Unix
| Developer | Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna at Bell Labs |
|---|---|
| Written in | C and assembly language |
| OS family | Unix |
| Working state | Current |
| Source model | Historically proprietary software, while some Unix projects (including BSD family and illumos) are open-source |
| Initial release | Development started in 1969
First manual published internally in November 1971 (1971-11) Announced outside Bell Labs in October 1973 (1973-10) |
| Available in | English |
| Kernel type | Varies; monolithic, microkernel, hybrid |
| Default user interface | Command-line interface and Graphical (Wayland and X Window System; Android SurfaceFlinger; macOS Quartz) |
| License | Varies; some versions are proprietary, others are free/open-source software |
| Official website |
Unix (/ˈjuːnɪks/; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, development starting in the 1970s at the Bell Labs research center by Ken Thompson, Dennis Ritchie, and others.
Initially intended for use inside the Bell System, AT&T licensed Unix to outside parties in the late 1970s, leading to a variety of both academic and commercial Unix variants from vendors including University of California, Berkeley (BSD), Microsoft (Xenix), Sun Microsystems (SunOS/Solaris), HP/HPE (HP-UX), and IBM (AIX).
In the early 1990s, AT&T sold its rights in Unix to Novell, which then sold its Unix business to the Santa Cruz Operation (SCO) in 1995.
The UNIX trademark passed to The Open Group, a neutral industry consortium founded in 1996, which allows the use of the mark for certified operating systems that comply with the Single UNIX Specification (SUS).
However, Novell continues to own the Unix copyrights, which the SCO Group, Inc. v. Novell, Inc. court case (2010) confirmed.
Unix systems are characterized by a modular design that is sometimes called the "Unix philosophy".
According to this philosophy, the operating system should provide a set of simple tools, each of which performs a limited, well-defined function.
A unified (the ) and an inter-process communication mechanism known as "pipes" serve as the main means of communication, and a shell scripting and command language (the Unix shell) is used to combine the tools to perform complex workflows.
Unix distinguishes itself from its predecessors as the first portable operating system: almost the entire operating system is written in the C programming language, which allows Unix to operate on numerous platforms.
Overview
Unix was originally meant to be a convenient platform for programmers developing software to be run on it and on other systems, rather than for non-programmers.
The system grew larger as the operating system started spreading in academic circles, and as users added their own tools to the system and shared them with colleagues.
At first, Unix was not designed to be portable or for multi-tasking.
Later, Unix gradually gained portability, multi-tasking and multi-user capabilities in a time-sharing configuration.
Unix systems are characterized by various concepts: the use of plain text for storing data; a hierarchical ; treating devices and certain types of inter-process communication (IPC) as files; and the use of a large number of software tools, small programs that can be strung together through a command-line interpreter using pipes, as opposed to using a single monolithic program that includes all of the same functionality.
These concepts are collectively known as the "Unix philosophy".
Brian Kernighan and Rob Pike summarize this in The Unix Programming Environment as "the idea that the power of a system comes more from the relationships among programs than from the programs themselves".
By the early 1980s, users began seeing Unix as a potential universal operating system, suitable for computers of all sizes.
The Unix environment and the client–server program model were essential elements in the development of the Internet and the reshaping of computing as centered in networks rather than in individual computers.
Both Unix and the C programming language were developed by AT&T and distributed to government and academic institutions, which led to both being ported to a wider variety of machine families than any other operating system.
The Unix operating system consists of many libraries and utilities along with the master control program, the kernel.
The kernel provides services to start and stop programs, handles the and other common "low-level" tasks that most programs share, and schedules access to avoid conflicts when programs try to access the same resource or device simultaneously.
To mediate such access, the kernel has special rights, reflected in the distinction of kernel space from user space, the latter being a priority realm where most application programs operate.
History
Main article: History of Unix
The origins of Unix date back to the mid-1960s when the Massachusetts Institute of Technology, Bell Labs, and General Electric were developing Multics, a time-sharing operating system for the GE-645 mainframe computer.
Multics featured several innovations, but also presented severe problems.
Frustrated by the size and complexity of Multics, but not by its goals, individual researchers at Bell Labs started withdrawing from the project.
The last to leave were Ken Thompson, Dennis Ritchie, Douglas McIlroy, and Joe Ossanna, who decided to reimplement their experiences in a new project of smaller scale.
This new operating system was initially without organizational backing, and also without a name.
The new operating system was a single-tasking system.
In 1970, the group coined the name Unics for Uniplexed Information and Computing Service as a pun on Multics, which stood for Multiplexed Information and Computer Services.
Brian Kernighan takes credit for the idea, but adds that "no one can remember" the origin of the final spelling Unix.
Dennis Ritchie, Doug McIlroy, and Peter G. Neumann also credit Kernighan.
The operating system was originally written in assembly language, but in 1973, Version 4 Unix was rewritten in C.
Version 4 Unix, however, still had many PDP-11 dependent codes, and was not suitable for porting.
The first port to another platform was made five years later (1978) for the Interdata 8/32.
Bell Labs produced several versions of Unix that are collectively referred to as "Research Unix".
In 1975, the first source license for UNIX was sold to Donald B. Gillies at the University of Illinois at Urbana–Champaign Department of Computer Science.
UIUC graduate student Greg Chesson, who had worked on the UNIX kernel at Bell Labs, was instrumental in negotiating the terms of the license.
