Patent ID: 8670002

Claim:
A portable electronic device adapted to change an operation mode, comprising: a display unit configured to display a user interface corresponding to a plurality of operation modes according to a rotation of the portable electronic device; an operation mode identifier display unit configured to display a plurality of operation mode identifiers indicating that the user interface is displayed in the plurality of operation modes, respectively, locations of the operation mode identifiers being fixed on the portable electronic device; a sensor unit configured to detect the rotation of the portable electronic device; and a control unit configured to determine which one of the plurality of operation mode identifiers is presented upright relative to a viewpoint of a user in response to detecting the rotation of the portable electronic device and to switch to one of the plurality of operation modes corresponding to the operation mode identifier determined as presented upright, wherein the plurality of operation mode identifiers are positioned on an upper edge, a lower edge, a left edge, and a right edge of the display unit, respectively, and only the one of the plurality of operation mode identifiers is presented upright relative to the viewpoint of the user in the corresponding one of the plurality of operation modes.