Nokia was once dominant in the mobile phone market using its Symbian operating system, but Symbian lost popularity to Android and iOS. Nokia then adopted Windows Phone and some Android phones. Symbian had many versions like S60, S60v1, and S60v5. Windows Phone included versions like WP7, WP8, and the upcoming WP10. Android is now most popular and also used in some Nokia phones like the Nokia X series, with versions including Cupcake, Donut, and Lollipop.