Architecture of macOS

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Additional diagram of macOS architecture (2017 update) MacOS Architecture.svg
Additional diagram of macOS architecture (2017 update)

The architecture of macOS describes the layers of the operating system that is the culmination of Apple Inc.'s decade-long research and development process to replace the classic Mac OS.

Contents

After the failures of their previous attempts—Pink, which started as an Apple project but evolved into a joint venture with IBM called Taligent, and Copland, which started in 1994 and was cancelled two years later—Apple began development of Mac OS X, later renamed OS X and then macOS, with the acquisition of NeXT's NeXTSTEP in 1997.

Development

NeXTSTEP

NeXTSTEP used a hybrid kernel that combined the Mach 2.5 kernel developed at Carnegie Mellon University with subsystems from 4.3BSD. NeXTSTEP also introduced a new windowing system based on Display PostScript that intended to achieve better WYSIWYG systems by using the same language to draw content on monitors that drew content on printers. NeXT also included object-oriented programming tools based on the Objective-C language that they had acquired from Stepstone and a collection of Frameworks (or Kits) that were intended to speed software development. NeXTSTEP originally ran on Motorola's 68k processors, but was later ported to Intel's x86, Hewlett-Packard's PA-RISC and Sun Microsystems' SPARC processors. Later on, the developer tools and frameworks were released, as OpenStep, as a development platform that would run on other operating systems.

Rhapsody

On February 4, 1997, Apple acquired NeXT and began development of the Rhapsody operating system. Rhapsody built on NeXTSTEP, porting the core system to the PowerPC architecture and adding a redesigned user interface based on the Platinum user interface from Mac OS 8. An emulation layer called Blue Box allowed Mac OS applications to run within an actual instance of the Mac OS and an integrated Java platform. [1] The Objective-C developer tools and Frameworks were referred to as the Yellow Box and also made available separately for Microsoft Windows. The Rhapsody project eventually bore the fruit of all Apple's efforts to develop a new generation Mac OS, which finally shipped in the form of Mac OS X Server.

Mac OS X

A diagram of the Mac OS X architecture Diagram of Mac OS X architecture.svg
A diagram of the Mac OS X architecture

At the 1998 Worldwide Developers Conference (WWDC), Apple announced a move that was intended as a response to complaints from Macintosh software developers who were not happy with the two options (Yellow Box and Blue Box) available in Rhapsody. Mac OS X would add another developer API to the existing ones in Rhapsody. Key APIs from the Macintosh Toolbox would be implemented in Mac OS X to run directly on the BSD layers of the operating system instead of in the emulated Macintosh layer. This modified interface, called Carbon, would eliminate approximately 2000 troublesome API calls (of about 8000 total) and replace them with calls compatible with a modern OS. [2]

At the same conference, Apple announced that the Mach side of the kernel had been updated with sources from the OSFMK 7.3 (Open Source Foundation Mach Kernel) [3] and the BSD side of the kernel had been updated with sources from the FreeBSD, NetBSD and OpenBSD projects. [2] They also announced a new driver model called I/O Kit, intended to replace the Driver Kit used in NeXTSTEP citing Driver Kit's lack of power management and hot-swap capabilities and its lack of automatic configuration capability. [4]

At the 1999 WWDC, Apple revealed Quartz, a new Portable Document Format (PDF) based windowing system for the operating system that was not encumbered with licensing fees to Adobe like the Display PostScript windowing system of NeXTSTEP. Apple also announced that the Yellow Box layer had been renamed Cocoa and began to move away from their commitment to providing the Yellow Box on Windows. At this WWDC, Apple also showed Mac OS X booting off of a HFS Plus formatted drive for the first time.

The first public release of Mac OS X released to consumers was a Public Beta released on September 13, 2000.

Related Research Articles

macOS Operating system for Apple computers

macOS is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac computers. Within the market of desktop and laptop computers it is the second most widely used desktop OS, after Microsoft Windows and ahead of ChromeOS.

<span class="mw-page-title-main">NeXT</span> American technology company (1985–1997)

NeXT, Inc. was an American technology company that specialized in computer workstations intended for higher education and business use. Based in Redwood City, California, and founded by Apple Computer co-founder and CEO Steve Jobs after he was forced out of Apple, the company introduced their first product, the NeXT Computer, in 1988, and then the smaller NeXTcube and NeXTstation in 1990. These computers had relatively limited sales, with only about 50,000 units shipped in total. Nevertheless, their object-oriented programming and graphical user interfaces were trendsetters of computer innovation, and highly influential.

<span class="mw-page-title-main">NeXTSTEP</span> Operating system from NeXT Computer

NeXTSTEP is a discontinued object-oriented, multitasking operating system based on the Mach kernel and the UNIX-derived BSD. It was developed by NeXT Computer in the late 1980s and early 1990s and was initially used for its range of proprietary workstation computers such as the NeXTcube. It was later ported to several other computer architectures.

Darwin is the core Unix operating system of macOS, iOS, watchOS, tvOS, iPadOS and bridgeOS. It previously existed as an independent open-source operating system, first released by Apple Inc. in 2000. It is composed of code derived from NeXTSTEP, BSD, Mach, and other free software projects' code, as well as code developed by Apple.

OpenStep is a defunct object-oriented application programming interface (API) specification for a legacy object-oriented operating system, with the basic goal of offering a NeXTSTEP-like environment on non-NeXTSTEP operating systems. OpenStep was principally developed by NeXT with Sun Microsystems, to allow advanced application development on Sun's operating systems, specifically Solaris. NeXT produced a version of OpenStep for its own Mach-based Unix, stylized as OPENSTEP, as well as a version for Windows NT. The software libraries that shipped with OPENSTEP are a superset of the original OpenStep specification, including many features from the original NeXTSTEP.

