Two's complement definition

two's complement

The number obtained by complementing every bit of a given number and adding one. A number and its complement add to 2ⁿ, where n is the word size of the machine.

The two's complement of 0xAAAA is 0x5556 on a 16-bit machine, and 0xFFFF5556 on a 32-bit machine.
The convention by which bit patterns with high bit 0 represent positive numbers from 0 to $2^{n-1} - 1$ directly, while bit patterns with high bit 1 represent negative numbers from -1 to $-2^{n - 1}$ , n being the word size of the machine, and the numeric complement of a number is its two's complement.

Nearly all modern computers use twos complement for integer arithmetic.