The operation code attribute shows whether a given operation code has been defined prior to the attribute reference. The operation code can be represented by a character string or by a variable symbol containing a character string. The variable must be set using a SETC assembler instruction prior to being referenced by the operation code (O') attribute.
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:
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 O'MAC1
AIF ('&CHECKIT' EQ 'U').NOMAC
MAC1
.NOMAC ANOP
.
Redefined Operation Codes: If an operation code is redefined using the OPSYN instruction then the value returned by a subsequent operation code attribute reference represents the new operation code. If the operation code is deleted using the OPSYN instruction then the value returned is U.
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