PURPOSE: To improve document input efficiency by providing a control program which functions to perform internal processing so that an input mode is switched only while a key switch is pressed.

CONSTITUTION: A keyboard device is equipped with a HIRAGANA(cursive form of Japanese syllabary) input mode key 5 which is pressed to select a HIRAGANA input mode, an alphanumeric input mode key 9 which is pressed to select an alphanumeric input mode, and a mode inversion key 4. The mode inversion key 4 is pressed in the HIRAGANA input mode simultaneously with an input character and then the input mode can be switched to the alphanumeric input mode only while the mode inversion key 4 is pressed. In the alphanumeric input mode, the input mode can be changed temporarily into the HIRAGANA input mode by this operation. Then the hand is released after a character of different input mode is inputted to put the mode back to the original mode.