Question: What is difference between 

```
int x=7;

```

and 

```
register int x=7;

```

?

I am using C++.

Answer: 
`register` is a hint to the compiler, advising it to store that variable in a processor register instead of memory (for example, instead of the stack).

The compiler may or may not follow that hint.

According to Herb Sutter in ["Keywords That Aren't (or, Comments by Another Name)"](http://www.drdobbs.com/184403859):

> 
> A register specifier has the same
>  semantics as an auto specifier...
> 
> 
>
With today's compilers, probably nothing. Is was orginally a hint to place a variable in a register for faster access, but most compilers today ignore that hint and decide for themselves.