Siri, Tabs and iCloud DriveBy the time you read this, the latest version of Mac OS X ? sorry ? macOS, will be available to download from the App Store. macOS 10.12 Sierra, to give it its full title, finally sees Apple move away from the OS X nomenclature given to every version of its desktop operating system since 2001.You might be thinking, "Why macOS?" Well, the answer is simple: the new naming convention brings it in line with Apple's other operating systems: iOS, watchOS and tvOS. After previously naming versions of OS X after big cats of some description, the company turned to locations in California for recent releases.This latest one name-checks Sierra County, which is home to the beautiful Sierra Nevada mountain range depicted in the default wallpaper.