PURPOSE: To simplify modification of character patterns, by a construction wherein an operating switch for switching an input level for a mode program terminal to a high level or a low level is connected to the terminal.

CONSTITUTION: With an operating switch 11 turned OFF, a terminal MP0 is set to a low level, while a terminal MP1 is set to a high level, and a mode-2 is selected. Therefore, with an external ROM 9 connected, printing data (a) inputted can be printed both in normal character patterns and in optional character patterns. When the switch 11 is turned ON, the terminal MP0 set to a high level, while the terminal MP1 is set to a low level, and a mode-1 is selected. Therefore, with the external ROM 9 connected, the printing data (a) inputted can be printed in optional character patterns determined by the external ROM 9. Accordingly, when it is desired to change the mode, for example, from the mode-1 to the mode-2 through operating the switch 11, the change can be easily effected without need to replace a ROM, and can be satisfactorily achieved on the user's side.