Calling user exits
The assembler calls user exits using the standard OS Linkage conventions.
The user exit can be written in any language that conforms to these
constraints:
- Can be called many times, using the exit module entry point
- Retains storage for private variables across invocations
High Level Assembler provides an anchor word
in the Exit
Parameter List to allow you to maintain information across calls to
the exit.
Refer to the language's Programming Guide to find out if you can use it to write a user exit for the assembler.
The contents of the registers upon entry to the user exit are as
follows:
- Register 0
- Undefined
- Register 1
- Address of Exit Parameter List, see Figure 1.
- Registers 2 through 12
- Undefined
- Register 13
- Address of 72 byte save area
- Register 14
- Return address
- Register 15
- Address of entry point of user exit