Before the end of 2010, what was the most widely used operating system in smartphones?

Smartphones before Android, iOS and BlackBerry, typically ran on Symbian, which was originally developed by Psion. Symbian was an open-source platform developed by the now defunct 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 briefly the most popular smartphone OS on a worldwide average until the end of 2010.