Preparing to pass control

Use registers 15 and 1 in the same manner they are used to pass control without return.
Register 15 contains the entry address in the new control section and register 1 is used to pass a parameter list.
Ensure that register 14 contains the address of the location to which control is to be returned when the called control section completes execution.
The address can be the instruction following the instruction which causes control to pass, or it can be another location within the current control section designed to handle all returns.

Registers 2-12 are not involved in the passing of control; the called control section should not depend on the contents of these registers in any way.
Provide a new save area for use by the called control section as previously described, and pass the address of that save area in register 13.
Note that the same save area can be reused after control is returned by the called control section. One new save area is ordinarily all you will require regardless of the number of control sections called.