1. A computing device, comprising: a display unit; and a processor configured to define an application program preview interface displayed on the display unit, wherein the application program preview interface comprises: a first display area simultaneously displaying thumbnails of desktop layouts of multiple operation modes on the display unit by showing graphic objects, wherein each of the operation modes includes an application program which is opened or executed, and run within the selected mode; a second display area displaying a selectable object as an application preview, wherein the selectable object is corresponding to the application program included in a selected operation mode; a third display area displaying a list or a program shortcut icon of all the application programs corresponding to the selected operation mode, wherein when the selectable object is displayed in the second display area, the multiple operation modes are displayed in the first display area, and wherein the first display area and the second display area are simultaneously displayed on the display unit, and wherein the application modes comprise a desktop mode and a modern mode.