hi everyone, I have recently started studying abvout control engineering, but am not getting a grasp on the basic idea behind controls. All the textbooks say that the output should track the input ideally , but why is it so? i.e if i give a step input to a system, the response should ideally be an step. i mean, say you characterise a system by G(s), and give input X(s). the output is Y(s). say i want a some desired output , why cant after knowing G(S) give an appropriate input X(S) so as to produce the desired output.