Macintosh original operating system OS

“Classic” Mac OS (1984-2001)

Original 1984 Mac OS desktop
Main article: Mac OS history

The “classic” Mac OS is characterized by its total lack of a command line; it is a completely graphical operating system. Heralded for its ease of use, it is also criticized for its singletasking (in early versions) or cooperative multitasking (in later versions), very limited memory management, lack of protected memory, and susceptibility to conflicts among “extensions” that extend the operating system, providing additional functionality (such as networking) or support for a particular device. Some extensions may not work properly together, or work only when loaded in a particular order. Troubleshooting Mac OS extensions can be a time-consuming process of trial and error.

Mac OS originally used the Macintosh File System (MFS), a flat file system with only one level of folders. This was replaced by the Hierarchical File System (HFS), which had a true directory tree. Both file systems are otherwise compatible.

Most file systems used with DOS, Unix, or other operating systems treat a file as simply a sequence of bytes, requiring an application to know which bytes represented what type of information. By contrast, MFS and HFS gave files two different “forks”. The data fork contained the same sort of information as other file systems, such as the text of a document or the bitmaps of an image file. The resource fork contained other structured data such as menu definitions, graphics, sounds, or code segments. A file might consist only of resources with an empty data fork, or only a data fork with no resource fork. A text file could contain its text in the data fork and styling information in the resource fork, so that an application which didn’t recognize the styling information could still read the raw text. On the other hand, these forks provided a challenge to interoperability with other operating systems; copying a file from a Mac to a non-Mac system would strip it of its resource fork.

The Classic OS is still supported and Classic Applications Support is shipped in addition to OS X with PowerPC (but not Intel) Macs as late as early 2006.

Macintosh operating system ( new age OSX ) Mac OSX ten

Mac OS X (officially pronounced “Mac OS Ten”) is a line of proprietary, graphical operating systems developed, sold, and marketed by Apple Computer, the latest of which is included with all currently-shipping Apple Macintosh computers. Mac OS X is the successor to the original Mac OS, which had been Apple’s primary operating system since 1984. Unlike its predecessor, Mac OS X is a multi-user, pre-emptively multitasking, Unix-like operating system built on technology that had been developed at NeXT through the second half of the 1980’s and up until Apple Computer purchased the company in early 1997. The operating system was first released in 1999 as Mac OS X Server 1.0, with a desktop-oriented version (Mac OS X v10.0) following in March, 2001.

The server edition, Mac OS X Server, is architecturally identical to its desktop counterpart but usually runs on Apple’s line of Macintosh server hardware. Mac OS X Server includes workgroup management and administration software tools that provide simplified access to key network services, including a mail server, a Samba server, a directory server, and a domain name server.

History
Main article: History of Mac OS X

Despite its branding as simply “version 10″ of the Mac OS, Mac OS X has a history that is almost completely independent of the earlier Mac OS releases.

Mac OS X is based on the Mach kernel and the BSD implementation of Unix, which were incorporated into NEXTSTEP, the object-oriented operating system developed by Steve Jobs’ NeXT company after he left Apple in 1985.[1] Meanwhile, during the years without Jobs at the helm, Apple attempted to create a “next-generation” operating system of its own (see Taligent and Copland) with little success.

Eventually, NeXT’s OS—called OPENSTEP at the time—was selected to form the basis for Apple’s next OS, and Apple purchased NeXT outright[2]. Jobs was re-hired, and later returned to the leadership of the company, shepherding the transformation of the programmer-friendly OPENSTEP into a system that would be welcomed by Apple’s primary market of home users and creative professionals, as a project known as Rhapsody. After some missteps which threatened the loyalty of independent developers to Mac OS, and changes of strategy to ease the transition from Mac OS 9 to the new system, Rhapsody evolved into Mac OS X.

Mac OS X has evolved through its successive versions, away from a focus on backward compatibility and toward “digital lifestyle” applications such as the iLife suite, enhanced business applications (iWork), and integrated home entertainment (the Front Row media center).
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Description

The original (left) and revised (right) retail packaging for Mac OS X v10.4 “Tiger”

Mac OS X is a radical departure from previous Macintosh operating systems as its underlying code base is completely different from previous versions. Its core, named Darwin, is an open source, Unix-like operating system, built around the XNU kernel with standard Unix facilities available from the command line interface. On top of this core, Apple designed and developed a number of proprietary closed source components, including the Aqua user interface and the Finder shell.

Mac OS X includes a number of features intended to make the operating system more stable and reliable than Apple’s previous operating systems. Pre-emptive multitasking and memory protection, for example, improve the ability of the operating system 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 with portability in mind, thus easing the transition from one platform to another. (For example, NEXTSTEP was ported from the original 68k-based NeXT workstations to PA-RISC/SPARC/x86-based machines before NeXT was purchased by Apple, and OPENSTEP was subsequently ported to the PowerPC architecture as part of Apple’s Rhapsody project.)

