Just days ahead of the release of the Apple iPhone 4, Apple has released the iOS 4 software update. Unveiled back in April as iPhone OS 4.0, it was renamed to iOS 4 given its broadening device base.
Apple iOS 4.0 introduces over 100 new features, including multitasking, folders, the iBook app, and more. Note that not all features are compatible with all devices. For example, multitasking is available only with iPhone 4 and iPhone 3GS.
The iOS 4 software update is now available through iTunes (you will need version 9.2).