title: Storing user information on first use of iPad app
body: <p>I am writing an app and would like to do the following: When the app is first used it prompts the user for a username given at the time of purchase. When entered this is then stored and cannot be changed.</p>
  
  <p>I am unsure whether this is possible or if it is what method I should use to store it. I am right in thinking this is one for KeyChain?</p>
  
  <p>Any advice much appreciated. </p>