HLASM: V1R6 Language Ref

Data attributes&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, theMAC1 macro instruction is bypassed. This prevents the assembly from failingwhen the macro is not available.Name Operation Operand&CHECKIT SETC O’MAC1AIF (’&CHECKIT’ EQ ’U’).NOMACMAC1.NOMAC ANOP.Redefined Operation Codes: If an operation code is redefined using the OPSYNinstruction then the value returned by a subsequent operation code attributereference represents the new operation code. If the operation code is deleted usingthe OPSYN instruction then the value returned is U.SequencesymbolsYou can use a sequence symbol in the name field of a statement to branch to thatstatement during conditional assembly processing, thus altering the sequence inwhich the assembler processes your conditional assembly and macro instructions.You can select the model statements from which the assembler generates assemblerlanguage statements for processing at assembly time.A sequence symbol consists of a period (.) followed by an alphabetic character,followed by 0 to 61 alphanumeric characters.Examples:.BRANCHING_LABEL#1.ASequence symbols can be specified in the name field of assembler languagestatements and model statements; however, sequence symbols must not be used asname entries in the following assembler instructions:ALIAS EQU OPSYN SETCAREAD ICTL SETA SETAFCATTR LOCTR SETB SETCFDXDAlso, sequence symbols cannot be used as name entries in macro prototypeinstructions, or in any instruction that already contains an ordinary or a variablesymbol in the name field.Sequence symbols can be specified in the operand field of an AIF or AGOinstruction to branch to a statement with the same sequence symbol as a label.Scope: A sequence symbol has a local scope. Thus, if a sequence symbol is used inan AIF or an AGO instruction, the sequence symbol must be defined as alabel in the same part of the program in which the AIF or AGO instructionappears; that is, in the same macro definition or in open code.Symbolic Parameters:If a sequence symbol appears in the name field of a macro instruction, andthe corresponding prototype statement contains a symbolic parameter inthe name field, the sequence symbol does not replace the symbolicChapter 9. How to write conditional assembly instructions 335