title: Why do @synthesize variable names begin with an _?
body: <p>I'm just starting to use Objective-C and I need to clarify something</p>
  
  <p>When I @synthesize a @property, it is common convention to do the following:</p>
  
  <pre><code>@interface Class : ParentClass
  
  @property propertyName
  
  @end
  
  @implementation
  
  @synthesize propertyName = _propertyName;
  
  @end
  </code></pre>
  
  <p>I've seen plenty of questions and answers suggesting that "_propertyName" is widely accepted as the "correct" way to synthesize properties.  However, does it serve ANY purpose? Or is it merely to increase readability and identify instance variables?</p>