OS X

OS X (pronounced oh ess ten) is the brand name of a series of Unix-compatible 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, the final release of the "classic" Mac OS, which had been Apple's primary operating system since 1984. OS X was rebranded macOS by Apple in 2016.

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 (from the second half of the 1980s to Apple's purchase of the company in late 1996) in combination with technologies from Apple's "classic" OS and technologies from FreeBSD. From its sixth release Mac OS X 10.5.0 "Leopard" onwards, every release of Mac OS X for Intel processors gained UNIX 03 certification.

The first version released was Mac OS X Server 1.0 on March 16, 1999, and a desktop-oriented version, Mac OS X 10.0.0 "Cheetah" followed on March 24, 2001. From 10.0 through 10.8, releases of Mac OS X were named after big cats: for example, Mac OS X 10.6 is usually referred to by Apple and users as "Snow Leopard". 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, a Samba server, an LDAP server, a domain name server, and others. It came pre-loaded on Apple's Xserve server hardware, but can be run on almost all of Apple's PowerPC-based computer models made after 1999.

Apple also produces specialized variants based on Mac OS X's core, "Darwin," for use on its consumer devices: iOS for the iPhone, iPod Touch, and iPad, watchOS for the Apple Watch, and tvOS for the Apple TV.

History
Mac OS X's XNU kernel is based on the Mach kernel. Certain parts from FreeBSD's and NetBSD's implementation of Unix were incorporated in Nextstep, 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 three times to create a "next-generation" OS through the Taligent, Copland and Gershwin projects, 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 title bar 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.

Description
Mac OS X is the tenth major version of Apple's operating system for Macintosh computers. Previous Macintosh operating systems were named using Arabic numerals, e.g. Mac OS 8 and Mac OS 9. The letter X in Mac OS X's name refers to the number 10, a Roman numeral. It is therefore correctly pronounced "ten" in this context, though "X"  is also a common pronunciation.

Mac OS X's core is a POSIX compliant operating system (OS) built on top of the XNU kernel, with standard Unix facilities available from the command line interface. Apple has released this family of software as a free and open source operating system named Darwin. On top of Darwin, Apple layered a number of components, including the Aqua interface and the Finder, to complete the GUI-based operating system which is Mac OS X.

Mac OS X introduced a number of new capabilities to provide a more stable and reliable platform than its predecessor, Mac OS 9. For example, pre-emptive multitasking and memory protection improved the system's ability to run multiple applications simultaneously without them interrupting or corrupting each other.

Many aspects of Mac OS X's architecture are derived from OpenStep, which was designed to be portable, to ease the transition from one platform to another. For example, NeXTSTEP was ported from the original 68k-based NeXT workstations to x86 and other architectures before NeXT was purchased by Apple, and OpenStep was later ported to the PowerPC architecture as part of the Rhapsody project.

The most visible change was the Aqua theme. The use of soft edges, translucent colors, and pinstripes – similar to the hardware design of the first iMacs – brought more texture and color to the user interface when compared to what OS 9 and OS X Server 1.0's "Platinum" appearance had offered. According to John Siracusa, an editor of Ars Technica, the introduction of Aqua and its departure from the then conventional look "hit like a ton of bricks." Bruce Tognazzini (who founded the original Apple Human Interface Group) said that the Aqua interface in Mac OS X 10.0.0 represented a step backwards in usability compared with the original Mac OS interface. Third-party developers started producing skins for customizable applications for Mac and other operating systems which mimicked the Aqua appearance. To some extent, Apple has used the successful transition to this new design as leverage, at various times threatening legal action against people who make or distribute software with an interface the company claims is derived from its copyrighted design.

Mac OS X Architecture implements a layered framework. The layered framework aids rapid development of applications by providing existing code for common tasks.

Mac OS X includes its own software development tools, most prominently an integrated development environment called Xcode. Xcode provides interfaces to compilers that support several programming languages including C, C++, Objective-C, and Java. For the Apple–Intel transition, it was modified so that developers could build their applications as a universal binary, which provides compatibility with both the Intel-based and PowerPC-based Macintosh lines.

