If the EDT session is terminated by EXIT or QUIT, the status will
    be a successful value (bit <0> = 1). If the session is terminated
    because the file was not found and if the /NOCREATE qualifier
    was in effect, the failure code EDT$_INPFILNEX is returned. In an
    unsuccessful termination caused by an EDT error, a failure code
    corresponding to that error is returned. Each error status from
    the FILEIO and WORKIO routines is explained separately.

    Three of the arguments to the EDT$EDIT routine, fileio, workio,
    and xlate are the entry point names of user-supplied routines.