I am looking at control theory but I don't understand how this is used in real systems. Lets take an example of a cruise control system on a car which is also a control system. I can use an embedded computer connected to a hall effect sensor which measures the speed of the vehicle and also connect it to the throttle input which controls the speed of the vehicle. From a programmers perspective, I can just simply use if else statements to control the vehicle's speed e.g. if the hall effect sensor reads a significant drop in vehicle speed due to an upwards hill the the throttle input is increased until the desired speed is reached again and vice versa for a downwards hill. Why would I need transfer functions etc? Or can you give me an example where something like transfer functions and things like that would be used?