Introduction

Atom is a single-pass Z80 assembler whose assembler core is written in Z80 assembly. The current Mac command runs that core through Debug80. A host layer reads files, resolves dependencies and conditional source, supplies binary inputs, and renders finished artifacts.

This book defines the current source language and the public Mac interfaces. It covers source lines and symbols, expressions and forward references, instructions, data and storage, project composition, diagnostics and output artifacts. The appendices collect the JavaScript API and exact lookup tables.

The intended reader

The manual assumes that you can read Z80 assembly and recognise its registers, instructions, flags, stack and addressing forms. Atom Book 2 — Z80 Programming provides a from-zero introduction to the processor.

Programmers coming from another assembler should begin with Chapters 1 and 2. The two source conventions most likely to differ are visible immediately: assembler directives are bare words such as ORG and DB, while a leading period marks a private symbol such as .LOOP.

Native and host responsibilities

The native core tokenises prepared source, manages symbols, evaluates expressions, validates and encodes instructions, processes assembler directives, and emits IMAGE and PATCH operations. It reads each prepared source part once. Forward references remain in a resident pending list until the corresponding symbol is defined.

The host resolves %INCLUDE, %DEFINE, %IF, %ELSE, %ENDIF, and filesystem-backed INCBIN. It also writes NOBJ, binary, Intel HEX, listing, D8, and manifest files. Dependency resolution followed by native assembly is a two-stage build, not a second assembler pass.

The first chapter installs the command and assembles a small .asm program.