VMS Help RTL Routines, SMG$, SMG$COPY_VIRTUAL_DISPLAY, Arguments  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 current-display-id

    OpenVMS usage:identifier
    type:         longword (unsigned)
    access:       read only
    mechanism:    by reference

    Display identifier of the virtual display to be replicated.
    The current-display-id argument is the address of the unsigned
    longword that contains the display identifier.

 new-display-id

    OpenVMS usage:identifier
    type:         longword (unsigned)
    access:       write only
    mechanism:    by reference

    Receives the display identifier of the newly created virtual
    display. The new-display-id argument is the address of the
    unsigned longword that receives the new display identifier.