Executing a desired processing immediately by a simple operation using a jog dial for example. The display unit (3) has a jog dial (4) (a first operating means) and a back button (5) (second operating means) provided vertically at the right upper corner thereof. The jog dial (4) can be rotated and pushed. The back button (5) is to undo an operation having been made by pushing the jog dial (4), and it is located near the jog dial (5).