This is the official User Guide, as seen in the Acornsoft catalogue, so you might expect it to be a killer! And it is! This one is published by Adder by the Electron Advanced User Guide will be by Adder/Acornsoft, and it's written by Dickens and Holmes. In other words the separate elements in Cambridge publishing about their beloved Micro are coming together powerfully.

Your £9.95 (everything for the BBC seems to cost £9.95!) buys you 359 pages of very well produced factual information and programming examples. The layout of the book is excellent, with nice use of typesetting styles. The listings are readable and well documented.

Large chunks of the book are naturally given over to listing detailed information about the BASIC routines which are the subject of the book. There are appendices on Syntax, on BASIC ROM routines (a "Summary"), lists of Keywords, OS calls and vectors, OSBYTE summary, Variable locations, Bibliography, Glossary and Index. Phew, nothing for the poor old reviewer to grip about. The ROM routine summary is particularly interesting and with a Disassembler in tow, the reader has all he or she requires to take a good look at this most famous of British BASICs.

A good half of the book is devoted to more detailed explanation of the routines and error handling in BASIC. Each routine is broken down into execution address, entry conditions, exit conditions, description and other entry points. There is a similar section on BRK handling, with error descriptions and explanations. This is surprisingly enlightening since it highlights how BASIC does things.

All this information is pretty difficult to digest in its pure form but don't worry because the first helf of the book is given over to a clear description of how BASIC goes about interpreting what you care to throw at at. The author takes a quick look at the 6502. This duplicates information available in all books on similar subjects but is not so long as to be wasteful of space.

BASIC is such as huge program that it is difficult to grasp the complexities. Here at least we have an overview of how it is organised as well as details on pointers, workspace, heaps and stacks. A couple of programs are listed which help out with finding variables and disassembly. Not content with finding out how BASIC deals with situations such as errors, the author details interesting methods of using them to add commands (in vogue at the moment with Addcomm and Extension ROM) and to overlay procedure and function routines.

There's also a renumber program and error lister (Toolkit-like), and recovery programming for Bad Mode (when changing Mode within PROC or FN) and Bad Program.

Overall, the ROM User Guide offers a good mix of well presented reference material, clear explanation and "hands on" practice. If you are the sort who already scans BASIC and would like to delve further than even £9.95 is worth it!