Macos Sierra: An Easy Guide to the Best Features OS Sierra is the 13th operation system version for Macintosh computers. It was previously called OS X and is the successor to OS X El Capitan with it being the first OS issued under their rebranding as macOS. It was named after the Sierra Nevada Mountain range in California. The major features that the system boasts are the iCloud system, windowing and Continuity. There is also support for Apple Pay and Siri. The initial preview of the system was given to developers around the time of the WWDC keynote that was done on June 13, 2016. It was formally released to the Apple Beta Software Program in July 2016 and released to end users in September 2016 as a free upgrade through the Apple Store. This book will review some of the key features of the macOS and educate the reader on the capabilities.