Diagram of the relationships between several Unix-like systems

A Unix-like (sometimes shortened to *nix) operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification. An operating system (commonly abbreviated OS and O/S) is the software component of a Computer system that is responsible for the management and coordination Unix (officially trademarked as UNIX, sometimes also written as Unix with Small caps) is a computer The Single UNIX Specification ( SUS) is the collective name of a family of standards for Computer Operating systems to qualify for the name " Unix The term can include free software / open source operating systems inspired by Bell Labs’ Unix or designed to emulate its features, commercial and proprietary work-alikes, and even versions based on the |licensed UNIX source code (which may be deemed so “Unix-like” that they are certified to bear the “UNIX” trademark). Free software or software libre is Software that can be used studied and modified without restriction and which can be copied and redistributed in modified or unmodified Open source software (OSS began as a marketing campaign for Free software. Bell Laboratories (also known as Bell Labs and formerly known as AT&T Bell Laboratories and Bell Telephone Laboratories) is the Research organization A software license (or software licence in commonwealth usage is a Legal instrument governing the usage or redistribution of copyright protected software There is no standard for defining the term, and some difference of opinion is possible as to whether a certain OS is “Unix-like” or not. A technical standard is an established norm or requirement It is usually a formal document that establishes uniform engineering or technical criteria methods processes and practices

The term “Unix-like” and the UNIX trademark

The Open Group owns the UNIX trademark and administers the Single UNIX Specification, with the “UNIX” name being used as a certification mark. The Open Group is an industry Consortium to set vendor- and technology-neutral open standards for Computing infrastructure A trademark or trade mark, represented by the symbols ™ and ®, or mark is a distinctive sign or indicator used by an individual A certification mark on a commercial product indicates five things The existence of a legal follow-up or Product certification agreement between the manufacturer They do not approve of the construction “Unix-like”, and consider it misuse of their trademark. Their guidelines require “UNIX” to be presented in uppercase or otherwise distinguished from the surrounding text, strongly encourage using it as a branding adjective for a generic word such as “system”, and discourage its use in hyphenated phrases. The closest phrase they consider correct is “UNIX system-like”. ^[1]

Other parties frequently treat “Unix” as a genericized trademark, in much the same way that “Band-Aid” is used in reference to any adhesive bandage or “Xerox” to any photocopier. A genericized trademark (also known as a generic trademark or proprietary eponym) is a Trademark or Brand name that has become the colloquial History The Band-Aid was invented in 1920 by Earle Dickson, an employee of Johnson & Johnson for his wife Josephine who frequently cut and burned herself while cooking A bandage is a piece of material used either to support a medical device such as a dressing or splint, or on its own to provide support to the body Xerox Corporation ( (name ˈziːrɒks is a global document management company which manufactures and sells a range of color and black-and-white printers, multifunction A photocopier (or copier is a machine that makes Paper copies of documents and other visual images quickly and cheaply Some add a wildcard character to the name to make a euphemistic abbreviation like “Un*x” or “*nix” (the latter pronounced as "asternix", a play on the asterisk used for the wildcard), since Unix-like systems often have Unix-like names such as AIX, HP-UX, IRIX, Linux, Minix, Ultrix, and Xenix. For other meanings of 'wild card' see Wild card. The term wildcard character has the following meanings Telecommunication In A euphemism is a substitution of an agreeable or less offensive expression in place of one that may offend or suggest something unpleasant to the listener or in the case of doublespeak HP-UX (Hewlett Packard UniX is Hewlett-Packard 's proprietary implementation of the Unix Operating system, based on System V (initially IRIX is a computer Operating system developed by Silicon Graphics Inc Linux (commonly pronounced ˈlɪnəks MINIX is a Unix-like computer Operating system based on a Microkernel architecture. Ultrix (officially all-caps ULTRIX) was the brand name of Digital Equipment Corporation 's (DEC native Unix systems Xenix is a version of the Unix Operating system, licensed by Microsoft from AT&T in the late 1970s These patterns do not literally match many system names, but are still generally recognized to refer to any UNIX descendant system, even those with completely dissimilar names such as Solaris, FreeBSD or Mac OS X. Solaris is a Unix -based Operating system introduced by Sun Microsystems in 1992 as the successor to SunOS. FreeBSD is a Unix-like free Operating system descended from AT&T UNIX via the Berkeley Software Distribution (BSD branch through Mac OS X (mæk oʊ ɛs tɛn is a line of computer Operating systems developed marketed and sold by Apple Inc, the latest of which is pre-loaded on all currently This is still contrary to Open Group guidelines.

