The full subtractor is a combinational circuit, which is used to perform subtraction of three input bits: the minuend X, subtrahend Y, and borrow in Bin. The full subtractor generates two outputs bits: the difference D and borrow out Bout Bin is set when the previous digit borrowed from X. Thus, Bin is also subtracted from X as well as the subtrahend Y, or in symbols: X-Y- Bin. The full subtractor generates a borrow out when it needs to borrow from the next digit. Since we are subtracting X by Y and Bin, a borrow out needs to be generated when X