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POWhat are the differences between a pointer variable and a reference variable in C++?
 

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  1. POWhat are the differences between a pointer variable and a reference variable in C++?
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    <p>I know references are syntactic sugar, so code is easier to read and write.</p> <p>But what are the differences?</p> <hr> <p>Summary from answers and links below:</p> <ol> <li>A pointer can be re-assigned any number of times while a reference cannot be re-assigned after binding.</li> <li>Pointers can point nowhere (<code>NULL</code>), whereas a reference always refers to an object.</li> <li>You can't take the address of a reference like you can with pointers.</li> <li>There's no "reference arithmetic" (but you can take the address of an object pointed by a reference and do pointer arithmetic on it as in <code>&amp;obj + 5</code>).</li> </ol> <p>To clarify a misconception:</p> <blockquote> <p><em>The C++ standard is very careful to avoid dictating how a compiler may implement references, but every C++ compiler implements references as pointers. That is, a declaration such as:</em></p> <pre><code>int &amp;ri = i; </code></pre> <p><strong><em>if it's not optimized away entirely</em></strong>, <em>allocates the same amount of storage as a pointer, and places the address of <code>i</code> into that storage.</em></p> </blockquote> <p><strong><em>So, a pointer and a reference both use the same amount of memory.</em></strong></p> <p>As a general rule,</p> <ul> <li>Use references in function parameters and return types to provide useful and self-documenting interfaces.</li> <li>Use pointers for implementing algorithms and data structures.</li> </ul> <p>Interesting read:</p> <ul> <li>My all-time favorite <a href="http://yosefk.com/c++fqa/ref.html" rel="noreferrer">C++ FAQ lite</a>.</li> <li><a href="http://www.embedded.com/electronics-blogs/programming-pointers/4023307/References-vs-Pointers" rel="noreferrer">References vs. Pointers</a>.</li> <li><a href="http://www.embedded.com/electronics-blogs/programming-pointers/4024641/An-Introduction-to-References" rel="noreferrer">An Introduction to References</a>.</li> <li><a href="http://www.embedded.com/electronics-blogs/programming-pointers/4023290/References-and-const" rel="noreferrer">References and const</a>.</li> </ul>
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    1. COA local reference (i.e., one not in a struct or class) does not necessarily allocate storage. You can tell because of the sizeof difference between sizeof(int &) and sizeof(struct { int &x; }).
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    2. COI think point 2 should be "A pointer is allowed to be NULL but a reference is not. Only malformed code can create a NULL reference and its behavior is undefined."
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      1. POWhat are the differences between a pointer variable and a reference variable in C++?
      1. USMark Ransom
    3. COPointers are just another type of object, and like any object in C++, they can be a variable. References on the other hand are never objects, *only* variables.
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