The Darwin subsystem in Mac OS X is in charge of managing the filesystem, which includes the Unix permissions layer. In 2003 and 2005, two Macworld editors expressed criticism of the permission scheme; Ted Landau called misconfigured permissions "the most common frustration" in Mac OS X, while Rob Griffiths suggested that some users may even have to reset permissions every day, a process which can take up to 15 minutes. More recently, another Macworld editor, Dan Frakes, called the procedure of repairing permissions vastly overused. He argues that Mac OS X typically handles permissions properly without user interference, and resetting permissions should just be tried when problems emerge.

As of 2009, Mac OS X is the second most popular general-purpose operating system in use for the internet, after Microsoft Windows, with a 4.5% market share according to statistics compiled by Net Applications. In contrast, it is the most successful UNIX-like desktop operating system on the internet, estimated at over 4 times the penetration of the free Linux. Eighteen languages are available for the "base" language (that which is used for sub-user environments, such as the user login screen) at the first screen of the installation DVD. All of the eighteen user languages for the system menus, messages, and other functions are installed by default and can be chosen from the System Preferences. As of OS 10.6, the languages are English, Japanese, French, German, Spanish, Italian, Dutch, Swedish, Danish, Norwegian, Finnish, Traditional Chinese, Simplified Chinese, Korean, Brazilian Portuguese, European Portuguese, Russian, and Polish. Input methods for typing in dozens of scripts can be chosen independently of the system language.

Software
The APIs that Mac OS X inherited from OpenStep are not backward compatible with earlier versions of Mac OS. These APIs were created as the result of a 1993 collaboration between NeXT Computer and Sun Microsystems and are now referred to by Apple as Cocoa. This heritage is highly visible for Cocoa developers, since the "NS" prefix is ubiquitous in the framework, standing variously for NextStep or NeXT/Sun. The official OpenStep API, published in September 1994, was the first to split the API between Foundation and Application Kit and the first to use the "NS" prefix. Apple's Rhapsody project would have required all new development to use these APIs, causing much outcry among existing Mac developers. All Mac software that did not receive a complete rewrite to the new framework would run in the equivalent of the Classic environment. To permit a smooth transition from Mac OS 9 to Mac OS X, the Carbon Application Programming Interface (API) was created. Applications written with Carbon can be executed natively on both systems. Carbon was not included in the first product sold as Mac OS X, Mac OS X Server (now known as Mac OS X Server 1.x).

Mac OS X also used to support the Java Platform as a "preferred software package" – in practice, this means that applications are written in Java fit as neatly into the operating system as possible while still being cross-platform compatible and that graphical user interfaces written in Swing look almost exactly like native Cocoa interfaces. Traditionally, Cocoa programs have been mostly written in Objective-C, with Java as an alternative. However, on July 11, 2005, Apple announced that "features added to Cocoa in Mac OS X versions later than 10.4 will not be added to the Cocoa-Java programming interface."

Since Mac OS X is POSIX compliant, many software packages written for the * BSDs or Linux can be recompiled to run on it. Projects such as Fink, MacPorts, pkg-src and HomeBrew provide pre-compiled or pre-formatted packages. From version 10.3 through 10.8, Mac OS X included X11.The app, Apple's version of the X Window System graphical interface for Unix applications, as an optional component during installation. Up to and including Mac OS X 10.4.0 (Tiger), Apple's implementation was based on the X11 Licensed XFree86 4.3 and X11R6.6. All bundled versions of X11 feature a window manager which is similar to the Mac OS X look-and-feel and has fairly good integration with Mac OS X, also using the native Quartz rendering system. Earlier versions of Mac OS X (in which X11 has not been bundled) can also run X11 applications using XDarwin. With the introduction of version 10.5 Apple switched to the X.org variant of X11, and with 10.9, support was passed off to the XQuartz project.

Hardware
For the early releases of Mac OS X, the standard hardware platform supported was the full line of Macintosh computers (laptop, desktop, or server) based on PowerPC G3, G4, and G5 processors. Later versions discontinued support for some older hardware; for example, Mac OS X 10.3 "Panther" does not support "beige" G3s, and Mac OS X 10.4 "Tiger", which first supported the Intel architecture as well as PowerPC, does not support systems that pre-date Apple's introduction of integrated FireWire ports (the ports themselves are not a functional requirement). Mac OS X 10.5.0 "Leopard", introduced October 2007, dropped support for all PowerPC G3 processors and for PowerPC G4 processors with clock rates below 867 MHz. Mac OS X 10.6.0 "Snow Leopard" dropped all support for PowerPC hardware (but still ran PowerPC software that was not hardware-dependent under Rosetta emulation).

