On a circuit board we are supposed to use for laborations there are circuits for D flip-flops that looks like this (this picture shows how the connections actually look at the circuit board, the square signs are where connections can be made): Here CK = Clock, D is input and Q is output. However when I searched the web I found pictures of D flip-flops that looked like this: How are these pictures of D flip-flops related? CLK and CK are of course the same, CLEAR I guess is a way to reset the output value to zero and I assume D = J and Q = Q. But what then is K and Q-bar? How can one simplify a circuit that included K and Q-bar, so that it only uses D (J) and Q?