HLASM Language Reference

General Instructions
Chapter 4. Machine Instruction Statements
This chapter introduces a sample of the more common instruction formats and
provides general rules for coding them in their symbolic assembler language
format.
For the complete specifications of machine instructions, their object code format,
their coding specifications, and their use of registers and virtual storage areas, see
the applicable Principles of Operation manual for your processor. If your program
requires vector facility instructions, see the applicable Vector Operations manual for
the complete specifications of vector-facility instructions.
At assembly time, the assembler converts the symbolic assembler language
representation of the machine instructions to the corresponding object code. The
computer processes this object code at execution time. Thus, the functions
described in this section can be called execution-time functions.
Also at assembly time, the assembler creates the object code of the data constants
and reserves storage for the areas you specify in your data definition assembler
instructions, such as DC and DS (see Chapter 5, “Assembler Instruction
Statements”). At execution time, the machine instructions can refer to these
constants and areas, but the constants themselves are not normally processed.
As defined in the applicable Principles of Operation manual, there are five
categories of machine instructions:
General instructions
Decimal instructions
Floating-Point instructions
Control instructions
Input/Output operations
Each is discussed in the following sections.
General Instructions
Use general instructions to manipulate data that resides in general registers or in
storage, or that is introduced from the instruction stream. General instructions
include fixed-point, logical, and branching instructions. In addition, they include
unprivileged status-switching instructions. Some general instructions operate on
data that resides in the PSW or the TOD clock.
The general instructions treat data as four types: signed binary integers, unsigned
binary integers, unstructured logical data, and decimal data. Data is treated as
decimal by the conversion, packing, and unpacking instructions.
For further information, see “General Instructions” in the applicable Principles of
Operation manual.
78 © Copyright IBM Corp. 1982, 2004