Tools such as XPostFacto and patches applied to the installation disc have been developed by third parties to enable installation of newer versions of Mac OS X on systems not officially supported by Apple. This includes a number of pre-G3 Power Macintosh systems that can be made to run up to and including Mac OS X 10.2 Jaguar, all G3-based Macs which can run up to and including Tiger, and sub-867 MHz G4 Macs can run Leopard by removing the restriction from the installation DVD or enter a command in the Mac's Open Firmware interface to tell the Leopard Installer that it has a clock rate of 867 MHz or greater. Except for features requiring specific hardware (e.g. graphics acceleration, DVD writing), the operating system offers the same functionality on all supported hardware.

PowerPC versions of Mac OS X prior to Leopard retain compatibility with older Mac OS applications by providing an emulation environment called Classic, which allows users to run Mac OS 9 as a process within Mac OS X, so that most older applications run as they would under the older operating system. Classic is not supported on Intel-based Macs or in Mac OS X 10.5 "Leopard", but users still requiring Classic applications on Intel Macs can use an emulator such as SheepShaver or QEMU-PPC to run Mac OS 9 in an application on top of OS X.

Apple–Intel transition
In April 2002, eWeek announced a rumor that Apple had a version of Mac OS X code-named Marklar which ran on Intel x86 processors. The idea behind Marklar was to keep Mac OS X running on an alternative platform should Apple become dissatisfied with the progress of the PowerPC platform. These rumors subsided until late in May 2005, when various media outlets, such as the Wall Street Journal and CNET, announced that Apple would unveil Marklar in the coming months.

On June 6, 2005, Steve Jobs confirmed these rumors when he announced in his keynote address at the annual Apple Worldwide Developers Conference that Apple would be making the transition from PowerPC to Intel processors over the following two years, and that Mac OS X would support both platforms during the transition. Jobs also confirmed rumors that Apple had versions of Mac OS X running on Intel processors for most of its developmental life. The last time that Apple switched CPU families—from the Motorola 68K CPU to the IBM/Motorola PowerPC—Apple included a Motorola 68K emulator in the new OS that made almost all 68K software work automatically on the new hardware. Apple had supported the 68K emulator for 11 years but stopped supporting it during the transition to Intel CPUs. Included in the new OS for the Intel-based Macs is Rosetta, a binary translation layer which enables software compiled for PowerPC Mac OS X to run on Intel Mac OS X machines. Apple dropped support for Classic mode on the new Intel Macs. Third party emulation software such as Mini vMac, Basilisk II, SheepShaver and QEMU-PPC provides support for some early versions of Mac OS. A new version of Xcode and the underlying command-line compilers support building universal binaries that will run on either architecture.

PowerPC-only Carbon and Cocoa software is mostly supported on Intel versions of OS X 10.4 through 10.6 through Rosetta, though some applications may have to be rewritten to run properly. Apple initially encouraged developers to produce universal binaries with support for both PowerPC and x86. There is a performance penalty when PowerPC binaries run on Intel Macs through Rosetta. Moreover, some PowerPC software, such as kernel extensions and System Preferences plugins, are not supported on Intel Macs. Some PowerPC applications would not run on Intel OS X at all. Plugins for Safari need to be compiled for the same platform as Safari, so when Safari is running on Intel it requires plug-ins that have been compiled as Intel-only or universal binaries, so PowerPC-only plug-ins will not work. While Intel Macs through 10.6 are able to run PowerPC, x86, and universal binaries, PowerPC Macs support only universal and PowerPC builds. Native support for the PowerPC platform was dropped after Mac OS X 10.5.

Such cross-platform capability already existed in Mac OS X's lineage; Openstep was ported to many architectures, including x86, and Darwin included support for both PowerPC and x86. Apple stated that Mac OS X would not run on Intel-based personal computers aside from its own, but a hacked version of the OS compatible with conventional x86 hardware was developed by the OSx86 community.

