Int 2F Fn D44F  - 4dos V4.0+ - Kstack.com - Installation Check             [K]

   AX = D44Fh
   BX = 0000h

Return: AX = 44DDh if installed

Note:  this function is also supported by ANSIPLUS v3.01+ and K3PLUS v6.20+,
     which emulate the 4DOS and NDOS keystack

See Also: AX=D44Dh,AX=D44Fh/BX=0001h,AX=E44Fh/BX=0000h