Source : Free On-Line Dictionary of Computing

feedback control
     
         A control system which monitors its effect on
        the system it is controlling and modifies its output
        accordingly.  For example, a thermostat has two inputs: the
        desired temperature and the current temperature (the latter is
        the feedback).  The output of the thermostat changes so as to
        try to equalise the two inputs.
     
        Computer {disk drives} use feedback control to position the
        read/write heads accurately on a recording track.  Complex
        systems such as the human body contain many feedback systems
        that interact with each other; the homeostasis mechanisms that
        control body temperature and acidity are good examples.
     
        (1996-01-02)