Question: What is difference between 

```
int x=7;

```

and 

```
register int x=7;

```

?

I am using C++.

Answer: 
According to [Herb Sutter](https://stackoverflow.com/users/297582/herb-sutter), `register` is "[exactly as meaningful as whitespace](http://www.drdobbs.com/184403859)" and has no effect on the semantics of a C++ program.
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.