AR mode programs calling another program

The definition of an AR mode program, as stated in the beginning of this chapter, includes the fact that such a program might switch from one ASC mode to another. Procedures for an AR mode program calling another program differ depending on whether the AR mode program is in primary ASC mode or AR mode at the time of the call.

To make the call while in AR mode, an AR mode program must:

Load parameter information, if any, into AR/GPR 0, AR/GPR 1, or both. For information about passing information through a parameter list, see Conventions for passing information through a parameter list.
Place the entry point address of the target program into GPR 15. There is no need to load an ALET into AR 15.
Call the target program.

To make the call while in primary ASC mode, an AR mode program must follow the linkage conventions described in Primary mode programs calling another program.