Question

Why does “type demotion” does not exist instead of “type promotion”? Also, it would consume less space resource than by doing it from type promotion.? 

Answer 1

Let’s take an example to understand it. 
Suppose 
double a=1.5; int b=10 and we want to calculate a+b 
By type demotion, float type a will convert to int. Therefore a=1 and a+b=1+10=11 but we know that correct answer is 11.5 which will only get by type promotion. So the conclusion is that by type demotion we will not get the correct answer.