This invention pertains to mechanisms for opening and closing sliding windows especially in homes and buildings. A sliding window comprises a pane which is installed in a sliding frame. The frame is sliding vertically or horizontally within a static outer frame which has two parallel guides that guide the sliding frame. There are three similar approaches for such a mechanism: a two cables mechanism, a single roller chain mechanism and a two roller chains mechanism. The two cable approach uses four pulleys and two flexible cables. The single roller chain approach employs two sprockets. The two roller chains approach uses four sprockets. The window can be operated manually or by using an electric motor. The window assembly includes two safety systems which protect persons from being caught by a closing window. The window assembly also includes a burglar alarm and does not require a latch for window locking.