title: What is the difference between synthesize propertyname = _propertyname
body: <p>I am new to objective c. I create a property at .h header file of the class and then i synthesize.</p>
  <p>What is the difference between</p>
  <pre><code>@synthesize propertyname;
  </code></pre>
  <p>and</p>
  <pre><code>@synthesize propertyname = _propertyname;
  </code></pre>
  <p>Both work but what is the purpose of using the first one or the second one.</p>
  <p>Any help appreciated.</p>