BBC Microcomputer System User Guide

1 BBC Microcomputer System user Guide Original edition written by John Coll, edited by David Allen. Amendments and corrections to this edition by Acorn Computers Limited Part no 0433 000. Issue 1. Date October 1984. WARNING: THE COMPUTER MUST BE EARTHED. Important: The wires in the mains lead to the computer are coloured in accordance with the following code: Green and yellow Earth Blue Neutral Brown Live As the colours of the wires may not correspond with the coloured markings identifying the terminals in your plug, proceed as follows: The wire which is coloured green and yellow must be connected to the terminal in the plug which is marked by the letter E, or by the safety earth symbol or coloured green, or green and yellow. The wire which is coloured blue must be connected to the terminal which is marked with the letter N, or coloured black.

2 The wire which is coloured brown must be connected to the terminal which is marked with the letter L, or coloured red. If the socket outlet available is not suitable for the plug supplied, the plug should be cut off and the appropriate plug fitted and wired as previously noted. The moulded plug which was cut off should be disposed of as it could be a potential shock hazard if it were to be plugged in with the cut off end of the mains cord exposed. The moulded plug must be used with the fuse and fuse carrier firmly in place. The fuse carrier is of the same basic colour* as the coloured insert in the base of the plug. Different manufacturers' plugs and fuse carriers are not interchangeable. In the event of loss of the fuse carrier, the moulded plug MUST NOT be used. Either replace the moulded plug with another conventional plug wired as previously described, or obtain a replacement fuse carrier from an authorised BBC Microcomputer dealer.

3 In the event of the fuse blowing it should be replaced, after clearing any faults, with a 3 amp fuse that is ASTA approved to BS1362. *Not necessarily the same shade of that colour. Exposure Like all electronic equipment, the BBC Microcomputer should not be exposed to direct sunlight or moisture for long periods. Econet and The Tube are trademarks of Acorn Computers Limited The author and the British Broadcasting Corporation 1982. Neither the whole nor any part of the information contained in, or the product described in, this manual may be adapted or reproduced in any material form except with the prior written approval of Acorn Computers Limited (Acorn Computers). The product described in this manual and products for use with it are subject to continuous development and improvement. All information of a technical nature and particulars of the product and its use (including the information and particulars in this manual) are given by Acorn Computers in good faith.

4 However, it is acknowledged that there may be errors or omissions in this manual. A list of details of any amendments or revisions to this manual can be obtained upon request from Acorn Computers Technical Enquiries. Acorn Computers welcome comments and suggestions relating to the product and this manual. All correspondence should be addressed to: Technical Enquiries Acorn Computers Limited Newmarket Road Cambridge CB5 8PD. All maintenance and service on the product must be carried out by Acorn Computers' authorised dealers. Acorn Computers can accept no liability whatsoever for any loss or damage whatsoever caused by service or maintenance by unauthorised personnel. This manual is intended only to assist the reader in the use of the product, and therefore Acorn Computers shall not be liable for any loss or damage whatsoever arising from the use of any information or particulars in, or any error or omission in, this manual, or any incorrect use of the product.

5 First published 1984. Published by the British Broadcasting Corporation Typeset by Bateman Typesetters, Cambridge Within this publication the term BBC' is used as an abbreviation for British Broadcasting Corporation'. This book is part of the BBC Computer Literacy Project, prepared in consultation with the BBC. Continuing Education Advisory Council. The editor of the project is David Allen Note: If this manual is to be used in conjunction with a BBC Microcomputer which is fitted with an Operating System with version number lower than , then the following points should be borne in mind: Chapter 42 and all other references to the shadow screen' should be ignored. Chapter 49 should be ignored (unless the machine with which the manual is to be used is fitted with BASIC II). In all other respects this manual is functionally compatible with earlier versions of the BBC.

