Device Requests

     Cmd Name                     Ver. Usage Flags
     ▀▀▀ ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀ ▀▀▀▀ ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀
     00H Initialize device             ◄Chr►◄Blk►
     01H Media Check                        ◄Blk►
     02H Build BPB                          ◄Blk►
     03H IOCTL Input                   ◄Chr►◄Blk►◄IRW►
     04H Input (read from device)      ◄Chr►◄Blk►
     05H Non-destructive Input         ◄Chr►
     06H Input status                  ◄Chr►
     07H Input Flush                   ◄Chr►
     08H Output (write to device)      ◄Chr►◄Blk►
     09H Output with verify            ◄Chr►◄Blk►
     0aH Output Status                 ◄Chr►
     0bH Output Flush                  ◄Chr►
     0cH IOCTL Output                  ◄Chr►◄Blk►◄IRW►
     0dH Device Open              3.0+ ◄Chr►◄Blk►     ◄OCR►
     0eH Device Close             3.0+ ◄Chr►◄Blk►     ◄OCR►
     0fH Removable Media          3.0+      ◄Blk►     ◄OCR►
     10H Output until busy        3.0+ ◄Chr►                    ◄OTB►
     13H Generic IOCTL Request    3.2  ◄Chr►◄Blk►          ◄Gen►
     17H Get Logical Device       3.2       ◄Blk►          ◄Gen►
     18H Set Logical Device       3.2       ◄Blk►          ◄Gen►
     19H IOCTL Support Query      5.0  ◄Chr►◄Blk►          ◄Gen►     ◄Qry►
     ▀▀▀ ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀ ▀▀▀▀ ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀

 On entry to the Strategy routine (see Device Driver Basics), DOS passes
 the address of a request structure in ES:BX (see DevRequestHdrRec).  The
 bCmd field of that structure (at offset 2) will contain one of the above
 command codes.

 The variable-length data that follows the DevRequestHdrRec varies from
 command to command.  Some commands share identical request structures.
 Others have a unique structure and some use only the request header to
 communicate with DOS.

See Also: IOCTL Functions
          Device Attribute
          Device Status Word
          Installable Device Drivers