Although iOS devices are outpacing Mac sales, Apple is nonetheless forging ahead with the next iteration of its computer operating system. Apple on Thursday released a developer preview of OS X Mountain Lion.

Mountain Lion promises to bring apps and features from the iPad to the Mac. Some of the new features include Messages, Notes, Reminders and Game Center, as well as Notification Center, Share Sheets, Twitter integration and AirPlay Mirroring. Mountain Lion is also Apple's first OS X release that incorporates iCloud features.

Mountain Lion previewers also will get a sneak peek of something Apple is calling Gatekeeper, which is a security feature that works to protect Mac users against malicious software by blocking apps that aren't Apple-approved. Mountain Lion will hit the market in late summer.

"The Mac is on a roll, growing faster than the PC for 23 straight quarters, and with Mountain Lion things get even better," said Philip Schiller, Apple's senior vice president of worldwide marketing. He also noted that Mountain Lion is making its debut just seven months after Lion, the current Mac operating system, went on the market.

New Features Up Close

As part of Mountain Lion, the Messages App will replace iChat. Messages lets users send unlimited messages, photos and videos directly from one Apple product to another. Messages will continue to support AIM, Jabber, Yahoo Messenger and Google Talk. Meanwhile, Reminders and Notes are sort of virtual to-dos. And Game Center lets users personalize the Mac gaming experience.

Mountain Lion's Notification Center offers easier access to alerts from Mail, Calendar, Messages, Reminders, system updates and third party apps. Systemwide Share Sheets let users share links, photos and videos directly from Apple and third-party apps. And Twitter is integrated throughout Mountain.

"Apple is being less aggressive than Microsoft is with Windows 8, mostly because Microsoft doesn't have a large...