Output Register Information

When control returns to the caller, the GPRs contain:

Register: Contents
0-1: Used as work registers by the system
2-13: Unchanged
14: Used as work registers by the system
15: Return code

When control returns to the caller, the ARs contain:

Register: Contents
0-1: Used as work registers by the system
2-13: Unchanged
14-15: Used as work registers by the system

Some callers depend on register contents remaining the same before and after issuing a service. If the system changes the contents of registers on which the caller depends, the caller must save them before issuing the service, and restore them after the system returns control.