Apple Inc. (Nasdaq: AAPL) on Thursday released a developer preview of an update for the Mac operating system, dubbed “Mountain Lion,” that will copy more features and apps from the iPhone and iPad to the Mac.

Apple said the new software will be on sale this summer, a year after it released the latest update, “Lion.” The preview version will help software developers make products that take advantage of the new features of the operating system.

Mountain Lion will include Game Center, an iPhone app which stores high game scores and helps users find opponents. It will be integrated with iCloud, the new Internet storage service designed for the mobile devices.

The new Messages app, also copied from the mobile operating system, will replace iChat. Lion users can download a preview version of the app for free.

A new Notification Center will show alerts from email and calendar programs, just like on the iPhone.

Highlights from Apple:

“iCloud – It just works. In more ways than ever: In OS X Mountain Lion, sign in once with your Apple ID and iCloud is automatically set up across your Mac.1 That means right away iCloud keeps your mail, calendars, contacts, documents, and more up to date on every device you use. So when you add, delete, or edit something on your Mac, it happens on your iPad, iPhone, and iPod touch. And vice versa.”

“Messages – Mac keeps the conversation going: Messages does everything iChat does, and so much more. For starters, it comes with iMessage. And just like iMessage in iOS, it lets you send unlimited messages to anyone on a Mac or an iPhone, iPad, or iPod touch running iOS 5. Send photos, videos, documents, and contacts — even send messages to a group. You can see when your message has been delivered and when someone’s typing a reply. Turn on read receipts, and they’ll see when you’ve read a message. With end-to-end encryption, your messages stay safe and private. And you can start a conversation on your Mac and pick it up on your iPhone, iPad, or iPod touch. So nothing is left unsaid.”

“Reminders – Now nothing slips your mind: When you have so much to do, Reminders helps you get it done. It’s all in a list. More than one, in fact. Make as many lists as you need and easily add to them. Set due dates and you’ll get alerts as deadlines approach. Check items off your lists as you go and keep track of what you’ve completed. And to be sure you don’t forget anything, iCloud keeps your reminders up to date on your Mac, iPad, iPhone, and iPod touch.”

“Notes – A feature for your thoughts: Notes in OS X Mountain Lion is designed for whatever’s on your mind. Think it up. Jot it down. Make it even more noteworthy with photos, images, and attachments. You can add, delete, and flip through your notes or do a quick search. Use the Share button to send your notes to friends or colleagues with Mail or Messages. Pin important notes to your desktop so they’re easy to get to. And take them with you everywhere. Notes works with iCloud, so when you create or edit a note on your Mac, it automatically updates on your iPhone, iPad, and iPod touch.”

“Notification center – See what’s new with you: All in one place. Something new is always popping up somewhere on your Mac — an email, an instant message, a friend request, a calendar alert, and more. Notification Center makes it easy to stay up to speed, because there’s one place to see everything. Notification banners appear on your desktop and disappear quickly so they don’t interrupt what you’re doing. Swipe to the left, and you’ll see all your notifications in a simple, ordered list. So you’ll always know what’s up as soon as it comes up.”

“Share sheets – When you see it, share it: You’ll find the Share button in many OS X Mountain Lion apps. It’s the new, easy way to spread the word — links, photos, and videos, too. Send links from Safari. Send your notes via Mail and Messages. Post photos to Flickr. Send videos to Vimeo. And tweet just about anything.”

“Twitter – Tweet right from your apps: OS X Mountain Lion keeps you on top of all things Twitter. Sign in once and you’re all set to start tweeting — and you don’t have to leave the app you’re in. Tweet links and photos directly from Safari, iPhoto, or Photo Booth with the new Tweet Sheet. Tweet comments and add locations. And when someone mentions you in a tweet or sends you a direct message, you’ll get a Twitter notification right then and there.”

“Game Center – Mac gets in on the game: The Mac is about to go up against iPad, iPhone, and iPod touch — in a friendly Game Center way.2 Now it’s a bigger playing field with even more competition. Just create a Game Center account with your Apple ID. Then sign in and you’re in. Friends will find you fast, and you’ll track them down easily. Get a multiplayer game started or go up against people you don’t know. Check out leaderboards and see how your high score ranks against opponents’ scores around the world. And discover new games based on the ones you and your friends already play.”

“AirPlay Mirroring – Your Mac is on TV: This new feature in Mountain Lion is made for an audience. With AirPlay Mirroring, you can stream what’s on your Mac to your HDTV via Apple TV. Show web pages and videos to friends on the couch. Share lessons with a classroom. Present to a conference room. It’s a big deal for your Mac. And for everyone around it.”

“Gatekeeper – A more secure Mac: Under your control. Gatekeeper in OS X Mountain Lion makes the Mac safer than ever. It helps prevent you from unknowingly downloading and installing malicious software. And it gives you control over which applications to download and run on your Mac. Now you can choose from three security options. You can download and run applications from anywhere, just as in OS X Lion. To be even safer, download and run apps from the Mac App Store and apps with a Developer ID. Or download and run only apps from the Mac App Store — the safest setting of all. Gatekeeper lets you decide which setting is best for you.”

Cost Not Disclosed

Apple started the trend of making its Mac operating system more like its phone and tablet operating system, iOS, with the release of Lion. It borrowed phone features like a screen that shows all installed apps, and expanded the range of gestures that can be used to control a MacBook through the touchpad.

The Cupertino, Calif.-based company sells Lion for $30. It didn’t say what Mountain Lion would cost.

Apple has been growing Mac sales in a nearly stagnant PC market, but the sales aren’t growing as fast as those of the iPhone. In 2010, iPhone sales overtook those of Macs for the first time.

Apple has been using the names of big cats to differentiate its OS versions since 2001.

Microsoft Corp. is set to release Windows 8 later this year, and a preview version is already in developer hands. It, too, will be borrowing features from phone software, and one version of the operating system will run on phone-style chips, as opposed to the Intel-style chips that have been the bedrock of Microsoft software since the 1980s.

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