 The operation performed by the subtractor is to rewrite formula_6 (which can take the values -2, -1, 0, or 1) as the sum formula_7.Subtractors are usually implemented within a binary adder for only a small cost when using the standard two's complement notation, by providing an addition/subtraction selector to the carry-in and to invert the second operand.The half subtractor is a combinational circuit which is used to perform subtraction of two bits.