VMS Help EDT Routines, FILEIO, Returns  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    OpenVMS usage:cond_value
    type:         longword (unsigned)
    access:       write only
    mechanism:    by value

    A status code that your FILEIO routine returns to EDT$EDIT. The
    fileio argument is a longword containing the status code. The
    only failure code that is normally returned is RMS$_EOF from
    a GET call. All other OpenVMS RMS errors are signaled, not
    returned. The RMS signal should include the file name and both
    longwords of the RMS status. Any errors detected with the FILEIO
    routine can be indicated by setting status to an error code.
    That special error code will be returned to the program by the
    EDT$EDIT routine. There is a special status value EDT$_NONSTDFIL
    for nonstandard file opening.

    Condition values are returned in R0.