Introduction

This is an introduction to Z80 programming from first principles. The opening chapters define bytes, addresses and registers before using them in programs. Later chapters combine those mechanisms into routines and then apply them to larger algorithms.

The machine

The Z80 is an eight-bit processor from 1976 that still runs hobby computers, arcade boards and educational machines today. Its registers and instructions are small enough to study one by one. Following each instruction makes address calculation, memory transfer and control flow visible; larger processors implement the same operations with more layers.

The intended reader

The book assumes no previous programming or electronics. If you have used a high-level language, the early chapters connect familiar operations to their machine instructions. Each section defines a mechanism before a later example depends on it.

The book's method

We work in Atom, an assembler that turns assembly source into Z80 machine code. Each chapter introduces one mechanism, traces it through a small example and then relies on it in later programs. Complete companion sources begin in Chapter 12. Exercises appear along the way, with notes at the end of the book.

Atom Book 1 is the companion reference for exact source syntax, directives and output formats. The programming API is in the appendices.

Prerequisites

The easiest route is the Node-hosted atom command described in Book 1, Chapter 1. Native ATOM.COM can assemble on a CP/M 2.2 machine, although many examples in this book use a generic memory map rather than the CP/M $0100 program layout. A paper trace of register values is useful when a program produces an unexpected result. Chapter 1 begins with the processor, memory and I/O.