The Cupertino, Calif., company announced Mountain Lion on Thursday, detailing the new version of what was previously known as Mac OS X on its website for consumers.
Programmers, meanwhile, were offered the ability to download Mountain Lion so they can get started integrating their apps with the new operating system before its release.
Like Mac OS X Lion, Mountain Lion will be sold as a digital download through the Mac App Store on Apple laptops and desktops.
Apple said Mountain Lion will include more than 100 new features, many of them "inspired by the iPad."
Mountain Lion will gain iOS' widespread Twitter integration and will rely more on iCloud than previous versions of OS X. Apple says that more than 100 million Apple users have iCloud accounts and that those accounts, which are tied to a user's Apple ID, will be used to automatically set up Calendar, Contacts, Mail, Messages, FaceTime and Find My Mac apps in Mountain Lion.
More iOS-like additions will be found in the new OS X apps Messages, Reminders, Notes, Game Center and Notification Center. Each of these apps is supposed to work on Mac computers very much like way they do in iOS devices.
Messages replaces the old iChat app and will enable Mac users to send text and multimedia messages to other Mac users as well as to people with iPhones, iPads and the iPod Touch. The messaging system uses Web data rather than text messages from a phone plan and expands the free messaging service in a way that will contribute to the growing alternatives to text messaging plans offered by telecommunications companies.
The new Messages app, which is available to Lion users today as a beta download, will support online chat services such as AOL Instant Messenger, Jabber, Yahoo Messenger and Google Talk, just as iChat does.
Reminders and Notes use iCloud to sync across Macs and iOS devices to track to-do lists and notes taken in the apps, and in Mountain Lion they look and work the same as they do on iPhones and iPads.
Game Center, too, works exactly the same way on a Mac as it does on iOS devices, enabling users to see what games their friends are playing on Apple gadgets and to play some multiplayer games on a Mac with friends who are playing on an iPad, iPhone or iPod Touch.
Notification Center maintains the style of its iOS counterpart, but the OS X version is built for a desktop screen, with notification pop-ups appearing in the top right corner of a user's screen when an alert comes from apps such as Mail, Calendar, Messages, Reminders and third-party apps that tap into Apple's developer API. A new two-finger swipe from right to left across a Mac trackpad reveals a list of unseen notifications. To take the Notification Center off the screen, a users need to perform two-finger swipe from left to right on a trackpad or click on any of the notifications, which will take them to the corresponding app.
Apple has taken the Twitter integration found in iOS into OS X, with the ability to share to Twitter from Safari, Quick Look, Photo Booth, Preview and third-party apps that take advantage of the feature in Apple's API. Videos can also be shared in OS X Lion from QuickTime to Facebook, YouTube and Vimeo.
One of the more useful additions to Mountain Lion is AirPlay Mirroring, which, just as an iPad can do, can "wirelessly send a secure 720p video stream of what's on your Mac to an HDTV using Apple TV." Apple TV is Apple's $99 set-top box that streams video from Netflix, YouTube, Vimeo and iTunes to television sets.
On the security side, Mountain Lion is adding a new feature called Gatekeeper, which enables users to define what apps can and cannot run on their computers based on where they purchased from or who built them.
"You can choose to install apps from any source, just as you do on a Mac today, or you can use the safer default setting to install apps from the Mac App Store, along with apps from developers that have a unique Developer ID from Apple," the tech giant said. "For maximum security, you can set Gatekeeper to only allow apps from the Mac App Store to be downloaded and installed."
Gatekeeper could cause Apple a bit of blowback from developers who don't want to have to submit their apps to Apple for approval or distribution: Mountain Lion's default setting will be to run only apps from the Mac App Store or from developers with a recognized Apple DeveloperID.
That's more iOS-like -- iOS runs only apps from the iTunes App Store -- but the setting can be changed as a user sees fit. So far, the Mac App Store has been a hit for software sales, with more than 100 million downloads served up last year. Apple, unsurprisingly, would like to keep the Mac App Store the top place to get Mac apps.
Apple hasn't yet given a definite public release date or pricing for Mountain Lion. The previous version of OS X, Lion, was the first to be released as a digital download and not on disc, hitting the Mac App Store last July for $29.99 and selling more than 1 million downloads its first day out.
Click here to see an Apple-produced video of Mountain Lion in action.