HLASM Language Reference

Data Attributes
The operation code attribute has a value of a single alphabetic character that
shows the type of operation represented.
This attribute reference can be used in the operand field of the SETC instruction or
as one of the values used in the operand field of a SETB or AIF instruction.
The following letters are used for the value of the operation code attribute:
A
E
M
O
S
U
Notes:
Assembler operation code
Extended mnemonic operation code
Macro definition
Machine operation code
Macro definition found in library
Undefined, unknown, unassigned, or deleted operation code
1. The operation code (O') attribute can only be used in a conditional assembly
statement.
2. The assembler does not enter lookahead mode to resolve the operation code
type, therefore only operation codes defined at the time the attribute is
referenced return an operation code type value other than U.
3. When the operation code is not an assembler instruction or a machine
instruction, and the operation code is not a previously defined macro, then all
libraries in the library data set definition list are searched. This may have an
adverse impact on the performance of the assembly, depending on the number
of libraries assigned in the assembly job and the number of times the operation
code attribute is used.
Examples:
Name Operation Operand
&A SETC O'MVC
&A contains the letter O, because MVC is a machine operation code:
Name Operation Operand
&A SETC 'DROP'
&B SETC O'&A
&B contains the letter A, because DROP is an assembler operation code.
The following example checks to see if the macro MAC1 is defined. If not, the
MAC1 macro instruction is bypassed. This prevents the assembly from failing
when the macro is not available.
Name Operation Operand
&CHECKIT SETC
AIF
MAC1
.NOMAC ANOP
.
O'MAC1
('&CHECKIT' EQ 'U').NOMAC
338 HLASM V1R5 Language Reference