#1,113 – Addition of Integers Using Twos Complement

The primary benefit of using twos complement to represent signed integers is that addition and subtraction work the same, whether the number is positive or negative.

Below is an example, showing how we add the value -2 to the value +5, yielding a result of +3.  (Assuming that both values are stored as 16-bit integers).  The carry bits are shown in the top line.  We discard the final carry bit that results from adding the leftmost two bits.