On June 8, 2009, Apple announced at its Worldwide Developers Conference that Snow Leopard (version 10.6.0) would drop support for PowerPC processors and be Intel-only. However, Snow Leopard still supported Rosetta. It was not installed by default, but it was available on the installation DVD as an installable add-on and was installed automatically via the Internet when first attempting to run a PowerPC-based application.

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 DisplayPDF 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 model 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 as part of the OS, including 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 OS X 10.2, is called Quartz Extreme, a component of Quartz. Quartz's internal imaging model, based on DisplayPDF, 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 is a built-in feature.

In OS X 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 OS X 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 OS X 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-dimensional graphical 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, a virtual desktop implementation which enables the user to have more than one desktop and display them in an Exposé-like interface. Mac OS X 10.5 includes an automatic backup technology called Time 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 (metadata) and/or content. Mac OS X makes use of a Dock, 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
With the exception of Mac OS X Server 1.0 and the original public beta, Mac OS X versions were named after big cats until the release of OS X 10.9 (Mavericks) which was named after a surfing beach in California. Prior to its release, version 10.0 was code named "Cheetah" internally at Apple, and version 10.1 was codenamed internally as "Puma". After the immense buzz surrounding version 10.2, codenamed "Jaguar", Apple's product marketing began openly using the code names to promote the operating system. 10.3 was marketed as "Panther", 10.4 as "Tiger", and 10.5 as "Leopard". "Snow Leopard" is the name for version 10.6. "Panther", "Tiger", "Leopard", "Snow Leopard", "Lion" and "Mountain Lion" are registered as trademarks of Apple, but "Cheetah", "Puma" and "Jaguar" have never been registered. Apple has also registered "Lynx" and "Cougar" as trademarks, though these were allowed to lapse. Computer retailer Tiger Direct sued Apple for its use of the name "Tiger". On May 16, 2005, a US federal court in the Southern District of Florida ruled that Apple's use does not infringe on Tiger Direct's trademark.



Public Beta: "Kodiak"
On September 13, 2000, Apple released a "preview" version of Mac OS X (internally codenamed Kodiak) to the public in order to gain feedback from users. It cost $29.95. The "PB" as it was known marked the first public availability of the Aqua interface and Apple made many changes to the UI based on customer feedback. Mac OS X Public Beta expired and ceased to function in Spring 2001.



Version 10.0: "Cheetah"
On March 24, 2001, Apple released Mac OS X 10.0 (internally codenamed Cheetah). The initial version was slow, incomplete, and had very few applications available at the time of its launch, mostly from independent developers. While many critics suggested that the operating system was not ready for mainstream adoption, they recognized the importance of its initial launch as a base on which to improve. Simply releasing Mac OS X was viewed by the Macintosh community as a great accomplishment, for attempts to completely overhaul the Mac OS had been underway since 1996 and delayed by countless setbacks. Following some bug fixes, kernel panics became much less frequent.



Version 10.1: "Puma"
Later that year on September 25, 2001, Mac OS X 10.1 (internally codenamed Puma) was released. It had better performance and provided missing features, such as DVD playback. Apple released 10.1 as a free upgrade CD for 10.0 users, in addition to the US$129 boxed version for people running Mac OS 9. It was discovered that the upgrade CDs were full install CDs that could be used with Mac OS 9 systems by removing a specific file; Apple later re-released the CDs in an actual stripped-down format that did not facilitate installation on such systems. On January 7, 2002, Apple announced that Mac OS X was to be the default operating system for all Macintosh products by the end of that month.



Version 10.2: "Jaguar"
On August 23, 2002, Apple followed up with Mac OS X 10.2 "Jaguar", the first release to use its code name as part of the branding. It brought great performance enhancements, a sleeker look, and many powerful enhancements (over 150, according to Apple ), including Quartz Extreme for compositing graphics directly on an ATI Radeon or Nvidia GeForce2 MX AGP-based video card with at least 16 MB of VRAM, a system-wide repository for contact information in the new Address Book, and an instant messaging client named iChat. The Happy Mac which had appeared during the Mac OS startup sequence for almost 18 years was replaced with a large grey Apple logo with the introduction of Mac OS X v10.2.