<span class="mw-page-title-main">TextEdit</span> Open-source word processor and text editor

TextEdit is an open-source word processor and text editor, first featured in NeXT's NeXTSTEP and OPENSTEP. It is now distributed with macOS since Apple Inc.'s acquisition of NeXT, and available as a GNUstep application for other Unix-like operating systems such as Linux. It is powered by Apple Advanced Typography.

Cocoa is Apple's native object-oriented application programming interface (API) for its desktop operating system macOS.

<span class="mw-page-title-main">GNUstep</span> Open source widget toolkit and application development tools

GNUstep is a free software implementation of the Cocoa Objective-C frameworks, widget toolkit, and application development tools for Unix-like operating systems and Microsoft Windows. It is part of the GNU Project.

Carbon was one of two primary C-based application programming interfaces (APIs) developed by Apple for the macOS operating system. Carbon provided a good degree of backward compatibility for programs that ran on Mac OS 8 and 9. Developers could use the Carbon APIs to port (“carbonize”) their “classic” Mac applications and software to the Mac OS X platform with little effort, compared to porting the app to the entirely different Cocoa system, which originated in OPENSTEP. With the release of macOS 10.15 Catalina, the Carbon API was officially discontinued and removed, leaving Cocoa as the sole primary API for developing macOS applications.

The history of macOS, Apple's current Mac operating system formerly named Mac OS X until 2011 and then OS X until 2016, began with the company's project to replace its "classic" Mac OS. That system, up to and including its final release Mac OS 9, was a direct descendant of the operating system Apple had used in its Mac computers since their introduction in 1984. However, the current macOS is a Unix operating system built on technology that had been developed at NeXT from the 1980s until Apple purchased the company in early 1997.

<span class="mw-page-title-main">A/UX</span> Early Unix-based operating system from Apple Computer

A/UX is a Unix-based operating system from Apple Computer for Macintosh computers, integrated with System 7's graphical interface and application compatibility. It is Apple's first official Unix-based operating system, launched in 1988 and discontinued in 1995 with version 3.1.1. A/UX requires select 68k-based Macintosh models with an FPU and a paged memory management unit (PMMU), including the Macintosh II, SE/30, Quadra, and Centris series.

Copland is an operating system developed by Apple for Macintosh computers between 1994 and 1996 but never commercially released. It was intended to be released as System 8, and later, Mac OS 8. Planned as a modern successor to the aging System 7, Copland introduced protected memory, preemptive multitasking, and several new underlying operating system features, while retaining compatibility with existing Mac applications. Copland's tentatively planned successor, codenamed Gershwin, was intended to add more advanced features such as application-level multithreading.

MkLinux is an open-source software computer operating system begun by the Open Software Foundation Research Institute and Apple Computer in February 1996, to port Linux to the PowerPC platform, and Macintosh computers. The name refers to the Linux kernel being adapted to run as a server hosted on the Mach microkernel, version 3.0.

CodeWarrior is an integrated development environment (IDE) published by NXP Semiconductors for editing, compiling, and debugging software for several microcontrollers and microprocessors and digital signal controllers used in embedded systems.

<span class="mw-page-title-main">XNU</span> Computer operating system kernel

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<span class="mw-page-title-main">Rhapsody (operating system)</span> Apple operating system

Rhapsody is the development series of Apple Computer's next-generation operating system. Targeting only developers for a transition period, its releases came between Apple's purchase of NeXT in late 1996 and the announcement of Mac OS X in 1998. Rhapsody represented a new and exploratory strategy for Apple, more than an operating system, and runs on x86-based PCs and on Power Macintosh. Its OPENSTEP based Yellow Box API frameworks were ported to Windows NT for creating cross-platform applications. Eventually, the non-Apple platforms were discontinued, and later versions consist primarily of the OPENSTEP operating system ported to Power Macintosh, merging the Copland-originated GUI of Mac OS 8 with that of OPENSTEP. Several existing classic Mac OS frameworks were ported, including QuickTime and AppleSearch. Rhapsody can run Mac OS 8 and its applications in a paravirtualization layer called Blue Box for backward compatibility during migration to Mac OS X.

<span class="mw-page-title-main">Spinning pinwheel</span>

The spinning pinwheel is a type of throbber or variation of the mouse pointer used in Apple's macOS to indicate that an application is busy.

<span class="mw-page-title-main">Mac OS X Server 1.0</span> Server operating system developed by Apple

Mac OS X Server 1.0 is an operating system developed by Apple Computer, Inc. Released on March 16, 1999, it was the first version of Mac OS X Server.

A hybrid kernel is an operating system kernel architecture that attempts to combine aspects and benefits of microkernel and monolithic kernel architectures used in computer operating systems.

Two major families of Mac operating systems were developed by Apple Inc.

References

  1. ↑ Apple PR (1997-11-19). "Apple Extends Rhapsody Developer Release with Mac OS Compatibility Environment, Code-Named "Blue Box"". apple.com. Archived from the original on 1998-12-02. Retrieved 2006-10-13.
  2. 1 2 Scott Anguish (May 1998). "WWDC 98 Summary". stepwise.com. Retrieved 2006-10-13.[ permanent dead link ]
  3. ↑ Magee, Jim. WWDC 2000 Session 106 – Mac OS X: Kernel. 14 minutes in. Archived from the original on 2021-12-21.
  4. ↑ Scott Anguish (1998-05-14). "Rhapsody Core OS: Intro to the I/O Driver Architecture". stepwise.com. Retrieved 2006-10-13.[ permanent dead link ]

Bibliography

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