Apple has launched OS X 10.10, aka Yosemite, as a free upgrade for most Mac owners.
Mac users running last year's Mavericks, 2012's Mountain Lion, 2011's Lion and even 2009's Snow Leopard are able to download Yosemite from the Mac App Store starting today. The no-older-than-Snow-Leopard limitation was due to the App Store, the only distribution channel for Yosemite; versions of OS X that preceded Snow Leopard cannot access the online mart.
During a news conference today - which Apple live-streamed - Craig Federighi, who leads iOS and OS X development and has taken the roll of Jerry Lewis to Cook's Dean Martin straight man, spent considerable time summarising the new features of Yosemite.
He also boasted that a million users had registered for the public beta, the first OS preview from Apple since 2000.
Of the new features in Yosemite, the most prominent -- the Continuity collection that includes task hand-off from an iOS device to a Mac, or vice versa, requires iOS 8.1, which Apple will release on Monday, October 20.
The free Yosemite will be accompanied by upgrades to the also-free iWork suite - Pages, Numbers and Keynote - which are also available today, said Federighi.
OS X Yosemite tips the virtual scale at 5.2GB, slightly less than last year's Mavericks but still a massive download for customers with slower or metered Internet connections. It can be downloaded by choosing "Software Update" from the Apple menu at the far left of a Mac's menu bar.
Macs compatible with Yosemite include iMacs as old as mid-2007, MacBook Pro notebooks from late 2007 on and MacBook Air laptops from late 2008 going forward. All Macs sold from 2009 and later are able to run Yosemite, said Apple.