Version 10.3: "Panther"
Mac OS X 10.3 "Panther" was released on October 24, 2003. In addition to providing much-improved performance, it also incorporated the most extensive update yet to the user interface. Panther included as many or more new features as Jaguar had the year before, including an updated Finder, incorporating a brushed-metal interface, Fast user switching, Exposé (Window manager), FileVault, Safari, iChat AV (which added video conferencing features to iChat), improved Portable Document Format (PDF) rendering and much greater Microsoft Windows interoperability. Support for some early G3 computers such as "beige" Power Macs and "WallStreet" PowerBooks was discontinued.



Version 10.4: "Tiger"
Mac OS X 10.4 "Tiger" was released on April 29, 2005. Apple stated that Tiger contained more than 150+ new features. As with Panther, certain older machines were no longer supported; Tiger requires a Mac with a built-in FireWire port. Among the new features, Tiger introduced Spotlight, Dashboard, Smart Folders, updated Mail program with Smart Mailboxes, QuickTime 7, Safari 2, Automator, VoiceOver, Core Image and Core Video. The initial release of the Apple TV used a modified version of Tiger with a different graphical interface and fewer applications and services. On January 10, 2006, Apple released the first Intel-based Macs along with the 10.4.4 update to Tiger. This operating system functioned identically on the PowerPC-based Macs and the new Intel-based machines, with the exception of the Intel release dropping support for the Classic environment. Only PowerPC Macs can be booted from retail copies of the Tiger client DVD, but there is a Universal DVD of Tiger Server 10.4.7 (8K1079) that can boot both PowerPC and Intel Macs.

Some functions in newer OS versions might not work properly, such as deleting bookmarked sites. Take for instance Jeffrey Arsenault's concern in an Apple forum found here.



Version 10.5: "Leopard"
Mac OS X 10.5 "Leopard" was released on October 26, 2007. It was called by Apple "the largest update of Mac OS X". It brought more than 300 new features. Leopard supports both PowerPC- and Intel x86-based Macintosh computers; support for the G3 processor was dropped and the G4 processor required a minimum clock rate of 867 MHz, and at least 512 MB of RAM to be installed. The single DVD works for all supported Macs (including 64-bit machines). New features include a new 3D dock, an updated Finder, Time Machine, Spaces, Boot Camp pre-installed, full support for 64-bit applications (including graphical applications), new features in Mail and iChat, and a number of new security features. Leopard is an Open Brand UNIX 03 registered product on the Intel platform. It was also the first BSD-based OS to receive UNIX 03 certification. Leopard dropped support for the Classic Environment and all Classic applications.

This was the final version of Mac OS X to support the PowerPC architecture.



Version 10.6: "Snow Leopard"
Mac OS X 10.6 "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.



Version 10.7: "Lion"
On June 6, 2011, at the Apple Worldwide Developers Conference, it was announced that the official release for Lion would be in July 2011. The specific release date of July 20 was not confirmed until the day before by Apple CFO, Peter Oppenheimer, as part of Apple's 2011 third-quarter earnings announcement.[10]

Apple did not initially announce any physical media distribution for Lion, such as a set of CD-ROMs or a DVD-ROM as used for prior releases. Instead, the operating system was available exclusively as a download from the Mac App Store for US$29.99.[11][12] The only prior version of OS X that supported the Mac App Store was Snow Leopard, which implied that any machines that support Lion currently running Tiger or Leopard would first have to be upgraded to Snow Leopard, as opposed to permitting a direct upgrade to Lion.

Apple later announced two alternative distribution mechanisms for the benefit of users without broadband Internet access: in-store downloads at retail Apple Stores, and a USB flash drive containing the OS, priced at US$69, available through the online Apple Store beginning in August.[13] The USB distribution supported a direct upgrade to Lion from OS X versions prior to Snow Leopard and allowed for a "clean install" of 10.7. On August 4, 2011, Apple started to take orders for Mac OS X Lion's USB installation flash drives for $69.99.[14] The Server portion of Lion is available as a separate download from the Mac App Store for US$49.99, which is in addition to the purchase price of Lion itself.[15]



Version 10.8: "Mountain Lion"
Mac OS X 10.8 "Mountain Lion" was officially announced by Apple Inc. on their website on February 16 as a successor to Mac OS X 10.7 "Lion". As of 6 March 2012, it was still in development and available for download exclusively to Apple Developers with a paid membership for free as a beta version. Mountain Lion was officially released on July 25, 2012. It still has the Mac App store along with plenty of other features from iOS 5 and iOS 6. Some of these are iMessage, Reminders, Notification Center, Notes and Share Sheets.



