picture	96
	P48	Picture Editor	97
	P49	Zoom	100
	P50	Worm	102
	P51	Drawing	104
	P52	Writing Text At The Graphics Cursor	105
SECTION 7	DATA HANDLING PROGRAMS
	P53	Pie Chart	107
	P54	Bar Chart	109
	P55	Mean and Standard Deviation	111
	P56	Bubble Sort	114
	P57	Shell Sort	116
	P58	Merge	118
	P59	Binary Search	120
	P60	Permutations	122
	P61	Combinations	123
	P62	Least Squares	124
SECTION 8	RECREATION
	P63	Number of Days	126
	P64	Digital Clock	127
	P65	Kitchen Timer	128
	P66	Recipes	129
	P67	Encoder	134
	P68	Decoder	136
	P69	The Game of Life	138
	P70	Biorhythms	141
	P71	Dog Race	143
	P72	Magic Matrix	145
	P73	Dice	147
	P74	Pools Program	148
	P75	Shuffle	149
SECTION 9	THE SCIENCE LAB
	P76	Number Base Conversion	151
	P77	Colour Codes for Resistors	154
	P78	Volumes of Solids	156
	P79 and P80	Physics	159
		P79 Moment of Intertia
		P80 Focal Length
	P81	Resistors	164
	P82	Calculator	165
	P83	Coordinate Conversion	166
SECTION 10	GRAPHICS ROUTINES
	P84	Shading	168
	P85	Translation	170
	P86	Parallelogram	172
	P87	Drawing Circles	174
	P88	Shape Grabber	177
	P89	Rotation	179
	P90	Transformations	182
	P91	General Transformations	185
	P92	3D-Rotation--1	187
	P93	3D-Rotation--2	190
	P94	Perspective	192
	P95	Rotating House	196
SECTION 11	PROGRAMS FOR THE SCHOOL
	P96	Arithmetic Tutor	199
	P97 and P98	French and German Tutorial
		P97 French Tutorial
		P98 German Tutorial
	P99	Spelling	204
	P100	Counting	207

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100
PROGRAMS
FOR THE
ACORN ELECTRON

INTRODUCTION

I have, in my selection, attempted to answer the question "What do you use a microcomputer for?". You will find routines in this book which cover the use of micros at home, in business, in school and for pleasure.

It is intended that after you have entered any of these programs then you would wish to record them onto tape. To help you, here is a reminder as to the saving of programs.

To save a program:

   1.   Key the program in.
   2.   Insert cassette into recorder.

   3.   Type SAVE "PROG", where PROG is the name of your program, then press <RETURN>

   4.   A message then appears on the screen,

      RECORD then RETURN

   5.   Press PLAY and RECORD on the tape and press RETURN to let the computer know that you have done so.
   6.   If your cassette has MOTOR CONTROL then the tape will stop when the computer has finished recording your program. If MOTOR CONTROL is not present, you will have to stop the cassette yourself.
   7.   The prompt > will be displayed when the SAVE is complete.

1.   Place cassette in recorder and wind to correct position on tape.
2.   Type LOAD "PROG" and press return.
3.   The computer will present the message,
   Searching.
4.   Press PLAY on your recorder.
5.   When the computer finds your program it will display the message,
   Loading
6.   The prompt > will be displayed when the LOAD is complete. You can then LIST or RUN your program as required.

The Layout of The Book.

Each program is laid out in the following format:

   Program commentary.
   Program listing.
   Diagram of screen under execution, or printout where appropriate.

Program layout

The ELECTRON dialect of BASIC is an attempt to overcome some of the limitations of "traditional" BASIC. It is possible to write fairly well laid out and well structured code in ELECTRON BASIC.

These programs represent an attempt to exploit these features of ELECTRON BASIC. However, the language does have its limitations. You will occasionally find some rather long IF statements, which can be difficult to read. This is due to a lack of a multi-line IF statement, as is given in other versions of BASIC such as COMAL.

It is possible to lay out programs using what is known as LISTO features, as used in the User Guide. I have not used this feature of the ELECTRON machine. I prefer to layout code in a manner that I find more natural.

When writing the programs, I first of all sketched out the program using a pseudo form of BASIC, which was fairly well structured. Thus when I come to code the programs, I already know the layout I required, so I did not use the layout features of the machine.

The Machine Code Routine FNchar

The routine is:

    830 DEF FNchar(U,V)
    840 PRINT TAB(U,V);
    850 A%=135
    860 =(USR(&FFF4) AND &FF00)/&100

Line 840 places the text cursor at position (u,v) on the screen. Line 850 places the value 135 (87 hex) into the accumulator. The routine called by USR(&FFF4) is one of the OSBYTE calls documented in the User Guide. ANDing the integer returned from the USR call with &FF00, masks off the least significant byte. Division by &100 leaves us with the ASCII code for that character.

Keying in Your Programs

   1.   Use the AUTO feature, typically AUTO 100. This will automatically generate line numbers for you.
   2.   Use the fact that there is an automatic REPEAT on each key. If you have a lot of spaces to type in, just keep your finger on the space bar.
   3.   Use the cursor control and editing keys to keep the key press to a minimum.
   4.   To check your program listing, it is possible to put the ELECTRON micro into page mode.
      Press the control key and N together, then LIST. The computer will only LIST a portion of the program. To get the next portion, press the SHIFT key. If you want to stop the listing press ESCAPE. To switch off page mode press he control key and the letter O together.
   5.   Use cursor control and copy keys to edit your programs.
   6.   Use the single key entry feature of the ELECTRON as far as is possible, for example pressing the FUNCT key with the P key will give the BASIC keyword PLOT.
   7.   I have sometimes used rather long variable names which can occur many times in a program. To aid keying these in, you can program a function key. For example, in Program P13 you could program key f0 as *KEY "no_of_attempts" and simply press f0 whenever this name is used.

Bugs

Part of the fun in programming is the finding and correcting of bugs. Indeed, correcting bugs often contributes to the process of introducing bugs.

Bugs can be introduced in various ways. I might have left a few bugs in the code. Hopefully, through the efforts of Prentice-Hall in carrying out field tests, those will be at a minimum.

Bugs can be introduced when you are keing in your programs. To catch these bugs you have to go through each section of the program in turn and try to locate it bye eye and by testing the section. Using the page mode feature of the ELECTRON micro can be very helpful at this stage.

Common errors are:

   1.   Using the letter O rather than the number 0.
   2.   Using the number one rather than the letter I.
   3.   Using lower case rather than the upper case.
   4.   Using the wrong dataname.
   5.   Going beyon the capabilities of the program.

Developing The Programs

One of the joys of programming is to take a simple routine and give it a professional user friendly appearance. I have not attempted to make any programs complete in this sense. This is left up to you.

Do not feel shy about using the programs as routines within others. Consider this book to be a software library.

However, if you do use a routine within work of your own, I would be pleased if you were to acknowledge the source.

GO ON ENJOY YOURSELF.