The iPhone 4S is a touchscreen-based smartphone developed by Apple Inc. It is the fifth generation of the iPhone, succeeding the iPhone 4, and was announced on October 4, 2011. It became available for pre-order on October 7, 2011 in seven initial countries (United States, Canada, Australia, United Kingdom, France, Germany and Japan) with the first delivery date set for October 14, 2011, and available on that same day for direct in-store sales in those countries. It was released in 22 more countries, including Ireland, Mexico, and Singapore, on October 28.
The phone retains the exterior design of its predecessor, but hosts improved hardware specifications and software updates. It added a voice recognition system known as Siri from which the "4S" designator came, and a cloud storage service named iCloud. Some of the device's functions may be voice-controlled through Siri. The phone is available for 100 cell service carriers in 70 countries, including eight carriers in the United States. For US customers, unlocked (contract-free) sales started on November 11, 2011. The Associated Press said that AT&T described early iPhone 4S demand as "extraordinary". Reception to the iPhone 4S was generally favorable. Reviewers noted Siri, the new camera, and processing speeds as significant advantages over the prior model. Four million units of the iPhone 4S were sold in the first three days of release.
On September 12, 2012, Apple announced its successor, the iPhone 5.
A smartphone is a mobile phone built on a mobile operating system, with more advanced computing capability connectivity than a feature phone. The first smartphones combined the functions of a personal digital assistant (PDA) with a mobile phone. Later models added the functionality of portable media players, low-end compact digital cameras, pocket video cameras, and GPS navigation units to form one multi-use device. Many modern smartphones also include high-resolution touchscreens and web browsers that display standard web pages as well as mobile-optimized sites. High-speed data access is provided by Wi-Fi and mobile broadband. In recent years, the rapid development of mobile app markets and of mobile commerce have been drivers of smartphone adoption.
The mobile operating systems (OS) used by modern smartphones include Google's Android, Apple's iOS, Nokia's Symbian, RIM's BlackBerry OS, Samsung's Bada, Microsoft's Windows Phone, Hewlett-Packard's webOS, and embedded Linux distributions such as Maemo and MeeGo. Such operating systems can be installed on many different phone models, and typically each device can receive multiple OS software updates over its lifetime. A few other upcoming operating systems are Mozilla's Firefox OS, Canonical Ltd.'s Ubuntu Phone, and Tizen.