This  is the VMS Terminal Fallback Utility (TFU), the user interface
  to Terminal Fallback Facility (TFF). The TFU supersedes the function
  served  by  the  former  (VMS Version 4.x) DCL SET TERMINAL/FALLBACK
  command.

  Use the HELP command to display on the current default output device
  (SYS$OUTPUT) information available in the TFU help file.

  Format:

      TFU> HELP    [keyword ...]