HLASM: V1R6 Language Ref

Data attributes||||||defined attribute in your program to prevent the assembler from making thistime-consuming forward scan. This attribute reference can be used in the operandfield of a SETA instruction or as one of the values in the operand field of a SETBor AIF instruction.Notes:1. D' applied to a SETA or SETB symbol, or to a system variable symbol, is anerror.2. D' applied to a SETC symbol or symbolic parameter is valid only if the value ofthe SETC symbol or symbolic parameter is a valid ordinary symbol or literal.Operation code attribute (O')The operation code attribute shows whether a given operation code has beendefined prior to the attribute reference. The operation code can be represented by acharacter string or by a variable symbol containing a character string. The variablemust be set using a SETC assembler instruction prior to being referenced by theoperation code (O’) attribute.The operation code attribute has a value of a single alphabetic character that showsthe type of operation represented.This attribute reference can be used in the operand field of the SETC instruction oras 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 Assembler operation codeE Extended mnemonic operation codeM Macro definitionO Machine operation codeS Macro definition found in libraryU Undefined, unknown, unassigned, or deleted operation codeNotes:1. The operation code (O’) attribute can only be used in a conditional assemblystatement.2. The assembler does not enter lookahead mode to resolve the operation codetype, therefore only operation codes defined at the time the attribute isreferenced return an operation code type value other than U.3. When the operation code is not an assembler instruction or a machineinstruction, and the operation code is not a previously defined macro, then alllibraries in the library data set definition list are searched. This may have anadverse impact on the performance of the assembly, depending on the numberof libraries assigned in the assembly job and the number of times the operationcode 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’&A334 HLASM: V1R6 Language Ref