This is a large tome from a prolific writer on the BBC computer. It numbers some 547 pages and has nine chapters. The first chapter is an introduction to assembly language programming and it covers most of the aspects of 6502 programming such as the registers, modes of addressing, and then goes on to introduce each command in the 6502 instruction set, with a brief note on each. The second chapter covers arithmetic on the computer, explaining how simple numbers are stored and explains how to multiply them.

Chapter three covers boolean algebra (with a minor spelling mistake starting the second paragraph (f501p110s1120)) explaining AND, OR, EOR and NOT and going on to show the computer uses this in plotting graphics. Chapter four explains further on arithmetic showing how the computer stores floating point numbers.

Chapter five is entitled "Evaluating expressions" and introduces the reader to reverse Polish notation. It includes programs for evaluating reverse Polish calculations and converting between that and the normal algebraic form.

Chapter six and seven are about two separate languages FROTH and SLUG. These are programs that allow the BBC computer to run programs in languages other than BBC BASIC without the need for more sideways ROMs. I would have liked to have seen more examples of programs for these languages than those that were printed. The last but one chapter is about an intelligent disassembler that is used to disassemble the Basic ROM. The final chapter is an annotated disassembly of the Basic ROM and takes up more than three quarters of the book. At the end of most chapters is a "diversion", this is a program that is either an interesting graphic display or a useful utility.

Aside from a few minor printing errors, this is a very good book that I would recommend it to anyone who had a good basic knowledge of assembly language programming and wanted to see what made their computer work.