iOS 2, originally called iPhone OS 2, is the second major release of Apple's iOS mobile operating system. It was released on July 11, 2008, alongside the iPhone 3G and was the first version to introduce the App Store, allowing official support for third-party applications. iOS 2 brought many new features such as a redesigned Mail app with push email, support for Microsoft Office attachments, multiple calendars in the Calendar app, a scientific calculator mode, parental controls, and more robust Wi-Fi and security protocols. It was available as a free update for iPhones and for a fee on the iPod Touch. The final version of iOS 2 was 2.2.1, released in January 2009, after which it was succeeded by iOS 3.
