iOS 2 (originally called iPhone OS 2) was released on July 11, 2008. It was the second major release of Apple's mobile operating system for iPhone and iPod Touch, debuting alongside the iPhone 3G. This version introduced the App Store, the first official way to download and install third-party applications on iOS devices. Some key features included push email, support for Microsoft Office attachments in Mail, multiple calendars, parental controls, and support for new languages and Wi-Fi security protocols. The update was free for iPhone users but cost $9.95 for iPod Touch users at the time. iPhone OS 2 was succeeded by iPhone OS 3 in June 2009.