The serial binary adder or bit-serial adder is a digital circuit that performs binary addition bit by bit.
The serial full adder has three single-bit inputs for the numbers to be added and the carry in.
The addition is performed by adding each bit, lowest to highest, one per clock cycle.
Serial binary addition is done by a flip-flop and a full adder.
Alternatively, the number to be subtracted is converted to its ones' complement, by inverting its bits, and the carry flip-flop is initialized to a 1 instead of to 0 as in addition.