Macro expansion

Macros are implemented by supervisor calls (SVCs). In a few cases, the CALL macro for instance, the macro expansion contains no SVC. The supervisor call causes an SVC interrupt which activates the interrupt analysis. With the aid of an SVC index table the interrupt analysis determines the program module associated with the relevant macro. The validation of parameter values and the transfer to the calling program of information on any errors or on the processing status are controlled by the program module itself.

Figure 3: Flow diagram of SVC processing