PURPOSE: To distinctively display the undisplayable code and securely hold communication data by holding the undisplayable code in a reception state when the undisplayable code is received, and displaying a specific symbol in the opposite color from a background color at its corresponding display place.

CONSTITUTION: When one electronic equipment sends data with which the code that can not be displayed on the other electronic equipment is mixed to the other electronic equipment, the sent data are held as received data as they are without converting the code which can not be displayed on the other electronic equipment into another space code, etc. At the display place of the undisplayable code, the displayable symbol is displayed in the opposite color from the background color. For, for example, lowercase character codes of undisplayable (b), (d), and (f), undisplayable symbols painted out in black as the opposite color from white as the background color are displayed at the display places corresponding to the respective lower case character codes when a background color flag 6c is set to '1' and white is set as the background color.