Atom

Atom is a single-pass Z80 assembler with an assembler core written in Z80. The same assembler runs in two settings: the desktop command executes it in a Z80 emulator, while ATOM.COM executes it directly under CP/M 2.2.

Desktop command

Atom is published as the public atom-z80 package and requires Node.js 20 or later:

npm install --global atom-z80

Create main.asm:

ORG 4000H

START:
    LD A,42
    HALT

Then assemble it:

atom main.asm build/main.bin build/main.lst

Atom writes only the outputs named on the command line. If no output is named, it writes build/main.bin. The desktop command can produce BIN, Intel HEX, CP/M COM, NOBJ, listing and D8 files.

Native CP/M command

The npm package also contains assets/atom-cpm22.com. Copy it to a CP/M disk as ATOM.COM, then use the compact native command:

A>ATOM HELLO

HELLO.COM written

With one name, Atom reads HELLO.ASM and writes HELLO.COM. An explicit second name may select COM, BIN or Intel HEX output. Native CP/M uses current drive 8.3 filenames and leading %INCLUDE directives; it does not read Node project files.

The language

Atom covers the complete Z80 instruction set, including indexed, CB, ED and classic undocumented forms. Its source language provides global and period-prefixed private labels, EQU, ORG, DB, DW, DS, ALIGN, string data, arithmetic expressions and LOW() and HIGH(). The desktop host also supports INCBIN.

On the desktop, host directives beginning with % select dependencies and conditional source. Native CP/M recognizes leading %INCLUDE directives only. Included files remain distinct source parts, preserving their filenames and positions in diagnostics and desktop D8 maps.

Read and use

• Atom Book 1 — Assembler Reference defines the command, source language and output formats.
• Atom Book 2 — Z80 Programming begins with registers and opcodes, then develops complete routines, algorithms and recursion.
• Atom and Z80 Reference contains the programming API and lookup tables for Atom and the Z80.
• Atom on npm provides the current package and version history.
• Atom source contains the assembler, desktop host and native platform providers.

Atom is licensed under GPL-3.0-only.