title: Is `operator new` a part of C++ core language?
body: <p>I have been told that "new-expression will call <code>operator new</code> to manage dynamic storage and initialize the object at the same time" many times. And I don't doubt about that. But I'm wondering that since <code>operator new</code> is declared in standard library header <code>&lt;new&gt;</code>, how could we still using new-expression even if we include no header files.</p>
  
  <p>Is <code>operator new</code> a part of C++ core language or the compiler includes <code>&lt;new&gt;</code> implicitly?</p>