Mac OS X

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 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.

The first version released was Mac OS X Server 1.0 in 1999, and a desktop-oriented version, Mac OS X v10.0 "Cheetah" followed on March 24, 2001. Releases of Mac OS X are named after big cats: for example, Mac OS X v10.7 is usually referred to by Apple and users as "Lion". The server edition, Mac OS X Server, is architecturally identical to its desktop counterpart, and includes tools to facilitate management of workgroups of Mac OS X machines, and to provide access to network services. These tools include a mail transfer agent, an LDAP server, adomain name server, and others. It is pre-loaded on Apple's Xserve server hardware, but can be run on almost all of Apple's current selling computer models.

Apple also produces specialized versions of Mac OS X for use on its consumer devices. iOS, which is based on Mac OS X, runs on the iPhone,iPod Touch, iPad, and the 2nd generation Apple TV. An unnamed variant of Mac OS X powered the 1st generation Apple TV.

Mac OS X is based upon the Mach kernel. Certain parts from FreeBSD's and NetBSD's implementation of Unix were incorporated inNeXTSTEP, the core of Mac OS X. NeXTSTEP was the object-oriented operating system developed by Steve Jobs' company NeXT after he left Apple in 1985.  While Jobs was away from Apple, Apple tried to create a "next-generation" OS through the Taligent, Copland and Gershwinprojects, with little success.

Eventually, NeXT's OS, then called OPENSTEP, was selected to be the basis for Apple's next OS, and Apple purchased NeXT outright.Steve Jobs returned to Apple as interim CEO, and later became CEO, shepherding the transformation of the programmer-friendly OPENSTEP into a system that would be adopted by Apple's primary market of home users and creative professionals. The project was first known as Rhapsody and was later renamed to Mac OS X.

Mac OS X Server 1.x, was incompatible with software designed for the original Mac OS and had no support for Apple's own IEEE 1394 interface (FireWire). Mac OS X 10.x included more backward compatibility and functionality by including the Carbon API as well as FireWire support. As the operating system evolved, it moved away from the legacy Mac OS to an emphasis on new "digital lifestyle" applications such as the iLife suite, enhanced business applications (iWork), and integrated home entertainment (the Front Row media center).Each version also included modifications to the general interface, such as the brushed metal appearance added in version 10.3, the non-pinstriped titlebar appearance in version 10.4, and in 10.5 the removal of the previous brushed metal styles in favor of the "Unified" gradient window style.

Features

One of the major differences between the previous versions of Mac OS and OS X was the addition of the Aqua GUI, a graphical user interface with water-like elements. Every window element, text, graphic, or widget is drawn on-screen using anti-aliasing technology. ColorSync, a technology introduced many years before, was improved and built into the core drawing engine, to provide color matching for printing and multimedia professionals. Also, drop shadows were added around windows and isolated text elements to provide a sense of depth. New interface elements were integrated, including sheets (document modal dialog boxes attached to specific windows) and drawers.

Apple has continued to change aspects of the OS X appearance and design, particularly with tweaks to the appearance of windows and the menu bar. One example of a UI behavioral change is that previewed video and audio files no longer have progress bars in column view; instead, they have mouse-over start and stop buttons as of 10.5.

The human interface guidelines published by Apple for Mac OS X are followed by many applications, giving them consistent user interface and keyboard shortcuts. In addition, new services for applications are included, which include spelling and grammar checkers, special characters palette, color picker, font chooser and dictionary; these global features are present in every Cocoa application, adding consistency. The graphics system OpenGL composites windows onto the screen to allow hardware-accelerated drawing. This technology, introduced in version 10.2, is called Quartz Extreme, a component of Quartz. Quartz's internal imaging model correlates well with the Portable Document Format (PDF) imaging model, making it easy to output PDF to multiple devices.As a side result, PDF viewing and creating PDF documents from any application are built-in features.

In version 10.3, Apple added Exposé, a feature which includes three functions to help accessibility between windows and desktop. Its functions are to instantly display all open windows as thumbnails for easy navigation to different tasks, display all open windows as thumbnails from the current application, and hide all windows to access the desktop.Also, FileVault was introduced, which is an optional encryption of the user's files with Advanced Encryption Standard (AES-128).

Features introduced in version 10.4 include Automator, an application designed to create an automatic workflow for different tasks;Dashboard, a full-screen group of small applications called desktop widgets that can be called up and dismissed in one keystroke;and Front Row, a media viewer interface accessed by the Apple Remote.Moreover, the Sync Services were included, which is a system that allows applications to access a centralized extensible database for various elements of user data, including calendar and contact items. The operating system then managed conflicting edits and data consistency.

As of version 10.5, all system icons are scalable up to 512×512 pixels, to accommodate various places where they appear in larger size, including for example the Cover Flow view, a three-dimensionalgraphical user interface included with iTunes, the Finder, and other Apple products for visually skimming through files and digital media libraries via cover artwork.This version includes Spaces, avirtual desktop implementation which enables the user to have more than one desktop and display them in an Exposé-like interface.Mac OS X v10.5 includes an automatic backup technology calledTime Machine, which provides the ability to view and restore previous versions of files and application data; and Screen Sharing was built in for the first time.

Finder is a file browser allowing quick access to all areas of the computer, which has been modified throughout subsequent releases of Mac OS X.Quick Look is part of Mac OS X Leopard's Finder. It allows for dynamic previews of files, including videos and multi-page documents, without opening their parent applications. Spotlight search technology, which is integrated into the Finder since Mac OS X Tiger, allows rapid real-time searches of data files; mail messages; photos; and other information based on item properties (meta data) and/or content.Mac OS X makes use of aDock, which holds file and folder shortcuts as well as minimized windows. Mac OS X Architecture implements a layered framework.The layered framework aids rapid development of applications by providing existing code for common tasks.

Versions

Mac OS X Version Information
Version	Codename	Date Announced	Release Date	Most Recent Version
Rhapsody Developer Release	Grail1Z4 / Titan1U		August 31, 1997	May 14, 1998
Mac OS X Server 1.0	Hera		March 16, 1999	1.2v3 (October 27, 2000)
Public Beta	Kodiak		September 13, 2000
10.0	Cheetah		March 24, 2001	10.0.4 (June 22, 2001)
10.1	Puma	July 18, 2001	September 25, 2001	10.1.5 (June 6, 2002)
10.2	Jaguar	May 6, 2002	August 24, 2002	10.2.8 (October 3, 2003)
10.3	Panther	June 23, 2003	October 24, 2003	10.3.9 (April 15, 2005)
10.4	Tiger	May 4, 2004	April 29, 2005	10.4.11 (November 14, 2007)
10.5	Leopard	June 26, 2006	October 26, 2007	10.5.8 (August 5, 2009)
10.6	Snow Leopard	June 9, 2008	August 28, 2009	10.6.8 (June 23, 2011)
10.7	Lion	October 20, 2010	July 20, 2011	10.7.2 (October 12, 2011)

Source: wikipedia