iPhone (/ˈaɪfoʊn/ eye-fohn) is a line of smartphones designed and marketed by Apple Inc. They run Apple's iOS mobile operating system.[14] The first generation iPhone was released on June 29, 2007; the most recent iPhone models are the iPhone 6s and iPhone 6s Plus, which were unveiled at a special event on September 9, 2015.[15]

The user interface is built around the device's multi-touch screen, including a virtual keyboard. The iPhone has Wi-Fi and can connect to cellular networks. 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, GPS navigation, record notes, do mathematical calculations, and receive visual voicemail.[16] Other functions—video games, reference works, social networking, etc.—can be enabled by downloading application programs (‘apps’); as of October 2013, the App Store offered more than one million apps by Apple and third parties[17] and is ranked as the world's largest mobile software distribution network of its kind (by number of currently available applications).[citation needed]

There are nine generations of iPhone models, each accompanied by one of the nine major releases of iOS. The original 1st-generation iPhone was a GSM phone and established design precedents, such as a button placement that has persisted throughout all releases and a screen size maintained for the next four iterations. 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 VGA front-facing camera for video calling and other apps, and a 5-megapixel rear-facing camera with 720p video capture.[18] The iPhone 4S upgrades to an 8-megapixel camera with 1080p video recording, a dual-core A5 processor, and a natural language voice control system called Siri.[19] iPhone 5 features the dual-core A6 processor, increases the size of the Retina display to 4 inches, introduces LTE support and replaces the 30-pin connector with an all-digital Lightning connector. The iPhone 5C features the same A6 chip as the iPhone 5, along with a new backside-illuminated FaceTime camera and a new casing made of polycarbonate. The iPhone 5S features the dual-core 64-bit A7 processor, an updated camera with a larger aperture and dual-LED flash, and the Touch ID fingerprint scanner, integrated into the home button, and fitness tracking facilities. The iPhone 6 and iPhone 6 Plus further increased screen size, measuring at 4.7 inches and 5.5 inches, respectively. In addition, they also feature a new A8 chip and M8 motion coprocessor. As of 2013, the iPhone 3GS had the longest production run, 1,181 days; followed by the iPhone 4, produced for 1,174 days.