6 Microcomputer . Contents Introduction 1. Equipment required 1. Text conventions used in this manual 1. What this user Guide can and can't do 2. 1 Getting started 3. Experimenting 5. Connecting up the cassette recorder 7. Leads 7. Volume 8. Running the WELCOME programs 8. The keyboard 11. Cursor control keys 13. Giving the computer instructions Part 1. 2 Commands 15. 3 An introduction to variables 18. 4 A simple program 20. Using the screen editor 22. Deleting part of a program 24. Removing a program 25. 5 Recording programs on cassette 26. Saving a program on cassette 26. Checking a recording 27. Loading a program from cassette 27. Cataloguing a tape 28. What the numbers mean 28. 6 Sample programs 30. 7 AUTO, DELETE, REM, RENUMBER 43. 8 Introducing graphics 45. Modes, colours, graphics and windows 45.

7 Graphics 46. Windows 47. Making a graphics window 47. Making a text window 48. Changing the colours of text and graphics 50. 9 More on variables 52. Numbers and characters 52. String variables 53. How numbers and letters are stored in the computer's memory 54. Real and integer variables 55. Summary 56. 10 print formatting and cursor control 57. Field widths in different screen modes 57. Altering the width of the field and the way in which numbers are printed 60. For the more technically minded 60. TAB(X) 62. TAB(X,Y) 62. Advanced print positioning 63. Cursor control 65. Cursor on/off 66. 11 Input 67. 12 GET, INKEY 70. Advanced features 71. 13 TIME, RND 73. Structure in BASIC. 14 , TRUE, FALSE 74. 15 77. A note on LISTO 80. 16 More on TRUE and FALSE 84. Multiple statement lines 84. For the slightly more advanced 85.

8 More on TRUE and FALSE 85. 17 Procedures 87. Local variables in procedures 90. 18 Functions 94. 19 GOSUB 96. GOTO 99. 20 ON GOTO, ON GOSUB 100. Giving the computer instructions Part 2. 21 Even more on variables 102. Arrays 102. 22 READ, DATA, RESTORE 107. 23 Integer handling 110. 24 String handling 114. 25 Programming the red user -defined keys 119. The BREAK key 120. Other keys 120. 26 Operator priority 122. 27 Error handling 125. 28 Teletext control codes and MODE 7 128. To change the colour of the text 129. To make characters flash 129. To produce double-height characters 130. Graphics 132. Graphics codes 133. Making a large shape 133. Teletext graphics codes for the more adventurous 134. 29 Advanced graphics 137. How to change the screen display modes 137. How to draw lines 138. How to draw a square in the centre of the screen 138.

9 Changing the colour of the square 138. How to fill in with colour 138. How to change colours 139. How to plot a point on the screen 144. How to remove a point selectively 144. Animation 145. How to make a ball and move it on the screen 145. How to create your own graphics' characters 146. How to make a character (eg a man) 146. How to make him move 147. How to make a larger character 148. How to make the movement smoother 149. Making a complete lunar landing game 151. Running the program 154. 30 Sound 155. The pitch envelope 158. The amplitude envelope 159. Note synchronisation and other effects 161. 31 File handling 163. 32 Speeding up programs and saving memory space168. Reference section 33 BASIC keywords alphabetical summary 170. 34 VDU drivers 347. VDU code summary 348. Detailed description 349.

10 35 Cassette files 360. Cassette motor control 360. Recording levels 360. Playback volume and tone 360. Keeping an index of programs 360. Saving a BASIC program 361. Saving a section of memory 362. Loading a BASIC program 362. Loading a machine code program 363. Loading and running a BASIC program 363. Loading and running a machine code program 364. Using a cassette file to provide keyboard input 364. Reading cassette data files 365. Testing for end of file 365. Storing data on tape 366. Recording single characters on tape 366. File names 366. Responses to errors 367. Changing responses to errors 368. Cassette tape format 369. 36 Changing filing systems 370. 37 How to merge two BASIC programs 371. 38 Using printers 373. Connecting the printer to the computer 373. A parallel printer cable 374. Parallel printer connections 375.