The new operating system for Apple's Mac computers is now available free of charge, Apple has announced.
"The days of spending hundreds of dollars to get more out of your computer are over, " Craig Federighi, Apple Inc. Senior Vice President of Software Engineering told an audience at an Apple product event in San Francisco.
Apple has kicked off a product event at which the company is expected to introduce slimmer, faster iPads in time for the holidays.
The new tablets will face stiff competition, with Microsoft Corp, Nokia and Amazon.com Inc all plugging rival devices in coming months.
Apple, which jumpstarted the tablet computing market in 2010 with the first iPad, has already come under increasing pressure from cheaper devices from Amazon's Kindle Fire to Samsung Electronics Co Ltd's Note.
Technology giant Nokia has launched a raft of new products including its first Windows tablet device and two new large-screen smartphones, or "phablets".
The new Lumia 2520 tablet, designed to "work anywhere", was unveiled at a news conference in Abu Dhabi.
Two new 6in (15cm) screen smartphones, or phablets, were unveiled - the Lumia 1520 and Lumia 1320 - offering easier access to apps and other new features.
"At Nokia we have found that tablet usage peaks between six and eight in the morning and between six and nine in the evening. During the rest of the day tablet usage drops quite dramatically," Nokia chief executive Stephen Elop said.
"We are looking to shift this trend - your tablet should be as mobile and as connected as you are."
Technology giant Apple is expected to release a new iPad today but has kept tight-lipped about the details.
The iPad 5 and iPad mini 2 devices are thought to be due for an unveiling.
Experts say they expect the iPad mini 2 will contain a better camera and a retina display, and could trigger the customary pre-Christmas technology rush.
There are also suggestions it could feature a fingerprint scanner, similar to the one used on the iPhone 5S, launched last month.
Tablet ownership has more than doubled in the past year alone, with 24 percent of homes now owning at least one of the devices, up from 11 percent the year before, according to a report by Ofcom.
More than half of adults - 51 percent - own a smartphone, up from 27 percent two years ago.
Two-thirds of tablet users say they use the device every day, and 95 percent use it at least once a week.