A control system is a system, which provides the desired response by controlling the output. Fig. 1 shows the simple block diagram of a control system.

Engineering is concerned with understanding and controlling the materials and forces of nature for the benefit of humankind. Control system is concerned with understanding and controlling segments of the environment, often called systems, to provide useful economic products for society. In today's era the present challenges are the modeling and control of modern, complex, interrelated systems such as traffic control systems, chemical processes, robotic systems, useful and interesting industrial automation systems. Perhaps the most characteristic quality of control engineering is the opportunity to control machines and industrial and economic processes for the benefit of the society. Control engineering is based on the foundations of feedback theory and linear system analysis. It integrates the concepts of network theory and communication theory. Therefore control engineering is not limited to any engineering discipline but is equally applicable to aeronautical, chemical, mechanical, environmental, civil, and electrical engineering.

Real Life Example of a Control System:
we are literally surrounded by control systems, these days. Keeping this simple, let’s have a look at the example of a water level control system (Fig. 2), where the level of water is measured by a level transducer and the flow of water is controlled by an automatic controller.