SS$_NORMAL         Successful completion. The user input routine
                       has completed the function that the symbiont
                       requested.
    PSM$_FLUSH         Flush output stream. The user input routine
                       can return this status only when called with
                       the PSM$K_READ function code. When this status
                       is returned to the symbiont, the symbiont
                       stops calling the input routine with the
                       PSM$K_READ function code until all outstanding
                       format and output operations have completed.
    PSM$_FUNNOTSUP     Function not supported. The user input routine
                       does not support or does not recognize the
                       function code supplied by the symbiont.
                       To ensure future compatibility, your input
                       routine should return this status for any
                       unrecognized status codes.
    PSM$_PENDING       Requested function accepted but not completed.
                       Your input routine can return this status only
                       with the PSM$K_READ function call. Further,
                       if your routine returns PSM$_PENDING, your
                       routine must eventually signal completion
                       via the PSM$REPORT routine. Refer to the
                       description of the PSM$REPORT routine for
                       more information about asynchronous operations
                       and the PSM$_PENDING condition value.

    This routine also returns any error condition values that you
    have coded your format routine to return.