We have also designed a three bit ripple-carry adder, which operates in a similar fashion to the queue but instead of latches we compose adders in series, seen in Fig. 20b. An adder, the circuit design for which is seen in Fig. 20a, is a composition of two XOR gates, two OR gates and an AND gate. The adder produces two outputs, the value of the summation and the carry. Within the ripple-carry adder, the carry output of each adder is fed into the next adder, which outputs the sum and a carry. In this way, with three adders, we can add three two-bit numbers together.Fig. 20 a Circuit diagram for a ripple-carry adder. b Three adders in series controlled by the C-pipeline. A carry-bit output from one adder is fed into the next as part of the input