Version 10.9: "Mavericks"
OS X 10.9 "Mavericks" was announced on June 10, 2013, at WWDC 2013, and was released on October 22, 2013, as a free update through the Mac App Store.

The update places emphasis on battery life, Finder enhancements, other enhancements for power users, and continued iCloud integration, as well as bringing more of Apple's iOS apps to the OS X platform. Mavericks marks the beginning of a change in the naming scheme of OS X, departing from the use of big cats and moving to names based on places in California. Following the new naming scheme, the current version of the operating system is named Mavericks, after the surfing location in California. The new naming scheme also removes the "Mac" prefix from the name.



Version 10.10: "Yosemite"
OS X 10.10 "Yosemite" was the eleventh major release of OS X, Apple Inc's desktop and server operating system for Macintosh computers. OS X Yosemite was announced on June 2, 2014, at WWDC 2014, and was released to the public on October 16, 2014, as a free update through the Mac App Store. With this release of OS X, Apple also instituted a public beta program by sign-up, seeded in the summer of 2014.



Version 10.11: "El Capitan"
OS X 10.11 "El Capitan" was announced on June 8, 2015, at WWDC 2015, where it was seeded to developers. This is the twelfth major release of OS X, Apple Inc's desktop and server operating system for Macintosh computers. As with "Snow Leopard" and "Mountain Lion", El Capitan is a maintenance release instead of a feature release; it polishes off some rough edges of the OS and adds a number of usability and speed improvements.



Version 10.12: "Sierra"
macOS 10.12 "Sierra" is the thirteenth major release of OS X, re-named MacOS, Apple Inc's desktop and server operating system for Macintosh computers. It is the successor to OS X El Capitan and is a new feature release. Following the California landmark-based naming scheme introduced with OS X Mavericks, Sierra was named after the entire Sierra Nevada mountain range that includes Yosemite National Park and Lake Tahoe.



Version 10.13: "High Sierra"
macOS 10.13 "High Sierra," released on September 25, 2017, is the fourteenth major release of OS X, renamed macOS, Apple's desktop and server operating system for Macintosh computers. It is the successor to macOS Sierra and is a new feature release. Following the California landmark-based naming scheme introduced with OS X Mavericks, High Sierra was named after the High Sierras in the Sierra Nevada mountain range.



Version 10.14: "Mojave"
macOS 10.14 "Mojave," released on September 24, 2018, is the fifteenth major release of OS X, renamed macOS, Apple's desktop and server operating system for Macintosh computers. It is the successor to macOS High Sierra and is a new feature release. Following the California landmark-based naming scheme introduced with OS X Mavericks, Mojave was named after the Mojave desert.



Version 10.15: "Catalina"
macOS 10.15 "Catalina", released on October 7, 2019, is the sixteenth major release of OS X, renamed macOS, Apple's desktop and server operating system for Macintosh computers. It is the successor to macOS Mojave and is a new feature release. Following the California landmark-based naming scheme introduced with OS X Mavericks, Catalina was named after Catalina Island.



Version 11: "Big Sur"
macOS 11 "Big Sur", announced on June 22, 2020 and released on November 12, is the seventeenth major release of OS X / macOS, finally moving from version "ten" to "eleven". It is the successor to macOS Catalina and is a new feature release. Following the California landmark-based naming scheme introduced with OS X Mavericks, Big Sur was named after the coastal area of California.



Version 12: "Monterey"
macOS 12 "Monterey", announced on June 7, 2021, is the eighteenth major release of OS X / macOS, continuing the new version numbering increments by moving from version "eleven" to "twelve". It is the successor to macOS Big Sur and is a new feature release. Following the California landmark-based naming scheme introduced with OS X Mavericks, Big Sur was named after the town on California's central coast.