During the late 1970s and early 1980s, the influence of Unix in academic circles led to large-scale adoption of Unix (BSD and System V) by commercial startups, which in turn led to Unix fragmenting into multiple, similar but often slightly mutually-incompatible systems including DYNIX, HP-UX, SunOS/Solaris, AIX, and Xenix.
In the late 1980s, AT&T Unix System Laboratories and Sun Microsystems developed System V Release 4 (SVR4), which was subsequently adopted by many commercial Unix vendors.
In the 1990s, Unix and Unix-like systems grew in popularity and became the operating system of choice for over 90% of the world's top 500 fastest supercomputers, as BSD and Linux distributions were developed through collaboration by a worldwide network of programmers.
In 2000, Apple released Darwin, also a Unix system, which became the core of the Mac OS X operating system, later renamed macOS.
Unix operating systems are widely used in modern servers, workstations, and mobile devices.
Standards
In the late 1980s, an open operating system standardization effort now known as POSIX provided a common baseline for all operating systems; IEEE based POSIX around the common structure of the major competing variants of the Unix system, publishing the first POSIX standard in 1988.
In the early 1990s, a separate but very similar effort was started by an industry consortium, the Common Open Software Environment (COSE) initiative, which eventually became the Single UNIX Specification (SUS) administered by The Open Group.
Starting in 1998, the Open Group and IEEE started the Austin Group, to provide a common definition of POSIX and the Single UNIX Specification, which, by 2008, had become the Open Group Base Specification.
In 1999, in an effort towards compatibility, several Unix system vendors agreed on SVR4's Executable and Linkable Format (ELF) as the standard for binary and object code files.
The common format allows substantial binary compatibility among different Unix systems operating on the same CPU architecture.
The was created to provide a reference directory layout for Unix-like operating systems; it has mainly been used in Linux.
Components
See also: List of Unix commands
Impact
See also: Unix-like
Branding
See also: List of Unix systems
In October 1993, Novell, the company that owned the rights to the Unix System V source at the time, transferred the trademarks of Unix to the X/Open Company (now The Open Group), and in 1995 sold the related business operations to Santa Cruz Operation (SCO).
Whether Novell also sold the copyrights to the actual software was the subject of a federal lawsuit in 2006, SCO v. Novell, which Novell won.
The case was appealed, but on August 30, 2011, the United States Court of Appeals for the Tenth Circuit affirmed the trial decisions, closing the case.
Unix vendor SCO Group Inc. accused Novell of slander of title.
The present owner of the trademark UNIX is The Open Group, an industry standards consortium.
Only systems fully compliant with and certified to the Single UNIX Specification qualify as "UNIX" (others are called "Unix-like").
By decree of The Open Group, the term "UNIX" refers more to a class of operating systems than to a specific implementation of an operating system; those operating systems which meet The Open Group's Single UNIX Specification should be able to bear the UNIX 98 or UNIX 03 trademarks today, after the operating system's vendor pays a substantial certification fee and annual trademark royalties to The Open Group.
Systems that have been licensed to use the UNIX trademark include AIX, EulerOS, HP-UX, Inspur K-UX, IRIX, macOS, Solaris, Tru64 UNIX (formerly "Digital UNIX", or OSF/1), and z/OS.
Notably, EulerOS and Inspur K-UX are Linux distributions certified as UNIX 03 compliant.
Sometimes a representation like Un*x, *NIX, or *N?X is used to indicate all operating systems similar to Unix.
This comes from the use of the asterisk (*) and the question mark characters as wildcard indicators in many utilities.
This notation is also used to describe other Unix-like systems that have not met the requirements for UNIX branding from the Open Group.
The Open Group requests that UNIX is always used as an adjective followed by a generic term such as system to help avoid the creation of a genericized trademark.
Unix was the original formatting, but the usage of UNIX remains widespread because it was once typeset in small caps (Unix).
According to Dennis Ritchie, when presenting the original Unix paper to the third Operating Systems Symposium of the American Association for Computing Machinery (ACM), "we had a new typesetter and troff had just been invented and we were intoxicated by being able to produce small caps".
Many of the operating system's predecessors and contemporaries used all-uppercase lettering, so many people wrote the name in upper case due to force of habit.
It is not an acronym.
Trademark names can be registered by different entities in different countries and trademark laws in some countries allow the same trademark name to be controlled by two different entities if each entity uses the trademark in easily distinguishable categories.
The result is that Unix has been used as a brand name for various products including bookshelves, ink pens, bottled glue, diapers, hair driers and food containers.
Several plural forms of Unix are used casually to refer to multiple brands of Unix and Unix-like systems.
Most common is the conventional Unixes, but Unices, treating Unix as a Latin noun of the third declension, is also popular.
The pseudo-Anglo-Saxon plural form Unixen is not common, although occasionally seen.
Sun Microsystems, developer of the Solaris variant, has asserted that the term Unix is itself plural, referencing its many implementations.
See also
- Comparison of operating systems and free and proprietary software
- List of operating systems, Unix systems, and Unix commands
- Market share of operating systems
- Timeline of operating systems
- Plan 9 from Bell Labs
- Unix time
- Year 2038 problem
Credits to the contents of this page go to the authors of the corresponding Wikipedia page: en.wikipedia.org/wiki/Unix.