IPhone 4S announced iPhone 5s and iPhone 5c. This was unusual for Apple as an upper case 'S' had been used since the introduction of the iPhone 3GS in 2009. On September 9, 2014, the iPhone 4S was officially discontinued following the reveal of the iPhone 6 and the iPhone 6 Plus. However, 4S production did continue for developing markets until February 17, 2016. On June 13, 2016, following the release of iOS 10, Apple dropped support on the iPhone 4S, making iOS 9.3.5 the last version available for the device. The runs iOS, Apple's mobile operating system. The user interface of
IPhone its older iPhones when issuing operating system upgrades. It has spurred allegations that the firm has been using this as a tactic to prompt users of older iPhones to buy newer models. Up to the iPhone 4, all iPhone models, as well as other iOS devices were manufactured exclusively by Foxconn, based in Taiwan. In 2011, after Tim Cook became CEO of the company, Apple changed its outsourcing strategy, for the first time increasing its supply partners. The iPhone 4s in 2012 was the first model which was manufactured simultaneously by two stand-alone companies: Foxconn as well as Pegatron, also