Image data (44) assigned to a specific language is included in a second data file (28) at a specific position. A first data file includes a position information data specifying the position of the image data. A processing unit obtains the image data assigned to the specific language based on the position information data in the first data file. An image is displayed on the screen based on the obtained image data (44). The language is set in the first data file for generation of the image. A change of the position information data in the first data file enables a facilitated change of language included in the display image data.