Directives

Directives in SIC and SIC/XE are used to give information to the assembler and do not generate any instructions in the object code, but some may allocate memory. Book section indicates where in System Software: An Introduction to Systems Programming the directive is introduced.

Directive	Details	Book Section
`START`	Specifies the name (in label) and starting address for the program.	2.1
`END`	Indicates the end of the source program and (optionally) the first executable instruction.	2.1
`CSECT`	Begins a new control section. Label specifies the name.	2.3.5
`EXTDEF`	Operand is a comma-separated list of symbols declared in the current control section that other control sections can refer to.	2.3.5
`EXTREF`	Operand is a comma-seperated list of external symbols that the current control section uses.	2.3.5
`BYTE`	Generates a constant value, occupying as many bytes as needed.	2.1
`WORD`	Generates a one-word constant.	2.1
`RESB`	Reserves the indicated number of bytes.	2.1
`RESW`	Reserves the indicated number of bytes.	2.1
`BASE`
`NOBASE`
`EQU`	Stores a value in the symbol table.
`ORG`	Overrides the location counter when the assembler encounters this.
`LTORG`	Literal pool. All literal values placed before this directive are placed where it is located.
`MACRO`	Defines the start of a macro, used by macro processor.
`MEND`	Defines the end of a macro started by `MACRO`. Used by macro processor.
`IF`	Used by macro processor.
`ELSE`	Used by macro processor.
`ENDIF`	Used by macro processor.
`WHILE`	Used by macro processor.
`ENDW`	Used by macro processor.
`SET`
`USE`	Used for program blocks. The operand indicates the name of the program block.	2.3.4

17 October 2025