Apple has released ten generations of their iPhone smartphone. Each generation has been accompanied by a major releases of the Apple iOS or operating system. Millions of iPhones have been sold and the popularity of the device has spurred a strong market of used devices that range from $25 to $1000.
The original 1st-generation iPhone was a GSM phone and established core design precedents, such as the button placement and screen size. And hose persisted throughout all releases for the first four generations. The iPhone 3G added 3G network support, and was followed by the 3GS with improved hardware, the iPhone 4 saw the introduction of a metal chassis, higher display resolution and a front-facing camera. The iPhone 4S continued with improved hardware and the introduction of the Siri voice assistant. The iPhone 5 featured a taller, 4-inch display and Apple’s newly introduced Lightning connector. In 2013, Apple released the 5S with improved hardware and a fingerprint reader. Apple also introduced a lower cost iPhone 5C, which was a version of the 5 with colored plastic casings instead of metal. The next generation was the larger iPhone 6 and iPhone 6 Plus, with models featuring 4.7 and 5.5-inch displays. The iPhone 6S was introduced the following year, which featured hardware upgrades and support for pressure-sensitive touch inputs. The iPhone SE featured hardware from the 6S but used the smaller form factor of the iPhone 5S. In 2016, Apple unveiled the iPhone 7 and iPhone 7 Plus, which added water resistance, improved system and graphics performance. A new rear dual-camera setup was included on the Plus model along with new color options, Apple also removed the 3.5 mm headphone that was used on previous models in favor of using the lightning connector.