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 5S so customers could keep checking for units available at their local Apple Stores, and order for pickup. Online orders were also in short supply on launch day, with the shipping date across all model sizes and colors changing from "7-10 working days" to "October" in all countries, within hours of online orders being taken. The iPhone 5S was the best selling phone on AT&T, Sprint, Verizon, and T-Mobile in September 2013 in the United States, outselling the iPhone 5C and Samsung Galaxy S4. According to Consumer Intelligence Research Partners, the iPhone 5S outsold the 5C by a two-to-one margin during