Appendix 1 — Directive Reference

Atom has two directive layers. Bare assembler directives run in the native Z80 core. % host directives are consumed during filesystem preparation and never reach the native tokenizer. Both layers are case-insensitive.

Assembler directives

Directive	Syntax	Effect
EQU	NAME EQU EXPR or NAME: EQU EXPR	Declares one resolved constant without changing private scope
ORG	ORG EXPR	Sets the logical output cursor; emits no byte
DB	DB ITEM[,ITEM…]	Emits low bytes from expressions and decoded double-quoted strings
DW	DW EXPR[,EXPR…]	Emits little-endian words
DS	DS COUNT	Reserves uninitialised bytes and advances the cursor
DS	DS COUNT,FILL	Emits COUNT initialized fill bytes
ALIGN	ALIGN BOUNDARY	Emits zeros to the next address divisible by a positive boundary
INCBIN	INCBIN "PATH"	Emits one complete confined host binary snapshot
CSTR	CSTR "TEXT"	Emits decoded bytes followed by zero
PSTR	PSTR "TEXT"	Emits a decoded-byte count followed by the bytes
ISTR	ISTR "TEXT"	Sets bit 7 on the final decoded byte; empty text emits nothing

Dotted directive aliases are invalid. A leading period begins a private symbol:

ORG 4000H       ; ASSEMBLER DIRECTIVE
.ORG:           ; PRIVATE LABEL

EQU, ORG, DS, and ALIGN require already resolved expressions. DB and DW accept Atom's restricted forward affine form.

Host directives

Directive	Syntax	Effect
%DEFINE	%DEFINE NAME VALUE	Binds one immutable 16-bit host value in the entry header
%INCLUDE	%INCLUDE "PATH"	Adds one import-once dependency edge from a leading part header
%IF	%IF VALUE	Selects the following branch when the value is non-zero
%ELSE	%ELSE	Selects the alternate branch
%ENDIF	%ENDIF	Closes the current host conditional

%DEFINE performs no source substitution and declares no assembler symbol. Dependencies may test entry definitions but may not add definitions. Body conditionals may select ordinary source but cannot add includes or definitions.

The host masks directive and inactive lines with spaces while preserving CR and LF bytes.