ATOMIC THEORY AND PRACTICE

                               Contents

Introduction -                                               1

BASIC PROGRAMMING

Chapter  1 - Start Here                                      3
         2 - Calculating in BASIC                           11
         3 - Planning a Program                             17
         4 - Writing a BASIC Program                        23
         5 - Loops                                          33
         6 - Subroutines                                    39
         7 - Arrays and Vectors                             45
         8 - Strings                                        57
         9 - Reading and Writing Data                       67
        10 - More Space and More Speed                      73
        11 - Advanced Graphics                              79
        12 - What to do if Baffled                          91

ASSEMBLER PROGRAMMING

Chapter 13 - Assembler Programming                          95
        14 - Jumps, Branches, and Loops                    105
        15 - Logical Operations, Shifts, and Rotates       111
        16 - Addressing Modes and Registers                117
        17 - Machine-Code in BASIC                         123

REFERENCE SECTION

Chapter 18 - ATOM Operating System                         131
        19 - Cassette Operating System                     139
        20 - BASIC Statements, Functions, and Commands     143
        21 - BASlC Characters and Operators                155
        22 - Extending the ATOM                            161
        23 - Mnemonic Assembler                            171
        24 - Assembler Mnemonics                           181
        25 - Operating System Routines and Addresses       191
        26 - Syntax Definition                             199
        27 - Error Codes                                   205

Index -                                                    211

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Introduction

This manual explains how to connect up the ATOM, and how to program it 
in BASIC or Assembler. The manual is arranged in three sections 
printed  on  different  coloured  paper.  If  you  have  never  programmed 
before you should read the  BASIC section, on plain paper, starting 
from Chapter 1; but be warned that you are setting off on an adventure 
which  will  require  some changes of attitude towards computers. The 
only way to learn the art of programming is by practice, and so every 
section of this manual includes many example programs which illustrate 
the concepts being explained. These should be typed in and tried out, 
even if at first you do not fully understand how they work. By the end 
of chapter 4 you will  be able  to write your own programs for many 
different types of problem, and you may wish to stop there. The 
subsequent chapters, 5 to 12, deal with progressively more advanced
features of the ATOM's BASIC.
    If you have already programmed in BASIC you may prefer to turn to 
chapters 20 and 21 in the reference section; these contain a complete 
summary  of  all  the  BASIC  statements,  functions,  commands,  and 
operators. You will be pleased to discover a number of extensions in 
ATOM BASIC that are not found in other BASICS.
    If you want to learn to program in Assembler you should turn to 
the second section of the manual which is printed on coloured paper, 
and  read  from  chapter 13 onwards. Readers experienced  in Assembler 
programming  can jump to chapter 23 in  the reference section, which 
gives a concise description of the ATOM assembler.
    The third section of the manual, printed on plain paper, is the 
reference section. It contains a summary of all the ATOM's facilities, 
a listing of the special addresses in the ATOM, and the error codes.
    If you have a minimal ATOM you will be able to run all programs 
whose sizes are given as less than 512 bytes, or which are so short 
that no size is given. Longer programs will require additional memory, 
but many programs can be reduced in size by using the abbreviations 
explained in chapter 10.

                         Acknowledgements

The preparation of this manual would not have been possible without 
the continuous assistance of everyone at Acorn. In particular I am 
grateful to Roger Wilson for providing details of the operation of the 
BASIC interpreter, and for assistance with editing the source of this 
manual;  to Nick  Toop  for  explaining many details of the ATOM's 
circuitry; and to Laurence Hardwick for testing the example programs. 
I would also like to thank the many people who provided comments on 
previous drafts of the manual.
    The following example programs were provided by Roger Wilson: 
Curve Stitching in a Square, Tower of Hanoi, Eight Queens, Prime 
Numbers, Arbitrary Precision Powers, Day of Week, Random Rectangles, 
and Renumber; and the following by Nick Toop: Simultaneous Equations, 
Encoder/Decoder, Three-Dimensional Plotting, and Saddle Curve.
    The manual was prepared and edited on an Acorn System Three, and 
the final artwork  was  prepared  using  the  Acorn  Text Processing 
Package.

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CONNECTIONS TO ATOM



ATOM KEYBOARD



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