Split screen is a display technique in computer graphics that consists of dividing graphics and/or text into adjacent (and possibly overlapping) parts, typically as two or four rectangular areas. This is done to allow the simultaneous presentation of (usually) related graphical and textual information on a computer display. TV sports used this presentation methodology in the 1960s for instant replay. The original non-dynamic split screens differed from windowing systems in that the latter always allowed overlapping and freely movable parts of the screen (the "windows") to present related as well as unrelated application data to the user, while the former were strictly limited to fixed non-overlapping positions. The split screen technique can also be used to run two instances of an application, possibly with another user interacting with the other instance. From Wikipedia
