Function 4403h          Send Control Data to Character Device

    Writes control information of any length and format to a character
    device driver. The format of the information is device-specific
    and does not follow any standard.

        Entry   AX    = 4403h
                BX    = Device handle
                CX    = Number of bytes to write
                DS:DX = Address of data buffer

        Return  AX = Error code, if CF is set
                     | 01h Invalid function
                     | 05h Access denied
                     | 06h Invalid handle
                     | 0Dh Invalid data

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    Character-device drivers are not required to support this function
    or function 4402h. A program should use function 4400h and examine
    bit 14 in the device-status value to ensure that the device driver
    can process control data.