Int 10h, 04h            Read Light-Pen Position                       Not VGA

    Reports the position and status of the light pen.

        Entry   AH = 04h

        Return  AH = Status (0=not triggered, 1=triggered)
                BX = Pixel column number (0-639)
                CH = Pixel line number (0-199)
                CX = Pixel line number for modes 0Fh-10h (0-nnn)
                DH = Character row number (0-24)
                DL = Character column number (0-39 or 0-79)


    This service is not supported on the VGA.