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  Interrupt:   21h     Function:   44h     Subfunction:   04h
 
  Title:       IOCTL: Read Control Data from Block Device Driver
 
  Description:
 
     Transfers control data from a block device driver directly into an
     application program's buffer. The length and contents of the data
     are specific to each device driver and do not follow any standard
     format. This function does not necessarily result in any input
     from the physical device.
 
     Input                                Output
 
     AH = 44h                             If function successful
     AL = 04h                               Carry flag: clear
     BL = Drive code (0 = default,          AX = Bytes transferred and
          1 = A, 2 = B,...)                      buffer contains
     CX = Number of bytes to read                control data from
     DS:DX = segment:offset of buffer            device driver
 
                                          If function unsuccessful
                                            Carry flag: set
                                            AX = Error code (01h, 05h,
                                                 06h,or 0Dh)
                                            See: ◄Error codes►
                                    -♦-