Device Request 06H: Input Status

 This tells the driver to return its input status; in particular, to
 indicate whether there are characters in the device input buffer ready for
 immediate retrieval.

  Offset Size Contents
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   +0      1  bLen         0dH (length of this request packet)
   +1      1  bUnitNo      (not used)
   +2      1  bCmd         06H (command code)
   +3      2  rStatus      OUTPUT: Device Status Word must fill before exit
   +5H     8  res          (reserved)
          13               size of this structure

     rStatus  On exit, the driver must place a DevStatusWord here.  Always
              set the Done bit (bit 8).

              If no characters are ready, set the Busy bit (bit 9).
              Otherwise, clear bit 9 to indicate that a call to DvRq 04H
              will be satisfied without waiting.

   Notes: ■ This is the device driver "catch-point" for DOS fn 0bH (get
            input status).

            It is also called by DOS to avoid waiting in an input loop.

See Also: Device Requests
          Installable Device Drivers