Mac OS X

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Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, Mac OS X has been included with all new Macintosh computer systems. It is the successor to Mac OS 9, released in 1999, the final release of the "classic" Mac OS, which had been Apple's primary operating system since 1984.

Mac OS X, whose X is the Roman numeral for 10 and is a prominent part of its brand identity, is a Unix-based graphical operating system,[8] built on technologies developed at NeXT between the second half of the 1980s and Apple's purchase of the company in late 1996. From its sixth release, Mac OS X v10.5 "Leopard" and onward, every release of Mac OS X gained UNIX 03 certification while running on Intel processors.

Source: Wikipedia

 

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Update on version history

Mac OS X v10.6 "Snow Leopard" was released on August 28, 2009. Rather than delivering big changes to the appearance and end user functionality like the previous releases of Mac OS X, Snow Leopard focuses on "under the hood" changes, increasing the performance, efficiency, and stability of the operating system. For most users, the most noticeable changes are: the disk space that the operating system frees up after a clean install compared to Mac OS X 10.5 Leopard, a more responsive Finder rewritten in Cocoa, faster Time Machine backups, more reliable and user friendly disk ejects, a more powerful version of the Preview application, as well as a faster Safari web browser.

Mac OS X v10.7 "Lion" was released on July 20, 2011. It includes support for the Mac App Store, and brings many other developments made in Apple's iOS, such as an easily-navigable display of installed applications, to the Mac. This release removed Rosetta, making it incapable of running PowerPC applications.

Changes made to the GUI (Graphical User Interface) include the Launchpad (similar to the home screen of iOS devices), auto-hiding scrollbars that only appear when they are being used, and Mission Control, which unifies Exposé, Spaces, Dashboard, and full-screen applications within a single interface.[99] Apple also made changes to applications: they resume in the same state as they were before they were closed (similar to iOS). In addition to this, documents auto-save by default so users don't have to worry about manually managing their documents.

Source: wikipedia