Each of the user functions is described in detail in the following
sections. The following guidelines apply to all Monitor II user exit
routines.
- All of the user exit routines must be reenterable.
- All user-written exit routines receive control in 31-bit addressing
mode.
- The routines must save registers when they receive control and
restore registers when they return control. Register 13 contains
the address of the register save area; register 14 contains the return
address; and register 15 contains the entry address.
- All of the user exit routines receive control in problem state,
key 8.