Safari Books Online is a digital library providing on-demand subscription access to thousands of learning resources.
To check to see if your apps have any available updates, just open iTunes on your computer and click on your Apps Library in the Source list on the left side of the window. Then, click the Check for Updates link in the bottom-right corner of the iTunes window, and if there are any updates available, you’ll be taken to a screen that lists them, where you can then update your apps individually or all at once.