The two major smartphone operating systems are Android and iOS (iPhone/iPad/iPod touch), with Android being the market leader worldwide. BlackBerry switched to Android in 2015.
In the past, Nokia's native Symbian OS was extremely popular. More Symbian phones were sold around the globe than any other prior to 2011, at which time Nokia switched from Symbian to Windows. In 2017, Microsoft announced the demise of Windows phones.
Tablets Are Also Android and iOS
iPads outsold Android tablets until 2014, when, according to IDC, Android became the worldwide market leader. See
iPhone,
Android,
Windows Phone,
BlackBerry,
Symbian and
how to select a mobile device.