Prolog and epilog code

The primary functions of prolog code are:

To save the calling function’s general-purpose registers in the calling function’s save area.
To obtain the dynamic storage area for this function.
To chain this function’s save area to the calling function’s save area, in accordance with the MVS™ linkage convention.

The primary functions of epilog code are:

Note: AR-mode functions require additional prolog and epilog functions. See AR-mode programming support for details.