HLASM Language Reference

Assembler Language Coding Conventions
Instruction Statement Format
Instruction statements must consist of one to four entries in the statement field.
They are:
A name entry
An operation entry
An operand entry
A remarks entry
These entries must be separated by one or more spaces, and must be written in
the order stated.
Statement Coding Rules
The following general rules apply to the coding of an instruction statement:
The entries must be written in the following order: name, operation, operand,
and remarks.
The entries must be contained in the begin column (1) through the end column
(71) of the first line and, if needed, in the continue column (16) through the end
column (71) of any continuation lines.
The entries must be separated from each other by one or more spaces.
If used, a name entry must start in the begin column.
The name and operation entries, each followed by at least one space, must be
contained in the first line of an instruction statement.
The operation entry must begin at least one column to the right of the begin
column.
Statement Example: The following example shows the use of name, operation,
operand, and remarks entries. The symbol COMP names a compare instruction, the
operation entry (CR) is the mnemonic operation code for a register-to-register
compare operation, and the two operands (5,6) designate the two general registers
whose contents are to be compared. The remarks entry reminds readers that this
instruction compares NEW SUM to OLD.
COMP CR 5,6 NEW SUM TO OLD
Descriptions of the name, operation, operand, and remarks entries follow:
Name Entry: The name entry is a symbol created by you to identify an instruction
statement. A name entry is usually optional. Except for two instances, the name
entry, when provided, must be a valid symbol at assembly time (after substituting
variable symbols, if specified). For a discussion of the exceptions to this rule, see
“TITLE Instruction” on page 215 and “Macro Instruction Format” on page 297.
| The symbol must consist of 63 or fewer alphanumeric characters, the first of which
must be alphabetic. It must be entered with the first character appearing in the
begin column. If the begin column is a space, the assembler program assumes no
name has been entered. No spaces or double-byte data may appear in the
symbol.
Operation Entry: The operation entry is the symbolic operation code specifying
the machine, assembler, or macro instruction operation. The following rules apply
to the operation entry:
Chapter 2. Coding and Structure 19