title: error: invalid initialization of non-const reference of type ‘int&’ from an rvalue of type ‘int’
body: <p>Wrong form:  </p>
  
  <pre><code>int &amp;z = 12;
  </code></pre>
  
  <p>Correct form:</p>
  
  <pre><code>int y;
  int &amp;r = y;
  </code></pre>
  
  <p><em><strong>Question</em></strong>:<br>
  Why is the first code wrong? What is the "<strong>meaning</strong>" of the error in the title?</p>