Function 440Ch /5fh     Set Display Mode                             DOS 4.0+

    Sets the display mode for the screen device.

        Entry   AX    = 440Ch
                BX    = Device handle
                CH    = 03h (screen device category)
                CL    = 5fh
                DS:DX = Pointer to a DisplayMode structure

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

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    This function returns 01h (invalid function) if the ANSI.SYS
    driver has not been loaded.