The VMS Terminal Fallback Facility (TFF) provides table-driven
      character conversion for  terminals.  The  conversion  is done
      transparent to the application  (unnoticed  by the application
      software  unless  explicit  inquiries are made).  TFF can also
      perform character compose emulation on input. Furthermore, you
      can control which terminal keys are auto-compose keys.

      One of  the  applications  of  TFF  is  to  allow  users  with
      National  Replacement  Character  (NRC)  set  terminals to use
      software  developed  with  the Digital Multinational Character
      Set (MCS). MCS is essentially the ASCII character set plus 128
      characters currently  used  by  owners of NRC terminals around
      the world.

      You can use TFF functions  through Terminal  Fallback  Utility
      (TFU) commands.

      More on-line  help  is  available  from  the Terminal Fallback
      Utility. To invoke TFU enter the following command in response
      to the DCL prompt:

      $ RUN SYS$SYSTEM:TFU


      The utility responds with the prompt:

      VAX/VMS Terminal Fallback Facility (TFF)
      TFU>

      After you invoke TFU, you can enter HELP or any of the
      TFU commands.