Int 2F/AX=D44Fh/BX=0000h

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