Screen-saving begins on AXP after a SAVE_SCREEN command has been
   done.

   (On VAX, screen-saving is begun by turning on NDC's MultiSessions.)

   On AXP, RTA terminals may ONLY be watched after they've done a
   PEEK/SAVE_SCREEN. (The command on VAX is PEEK/RT_ENABLE.)

   On AXP it is wise, therefore, to do a PEEK/SAVE_SCREEN ahead of
   time, such as from SYLOGIN.COM or LOGIN.COM, so enough time
   elapses before watching begins for a full screen to be saved for
   display when watching begins.

   On AXP, if screen-saving has not yet been started when watching
   begins, then PEEK automatically turns on the screen-saver (this
   does not apply to RTA terminals which must issue a
   PEEK/SAVE_SCREEN on AXP in order to be watched with Peek/Spy), but
   in this case there hasn't yet been enough time to save a full
   screen, so only a partial screen is initially displayed for the
   watcher, or even no screen at all if nothing has been sent to the
   terminal since screen-saving started.

   For VAX, terminal-logging is now begun by using PEEK/SAVE_SCREEN/LOG.

   Screen-saving and any terminal-logging are both turned off by the
   NOSAVE_SCREEN command. Terminal-logging alone is turned off with
   the SAVE_SCREEN/CLOSE_FILE command, without also turning off
   screen-saving.

   If a screen-saver is on without a log file, then a log file can
   be started using the SAVE_SCREEN/LOG[=file] command.

   When logging is in progress, a new log file can be started with
   PEEK/SAVE_SCREEN/LOG/NEW_FILE. This closes any existing log file
   and starts terminal-logging to a new log file.