As of 2007, there is an active legal battle between Wayne R. Gray and Open Group that centers on the use of UNIX as a trademark. Wayne R Gray is the president of InuX Inc a Florida company that is involved in Trademark litigation with X/Open over the UNIX ^[2] Trademark Trial and Appeal Board court documents indicate that Gray’s legal team is seeking for the Open Group to provide documentation for their trademark claim. The Trademark Trial and Appeal Board (or " TTAB " is a body within the United States Patent and Trademark Office (USPTO responsible for hearing and deciding

Also in 2007, the Open Group forced the German University of Kassel not to use "UNIK" as their short form. Kassel (until 1926 officially Cassel) is a city situated along the Fulda River in northern Hessen, Germany, one of the two sources of the

Categories

Dennis Ritchie, one of the original creators of UNIX, has expressed his opinion that Unix-like systems such as Linux are de facto UNIX systems. Dennis MacAlistair Ritchie (born September 9, 1941) is an American computer scientist notable for his influence on C and other Programming Linux (commonly pronounced ˈlɪnəks Eric S. Raymond has suggested that there are three kinds of Unix-like systems:

Genetic UNIX

Those systems with a historical connection to the AT&T codebase. Eric Steven Raymond (born December 4 1957 often referred to as ESR, is a Computer programmer, author and Open source software advocate Before proposing a merge request please see Talk and see if the merger you propose has recently been made and Most but not all commercial UNIX systems fall into this category. So do the BSD systems, which are descendants of work done at the University of California, Berkeley in the late 1970s and early 1980s. The University of California Berkeley (also referred to as Cal, Berkeley and UC Berkeley) is a major research university located in Berkeley Some of these systems have no original AT&T code but can still trace their ancestry to AT&T designs.

Trademark or Branded UNIX

These systems—largely commercial in nature—have been determined by the Open Group to meet the Single UNIX Specification and are allowed to carry the UNIX name. The Open Group is an industry Consortium to set vendor- and technology-neutral open standards for Computing infrastructure The Single UNIX Specification ( SUS) is the collective name of a family of standards for Computer Operating systems to qualify for the name " Unix Most such systems are commercial derivatives of the System V code base in one form or another, though a few (such as IBM's z/OS) earned the trademark through a POSIX compatibility layer and are not otherwise inherently Unix systems. Unix System V, commonly abbreviated SysV (and usually pronounced though rarely written as System 5 was one of the versions of the Unix Operating system z/OS is a 64-bit Operating system for Mainframe computers, created by IBM. POSIX (ˈpɒzɪks or "Portable Operating System Interface" is the collective name of a family of related standards specified by the IEEE to define Many Ancient UNIX Systems no longer meet this definition. Ancient UNIX is a term coined by Santa Cruz Operation (now SCO) to describe early releases of the Unix code base released prior to Unix System III

Functional UNIX

Broadly, any Unix-like system that behaves in a manner roughly consistent with the UNIX specification; more specifically, this can refer to systems such as Linux or Minix that behave similarly to a UNIX system but have no genetic or trademark connection to the AT&T code base. Linux (commonly pronounced ˈlɪnəks MINIX is a Unix-like computer Operating system based on a Microkernel architecture. Most free/open-source implementations of the UNIX design, whether Genetic Unix or not, fall into the restricted definition of this third category due to the expense of obtaining Open Group certification which costs thousands of dollars.

Cygwin, while not being an operating system, does provide a Unix-like environment on top of Microsoft Windows. Cygwin (ˈsɪɡwɪn is a collection of tools originally developed by Cygnus Solutions to provide in Microsoft Windows a command line and programming interface familiar

Development of Unix-like systems

“Unix-like” systems started to appear in the late ’70s and early ’80s. Many proprietary versions, such as Idris (1978), Coherent (1983), and UniFlex (1985), aimed to provide businesses with the functionality available to academic users of UNIX. Proprietary software is Computer software on which the producer has set restrictions on use private modification copying, or republishing. Idris is a multi-tasking Unix-like, multi-user Real-time operating system released by Whitesmiths, of Westford Massachusetts. The Coherent Operating system was a Unix Version 7 clone by the now-defunct Mark Williams Company, originally produced for the PDP-11 UniFlex is Unix-like Operating system developed by Technical Systems Consultants (TSC for Multitasking, Multiprocessing for the

When AT&T later allowed commercial licensing of UNIX in the 1980s, a variety of proprietary systems were developed based on it, including AIX, HP-UX, IRIX, Solaris, Tru64, Ultrix, and Xenix. HP-UX (Hewlett Packard UniX is Hewlett-Packard 's proprietary implementation of the Unix Operating system, based on System V (initially IRIX is a computer Operating system developed by Silicon Graphics Inc Solaris is a Unix -based Operating system introduced by Sun Microsystems in 1992 as the successor to SunOS. Tru64 UNIX is a 64-bit UNIX Operating system for the Alpha Microprocessor architecture currently owned by Hewlett-Packard Ultrix (officially all-caps ULTRIX) was the brand name of Digital Equipment Corporation 's (DEC native Unix systems Xenix is a version of the Unix Operating system, licensed by Microsoft from AT&T in the late 1970s These largely displaced the proprietary clones. Growing incompatibility between these systems led to the creation of interoperability standards, including POSIX and the Single UNIX Specification. POSIX (ˈpɒzɪks or "Portable Operating System Interface" is the collective name of a family of related standards specified by the IEEE to define The Single UNIX Specification ( SUS) is the collective name of a family of standards for Computer Operating systems to qualify for the name " Unix

