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Darwin is a free, open source, Unix-like operating system first released by Apple Inc. in 2000. It is a standalone operating system as well as the core set of components upon which Mac OS X was developed. It is primarily developed by Apple to support Mac OS X.
History
Darwin can trace its heritage back to NeXT's NEXTSTEP operating system (later known as OPENSTEP), originally released in 1989. After Apple's 1997 acquisition of NeXT, the company announced it would use OPENSTEP as the basis for its next operating system. This was developed into Rhapsody in 1997 and the Rhapsody-based Mac OS X Server 1.0 in 1999. In 2000, Rhapsody was forked into Darwin and released as open-source software under the Apple Public Source License (APSL).
Design
Kernel
Darwin is built around XNU, a hybrid kernel that combines the Mach 3 microkernel, various elements of FreeBSD 5 (including the process model, network stack, and virtual file system), and an object-oriented device driver API called I/O Kit. [http://www.opensource.apple.com/]
Some of the benefits of this choice of kernel are the Mach-O binary format, which allows a single executable file (including the kernel itself) to support multiple CPU architectures, and the mature support for symmetric multiprocessing in Mach. The hybrid kernel design compromises between the flexibility of a microkernel and the performance of a monolithic kernel.
Hardware and software support
Darwin currently includes support for PowerPC and Intel x86 processors.
Darwin does not include many of the defining elements of Mac OS X, such as the Carbon and Cocoa APIs or the Quartz Compositor and Aqua user interface, and thus cannot run Mac applications. It does, however, support a number of lesser known features of OS X, such as mDNSResponder, the multicast DNS responder and a core component of the Bonjour networking technology, and launchd, an advanced service management framework.
It also supports the POSIX API by way of its FreeBSD lineage and can run a large number of programs written for various other Unix-like systems.
Darwin and OS X both use I/O Kit for their drivers and therefore support the same hardware, file systems, and so forth. Apple's distribution of Darwin includes binary-only (closed-source) drivers for their AirPort wireless cards.
License
In July 2003, Apple released Darwin under version 2.0 of the APSL license, which the Free Software Foundation (FSF) approved as a free software license. Previous releases had taken place under an earlier version of the APSL that did not meet the FSF's definition of free software, although it met the requirements of the Open Source Definition.
Mascot
The Darwin developers decided to adopt a mascot in 2000, and chose Hexley the platypus over other contenders, such as an Aqua Darwin fish, Clarus the dogcow, and an orca. Apple does not sanction Hexley as a logo for Darwin.
Darwin projects
Due to the free software nature of Darwin, there are many projects that aim to modify or enhance the operating system:
* OpenDarwin was a community-led operating system based on the Darwin platform, founded in April 2002 by the Internet Software Consortium and Apple. In July 2006, the OpenDarwin Core Team and Administrators announced that all development on OpenDarwin would cease, citing concerns over lack of interest from the community [http://www.opendarwin.org/en/news/shutdown.html].
* MacPorts (formerly DarwinPorts) and Fink are both well known projects to port Unix programs to the Darwin operating system and provide package management.
* GNU-Darwin is a project that ports packages of open-source software to Darwin.
* The Darbat project is an experimental port of Darwin to the L4 microkernel family. It aims to be binary compatible with existing Darwin binaries. [http://www.ertos.nicta.com.au/software/darbat/]
* There are various projects that focus on driver support (e.g., wireless drivers, such as [http://wirelessdriver.sourceforge.net/ a port of prism/prism2] or [http://sourceforge.net/projects/iwi2200 a port of ipw2200]; wired NICs, such as [http://sourceforge.net/projects/darwin-tulip/ a port of the tulip drivers], a driver for the ADMtek 985 clone and the PNIC 82c169 chipsets, or [http://sourceforge.net/projects/darwin-rtl8139 a port of the rlt8139 driver] and [http://sourceforge.net/projects/rtl8150lm the rtl8150lm driver], drivers for some Realtek cards; and even ports of modem drivers, such as [http://sourceforge.net/projects/darwinmodems for ZyXEL modems], and a [http://pccardata.sourceforge.net/ project for adding support to card readers -->. Darwin also has support for ext2/ext3 file systems [http://sourceforge.net/projects/ext2fsx/].
* Others focus on software for running Microsoft Windows software on Darwin (e.g., the Darwine project, a port of Wine [http://darwine.opendarwin.org/ --> or for running Mac OS X/Darwin software on other Unix platforms such as FreeBSD (e.g., the [http://www.softpear.org/wiki/Main_Page softpear] project).
* In addition, several standard Unix package manager projects are working on Darwin ports, such as RPM for Darwin [http://rpm4darwin.sourceforge.net/RPM], pkgsrc (the NetBSD package manager), and Gentoo. Some of these operate in their own namespace so as not to interfere with the base system.
* There is a port of SELinux to Darwin [http://www.trustedbsd.org/sedarwin.html].
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