Apple released the 10th major upgrade of its OS X Mac operating system, Mavericks, at the unveiling of its new iPad Air and MacBooks yesterday.

Since then, OS X Mavericks has been available as a free download from the Mac App Store.

Here are 6 new things about Apple's latest OS X.

  • It’s free

Upgrading to Mountain Lion, the latest version of OS X before Mavericks, cost $20.

But Apple announced that starting with OS X Mavericks, users won’t have to pay to upgrade ever again.

“We want every Mac user to experience the latest features, the most advanced technologies, and the strongest security,” said Craig Federighi, Apple’s senior vice-president of Software Engineering in a statement. “We believe the best way to do this is to begin a new era of personal computing software where OS upgrades are free.”

Analysts such as Jan Dawson of the technology business consulting firm Ovum, say that will affect customer expectations and create further pressure on Microsoft to bring down its prices.

Microsoft released Windows 8.1, its free upgrade of Windows 8, last week, in an effort to address gripes about the original release. However, new installations of Windows 8.1 cost $120 to $200.

  • It isn’t named after a cat

Previous releases of OS X bore names of big felines from Cheetah to Snow Leopard to Mountain Lion. With Mavericks, Apple joked that it didn’t want to have to delay the release of the upgrade due to a shortage of big cat names, MacWorld reported.

Instead, the new upgrade is named after a popular surfing area in California.

It was the first in a new theme of “places that inspire us in California” that Apple plans to use for the next 10 years, Federighi said when first announcing the upgrade at Apple’s Worldwide Developers Conference in June.

  • It makes your battery last longer

Federighi said the goal of Mavericks was to extend the battery life of Apple computers, and to this end, the upgrade includes technologies that save energy, reduce power consumption, and automatically compress inactive data to boost performance.

  • iBooks and other new software

Mavericks includes a Mac version of an app that lets users organize and read e-books, but had previously been available only on mobile devices.

Other new software includes a new mapping tool and a password manager called iCloud keychain.

  • Pop-up notifications

The “interactive notifications” feature lets users respond to or delete messages or answer Facetime calls without leaving the app they are using.

  • New organizational tools

Users can now use a feature called Finder Tabs to combine multiple windows into a single window with multiple tabs. Users can also “tag” files with keywords to make it quicker and easier to search for them later.