struc IOCTLRWRequest            ; Device-Driver functions 03h, 0Ch
 irwrLength     db ?            ; Length of structure, in bytes
 irwrUnit       db ?            ; Unit number (block device only)
 irwrFunction   db ?            ; Function number (03h or 0Ch)
 irwrStatus     dw ?            ; Status
 irwrReserved   db 8 dup (?)    ; Reserved
 irwrData       db ?            ; Not used
 irwrBuffer     dd ?            ; INPUT:  buffer address
 irwrBytes      dw ?            ; INPUT:  no. of bytes requested
                                ; OUTPUT: no. of bytes read/written
ends                            ; = 20d bytes