A method for driving an input/output device, including: generating first data by putting a first region of a light unit in a lighted condition and a second region of the light unit in the lighted condition; generating second data by putting the first region in the lighted condition and the second region in an unlighted condition; generating third data by putting the first region in the unlighted condition and the second region in the lighted condition; generating fourth data by putting the first region in the unlighted condition and the second region in the unlighted condition; and generating difference data of either the first data or the third data and either the second data or the fourth data by using a data processor.