iPhone is Apple's smartphone line. All iPhones are shipped with iOS, Apple’s mobile Operating System. This tag can include questions about hardware, software and accessories.
iPhone was originally announced on January 9, 2007, and released on June 29, 2007. The first iPhone had no support for native third-party software, but Apple encouraged developers to write web-based applications that took advantage of iPhone features such as the touch screen. The iPhone Developer Program, which allows developers to submit their own applications to the iOS App Store for download or sale, was not announced until the release of the iPhone 3G/iPhone OS 2.2.1 in 2008.
In addition to the App Store, iPhone 3G added 3G wireless capabilities (hence its moniker), GPS, a redesigned body, a faster processor and more RAM.
iPhone 3GS started the now-entrenched trend of having a bi-yearly release cycle. In even-numbered years there is a major release, which, while of course upgrading internal components of the device, usually focuses on major external changes(such as iPhone 3G's redesigned body). In odd-numbered years, an "S" variant appears that focuses on internal improvements. iPhone 3GS added a 3 megapixel camera, up from 2 megapixels, which added the capability of shooting video. Voice Control was added and the RAM and processor were also bumped up.
Arguably the biggest new hardware feature of iPhone 4, released in 2010, was the Retina Display, a 316 ppi screen with eye-popping color. The internals were upgraded to include an A4 processor, a front facing .3 megapixel camera and a back facing 5.0 megapixel camera. For the first time, a CDMA variant was released in February 2011 for Verizon Wireless, who became only the second US carrier to sell iPhone, but due to their network structure was unable to utilize the GSM model in use on AT&T's network.
iPhone 4S was released in October 2011, debuting a new voice-driven assistant called Siri. It also included a new A5 processor, an 8.0 megapixel back-facing camera that was aimed squarely at the point-and-shoot camera market, and enhanced cellular capabilities that greatly increased download speeds on some carriers. The introduction of 4S marked the first time Sprint carried iPhone.
iPhone 5 was released on September 21, 2012. It is slimmer, lighter with 4-inch 16:9 screen. Although the screen is technically higher-res, it is of the same ppi (316). The phone also includes a custom-designed ARMv7 processor called the Apple A6.
Continuing the "S" trend in odd-numbered years, iPhone 5s came to market on September 20, 2013. Major new features included the A7 system-on-a-chip, which was the first 64-bit processor used in a smartphone; the M7 motion co-processor, a low-power chip which tracked data such as steps taken without the power usage that would be incurred by having the main CPU running; and Touch ID, a revised home button that read users' fingerprints to unlock the device and allow app purchases.
At the same time, Apple took the internal components of 2012's iPhone 5 and put them into a new candy-colored plastic shell, releasing it alongside iPhone 5s as the iPhone 5c. It was priced lower and appeared to be Apple's shot at the mid-tier smartphone market, which had previously been limited to simply re-pricing prior years' models.
After years of speculation that Apple would increase the size of their phones, iPhone 6 and iPhone 6 Plus were released in October 2014. The devices grew to 4.7-inch and 5.5-inch screens, respectively. Major refinements were made to the cameras in both devices, with 6 Plus gaining optical image stabilization due to having additional room for the camera sensor to physically move within the case. The A8 processor powers both devices.
In 2015, the additions to the lineup were the iPhones 6s and 6s Plus, released in September of 2015. These brought Force Touch, a haptic feedback component that allows users to open app shortcuts on the home screen as well as in the apps themselves, and Touch ID v2 featuring improved fingerprint scanning performance. Both models are powered by the A9 processor and the M9 motion coprocessor. The camera has a 12 MP sensor on both models.
In March of 2016, the iPhone SE was released, containing an A9 processor and a 12 MP camera capable of 4K video. It is the same size as the iPhone 5 series, and has a Touch ID v1 sensor. This is meant to cater to the people who prefer smaller, slightly less expensive phones.
In September of 2016, the iPhone 7 and 7 Plus were released. This was a minor upgrade to the 6s. The major changes were the A10 chip and the fact that the plus-size has a dual camera array, allowing for 2x zoom with no quality loss, as well as a portrait mode that adds a depth effect to pictures, much like a regular camera. These phones both have 12 MP cameras, and do not feature headphone jacks. In the box, there is a Lightning to 3.5 mm Headphone Jack adapter as well as a pair of EarPods with Lightning Connector, both of which are compatible with any iPhone that has a Lightning port.
In 2017, three iPhones were announced in September: iPhone 8, iPhone 8 Plus and iPhone X (pronounced "ten"). All models include a True Tone display, a 7 MP FaceTime HD camera, an A11 chip with a neural engine and Bluetooth 5.0. Wireless charging and fast charging capabilities were also added.
iPhone X is the first model to use an OLED screen with a minimal notch on the top and no Home button or Touch ID. Although it is just about 10 % larger than iPhone 8, its screen measures 5.8-inch as there are no bezels. New features include Face ID, tap to wake, dual stabilized iSight cameras and a TrueDepth camera for face detection and Animoji.
In September 2018 Apple announced three new iPhones: iPhone XS, iPhone XS Max and iPhone XR (pronounced "ten S", "ten S Max" and "ten R" respectively). Like a typical "S" upgrade, iPhone XS adopted the external design of iPhone X. Unlike a Plus variant, iPhone XS Max offers the exact same internals and camera subsystem as iPhone XS but with a bigger 6.5-inch display. iPhone XR on the other hand is priced slightly less and marketed as a budget iPhone. iPhone XS and XS Max use an OLED screen, while iPhone XR uses a LED screen. All three phones use the same new A12 Bionic chip with an upgraded octa-core Neural Engine. This is the first time in the history of iPhone that Apple included support for dual-SIM cards (Nano-SIM and eSIM) with dual Nano-SIM variant exclusively for Chinese market.
While iPhone XS and XS Max are practically the same device with the exception of screen size, iPhone XR is differentiated by having a 6.1-inch screen, single lens camera subsystem (still compatible with portrait mode), lesser 256 GB storage in top-end model (XS and XS Max are also available in 512 GB configuration), 3 GB RAM (against 4 GB in XS and XS Max) and absence of 3D Touch.
Along with dual SIM and eSIM support, this is also the first iPhone lineup to get rid of Touch ID as authentication mechanism and relying totally on face-id introduced in iPhone X. iPhone XR is also offered in candy-colored shell just like iPhone 5c.