1. A method for combining a plurality of windows on a display screen, the method comprising steps of: receiving an input to associate a first window and at least one second window, wherein the input is a signal corresponding to a movement of the at least one second window over a target location of the first window, wherein the target location is an object that appears on the first window when the at least one second window is dragged within a predefined area of the first window, wherein the first window corresponds to a first application program and the at least one second window corresponds to a second application program, and wherein the first application window displays content from the first application and the at least one second application window displays content from the second application program, wherein the first application program and the second application program are different application programs; associating the first window with the at least one second window said at least one second window being independent of and external to the first window; combining the first window and the at least one second window into a common window on a display screen, the first window and the at least one second window being configured to share a common window frame, wherein an operation performed on the common window automatically performs the operation on the first window and the at least one second window; and allowing each of the first window and the at least one second window to be selected from the common window frame.