Can somebody prove that when we add 2 bit integers and if there is an overflow then the result always will be lesser than the 2 operands used??
Suppose $a$ and $b$ are the numbers you are adding. Suppose that $0 \le a,b < 2^n$. Then we must have that $a+b - 2^n < a$ and $a+b - 2^n < b$. Hence if overflow occurs the result is smaller than $a$ or $b$.