why we have to know the address of store varable,whats the aim of finding its adress,what we will do with its address?

Answer 1

Hi!
We have not to know the address of variable. The compiler have to. So, get value of the variable by address is easier than looking for it by id for system.
For example, suggest you have some houses. And try to find it by description(red, blue, yellow, stone). Then try to find house by address. It's too much easier, isn't it?)

Answer 2

We dont have to find out its address, but it can help us to do some stuff like swaping variables data

Answer 3

then we use &?

Answer 4

Yes, of course. Compiler takes & and momentally finds the variable. It takes less RAM and time also.