Pseudo-ops overview

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A pseudo-op is an instruction to the assembler.

A pseudo-operation, commonly called a pseudo-op, is an instruction to the assembler that does not generate any machine code. The assembler resolves pseudo-ops during assembly, unlike machine instructions, which are resolved only at runtime. Pseudo-ops are sometimes called assembler instructions, assembler operators, or assembler directives.

In general, pseudo-ops give the assembler information about data alignment, block and segment definition, and base register assignment. The assembler also supports pseudo-ops that give the assembler information about floating point constants and symbolic debugger information (dbx).

While they do not generate machine code, the following pseudo-ops can change the contents of the assembler's location counter:

  • .align
  • .byte
  • .comm
  • .csect
  • .double
  • .dsect
  • .float
  • .lcomm
  • .long
  • .org
  • .short
  • .space
  • .string
  • .vbyte