A screenshot of Mac OS X v10.4 Tiger
developer: Apple Computer
OS family: BSD
Source model: Closed source (Darwin foundation is open source)
Latest stable release: 10.4.6 / April 3, 2006
Kernel type: Hybrid kernel
Default user interface: Aqua
License: Apple EULA (parts available under APSL)
Working state: Current
Mac OS, which stands for Macintosh Operating System, is a series of graphical user interface-based operating systems developed by Apple Computer for their Macintosh line of computer systems. The Mac OS is often credited with popularizing the graphical user interface. It was first introduced in 1984 with the original Macintosh 128K.
Apple deliberately played down the existence of the operating system in the early years of the Macintosh to help make the machine appear more user-friendly and to distance it from other operating systems such as MS-DOS, which were portrayed as arcane and technically challenging. Apple wanted Macintosh to be portrayed as a computer “for the rest of us”. The term “Mac OS” didn’t really exist until it was officially used during the mid-1990s. The term has since been applied to all versions of the Mac system software as a handy way to refer to it when discussing it in context with other operating systems.
Earlier versions of the Mac OS were compatible only with Motorola 68000-based Macintoshes, while later versions were also compatible with the PowerPC (PPC) architecture. Most recently, Mac OS X has become compatible with Intel’s x86 architecture.
Mac OS 9
developer: Apple Computer
OS family: Mac OS
Source model: Closed source
Latest stable release: 9.2.2 / December 6, 2001
Kernel type: Monolithic, later Nanokernel
Default user interface: Apple platinum (beginning with Mac OS 8)
Working state: Discontinued, still used by some (superseded by Mac OS X)
The early Macintosh operating system initially consisted of two pieces of software, called “System” and “Finder”, each with its own version number, as discussed in Mac OS history. System 7.5.1 was the first to include the Mac OS logo (a variation on the original “Happy Mac” smiley face Finder startup icon), and Mac OS 7.6 was the first to be named “Mac OS” (to ensure that users would still identify it with Apple, even when used in “clones” from other companies).
Until the advent of the later PowerPC G3-based systems, significant parts of the system were stored in physical ROM on the motherboard. The initial purpose of this was to avoid using up the limited storage of floppy disks on system support, given that the early Macs had no hard disk. (Only one model of Mac was ever actually bootable using the ROM alone, the 1991 Mac Classic model.) This architecture also helped to ensure that only Apple computers (and later licensed clones with the copyright-protected ROMs) could run Mac OS.
The Mac OS can be divided into two families of operating systems:
“Classic” Mac OS, the system which shipped with the first Macintosh in 1984 and its descendants, culminating with Mac OS 9.
The newer Mac OS X (the “X” refers to the Roman numeral, ten). Mac OS X incorporates elements of OpenStep (thus also BSD Unix and Mach) and Mac OS 9. Its low-level BSD-based foundation, Darwin, is free software/open source software.
“Classic” Mac OS (1984-2001)
Original 1984 Mac OS desktopMain 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.
Mac OS X (2001-present)
Mac OS X brought Unix-style memory management and pre-emptive multitasking to the Mac platform. It 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’s NeXT company. The new memory management system allowed more programs to run at once and virtually eliminated the possibility of one program crashing another. It is also the second Macintosh operating system to include a command line (the first is the now-discontinued A/UX, which supported classic Mac OS applications on top of a UNIX kernel), although it is never seen unless the user launches a terminal emulator.
However, since these new features put higher demands on system resources, Mac OS X only officially supported the PowerPC G3 and newer processors, and now has even higher requirements (the additional requirement of built-in USB and later FireWire). Even then, it runs somewhat slowly on older G3 systems for many purposes.
As of 2005, every update to Mac OS X since the original public beta has had the atypical quality of being perceptibly more responsive than the version it replaced, the opposite to the trend of most operating systems. As noted by John Siracusa of Ars Technica:
“For over three years now, Mac OS X has gotten faster with every releaseâ€”and not just “faster in the experience of most end users”, but faster on the same hardware. This trend is unheard of among contemporary desktop operating systems.”
This could, however, be attributed to the relative immaturity of the OS, and the speed gains have diminished as OS X has matured. Some reports regarding Mac OS X 10.4 suggested that it seemed similar to version 10.3 in responsiveness, or even slower at times.
Power PC builds of Mac OS X include a compatibility layer for running older Mac applications, the Classic Environment. This runs a full copy of the older Mac OS, version 9.1 or later, in a Mac OS X process. PowerPC-based Macs ship with OS 9.2 as well as OS X. OS 9.2 must be installed by the userâ€”it is not installed by default on all new hardware revisions released after the release of Mac OS X 10.4. Most well-written “classic” applications function properly under this environment, but compatibility is only assured if the software was written to be unaware of the actual hardware, and to interact solely with the operating system. The Classic Environment does not work in the x86 version of OS X.
Users of the original Mac OS generally upgraded to Mac OS X, but a few criticized it as being more difficult and less user-friendly than the original Mac OS, for the lack of certain features that had not been re-implemented in the new OS, or for being slower on the same hardware (especially older hardware), or other, sometimes serious incompatibilities with the older OS. Because drivers (for printers, scanners, tablets, etc.) written for the older Mac OS are not compatible with Mac OS X, and due to the lack of OS X support for older Apple machines, a significant number of Macintosh users have continued using the older OS. By 2005, it is reported that almost all users of systems capable of running Mac OS X are so doing, with only a small percentage still running the classic Mac OS.
In June 2005, Steve Jobs announced at his Worldwide Developers Conference keynote that Apple computers would be transitioning from PowerPC to Intel processors. At the same conference, Jobs announced Developer Transition Kits that included beta versions of Apple software including Mac OS X that developers could use to test their applications as they ported them to run on Intel-powered Macs. In January 2006, Apple released the first Macintosh computers with Intel processors, an iMac and the MacBook Pro, and in February 2006, Apple released a Mac Mini with an Intel Core Solo and Duo processor. Continuing the trend of switching Apple’s entire product line to the Intel chip, Apple released the MacBook on May 16, 2006.