Int 16 Fn FFA3  U - Pc Tools V7-8 Datamon, V9+ Dprotect - Installation Ch  [y]

   AX = FFA3h
   BX = 0000h
   CX = 0000h

Return: AX = segment of resident code
   BX = 5555h
   CX = 5555h

Note:  also supported by DOS 6 UNDELETE which is licensed from PC Tools

See Also: INT 21/AH=3Fh"NB.SYS",INT 21/AX=4101h,INT 2F/AX=6284h