Typically such macros expand into executable code, e . g ., for the EXIT macroinstruction, a list of " define constant " instructions, e . g ., for the DCB macro, or a combination of code and constants, with the details of the expansion depending on the parameters of the macro instruction ( such as a reference to a file and a data area for a READ instruction ); he executable code often terminated in either a " branch and link register " instruction to call a routine, or a supervisor call instruction to call an operating system function directly.
