What does {int &x;} means

Question

I think it should be different from both &x and int *x.

Answer 1

idk what's with the curly braces, but if you have:

int a = 2;
int &b = a;

now b is a. Not just equal to a, but b is a itself. If you make b++, now a is 3! We say that b is a reference to a.

If you have:
int *pa = &a;

here pa is a pointer, and &a is 'address of a'. To access a through pa you can do:

*pa = 9;

and now a is 9.

Now, if you have:

void func(int &x) { x = 7; }

and you call func(a), now a is 7.

We say that the parameter to func() is passed by reference. Btw, such a function can only be called with l-value variables as parameters, never with imediate or const values, I think. You can't call func(2) for example.

If you had
void funcp(int *px) { *px = 6; }

and call
funcp(&a); // see, you have to give the 'address of a' as argument!

now a is 6.

Answer 2

You are creating a reference variable with the former, and a pointer with the latter.

A reference variable is simply an alias to the variable it references. (i.e. Another name for the variable assigned to it).

A pointer variable is a variable which stores the address of another variable.