Unix System V (pronounced: "System Five") is one of the first commercial versions of the

Unix Unix (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, and ot ...

operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may also in ...

. It was originally developed by

AT&T AT&T Inc. is an American multinational telecommunications holding company headquartered at Whitacre Tower in Downtown Dallas, Texas. It is the world's largest telecommunications company by revenue and the third largest provider of mobile tel ...

and first released in 1983. Four major versions of System V were released, numbered 1, 2, 3, and 4. System V Release 4 (SVR4) was commercially the most successful version, being the result of an effort, marketed as ''Unix System Unification'', which solicited the collaboration of the major Unix vendors. It was the source of several common commercial Unix features. System V is sometimes abbreviated to SysV. , the AT&T-derived Unix market is divided between four System V variants: IBM's

AIX Aix or AIX may refer to: Computing * AIX, a line of IBM computer operating systems *An Alternate Index, for a Virtual Storage Access Method Key Sequenced Data Set * Athens Internet Exchange, a European Internet exchange point Places Belgi ...

Hewlett Packard Enterprise The Hewlett Packard Enterprise Company (HPE) is an American multinational information technology company based in Spring, Texas, United States. HPE was founded on November 1, 2015, in Palo Alto, California, as part of the splitting of the H ...

HP-UX HP-UX (from "Hewlett Packard Unix") is Hewlett Packard Enterprise's proprietary implementation of the Unix operating system, based on Unix System V (initially System III) and first released in 1984. Current versions support HPE Integrity Ser ...

and

Oracle An oracle is a person or agency considered to provide wise and insightful counsel or prophetic predictions, most notably including precognition of the future, inspired by deities. As such, it is a form of divination. Description The word '' ...

Solaris Solaris may refer to: Arts and entertainment Literature, television and film * ''Solaris'' (novel), a 1961 science fiction novel by Stanisław Lem ** ''Solaris'' (1968 film), directed by Boris Nirenburg ** ''Solaris'' (1972 film), directed by ...

, plus the free-software

illumos Illumos (stylized as illumos) is a partly free and open-source Unix operating system. It is based on OpenSolaris, which was based on System V Release 4 (SVR4) and the Berkeley Software Distribution (BSD). Illumos comprises a kernel, device ...

forked from

OpenSolaris OpenSolaris () is a discontinued open-source computer operating system based on Solaris and created by Sun Microsystems. It was also, perhaps confusingly, the name of a project initiated by Sun to build a developer and user community around th ...

Overview

Introduction

System V was the successor to 1982's UNIX System III. While AT&T developed and sold hardware that ran System V, most customers ran a version from a reseller, based on AT&T's

reference implementation In the software development process, a reference implementation (or, less frequently, sample implementation or model implementation) is a program that implements all requirements from a corresponding specification. The reference implementation o ...

. A standards document called the

System V Interface Definition The System V Interface Definition (SVID) is a standard that describes the AT&T UNIX System V behavior, including that of system calls, C libraries, available programs and devices. While it was not the first attempt at a standardizations document ...

outlined the default features and behavior of implementations.

AT&T support

During the formative years of AT&T's computer business, the division went through several phases of System V software groups, beginning with the Unix Support Group (USG), followed by Unix System Development Laboratory (USDL), followed by AT&T Information Systems (ATTIS), and finally

Unix System Laboratories Unix System Laboratories (USL), sometimes written UNIX System Laboratories to follow relevant trademark guidelines of the time, was an American software laboratory and product development company that existed from 1989 through 1993. At first wh ...

(USL).

Rivalry with BSD

In the 1980s and early-1990s, UNIX System V and the

Berkeley Software Distribution The Berkeley Software Distribution or Berkeley Standard Distribution (BSD) is a discontinued operating system based on Research Unix, developed and distributed by the Computer Systems Research Group (CSRG) at the University of California, Berk ...

(BSD) were the two major versions of UNIX. Historically, BSD was also commonly called "BSD Unix" or "Berkeley Unix".

