The iPhone is a popular smartphone. Introduced in January 2007 by Apple, the iPhone was the first phone to offer a multi-touch touchscreen interface which soon became the industry standard. The original iPhone ran on its own operating system called iOS which included a pre-installed set of multimedia and productivity applications. The platform was originally designed as a closed system but soon after the iPhone’s launch, independent developers introduced apps that added functions to unlocked or «jailbroken» iPhones.Apple reacted and (reluctantly) opened the system to third-party developers in 2008. TheApple App Store was introduced shortly thereafter and quickly became an essential part of the iPhone ecosystem and a billion-dollar business for Apple.

In the 2011 fiscal year, Apple sold 72 million iPhones, which brought the total number of units shipped (to date) to 140 million. In less than 5 years the iPhone has become Apple’s most important product: in the 2011 fiscal year, iPhone revenue amounted to 47 billion U.S. dollars, representing more than 40 percent of Apple’s total revenue. More importantly, the Cupertino-based company managed to maintain a high profit margin in the otherwise low-margin smartphone industry, which has helped Apple become one of the most profitable companies in the world.

Apple’s strongest competitors in the smartphone market are currently Google and Samsung. Google introduced Android, an open operating system for smartphones in 2008, and although considered an iOS rip-off by some (including Apple), Android has become a huge success. Backed by smartphone manufacturers such as HTC, Samsung and Sony, the system quickly acquired a substantial customer base and is now the leading operating system for smartphones with a market share of over 50 percent. Samsung, on the other hand, is the leading manufacturer of Android devices and has become the world’s largest smartphone vendor in the 3rd quarter of 2011. Apple dropped to second place, although the iPhone 4, and surprisingly the iPhone 3GS, have remained the two best-selling smartphones in the United States according to the NPD Group.

Since its launch in 2007, the iPhone has seen two major redesigns and three incremental updates. The iPhone 4S, introduced in September 2011, marks the popular smartphone’s fifth iteration and shares the design with its predecessor, the iPhone 4. It is widely expected that Apple will introduce a redesigned iPhone 5 in 2012.