Data processing system comprising at least a processing unit executing simultaneously a number of application programs, a memory for storing the application programs, a display subsystem for displaying on a screen a plurality of windows associated respectively with a plurality of application programs, each window being able to overlay partially or totally one or several windows already displayed on the screen, and a mouse for moving a cursor to a selected location of the screen. The display subsystem displays a focus buoy associated with each window at the same time the window is displayed, stores the coordinates of the location at which the focus buoy is displayed in a table in the memory, and in response to simply shaking the mouse, displays the focus buoys at each location defined in the table.