Int 21 Fn 64  U - Os/2 V2.0+ Virtual Dos Machine - Enable Automatic Title  [O]

   AH = 64h
   DX = 0000h (function number)
   CX = 636Ch (magic value, "cl")
   BX = 0000h (indicates special request)

Note:  if CX is not 636Ch on entry, INT 21/AH=6Ch is invoked, because a bug
     in OS/2 1.x FAPI erroneously called AH=64h instead of AH=6Ch

See Also: AH=64h/DX=0001h,INT 21/AH=4Bh