Source: unsplash.com The Binary subtraction of two numbers, as you know consists of adding one number to complement of the other. The complement can be a 2s or 1s complement. Consider the subtraction with 2s complement. After adding with 2s complement of the other number, there are two cases:- If carry occurs, ignore it, and the answer is the difference required. If carry does not occur, find the 2s complement of the result to get the magnitude of difference, and add a negative sign to answer... Now, we just go a little deep and try to make a sense of why these rules are framed... Let A and B the two binary numbers of n bits, and we need to find A - B, which we do by finding 2s complementing of B and adding it to A We can write the expression as:- A + 2s complement of B = A + (2 n - B) = A - B + 2 n Based on A is greater or lesser than B, we have two cases :- Case I: If A > B A - B + 2 n = (A - B) + 2 n = (required value) + 2 n Thus A - B + 2 n will be nothing but just