Eric S. Raymond Eric Steven Raymond (born December 4, 1957), often referred to as ESR, is an American software developer, open-source software advocate, and author of the 1997 essay and 1999 book ''The Cathedral and the Bazaar''. He wrote a guidebook for the ...

summarizes the longstanding relationship and rivalry between System V and BSD during the early period: While HP, IBM and others chose System V as the basis for their Unix offerings, other vendors such as

Sun Microsystems Sun Microsystems, Inc. (Sun for short) was an American technology company that sold computers, computer components, software, and information technology services and created the Java programming language, the Solaris operating system, ZFS, the ...

and DEC extended BSD. Throughout its development, though, System V was infused with features from BSD, while BSD variants such as DEC's

Ultrix Ultrix (officially all-caps ULTRIX) is the brand name of Digital Equipment Corporation's (DEC) discontinued native Unix operating systems for the PDP-11, VAX, MicroVAX and DECstations. History The initial development of Unix occurred on DEC equip ...

received System V features. AT&T and Sun Microsystems worked together to merge System V with BSD-based

SunOS SunOS is a Unix-branded operating system developed by Sun Microsystems for their workstation and server computer systems. The ''SunOS'' name is usually only used to refer to versions 1.0 to 4.1.4, which were based on BSD, while versions 5.0 and l ...

to produce

, one of the primary System V descendants still in use today. Since the early 1990s, due to standardization efforts such as

POSIX The Portable Operating System Interface (POSIX) is a family of standards specified by the IEEE Computer Society for maintaining compatibility between operating systems. POSIX defines both the system- and user-level application programming interf ...

and the success of

Linux Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, which ...

, the division between System V and BSD has become less important.

Releases

SVR1

System V, known inside Bell Labs as Unix 5.0, succeeded AT&T's previous commercial Unix called System III in January, 1983. Unix 4.0 was never released externally, which would have been designated as System IV. This first release of System V (called System V.0, System V Release 1, or SVR1) was developed by AT&T's UNIX Support Group (USG) and based on the Bell Labs internal USG UNIX 5.0. System V also included features such as the vi editor and

curses A curse (also called an imprecation, malediction, execration, malison, anathema, or commination) is any expressed wish that some form of adversity or misfortune will befall or attach to one or more persons, a place, or an object. In particular ...

from 4.1 BSD, developed at the

University of California, Berkeley The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California) is a public land-grant research university in Berkeley, California. Established in 1868 as the University of California, it is the state's first land-grant u ...

; it also improved performance by adding buffer and

inode The inode (index node) is a data structure in a Unix-style file system that describes a file-system object such as a file or a directory. Each inode stores the attributes and disk block locations of the object's data. File-system object attribute ...

caches. It also added support for

inter-process communication In computer science, inter-process communication or interprocess communication (IPC) refers specifically to the mechanisms an operating system provides to allow the processes to manage shared data. Typically, applications can use IPC, categori ...

using messages, semaphores, and

shared memory In computer science, shared memory is memory that may be simultaneously accessed by multiple programs with an intent to provide communication among them or avoid redundant copies. Shared memory is an efficient means of passing data between progr ...

, developed earlier for the Bell-internal CB UNIX. SVR1 ran on DEC

PDP-11 The PDP-11 is a series of 16-bit minicomputers sold by Digital Equipment Corporation (DEC) from 1970 into the 1990s, one of a set of products in the Programmed Data Processor (PDP) series. In total, around 600,000 PDP-11s of all models were sold, ...

and

VAX VAX (an acronym for Virtual Address eXtension) is a series of computers featuring a 32-bit instruction set architecture (ISA) and virtual memory that was developed and sold by Digital Equipment Corporation (DEC) in the late 20th century. The V ...

minicomputer A minicomputer, or colloquially mini, is a class of smaller general purpose computers that developed in the mid-1960s and sold at a much lower price than mainframe and mid-size computers from IBM and its direct competitors. In a 1970 survey, ...

SVR2

AT&T's UNIX Support Group (USG) transformed into the UNIX System Development Laboratory (USDL), which released System V Release 2 in 1984. SVR2 added

shell Shell may refer to: Architecture and design * Shell (structure), a thin structure ** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses ** Thin-shell structure Science Biology * Seashell, a hard o ...

functions and the

SVID The Svid (russian: Свидь) is a river in Kargopolsky District in the south-west of Arkhangelsk Oblast in Russia. It connects Lake Vozhe and Lake Lacha and belongs to the river basin of the Onega. It is long, and the area of its basin . Th ...

. SVR2.4 added

demand paging In computer operating systems, demand paging (as opposed to anticipatory paging) is a method of virtual memory management. In a system that uses demand paging, the operating system copies a disk page into physical memory only if an attempt is mad ...

copy-on-write Copy-on-write (COW), sometimes referred to as implicit sharing or shadowing, is a resource-management technique used in computer programming to efficiently implement a "duplicate" or "copy" operation on modifiable resources. If a resource is dupl ...

, and record and

file locking File locking is a mechanism that restricts access to a computer file, or to a region of a file, by allowing only one user or process to modify or delete it at a specific time and to prevent reading of the file while it's being modified or deleted ...