Meanwhile, the GNU Project was launched in 1983 with the goal of making GNU, an operating system which all computer users could freely use, study, modify, and redistribute. The GNU Project is a Free software, Mass collaboration project announced in 1983 by Richard Stallman. GNU ( pronounced) is a computer Operating system composed entirely of Free software. Various “Unix-like” operating systems developed alongside GNU, frequently sharing substantial components with it (leading to some disagreement about whether they should be called “GNU” or not). These primarily served as low-cost and unrestricted substitutes for UNIX, and include 4.4BSD, Linux, and Minix. Some of these have in turn been the basis for commercial “Unix-like” systems, such as BSD/OS and Mac OS X. BSD/OS (originally called BSD/386 and sometimes known as BSDi) was a proprietary version of the BSD Unix Operating system developed by Berkeley Mac OS X (mæk oʊ ɛs tɛn is a line of computer Operating systems developed marketed and sold by Apple Inc, the latest of which is pre-loaded on all currently Notably, Mac OS X 10.5, Leopard, is certified under the Single UNIX Specification. Mac OS X version 105 “Leopard” is the sixth major release of Mac OS X, Apple’s desktop and server Operating system for Macintosh ^[3]

The various BSD variants are notable in that they are in fact descendants of UNIX, developed by the University of California at Berkeley with UNIX source code from Bell Labs. However, the BSD code base has evolved since then, replacing all of the AT&T code. Since the BSD variants are not certified as compliant with the Single UNIX Specification (except for Mac OS X 10. 5 Leopard), they are referred to as "UNIX-'like'".

Current examples

Ubuntu, a popular GNU/Linux distribution

Most vendors of open source Unix-like systems do not seek UNIX branding for their product even if conformant: the costs for certification are generally considered prohibitive. Ubuntu Kubuntu Edubuntu Xubuntu Gobuntu --> Ubuntu Open source software (OSS began as a marketing campaign for Free software. The term Freenix is sometimes used to refer to such systems. Current examples include GNU, Linux, Minix, OpenSolaris, Plan 9, and BSD and its descendents. GNU ( pronounced) is a computer Operating system composed entirely of Free software. Linux (commonly pronounced ˈlɪnəks MINIX is a Unix-like computer Operating system based on a Microkernel architecture. OpenSolaris is an Open source project created by Sun Microsystems to build a developer community around Solaris Operating System technology Plan 9 from Bell Labs is a Distributed operating system, primarily used for research Notable BSD operating systems include FreeBSD, NetBSD, and OpenBSD. FreeBSD is a Unix-like free Operating system descended from AT&T UNIX via the Berkeley Software Distribution (BSD branch through NetBSD is a freely redistributable Open source version of the Unix -derivative Berkeley Software Distribution (BSD Computer Operating OpenBSD is a Unix-like computer Operating system descended from Berkeley Software Distribution (BSD a Unix derivative developed at the

There are a number of current proprietary Unix-likes, including AIX; HP-UX; IRIX; Mac OS X; LynxOS; QNX; SCO OpenServer; Solaris; Tru64 UNIX (based on OSF/1); UnixWare; Xenix; and VxWorks. HP-UX (Hewlett Packard UniX is Hewlett-Packard 's proprietary implementation of the Unix Operating system, based on System V (initially IRIX is a computer Operating system developed by Silicon Graphics Inc Mac OS X (mæk oʊ ɛs tɛn is a line of computer Operating systems developed marketed and sold by Apple Inc, the latest of which is pre-loaded on all currently LynxOS does not refer to the operating system for the Atari Lynx Game console. QNX (pronounced either Q-N-X or Q-nix is a commercial Unix-like Real-time operating system, aimed primarily at the Embedded systems market SCO OpenServer, previously SCO UNIX and SCO Open Desktop ( SCO ODT) is a closed source version of the Unix computer Operating system Solaris is a Unix -based Operating system introduced by Sun Microsystems in 1992 as the successor to SunOS. Tru64 UNIX is a 64-bit UNIX Operating system for the Alpha Microprocessor architecture currently owned by Hewlett-Packard Tru64 UNIX is a 64-bit UNIX Operating system for the Alpha Microprocessor architecture currently owned by Hewlett-Packard UnixWare is a Unix Operating system maintained by The SCO Group (SCO Xenix is a version of the Unix Operating system, licensed by Microsoft from AT&T in the late 1970s VxWorks is a real-time Operating system made and sold by Wind River Systems of Alameda, California, USA

See also

• Berkeley Software Distribution
• Linux distribution
• List of Linux distributions
• List of Unix programs
• List of operating systems

References

External links

• Unix-like Definition—by The Linux Information Project (LINFO)
• UNIX history—a history time line graph of most UNIX and Unix-like systems by Éric Lévénez
• Grokline's UNIX Ownership History Project—a project to map out the technical history of UNIX and Unix-like systems