An iPhone can shoot video (though this was not a standard feature until the iPhone 3GS), take photos, play music, send and receive email, browse the web, send texts, and receive visual voicemail. Other functions—games, reference, GPS navigation, social networking, etc.—can be enabled by downloading apps; as of 2012, the App Store offered more than 775,000 apps by Apple and third parties.
There are six generations of iPhone models, each accompanied by one of the six major releases of iOS. The original iPhone was a GSM phone, and established design precedents, such as a button placement that has persisted through all models and a screen size maintained until the launch of the iPhone 5 in 2012. The iPhone 3G added 3G cellular network capabilities and A-GPS location. The iPhone 3GS added a faster processor and a higher-resolution camera that could record video at 480p. The iPhone 4 featured a higher-resolution 960 × 640 "retina display", a higher-resolution