An iPhone functions as a camera phone, including text messaging and visual voicemail, a portable media player, and an Internet client, with e-mail, web browsing, and Wi-Fi connectivity. The user interface is built around the device’s multi-touch screen, including a virtual keyboard rather than a physical one. Third-party applications are available from the App Store, which launched in mid-2008 and now has well over 200,000 “apps” approved by Apple. These apps have diverse functionalities, including games, reference, GPS navigation, social networking, and advertising for television shows, films, and celebrities.
There are four generations of iPhone models, and they were accompanied by four major releases of iOS (formerly iPhone OS). The original iPhone established design precedents like screen size and button placement that have persisted through all models. The iPhone 3G added 3G cellular network capabilities and A-GPS location. The iPhone 3GS added a compass, faster processor, and higher resolution camera, including video. The iPhone 4 has two cameras for FaceTime video calling and a higher-resolution display. It was released on June 24, 2010.