Considerations for Assembler Programs in a DC/UCF Online System › Standard IBM calling conventions

Standard IBM calling conventions

An assembler program that is written using standard IBM calling conventions can be used as a top-level program or a subprogram in a DC/UCF online system. Such a program will typically issue an instruction to save its registers in an area pointed to by General Register 13 on entry. The following conventions must be observed:

• If the program is a top-level program or is invoked via a TRANSFER CONTROL, #LINK or ADS LINK, then the SAVEAREA parameter must be specified on the PROGRAM statement in the DC/UCF Sysgen. SAVEREA is not needed if the program is invoked via a COBOL or PL/I CALL, but the SAVEAREA parameter will not cause a problem if it is specified.
• If the program sets register 13 to point at its own save area and stores into it, then the save area must be in reentrant storage obtained using one of the methods described in section 7.3.