When we see television pictures of robots assembling and painting an assembly line of cars, we are viewing an example of control technology in action. A simpler example, and one that we meet many times in our lives is the sliding-door mechanism in the local supermarket. These doors open as we approach them, and the sliding doors are activated by a signal from us. It could be via a light-sensitive electric cell, or by pressure exerted by our bodies on a pad beneath our feet. Whichever example we chose, some form of computing is involved.