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A full adder is a digital circuit that performs addition. Full adders are implemented with logic gates in hardware. A full adder adds three one-bit binary numbers, two operands and a carry bit. The adder outputs two numbers, a sum and a carry bit. The term is contrasted with a half adder, which adds two binary digits.
A full adder takes two binary numbers plus a carry or overflow bit. The output is a sum and another carry bit. Full adders are made from XOR, AND and OR gates in hardware. Full adders are commonly connected to each other to add bits to an arbitrary length of bits, such as 32 or 64 bits. A full adder is effectively two half adders, an XOR and an AND gate, connected by an OR gate.