Int 16 Fn FFC4  U - PC Tools V5.1-8.0 Desktop - Get ???                    [U]

   AX = FFC4h

Return: AL = ???
   BX = segment of scratch space???
   CX = segment of stored screen data (section covered by window???)
   DX = segment of window parameters for ???
   ES:BP -> ???

Note:  available only when popped up in versions prior to 6.0