c pointers vs references

1Pointers: A pointer is a variable that holds memory address of another variable. A pointer needs to be dereferenced with * operator to access the memory location it points to.
2
3References : A reference variable is an alias, that is, another name for an already existing variable. A reference, like a pointer, is also implemented by storing the address of an object.
4A reference can be thought of as a constant pointer (not to be confused with a pointer to a constant value!) with automatic indirection, i.e the compiler will apply the * operator for you.
5*******************************************
6*******************************************
7  
8A pointer can be re-assigned:
9
10int x = 5;
11int y = 6;
12int *p;
13p = &x;
14p = &y;
15*p = 10;
16assert(x == 5);
17assert(y == 10);
18-----------------------------------------
19 A reference cannot, and must be assigned at initialization:
20
21int x = 5;
22int y = 6;
23int &r = x;
24-------------------------------------------
25A pointer has its own memory address and size on the stack (4 bytes on x86), whereas a reference shares the same memory address (with the original variable) but also takes up some space on the stack. Since a reference has the same address as the original variable itself, it is safe to think of a reference as another name for the same variable. Note: What a pointer points to can be on the stack or heap. Ditto a reference. My claim in this statement is not that a pointer must point to the stack. A pointer is just a variable that holds a memory address. This variable is on the stack. Since a reference has its own space on the stack, and since the address is the same as the variable it references. More on stack vs heap. This implies that there is a real address of a reference that the compiler will not tell you.
26
27int x = 0;
28int &r = x;
29int *p = &x;
30int *p2 = &r;
31assert(p == p2);
32-------------------------------------------
33You can have pointers to pointers to pointers offering extra levels of indirection. Whereas references only offer one level of indirection.
34
35int x = 0;
36int y = 0;
37int *p = &x;
38int *q = &y;
39int **pp = &p;
40pp = &q;//*pp = q
41**pp = 4;
42assert(y == 4);
43assert(x == 0);
44-------------------------------------------
45A pointer can be assigned nullptr directly, whereas reference cannot. If you try hard enough, and you know how, you can make the address of a reference nullptr. Likewise, if you try hard enough, you can have a reference to a pointer, and then that reference can contain nullptr.
46
47int *p = nullptr;
48int &r = nullptr; <--- compiling error
49int &r = *p;  <--- likely no compiling error, especially if the nullptr is hidden behind a function call, yet it refers to a non-existent int at address 0
50Pointers can iterate over an array; you can use ++ to go to the next item that a pointer is pointing to, and + 4 to go to the 5th element. This is no matter what size the object is that the pointer points to.
51
52-------------------------------------------
53A pointer needs to be dereferenced with * to access the memory location it points to, whereas a reference can be used directly. A pointer to a class/struct uses -> to access it's members whereas a reference uses a ..
54-------------------------------------------
55References cannot be stuffed into an array, whereas pointers can be!
56-------------------------------------------
57
58Const references can be bound to temporaries. Pointers cannot (not without some indirection):
59
60const int &x = int(12); //legal C++
61int *y = &int(12); //illegal to dereference a temporary.
62This makes const& safer for use in argument lists and so forth.