Int 2F Fn AD00  U - Dos 3.3+ Display.sys Internal - Installation Check     [V]

   AX = AD00h

Return: AL = FFh if installed
       BX = ??? (0100h for MS-DOS 3.3+)

Note:  DOS 5+ DISPLAY.SYS chains to previous handler if AL is not one of the
     subfunctions listed here

See Also: AX=AD01h"DISPLAY",AX=AD02h"DISPLAY"