PURPOSE: To easily input 2nd and succeeding characters by estimating a next input character and enlarging and displaying the software key of the character.

CONSTITUTION: A character which is inputted on an input device 11 is analyzed by a program stored in a program storage area 14 in a read-only memory 13 and a central arithmetic processor 12 and compared with a word list stored in a word list storage area 16 in a random access memory 15, and the software keyboard is displayed on a display device 17 according to the comparison result. In this case, when >1 characters are inputted, retrieval in a work list where the inputted characters are used is performed to estimate a next input character, and the software key corresponding to the next input is enlarged and displayed. For example, when the 1st character is 'O' and 'OF' and 'ON' are registered in the word list as words starting with 'O', F or N is estimated as the 2nd character and the software keys corresponding to F and N are enlarged and displayed.