$BRKTHRUW

   Sends a message to one or more terminals. The $BRKTHRUW service
   operates synchronously; that is, it returns to the caller after
   the message has been sent to the specified terminals.

   For asynchronous operations, use the Breakthrough ($BRKTHRU)
   service; $BRKTHRU returns to the caller after queuing the message
   request, without waiting for the message to be delivered.

   Aside from the preceding, $BRKTHRUW is identical to $BRKTHRU.
   For all other information about the $BRKTHRUW service, see the
   description of $BRKTHRU.

   The $BRKTHRU and $BRKTHRUW services supersede the Broadcast
   ($BRDCST) service. When writing new programs, you should use
   $BRKTHRU or $BRKTHRUW instead of $BRDCST. When updating old
   programs, you should change all uses of $BRDCST to $BRKTHRU or
   $BRKTHRUW. $BRDCST is now an obsolete system service and is no
   longer being enhanced.

   Format

     SYS$BRKTHRUW  [efn] ,msgbuf [,sendto] [,sndtyp] [,iosb]

                   [,carcon] [,flags] [,reqid] [,timout] [,astadr]

                   [,astprm]

   C Prototype

     int sys$brkthruw  (unsigned int efn, void *msgbuf, void

                       *sendto, unsigned int sndtyp, struct _iosb

                       *iosb, unsigned int carcon, unsigned int

                       flags, unsigned int reqid, unsigned int

                       timout, void (*astadr)(__unknown_params),int

                       astprm);