Final answer:
Two's complement allows a single adder circuit to be used for subtraction by inverting the bits of a number and adding one, which makes it possible to perform subtraction as an addition operation with the negated value.
Step-by-step explanation:
The use of two's complement in computer arithmetic allows us to reuse an adder circuit for the purpose of subtraction in addition to its primary function of performing addition operations. This technique saves on the need to design and implement a separate circuit for subtraction. The principle behind two's complement is to invert the bits of a binary number and add one to achieve the negative counterpart of the original number. When subtracting using an adder circuit, the subtraction of 'B' from 'A' (A - B) is performed by adding 'A' to the two's complement of 'B' (A + (-B)). This approach takes advantage of the commutative property of addition (A+B = B+A), and for subtraction, changes the sign of the number being subtracted before the operation (5 - (+3) = 5 - 3 and 2 - (-6) = 2 + 6).