CHARACTER STRING INPUT APPARATUS, INPUT CHARACTER STRING INFERENCE METHOD, AND INPUT CHARACTER STRING PRESUMPTION PROGRAM

Provided is a technique that is able to infer a character string input by an operator, regarding an input operation in which the operator slides his or her finger, a pen or the like on a screen of a display device, with relatively simple processing. A display unit displays, on the screen of the display device, a keypad image in which a plurality of character keys are arranged. An operation position detection unit detects pressed positions on the screen. A score calculation function unit calculates, for each character key of the keypad image, scores of the pressed positions on the screen. A score data generation function unit generates score data in which the scores of the character keys calculated by the score calculation function unit are registered, for each of the pressed positions on the screen detected by the operation position detection unit, during a character string input period. An input character string inference function unit infers a character string that was input, using score data generated by the score data generation function unit.