Difference Between &(Reference) and &(Address of Operator),

[Tanveer]

I come from a c background and am a bit confused with the topic of references in c++.Am confused between the (& address of operator) and (reference).

when we declare a reference :

int i = 3;
What’s the difference between these 2 statements.

int *ptr = &i;
vs
int &ref = i;

do we read &ref as address of ref or its something else?

please explain this in detail, Also share any relevant links.

thanks in advance.

[Morderkainer]

I am not an expert, but a reference is like an alias of the variable, it has to be initialized, never can be set to reference a different variable and can’t be null. While a pointer stores the the memory address of the value is pointing at, can be changed to point to another value, and can be null. So…

With int* ptr = &i; you declare a pointer, that stores the memory addres of i.
With &ref = i; you create a reference (like an alias) of i.

This is a bit weird, but * and & are different based on where they are, basically if they are after a type of object, like int, is to declare a * pointer or a &reference. But when they aren’t after a type of object, they are indirection and address-of operator, this means with * you get the value inside a memory address (of variable), with & you get the address of a variable. So…
int* ptr ← you declare a pointer
int& ref ← you declare a reference
i ← just a variable
ref ← just as i (3 in your example)
&i ← memory address of i
ptr ← a memory address (in your example, the memory address of i)
&ptr ← the memory address of ptr (its own memory address, not the address it is pointing at)
*ptr ← the indirection of the memory address it is pointing at (in your example, the indirection of the memory address of i, which is 3)
A weird example is you can do *(&i), so you get memory address of i, and then indirect its memory address, so you get 3.

Example of results:

As I said, this is how I understand em, maybe someone can explain it in a better way.

After my explanation, you can watch this video, that explains it in a more visual way What is the Difference Between a Pointer and a Reference C++ - YouTube

[DanM]

Just to avoid any confusion regarding this:

@Morderkainer

basically if they are after a type of object, like int, is to declare a * pointer or a &reference. But when they aren’t after a type of object,

That doesn’t mean the following declarations are different.

int* ptr;
int *ptr;

As those two mean exactly the same thing.
When used in a declaration:

• * means pointer
• & means reference

When used in an expression:

• * means dereference (go fetch the value at the address)
• & means address of.