Two's complement

Summary

Two's complement is a method for representing signed numbers (negative integers) in binary.
The two's complement of a given binary integer is its negative equivalent.

Two's complement divides the available word length (see Binary_encoding) into two subsets: one for negative integrs and one for positive integers.

Take the binary encoding of decimal five (0101). Its complement is 1011.

The procedure for deriving the complement is as follows.

To derive the complement of an unsigned number:

Take the unsigned number and invert its digits: 0 becomes 1, 1 becomes 0
Add one

To derive the unsigned equivalent of a signed number