Function 4406h (68-6)    IOCTL: Get Input Status

    Checks to see if the device or file is ready for input.

       On entry:      AH         44h
                      AL         06h
                      BX         Device or file handle

       Returns:
          (file)      AL         FFh      until EOF is reached
                                 00h      after EOF is reached

          (device)    AL         FFh      If device ready
                                 00h      If device not ready

  ──────────────────────────────────────────────────────────────────────────

    This subfunction reports the input status of the device or file. AL
    returns FFh for ready and 00h for not ready (or end of file).