PURPOSE: To eliminate the need to press a shift key at each time by inputting an upper-case character unless the shift key is pressed at the time of the input of the character when the character which does not affect the determination of a sentence head character and is inputted first is an English letter after a character meaning the tail of a sentence is inputted in a lower-case character input state.

CONSTITUTION: As characters meaning the tail of a sentence, '.', '?', and '!' are determined, and then characters which are not directly relevant to the meaning of sentences such as a space, '"', '(', and ')' are determined as characters which do not affect the determination of the head of a sentence. After one of the characters meaning the tail of a sentence is inputted in a lower-case character input state, a character which is inputted first except the characters which do not affect the determination of the sentence head character is regarded as the head of the sentence. When this character is an English letter or upper-case/lower-case distinctive character, only the character is inputted as the upper-case character with the shift key pressed or the lower-case character unless the shift key is pressed.