Control systems influence many applications, from space shuttles to automated manufacturing. They exist naturally, such as our body's blood sugar regulation and heart rate adjustments during stress. These systems consist of subsystems and processes producing specific outputs from given inputs. Consider an elevator: A passenger pressing a button initiates an input to the control system, directing it to the desired floor. The system's performance, indicated by the elevator's speed and ride smoothness, is measured using transient response, the system's reaction to changes, and steady-state error, the disparity between the actual and desired output. Controlled variables are measured and regulated; control signals guide these changes. Plants are the physical objects being controlled, and processes are the operations under control. Systems combine components for a goal, and disturbances affect output. Feedback control maintains balance by reducing output-reference differences.