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 of the iPhone have also garnered praise. The iPhone is one of the most widely used smartphones in the world, and its success has been credited with helping Apple become one of the world's most valuable publicly traded companies. Development of what was to become the iPhone began in 2004, when Apple started to gather a team of 1,000 employees (including Jonathan Ive, the designer behind the iMac and iPod) to work on the highly confidential "Project Purple." Apple CEO Steve Jobs steered the original focus away from a tablet (which Apple eventually revisited in the form of the iPad)