Note that the operation unit 70 includes the touch panel 70a which may detect a contact with the display unit 28. The touch panel 70a and the display unit 28 may be integrally configured. The touch panel 70a is configured such that transmissivity of light does not disturb display of the display unit 28 and is disposed on an upper layer of a display surface of the display unit 28, for example. Then an input coordinate on the touch panel 70a is associated with a display coordinate on the display unit 28. By this, a GUI (graphical user interface) may be configured as if the user may directly operate a screen displayed in the display unit 28. In this way, a setting for accepting an instruction after a position where a touch operation is performed is associated with a position in the display unit 28 is referred to as an absolute coordinate setting.

Furthermore, unlike the absolute coordinate setting, a setting for accepting an instruction relative to a position obtained after a shift from a predetermined position in the display unit 28 in accordance with a shift amount and a shift direction of a touch operation (a position shifted by an amount corresponding to a shift operation) is referred to as a relative coordinate setting.