This book is for the absolute beginner or, at least, it starts that way. Early chapters explain such things as binary and hexadecimal and what a micro is. Then comes a description of the 6809, the CPU that controls the Dragon, and its addressing modes.

Much of the book is devoted to the instruction set; anyone using a 6809 on a machine other than the Dragon might consider the book for this section alone as it is comprehensive. A minor criticism is the use of the word inherent when the author means implied, as that may cause confusion in relation to other books on the subject. The descriptions in this section tend to be complex, and may need repeat readings.

The final main section of the book contains example programs, starting with simple examples of the instruction set and ending up with useful routines that show how to access the Dragon's external chips, the PIA, screen, sound and so on.

The appendices are most informative, covering graphics modes, memory locations, ROM routines, ASCII codes and the instruction set summary.

This is a comprehensive book, useful for anyone trying machine code, which need not be harder than Basic. All you need is the instruction set, some idea of where to put your programs in memory, and how to get information in and out of the computer. The book covers all these features, making machine code straightforward.

Kenn Garroch