The Basic Rom User Guide is designed to cover one area of computer technology - the BASIC ROM. This book is therefore extremely useful if you want to find out how your computer really works.

You may not know it, but BASIC is a computer program. Its purpose in life is to convert the programs you write into machine code. BASIC is stored in a ROM chip so that it is available as soon as you switch on your machine.

It is an extremely complex program and includes all of the functions, statements, error handling routines and commands that you can use in your programs.

This book succeeds in describing that complex process in clearly-explained units. It begins with a brief introduction to machine code programming and a description of the 6502 microprocessor. This section includes an outline of the instruction set and registers.

The Guide then moves straight into the task of explaining the structure of the BASIC program, which is treated as a system.

The comprehensive glossary of terms at the back of the book is extremely useful. In addition there is an extensive index so cross-referencing and finding one's way around the book is relatively easy.

As I read further and further into the book I became more and more tempted to try things out. It certainly does encourage exploration and self-awareness - there are a lot of examples and programs to illustrate the text.

I kept discovering new and useful short-cuts to my programming and techniques to improve my old programs.

However, there is one serious drawback to using the facilities of the BASIC ROM directly and not through the usual *FX calls - the programs may not be transferable from one machine to another.

The book does list the differences between BBC BASIC I, BBC BASIC II and Electron BASIC, and, if you are writing for your machine only, then there is no problem. But, if the program is to be transferred to anohter machine, then problems may easily arise.

The text provides a very useful handbook for the advanced programmer and a useful guide to those who wish to find out more about their computer. It contains listings for a complete disassembler and a very useful routine for recovering "bad programs". The section on error analysis and recovery after an error is most enlightening.

In all, this book fills a gap left by many user guides and texts on the Acorn range of computers.

John Woollard