IBM Mainframe Forum

what are the pseudo instructions available in assembler?

ramachandran wrote:what are the pseudo instructions available in assembler?

I waited to see if anybody had any idea of what you meant by "pseudo instructions", but I guess everybody else is just a mystified as I am.......

Try again, are you referring to the "PLx" stuff the supervisor/nuclease is coded in? Or just macros?

Hello and welcome to the forum,

Might you mean macro instructions rather than pseudo?

Pseudo-code/instructions are often used to demonstrate logic so that something may explained rather than implemented in some specific instruction set.

EQU is an example of pseudo instruction in assembler. Pseudo instructions are never categorised as RR,RX,RS,SS1,SS2,Si instructions. Pseudo instructions do not occupy memory like A,AR and so on.

Hello and welcome to the forum,

I believe the term you are describing is a pseudo-operation:

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.

Additonal info is available here:
http://www.nersc.gov/vendor_docs/ibm/as ... _ovrvw.htm

dick scherrer wrote:Hello and welcome to the forum,

I believe the term you are describing is a pseudo-operation:

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.

Additonal info is available here:
http://www.nersc.gov/vendor_docs/ibm/as ... _ovrvw.htm

Such a very amazing link!

The HLASM Language Reference does not use either term "pseudo operation" or "pseudo instruction." I must admit I was surprised! HLASM calls them "assembler instructions," and defines several types. Taken as a generic, a "pseudo operation," "pseudo instruction, or "assembler instruction" refers to Assembler code that appear to be a machine code but serve other purposes. Many Assemblers have a REM pseudo instruction to define a comment, but HLASM does not define such an animal in the manual.

• Program control - AINSERT, CNOP, COPY, END, EXITCTL, ICTL, ISEQ, LTORG, ORG, POP, PUNCH, PUSH, and REPRO.
• Listing control - CEJECT, EJECT, PRINT, SPACE and TITLE.
• Operation code definition - OPSYN
• Program section and linking - ALIAS, AMODE, CATTR, COM, CSECT, CXD, DSECT, DXD, ENTRY, EXTERN, LOCTR, RMODE, RSECT, START, WXTRN and XATTR.
• Base register - DROP and USING.
• Data Definition - CCW, CCW0, CCW1, DC and DS.
• Symbol definition - EQU.
• Associated data - ADATA.
• Assembler options - *PROCESS (Since *PROCESS starts in column 1, arguably it's not a pseudo instruction), ACONTROL.

I have to admit I've never used many of these; I'm just copying them from the HLASM Language Reference.