CHARACTER INPUT SYSTEM AND METHOD USING KEYBOARD

A character input system (and method) is actualized using an "easy-to-operate" keyboard, which is downsized by reducing a number of keys and which has a good efficiency in performance and operation without increasing key-pressing numbers so much. The keyboard contains a first group of keys for inputting five vowel characters of Japanese in roman letters and a second group of keys for inputting consonant characters (and symbols). Herein, the first group of keys are separated in positions from the second group of keys on a panel of the keyboard. Two consonant characters are assigned to each of the keys of the second group in such a way that an unvoiced consonant character is input by a single key-pressing operation while a voiced consonant character is input by a double key-pressing operation. Assignment of the consonant characters to the keys is determined in consideration of appearance frequencies of kana characters in Japanese documents and/or appearance frequencies of alphabetic letters in English documents, for example. A predetermined time is set to distinguish between operations to repeatedly press the same key twice and the double key-pressing operation applied to the key. A .delta. key is further provided to establish a double key-pressing operation for a key which is previously pressed. Incidentally, the number of the keys can be further reduced by increasing a number of characters being applied to each of the keys. To selectively input each character, there are further provided two combination keys, i.e., * key and # key.