An adder is a combinational logic circuit. A half-adder inputs two bits to be added and outputs a sum and a carry bit. A full-adder inputs two bits and a carry-in bit and outputs a sum and a carry bit. One half-adder and multiple full adders are cascaded to provide multiple-bit adders. The 7483 4-bit full adder is available and can be cascaded into any number of bits desired. Adders can be converted to subtractors as well.