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copied!<ol> <li><p>A pointer can be re-assigned: </p> <pre><code>int x = 5; int y = 6; int *p; p = &x; p = &y; *p = 10; assert(x == 5); assert(y == 10); </code></pre> <p>A reference cannot, and must be assigned at initialization:</p> <pre><code>int x = 5; int y = 6; int &r = x; </code></pre></li> <li><p>A 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 <a href="https://stackoverflow.com/questions/79923/what-and-where-are-the-stack-and-heap#79936">stack vs heap</a>. This implies that there is a real address of a reference that the compiler will not tell you. </p> <pre><code>int x = 0; int &r = x; int *p = &x; int *p2 = &r; assert(p == p2); </code></pre></li> <li><p>You can have pointers to pointers to pointers offering extra levels of indirection. Whereas references only offer one level of indirection. </p> <pre><code>int x = 0; int y = 0; int *p = &x; int *q = &y; int **pp = &p; pp = &q;//*pp = q **pp = 4; assert(y == 4); assert(x == 0); </code></pre></li> <li><p>Pointer can be assigned <code>nullptr</code> directly, whereas reference cannot. If you try hard enough, and you know how, you can make the address of a reference <code>nullptr</code>. Likewise, if you try hard enough you can have a reference to a pointer, and then that reference can contain <code>nullptr</code>.</p> <pre><code>int *p = nullptr; int &r = nullptr; <--- compiling error int &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 </code></pre></li> <li><p>Pointers can iterate over an array, you can use <code>++</code> to go to the next item that a pointer is pointing to, and <code>+ 4</code> to go to the 5th element. This is no matter what size the object is that the pointer points to.</p></li> <li><p>A pointer needs to be dereferenced with <code>*</code> to access the memory location it points to, whereas a reference can be used directly. A pointer to a class/struct uses <code>-></code> to access it's members whereas a reference uses a <code>.</code>.</p></li> <li><p>A pointer is a variable that holds a memory address. Regardless of how a reference is implemented, a reference has the same memory address as the item it references.</p></li> <li><p>References cannot be stuffed into an array, whereas pointers can be (Mentioned by user @litb)</p></li> <li><p>Const references can be bound to temporaries. Pointers cannot (not without some indirection):</p> <pre><code>const int &x = int(12); //legal C++ int *y = &int(12); //illegal to dereference a temporary. </code></pre> <p>This makes <code>const&</code> safer for use in argument lists and so forth.</p></li> </ol>

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