Adder

The ADD operator is the fundamental instruction of many arithmetic operations (such as subtract, multiply, divide, and modulo).

Input and output

ADD takes in two binary digits. It then outputs the result, which consists of a digit and a carry.

Full adder

In contrast to the above, which is a half adder, a full adder has an additional input: carry-in, which modifies the result.

Full adders can be constructed with two half adders.

Ripple carry adder

A ripple carry adder is constructed with multiple full adders to compute multi-digit addition. Each full adder contributes some propagation delay due to the need to input carry to the next full adder.