VMS Help System Services, $DCLEXH, Argument  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 desblk

    OpenVMS usage:exit_handler_block
    type:         longword (unsigned)
    access:       write
    mechanism:    by reference
    Exit handler control block. The desblk argument is the address of
    this control block.

    Refer to the OpenVMS System Services Reference Manual to view the
    control block diagram.