A package-on-package electronic device may include first and second packaging substrates, a solder interconnection providing electrical and mechanical coupling between the first and second packaging substrates, and first and second sealing layers between the first and second packaging substrates. First, a substrate with a back surface and a front surface is provided. The apparatus also includes a window controller which causes the plurality of display units to display a window under control of an application software, holds display position information of the window, and controls input and output of data using the window.