title: Where is endl manipulator defined
body: <p>We know that <code>endl</code> is manipulator and internally it put <code>'\n'</code> to buffer and then flush up the buffer. Where is <code>endl</code> defined? What is <code>endl</code>, is it macro or function or variable or class or object? How can I define my own <code>endl</code> manipulator?</p>
  
  <pre><code>cout &lt;&lt; "hello" &lt;&lt; endl ; /*what is endl and  where it is defined */
  </code></pre>