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).