One's Complement Representation

Two's-Complement Representation

The two's-complement method is one of the most popular methods of representing binary numbers in digital circuits.
Most computers use an 8-bit or a 16-bit binary word.
The MSB is the sign bit and a 0 means positive and a 1 means negative.
Positive numbers are in true form and negative numbers are in two's-complement form.
the range of positive numbers is 0 to (2^N–1 – 1) where N is the number of bits. (0 to 127 for 8-bit numbers)
The range of negative numbers is –1 to 2^{N – 1} (–1 to –128 for 8-bit numbers)