Machine Language Programming Made Simple For Your Sinclair ZX80 and ZX81, Melbourne House (Publishers) Ltd., Glebe Cottage, Glebe House, Station Road, Cheddington, Leighton Buzzard, Bedfordshire LU7, England. 160 pp. ringbound. £8.95.
Machine Language Programming Made Simple is an excellent introduction to the complicated and bewildering world of Z80 machine code. This book eases you through a course of lessons with diagrams, examples, and exercises. Users of both the ZX80 and ZX81 will find this book to be of great value because both machines are based upon the Z80A Central Processor Unit which is a faster version of the Z80 Central Processor Unit (or CPU for short).
The book is organized into four chapters and one appendix. The first chapter, “Finding your way around machine language,” has seventeen sub-headings and discusses the way computers work, the concepts of binary and hexadecimal notation, counting up and down, logical operators (and how to use them), loops, jumps and block operators. Details are given on the uses of the twenty or so registers along with a discussion of what the stack is.
“Less frequently used instructions,” the next chapter, explains Register exchanges, Bit, Set, Reset, Rotates and Shifts and In and Out in great detail. Numerous worked examples are provided.
Chapter three, “Programming your Sinclair,” shows the user how powerful and fast low level languages are, how to plan a machine language program, and, once written, how to debug and edit it. Four different methods of program storage with their comparative advantages are given.
The final chapter contains four programs related to machine language programming—Displaying 100 Bytes in Hex, Machine Code Editor, Loading Code into Array and ZX81 Draughts. The first three programs are referred to throughout the book; the fourth is the same as Draughts in Not Only 30 Programs, also by Melbourne House.
Machine Language Programming Made Simple is a clear, concise volume which makes an excellent introduction to Z80 machine code. The price is a little heavy at £8.95, but this might be expected of a specialist book like this. To summarize, this book is highly recommended to the beginner.