Why is sizeof called a compile-time operator?
<p>Originally, this is a part of <a href="http://programmers.stackexchange.com/questions/193845/why-do-books-say-the-compiler-allocates-space-for-variables-in-memory">another</a> question.</p>

<p>Why is <code>sizeof</code> called a compile-time operator? Isn't it <strong>actually</strong> a run-time operator? And if it is indeed a compile-time operator, how does it help in producing portable code which runs the same in different computers ? Please explain in detail.</p>