The most visible change was the Aqua graphical user interface. The use of soft edges, translucent colors, and pinstripes (similar to the hardware of the first iMacs), brought more color and texture to the windows and controls on the Desktop than OS 9’s “Platinum” appearance had offered. Some, including numerous users of the older versions of the operating system, decried the new look as “cutesy”[3][4] and lacking in professional polish. Others, however, hailed Aqua as being a bold and innovative step forward in a time when user interfaces were seen as being “dull and boring”[5]. Despite the controversy, the look was instantly recognizable, and even before the first version of Mac OS X was released, third-party developers started producing skins for customizable applications, like Winamp, similar to 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[6].

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. It supports the ability to target both platforms for which Mac OS X is sold, allowing an application to be built to run only on PowerPC, only on x86, or on both processors as a Universal Binary.
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Compatibility
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PowerPC

PowerPC versions of Mac OS X 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. In addition, the Carbon APIs for Mac OS 9 and Mac OS X were created to permit code to be written to run natively on both systems. The OpenStep APIs are still available, but Apple now calls the technology Cocoa. (This heritage is visible in the Cocoa APIs, in which the class names mostly begin with “NS” for NEXTSTEP.) A fourth option for developers is to write applications in the Java platform, which Mac OS X has supported as a “first class citizen”—in practice this means that Java applications fit as neatly into the operating system as possible while still being “cross-platform”, and that GUIs, while being 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.” [7]

Mac OS X can run many BSD or Linux software packages, as long as they have been compiled for the platform. Compiled binaries are normally distributed as Mac OS X packages, but some may require command-line configuration or compilation. Projects such as Fink and DarwinPorts provide precompiled or preformatted packages for many standard packages. Since version 10.3, Mac OS X has included X11.app, the company’s version of the X11 graphical interface for Unix applications, as an optional component during installation. Apple’s implementation is based on XFree86 4.3 and X11R6.6, with a window manager which mimics the Mac OS X look, closer integration with Mac OS X, and extensions to use the native Quartz rendering system and to accelerate OpenGL. Earlier versions of Mac OS X can run X11 applications using XDarwin.

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 of Mac OS X discontinued support for some older hardware; for example, Panther does not support “beige” G3s, and Tiger does not support systems that pre-date Apple’s introduction of FireWire ports. However, free tools such as XPostFacto have enabled installation of versions of Mac OS X on certain older systems not officially supported by Apple, including some pre-G3 systems. Except for features requiring specific hardware (e.g. graphics acceleration, DVD writing), the operating system offers the same functionality on all supported hardware.
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Intel

In April 2002, eWeek reported a rumor that Apple had a version of Mac OS X running on x86 processors, code-named Marklar. 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. [8] These rumors subsided until late in May 2005, when CNet reported that Apple would unveil Marklar in the coming months.[9]

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 will be transitioning from PowerPC to Intel processors over the following two years, and that Mac OS X will support both platforms during this transition. 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 with legacy hardware. Apple has supported the 68K emulator for 11 years, however Apple will be dropping support for the 68K emulator during the transition to Intel CPUs. Included in the new OS for the Intel-based Macs is a new PowerPC emulator, named “Rosetta”, that enables software compiled for PowerPC Mac OS X to run on Intel Mac OS X machines. However, Apple dropped support for Classic mode on the new Intel Macs. (Third party emulation software, like Mini vMac, Basilisk II, and SheepShaver, 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.[10]

Software developers can support the new Intel Macs in any of the following ways:
They can continue to ship PowerPC-only software, which will automatically work by using the Rosetta emulator which is included with the new OS that runs on Intel-based Macs.
They can ship Universal Binaries, which include both the PowerPC and x86 versions of their application. When the user opens the application, depending upon which CPU the Mac has, the appropriate version of the application will be run automatically.
They can ship x86-only Mac OS X applications that will run only on the new Intel-based Macs.

Currently, a lot of software is available only for PowerPC, and is supported with Rosetta. However, Apple encourages Developers to produce Universal Binaries with support for both PowerPC and x86; that software should run faster on Intel-based Macs than would PowerPC-only software running on Rosetta, and some PowerPC software, such as kernel extensions and System Preferences plugins, is not supported on Intel Macs. Option 3 will likely start to be the norm several years from now when the demand for PowerPC software drops off.

Support for the PowerPC platform will remain in version 10.5, though it is unclear how long this dual-architecture support will be continued—but since Apple supported the Motorola 68K family for eleven years after the introduction of PowerPC systems, it is likely that they will support the PowerPC Macs for many years to come. Jobs also confirmed rumors that Apple has had versions of Mac OS X running on Intel processors for most of its developmental life. Such crossplatform capability already existed in Mac OS X’s lineage—the predecessor of Mac OS X, OPENSTEP, had been ported to many architectures, including Intel’s x86, and a port to x86 of the core operating system of Mac OS X, Darwin, has been available as a free download since Mac OS X was first released. Also note that Apple stated that Mac OS would only run on Apple x86 systems, not PCs, but several people have been using a development version of the OS on non-Apple machines.