What is the purpose of clocking the flip-flops?

Answer 1

Clocking flip flops is normally done to wait until the input has settled. Where one flip flop is feeding another, the delay in the clocking allows the circuitry in the first one to complete the choice and settle. This way the changing output of the first one is not half way down or half way up. In the case of an exterior input (a photo resistor pulse for example), clocking assures as stable signal, high or low and not a paused one part way along.