The iPhone 4S' setup screen. It is the first iPhone that does not need to connect to iTunes in order to be activated, due to iOS 5.

The iPhone 4S uses iOS, Apple's mobile operating system.^[24]The user interface of iOS is based on the concept of direct manipulation, using multi-touch gestures. Interface control elements consist of sliders, switches, and buttons. The response to user input is immediate and provides a fluid interface.^[25] Interaction with the OS includes gestures such asswipe, tap, pinch, and reverse pinch, all of which have specific definitions within the context of the iOS operating system and its multi-touch interface. Internal accelerometers are used by some applications to respond to shaking the device (one common result is the undo command) or rotating it in three dimensions (one common result is switching from portrait to landscape mode).^[25]

The iPhone 4S was first shipped with iOS 5.0, which was released on October 12, 2011, 2 days before the release of the device.^[26] The 4S uses iOS 5.1.1, which was released on May 7, 2012.^[27][28] As of March 2013, the device can be upgraded to iOS 6.1.3.^[29] It can act as a hotspot, sharing its internet connection over WiFi, Bluetooth, or USB,^[30] and also accesses the App Store, a digital application distribution platform for iOS developed and maintained by Apple. The service allows users to browse and download applicationsfrom the iTunes Store that were developed with Xcode and the iOS SDK and were published through Apple.

The 4S can play music, movies, television shows, ebooks, audiobooks, and podcasts and can sort its media library by songs, artists, albums, videos, playlists, genres, composers, podcasts, audiobooks, andcompilations. Options are always presented alphabetically, except in playlists, which retain their order from iTunes.^[31] The iPhone uses a large font that allows users plenty of room to touch their selection. Users can rotate their device horizontally to landscape mode to access Cover Flow. Like on iTunes, this feature shows the different album covers in a scroll-through photo library. Scrolling is achieved by swiping a finger across the screen. Alternatively, headset controls can be used to pause, play, skip, and repeat tracks. On the 4S, the volume can be changed with the included Apple Earphones, and the Voice Control feature can be used to identify a track, play songs in a playlist or by a specific artist, or create a Genius playlist.^[31]