A trackball is a pointing device which controls the ~cursor~ location on the |video display|. It is similar to the |mouse| in that a tracking ball is the primary interface mechanism, but the architecture is inverted. A tracking ball on the top of the device is in contact with rollers inside the trackball housing. The directional components of the movement of the tracking ball are translated, via these rollers, to movement of the cursor on the monitor display. A button (or buttons) on top or side of the trackball housing allow the selection of functions at desired cursor locations. Trackballs are especially desirable in situations where surface area for manipulation is minimal, as it does not require movement of the device housing. They are often integrated into |laptop| and |notebook| systems for this reason.
