Android is a mobile operating system developed by Google Inc., and backed by an industry consortium known as the Open Handset Alliance It is an open source platform with optional proprietary components, including a suite of flagship software for Google services, and the application and content storefront Google Play Android was officially introduced via the release of its inaugural device, the HTC Dream on 20 October 2008. As an open source product, Android has also been the subject of third-party development. Development groups have used the Android source code to develop and distribute their own modified versions of the operating system, such as CyanogenMod, to add features to the OS and provide newer versions of Android to devices that no longer receive official updates from their vendor. Forked versions of Android have also adopted by other vendors, such as Amazon.com, who used its " Fire OS " on a range of tablets and the Fire Phone As it is a non-proprietary platform that has shipped on devices covering a wide range of market segments, Android has seen significant adoption. Gartner Research estimated that 325 million Android smartphones were sold during the fourth quarter of 2015, leading all other platforms. Samsung Electronics, who produces Android devices, was also the top smartphone vendor across all platforms in the same period of time.