System variable symbols are read-only, local-scope or global-scope variable symbols whose values are determined and assigned only by the assembler. System variable symbols that have local scope are assigned a read-only value each time a macro definition is called by a macro instruction. You can only refer to local-scope system variable symbols inside macro definitions. System variable symbols that have global scope are assigned a read-only value for the whole assembly. You can refer to global-scope system variable symbols in open code and in macro definitions.

Some of the new system variable symbols introduced with High Level Assembler supplement the data provided by system variables available in previous assemblers.

&SYSCLOCK:

&SYSCLOCK provides the date and time the macro is generated.

&SYSDATE and &SYSDATC:

&SYSDATE provides the date in the format MM/DD/YY without the century digits, and the year digits are in the lowest-order positions.

The new variable symbol &SYSDATC provides the date with the century, and the year digits in the highest-order positions. Its format is YYYYMMDD.

&SYSECT and &SYSSTYP:

All previous assemblers have supported the &SYSECT variable to hold the name of the enclosing control section at the time a macro was invoked. This allows a macro that needs to change control sections to resume the original control section on exit from the macro. However, there was no capability to determine what type of control section to resume.

The &SYSSTYP variable provides the type of the control section named by &SYSECT. This permits a macro to restore the correct previous control section environment on exit.

&SYSMAC:

Retrieves the name of any macro called between open code and the current nesting level.

&SYSM_HSEV:

Provides the highest MNOTE severity code for the assembly so far.

&SYSM_SEV:

Provides the highest MNOTE severity code for the macro most recently called from this macro or open code.

&SYSOPT_XOBJECT:

Determines if the XOBJECT assembler option was specified.

&SYSNDX and &SYSNEST:

All previous assemblers have supported the &SYSNDX variable symbol, which is incremented by one for every macro invocation in the program. This permits macros to generate unique ordinary symbols if they are needed as local labels. Occasionally, in recursively nested macro calls, the value of the &SYSNDX variable was used to determine either the depth of nesting, or to determine when control had returned to a particular level.

Alternatively, the programmer could define a global variable symbol, and in each macro insert statements to increment that variable on entry and decrement it on exit. This technique is both cumbersome (because it requires extra coding in every macro) and unreliable (because not every macro called in a program is likely to be under the programmer's control).

High Level Assembler provides the &SYSNEST variable to keep track of the level of macro-call nesting in the program. The value of &SYSNEST is incremented globally on each macro entry, and decremented on each exit.