CALL instruction API output register information

When control returns to the caller, the general purpose registers (GPRs) contain:

Register: Contents
0-1: Used as work registers by the system
2-13: Unchanged
14: Used as a work register by the system
15: Contains the entry point address EZASOKET

When control returns to the caller, the access registers (ARs) contain:

Register: Contents
0-1: Used as work registers by the system
2-14: Unchanged
15: Used as a work register by the system.

If a caller depends on register contents to remain the same before and after issuing a service, the caller must save the contents of a register before issuing the service and must restore them after the system returns control.