Difference between pointer to a reference and reference to a pointer

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First, a reference to a pointer is like a reference to any other variable:

void fun(int*& ref_to_ptr)
{
    ref_to_ptr = 0; // set the "passed" pointer to 0
    // if the pointer is not passed by ref,
    // then only the copy(parameter) you received is set to 0,
    // but the original pointer(outside the function) is not affected.
}

A pointer to reference is illegal in C++, because -unlike a pointer- a reference is just a concept that allows the programmer to make aliases of something else. A pointer is a place in memory that has the address of something else, but a reference is NOT.

Now the last point might not be crystal clear, if you insist on dealing with references as pointers. e.g.:

int x;
int& rx = x; // from now on, rx is just like x.
// Unlike pointers, refs are not real objects in memory.
int* p = &x; // Ok
int* pr = ℞ // OK! but remember that rx is just x!
// i.e. rx is not something that exists alone, it has to refer to something else.
if( p == pr ) // true!
{ ... }

As you can see from the above code, when we use the reference, we are not dealing with something separated from what it refers to. So, the address of a reference is just the address of what it refers to. Thats why there is no such thing called the address of the reference in terms of what you are talking about.

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