title: what is NSNotification Center ? why is it used ? (iPhone SDK)
body: <blockquote>
    <p><strong>Possible Duplicate:</strong><br>
    <a href="https://stackoverflow.com/questions/1900352/what-is-nsnotification">What is NSNotification?</a>  </p>
  </blockquote>
  
  
  
  <p>what is NSNotification Center ? why is it used ? (iPhone SDK)</p>