title: is that possible to know my apps is first time run or not in xcode?
body: <p>i create an apps that i want to prompt an message for the user.. maybe using UIAlertview. After that, if the user run the apps for the second time, the alert won't prompt up anymore.</p>
  
  <p>is that possible? honestly i don't have any idea about how to doing this.
  Any idea? I search on STO, actually <a href="https://stackoverflow.com/questions/7090541/how-to-show-popup-alert-view-when-apps-run-first-time">this link</a>, still confused.</p>
  
  <p>what is NSUserDefaults? How can NSUserDefaults store this information? i mean this is my first time or second time. </p>
  
  <p>thanks. </p>