The BBC Micro is one of the most interfaceable micros currently available, due mainly to its user port, and the documentation that goes with it. If you have read all the books that tell you about programming, that sketchily describe ways of attaching your computer to the big wide world, then this is probably the book for you.

The book is divided into three main sections. The first describes the main parts of the system I/O (input output) and in addition, Boolean logic, the processor and its pin out, the connections, the analogue port (including light pens), interrupts, the RS423, the video processor, the user port, and the 1MHz bus.

It was at this point that I began to get an idea how comprehensive the book was, especially as each chapter in this section has its own bibliography.

The next section covers all of the above things in more detail with example routines and internal chip descriptions. It starts with the user port. The 6522 VIA is covered in a fair amount of detail with descriptions of how to use all the registers and timers. A number of machines use this chip and anybody who owns one could benefit form a glance at this section. The book then deals with interfacing light pens, and using the analogue inputs - not in quite so much detail, but perfectly adequately.

This section closes with the RS423, centronics port, and the 1MHz bus. The latter gives a few details on Fred, Jim and the lines that are labelled in the manual but don't mean a lot.

The final section of the book gives a selection of construction projects, including a motherboard. Unfortunately, this is where the book gets a little vague. Only the barest design details are given, for the motherboard especially, and, since the rest of the daughter designs are constructed to plug into 'mother', it is a bit of an oversight.

Overall, the book is valuable for its reference qualities. If, like me, you occasionally look at designs for attaching things to your micro, but never get around to building them, then this book is pretty well a must.

Kenn Garroch