MAC OS
Mac OS is a
series of graphical
user interface–based operating
systems developed
by Apple
Inc. for
their Macintosh line of computer systems
The original
operating system was
first introduced in 1984 as being integral to the original Macintosh, and referred to as the
"System". Referred to by its major revision starting with
"System 6" and "System 7", Apple rebranded version 7.6 as
"Mac OS" as part of their Macintosh
clone program
in 1996. The Macintosh, specifically its system software, is credited with
having popularized the early graphical
user interface concept.
There are two architectural legacies of Mac OS. Up to major
revision 9, from 1984 to 2000, it is historically known as Classic Mac OS. Major revision 10, from 2001
to present, is branded OS X (originally referred to as Mac
OS X). Both
legacies share a general interface design, and there has been some overlap of application frameworksfor
compatibility; but the two systems have different origins and use deeply
different architectures.
The "classic" Mac OS is characterized by its monolithic system. Versions of Mac OS up
through System 4 ran only one application at a time. Even so, it was noted for
its ease of use. Mac OS gained cooperative
multitasking with
System 5, which ran on the Macintosh
SE and Macintosh II. It was criticized for its
very limited memory
management, lack ofprotected memory, no access controls, and susceptibility to
conflicts among operating system "extensions"
that provide additional functionality (such as networking) or support for a
particular device. Some extensions didn't work properly together, or worked
only when loaded in a particular order. Troubleshooting Mac OS extensions could
be a time-consuming process of bisecting and trial and error.
The Macintosh originally used the Macintosh File System (MFS),
a flat file
system with
only one level of folders. This was quickly replaced in 1985 by the Hierarchical File System (HFS), which had a true directory tree.
Both file systems are otherwise compatible.
Files in most file systems used with DOS, Windows, Unix, or
other operating systems have only one "fork".
By contrast, MFS and HFS give files two different "forks". The data
fork contains the same sort of information as a file in other file systems,
such as the text of a document or the bitmaps of an image file. The resource fork contains other structured data
such as menu definitions, graphics, sounds, or code segments that would be
incorporated into a program's file
format on
other systems. An executable
file might
consist only of resources (including code
segments) with an empty data fork, while a data file might
have only a data fork with no resource fork. A word processor file could
contain its text in the data fork and styling information in the resource fork,
so that an application which doesn’t recognize the styling information can
still read the raw text.
On the other hand, these forks would provide a challenge to
interoperability with other operating systems. In copying or transferring a
MacOS file to a non-Mac system, the default implementations would simply strip
the file of its resource fork. Most data
files contained
only nonessential information in their resource fork, such as window size and
location, but program files would be inoperative without their resources. This
necessitated such encoding schemes as BinHex and MacBinary, which allowed a user to
encode a dual-forked file into a single stream, or inversely take a single
stream so-encoded and reconstitute it into a dual-forked file usable by MacOS.
PowerPC versions of OS X up to and including OS X v10.4 Tiger
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 an OS X process. Early New World PowerPC-based
Macs shipped with Mac OS 9.2 as well as OS X. Mac OS 9.2 had to be installed by
the user – it was not installed by default on hardware revisions released
after the release of OS X 10.4
Tiger. Most well-written "classic" applications function
properly under this environment, but compatibility is assured only if the
software was written to be unaware of the actual hardware, and to interact
solely with the operating system. The Classic Environment is not available on
Intel-based Macintosh systems due to the incompatibility of Mac OS 9 with
thex86 hardware.
Users of the classic Mac OS generally upgraded to OS X, but many
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 on 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 OS X, and due to the lack of OS X support for older
Apple machines, a significant number of Macintosh users continued using the
older classic Mac OS.
In June 2005, Steve
Jobs announced
at the Apple
Worldwide Developers Conference keynote
that Apple computers would be transitioning
from PowerPC to Intel processors and
thus dropping compatibility on new machines for Mac OS Classic. At the same
conference, Jobs announced Developer Transition Kits that included beta
versions of Apple software including 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. On May 16, 2006, Apple released the MacBook, before completing the Intel
transition on August 7 with the Mac Pro. To
ease the transition for early buyers of the new machines, Intel-based Macs
included an emulation technology called Rosetta, which allows them to run OS X
software that was compiled for PowerPC-based Macintosh models. Rosetta runs
transparently, creating a user experience identical to running the software on
a PowerPC machine, though execution is typically slower than with native code.
Rosetta was an optional installation in OS X 10.6 Snow Leopard and is not
available at all in OS X 10.7 Lion.
OS X
OS X, introduced as Mac OS
X in 2001
and renamed OS X in 2012, is the latest version of Apple's
operating system. Although it is officially designated as simply "version
10" of Mac OS, it has a history largely independent of the earlier Mac OS
releases. Major revisions to Mac OS are now issued as point revisions, such that,
for example, 10.2 is substantially different from 10.5.
The OS X architectural legacy is the successor to Mac OS 9 and the
"classic" Mac OS legacy. It is however a Unix operating
system, based on the NeXTSTEP operating
system which Apple acquired after purchasing NeXT Computer– with its CEO Steve Jobs returning
to Apple at that time. OS X also makes use of the BSD codebase and the XNU kernel. There have been twelve significant releases
of OS X, the most recent being OS X 10.11, referred to as "El Capitan".
Prior to 10.11 came OS X 10.10 "Yosemite",
10.9 "Mavericks", 10.8 "Mountain Lion",
10.7 "Lion", 10.6 "Snow Leopard",
10.5 "Leopard", 10.4 "Tiger",
10.3 "Panther", 10.2 "Jaguar",
10.1 ("Puma"), and 10.0 ("Cheetah").
OS X has six significant releases as OS X Server. The first of these, Mac OS X Server 1.0, was released in beta before
the client version in 1999. The server versions are architecturally identical
to the client versions, with the differentiation found in their inclusion of
tools for server management, including tools for managing OS X-based workgroups, mail servers, and web
servers, amongst other tools. As of the name change to OS X, OS X Server is no
longer sold as a separate operating system product. The server tools could then
be added to the singular OS X product, giving the same functionality.
OS X Server is available as an operating system to-order on Mac Mini and Mac Pro computers
as a part of a server package. Unlike the client version, OS X Server can be
run in a virtual
machine using
emulation software such as Parallels
Desktop for Mac and VMware Fusion.
OS X was used as the basis for iOS, (originally iPhone OS) used
on Apple's iPhone, iPod Touch, and iPad; iOS is, in turn the basis of WatchOS, used on the Apple
Watch, the "Apple TV Software" on the second-generation and
third-generation Apple TV, and
tvOS, used on the fourth-generation Apple TV.
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