title: Why is Mutable keyword used
body: <blockquote>
    <p><strong>Possible Duplicate:</strong><br>
    <a href="https://stackoverflow.com/questions/105014/c-mutable-keyword">C++ &#39;mutable&#39; keyword</a>  </p>
  </blockquote>
  
  
  
  <pre><code>class student {
  
     mutable int rno;
  
     public:
       student(int r) {
           rno = r;
       }
       void getdata() const {
           rno = 90;
       } 
  }; 
  </code></pre>