Abstract: A combination of character codes assigned to a plurality of existing data entry keys is switched when necessary, which makes it possible to input symbols and characters including kana characters by intuitive manipulations on keys that are smaller in number than the kinds of characters to be input. Further, providing a data entry keypad on a cover for covering a part of a display screen makes it possible to realize both a function of inputting characters and a function of presenting documents by using a large display screen that is necessary in electronic book players and so on.