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  Description:  IOCTL: Write Control Data to Character
                Device Driver
 
  Transfers control data from an application to a character device driver.
  The length and contents of the data are specific to each device driver
  and do not follow any standard format. This function does not neces-
  sarily result in any output to the physical device.
 
  Input                                   Output
  ════════════════════════════            ══════════════════════════════
  AH=44H                                  If function successful
  AL=03H                                  Carry flag=clear
  BX=handle                               AX=bytes transferred
  CX=number of bytes to write             If function unsuccessful
  DS:DX=segment:offset of data            Carry flag=set
                                          AX=error code
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