Computational Elements

The only computational element described here is a full adder. It is the basic building block of multi-bit adders and subtracters.

Full Adder

A full adder performs a single column of a binary addition. It has two inputs, X and Y for bits from the summands. It has another input, Ci for the carry from the column to the right.

The S output is the column sum. This output should be 1 whenever an odd number of the inputs are 1.

The Co output is the carry output, which is sent to the column to the left. This output should be 1 when at least two of the inputs are 1.

Full Adder Implementation