title: When do you make an underscore in front of an instance variable?
body: <blockquote>
    <p><strong>Possible Duplicate:</strong><br>
    <a href="https://stackoverflow.com/questions/822487/how-does-an-underscore-in-front-of-a-variable-in-a-cocoa-objective-c-class-work">How does an underscore in front of a variable in a cocoa objective-c class work?</a>  </p>
  </blockquote>
  
  
  
  <p>I've seen this at Apple, inside UIPickerView.h:</p>
  
  <pre><code>id&lt;UIPickerViewDataSource&gt; _dataSource;
  </code></pre>
  
  <p>why's that underscore there? Does it have a special meaning? A Convention I must know about?</p>