VMS Help DECTPU, HANDLER, Description  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    If you need more information about writing condition handlers and
    programming concepts, refer to OpenVMS Programming Interfaces:
    Calling a System Routine.

    Instead of writing your own condition handler, you can use the
    default condition handler, TPU$HANDLER. If you want to write your
    own routine, you must call TPU$HANDLER with the same parameters
    that your routine received to handle DECTPU internal signals.