HLASM: V1R6 Language Ref

Comment statementsSystem variable symbols3. Internal macro comment statements can be used in open code, however, theyare processed as ordinary comment statements.System variable symbols are a special class of variable symbols, starting with thecharacters &SYS. Their values are set by the assembler according to specific rules.You cannot declare them in local-scope SET symbols or global-scope SET symbols,nor use them as symbolic parameters in macro prototype statements. You can usethese symbols as points of substitution in model statements and conditionalassembly instructions.All system variable symbols are subject to the same rules of concatenation andsubstitution as other variable symbols.A description of each system variable symbols begins on page 260.You should not prefix your SET symbols with the character sequence &SYS. Theassembler uses this sequence as a prefix to all system variable symbol names,and using them for other SET symbol names might cause future conflicts.Scope and variability of system variable symbolsGlobalLocalScopeSome system variable symbols have values that are established at thebeginning of an assembly and are available both in open code and fromwithin macros. These symbols have global scope. Most system variablesymbols with global scope have fixed values, although there are somewhose value can change within a single macro expansion. The global-scopesystem variables symbols with variable values are &SYSSTMT,&SYSM_HSEV, and &SYSM_SEV.ScopeSome system variable symbols have values that are available only fromwithin a macro expansion. These system variables have local scope. Sincethe value of system variable symbols with local scope is established at thebeginning of a macro expansion and remains unchanged throughout theexpansion, they are designated as having constant values, even thoughthey might have different values in a later expansion of the same macro, orwithin inner macros.Over half of the system variable symbols have local scope and thereforeare not available in open code.Chapter 7. How to specify macro definitions 259