Device driver function 0Ch      IOCTL Write             b   c

    IOCTL Write transfers data from a buffer to a device driver.

    This function can be used for both block and character device
    drivers.

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    DOS calls this function only if bit 14 is set in the dhAttributes
    field of the DeviceHeader structure for the driver.

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    irwrUnit
    Specifies the device to which data is to be written. This field is
    used for block device drivers only.


    irwrStatus
    Specifies the status of the completed function. If the function
    was successful, the driver must set the done bit (bit 8).
    Otherwise, the driver must set both the error and done bits (bits
    15 and 8) and copy an error value to the low-order byte.


    irwrBuffer
    Contains the 32-bit address of the buffer containing data to write
    to the device.


    irwrBytes
    Contains the number of bytes to write and receives the number of
    bytes written.

        input   Specifies the number of bytes to write. This number
                must not exceed the amount of data in the specified
                buffer.

        output  Specifies the number of bytes written. This number
                cannot exceed the requested number of bytes.