Int 21 Fn FC  - Doubledos - Get Virtual Screen Address                     [T]

   AH = FCh

Return: ES = segment of virtual screen
Desc:  Determine the address of the virtual screen to which the program
     should write instead of the actual video memory, so that the
     multitasked programs do not interfere with each other's output.

Notes: screen address can change if task-switching is on!
   identical to AH=ECh

See Also: AH=ECh"DoubleDOS",INT FC"DoubleDOS"