Benchmark 3B
The Nature of Technology: Design and Systems
Grades 6-8, page 51

Almost all control systems have inputs, outputs, and feedback. The essence of control is comparing information about what is happening to what people want to happen and then making appropriate adjustments. This procedure requires sensing information, processing it, and making changes. In almost all modern machines, microprocessors serve as centers of performance control.

See the general discussion in Unifying Concepts and Processes: Systems, order, and organization.