iOS 5 is the next major update for the operating system that runs on the iPod touch, iPhone and iPad. The new system will include several enhancements that have been long wished-for by developers and end-users alike, such as a revamped notifications system known as Notification Center which replaces the old and intrusive pop-up notifications found in earlier versions, system wide Twitter integration, enhancements to Mobile Safari with features such as Reader mode and an enhanced user interface on the iPad, among many others. While iOS 5 is expected to come built right into the iPhone 5; iPhone 4, iPhone 3GS, iPad 2 and iPad owners, along with users of the 3rd-generation iPod touch and above, will be able to update their system through iTunes.