The TPU$MESSAGE routine performs the actual output of the
    message. The $PUTMSG system service only formats the message.
    It gets the settings for the message flags and facility name from
    the variables described in the OpenVMS Utility Routines Manual in
    the section about the TPU Shareable Image. Those values can be
    modified only by the TPU built-in procedure SET.

    If the condition value received by the handler has a FATAL status
    or does not have the TPU facility code, the condition is
    resignaled.

    If the condition is TPU$_QUITTING, TPU$_EXITING, or TPU$_
    RECOVERFAIL, a request to UNWIND is made to the establisher of
    the condition handler.

    After handling the message, the condition handler returns with
    a continue status. TPU error message requests are made by
    signaling a condition to indicate which message should be written
    out. The arguments in the signal array are a correctly formatted
    message argument vector. This vector sometimes contains multiple
    conditions and formatted ASCII output (FAO) arguments for the
    associated messages. For example, if the editor attempts to open
    a file that does not exist, the TPU message TPU$_NOFILEACCESS
    is signaled. The FAO argument to this message is a string for the
    name of the file. This condition has an error status, followed by
    the OpenVMS RMS status field (STS) and status value field (STV).
    Because this condition does not have a fatal severity, the editor
    continues after handling the error.

    The editor does not automatically return from TPU$CONTROL. If
    you call the TPU$CONTROL routine, you must explicitly establish a
    way to regain control (for example, using the built-in procedure
    CALL_USER). If you establish your own condition handler but call
    the TPU handler for certain conditions, the default condition
    handler must be established at the point in your program where
    you want to return control. You can also interrupt TPU$CONTROL
    by having your program specify and then trigger an asynchronous
    routine via the TPU$SPECIFY_ASNYC_ACTION and TPU$TRIGGER_ASYNC_
    ACTION routines.

    See the VSI OpenVMS Calling Standard for details on writing a
    condition handler.