Called routine's responsibilities

Prologs and epilogs are used in the called routines.

Prologs and epilogs are used in the called routines. On entry to a routine, the following steps should be performed:

1. Use some or all of the prolog actions described in the Prolog Actions table.
2. Store the back chain and decrement the stack pointer (SP) by the size of the stack frame.
   Note: If a stack overflow occurs, it will be known immediately when the store of the back chain is completed.

On exit from a procedure, use some or all of the epilog actions described in the Epilog Actions table.