Terminal Fallback Facility (TFF)

   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).  You  can  choose
   character conversion tables from a master character library, located
   on the VMS system disk in:

   SYS$SYSTEM:TFF$MASTER.DAT

   This  library  contains  all  the character tables supported by TFF.
   Conversions  can  be  one character to many on output to a terminal,
   and one to one on input from a terminal.

   TFF   can   also  perform  character  compose  emulation  on  input.
   Furthermore, you can control which 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.

   In addition,  TFF  also  allows  users  to  use 16-bit character set
   terminals,  such as  DOOSAN  Code  and  Telex  Code  Asian  language
   terminals, for software developed  with  the Asian Language National
   Standard Character Set.