In this unit children learn how to use input devices or switches to control a process. They learn that it is possible to attach devices such as pressure pads, light sensors, magnetic switches, on/off switches or other devices to a control box. The computer can then be programmed to carry out a process when it detects some sort of change, eg switch on the light when it gets dark. They learn the new control language necessary to program the control box to make such decisions, eg 'if... then...'