Melbourne House has two new books which cover machine code and related subjects more than adequately. The first is by Dr Ian Logan, author of several books and pamphlets on the ZX-81 ROM. Understanding Your Spectrum covers both Basic and machine code programming. Its aims are to show how the Spectrum works, to teach Z-80 machine code, and to give the reader an understanding of the ROM operating system in the machine. Logan does all those things in a very expert manner which even the beginner should understand.
The other book from Melbourne House is Spectrum Machine Language For The Absolute Beginner. It is even easier to understand than Logan's. It starts from a very simple base and takes the reader through most of the Z-80 instruction set as implemented on the Spectrum.
The theory is supported by practical examples which can be entered and run by anyone. The book is completed by taking the reader from conception to the completion of an arcade game, Frogger, written all in machine code.
Both books are excellent in content but a little over-priced. Understanding Your Spectrum costs £7.95 and Spectrum Machine Language For The Absolute Beginner £6.95. If you are thinking of programming in machine code, the books will teach you almost everything you want to know.