Symbian

Symbian is a mobile operating system (OS) and computing platform designed for smartphones and currently maintained by Accenture. Symbian was originally developed by Symbian Ltd., as a descendant of Psion's EPOC and runs exclusively on ARM processors, although an unreleased x86 port existed. The current form of Symbian is an open-source platform developed by Symbian Foundation in 2009, as the successor of the original Symbian OS. Symbian was used by many major mobile phone brands, like Samsung, Motorola, Sony Ericsson, and above all by Nokia. It was the most popular smartphone OS on a worldwide average until the end of 2010, when it was overtaken by Android.
Symbian rose to fame from its use with the S60 platform built by Nokia, first released in 2002 and powering most Nokia smartphones. UIQ, another Symbian platform, ran in parallel, but these two platforms were not compatible with each other. Symbian^3, was officially released in Q4 2010 as the successor of S60 and UIQ, first used in the Nokia N8, to use a single platform for the OS. In May 2011 an update, Symbian Anna, was officially announced, followed by Nokia Belle (previously Symbian Belle) in August 2011.
On 11 February 2011, Nokia announced that it would use Microsoft's Windows Phone OS as its primary smartphone platform, and Symbian will be its franchise platform, dropping Symbian as its main smartphone OS of choice. On 22 June 2011 Nokia made an agreement with Accenture for an outsourcing program. Accenture will provide Symbian-based software development and support services to Nokia through 2016; about 2,800 Nokia employees became Accenture employees as of October 2011. The transfer was completed on 30 September 2011. The Nokia 808 PureView was officially the last Symbian smartphone.