title: Version vs build in Xcode
body: <p>I have an app that I developed with Xcode 3 and recently started editing with Xcode 4. In the target summary I have the iOS application target form with fields: identifier, version, build, devices, and deployment target. The version field is blank and the build field is 3.4.0 (which matches the version of the app from when I was still editing with Xcode 3).</p>
  
  <p><strong>My questions are:</strong> </p>
  
  <ol>
  <li><p>What is the difference between the version and build fields?</p></li>
  <li><p>Why was the version field blank after I upgraded to Xcode 4?</p></li>
  </ol>