. The concept of the "porting base" was formalized, and the DEC

VAX-11/780 The VAX-11 is a discontinued family of 32-bit superminicomputers, running the Virtual Address eXtension (VAX) instruction set architecture (ISA), developed and manufactured by Digital Equipment Corporation (DEC). Development began in 1976. In ad ...

was chosen for this release. The "porting base" is the so-called original version of a release, from which all porting efforts for other machines emanate. Educational source licenses for SVR2 were offered by AT&T for US$800 for the first CPU, and $400 for each additional CPU. A commercial source license was offered for $43,000, with three months of support, and a $16,000 price per additional CPU.

Apple Computer Apple Inc. is an American multinational technology company headquartered in Cupertino, California, United States. Apple is the largest technology company by revenue (totaling in 2021) and, as of June 2022, is the world's biggest company b ...

A/UX A/UX is Apple Computer's Unix-based operating system for Macintosh computers, integrated with System 7's graphical interface and application compatibility. Launched in 1988 and discontinued in 1995 with version 3.1.1, it is Apple's first official ...

operating system was initially based on this release. SCO XENIX also used SVR2 as its basis. The first release of

was also an SVR2 derivative. Maurice J. Bach's book, ''The Design of the UNIX Operating System'', is the definitive description of the SVR2 kernel.

SVR3

AT&T's UNIX System Development Laboratory (USDL) was succeeded by AT&T Information Systems (ATTIS), which distributed UNIX System V, Release 3, in 1987. SVR3 included

STREAMS A stream is a continuous body of water, body of surface water Current (stream), flowing within the stream bed, bed and bank (geography), banks of a channel (geography), channel. Depending on its location or certain characteristics, a stream ...

, Remote File Sharing (RFS), the File System Switch (FSS)

virtual file system A virtual file system (VFS) or virtual filesystem switch is an abstract layer on top of a more concrete file system. The purpose of a VFS is to allow client applications to access different types of concrete file systems in a uniform way. A VFS ...

mechanism, a restricted form of

shared libraries In computer science, a library is a collection of non-volatile resources used by computer programs, often for software development. These may include configuration data, documentation, help data, message templates, pre-written code and su ...

, and the

Transport Layer Interface In computer networking, the Transport Layer Interface (TLI) was the networking API provided by AT&T UNIX System V Release 3 (SVR3) in 1987 and continued into Release 4 (SVR4). TLI was the System V counterpart to the BSD sockets programming inter ...

(TLI) network

API An application programming interface (API) is a way for two or more computer programs to communicate with each other. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how ...

. The final version was Release 3.2 in 1988, which added binary compatibility to

Xenix Xenix is a discontinued version of the Unix operating system for various microcomputer platforms, licensed by Microsoft from AT&T Corporation in the late 1970s. The Santa Cruz Operation (SCO) later acquired exclusive rights to the software, and ...

on Intel platforms (see

Intel Binary Compatibility Standard The Intel Binary Compatibility Standard (iBCS) is a standardized application binary interface (ABI) for Unix operating systems on Intel-386-compatible computers, published by AT&T, Intel and SCO in 1988, and updated in 1990. It extends source-leve ...

). User interface improvements included the "layers" windowing system for the DMD 5620 graphics terminal, and the SVR3.2 curses libraries that offered eight or more color pairs and other at this time important features (forms, panels, menus, etc.). The AT&T 3B2 became the official "porting base."

SCO UNIX Xinuos OpenServer, previously SCO UNIX and SCO Open Desktop (SCO ODT), is a closed source computer operating system developed by Santa Cruz Operation (SCO), later acquired by SCO Group, and now owned by Xinuos. Early versions of OpenServer were ...

was based upon SVR3.2, as was

ISC #REDIRECT ISC {{redirect category shell, {{R from other capitalisation{{R from ambiguous page ...

386/ix. Among the more obscure distributions of SVR3.2 for the 386 were ESIX 3.2 by

Everex Everex ("Ever for Excellence!") is a defunct American manufacturer of desktop and notebook personal computers. It was established in 1983 and headquartered in Fremont, California. The company was founded by Steve Hui, John Lee and Wayne Cheung ...

and "System V, Release 3.2" sold by Intel themselves; these two shipped "plain vanilla" AT&T's codebase. IBM's

AIX operating system AIX (Advanced Interactive eXecutive, pronounced , "ay-eye-ex") is a series of Proprietary software, proprietary Unix operating systems developed and sold by IBM for several of its computer platforms. Background Originally released for the ...

is an SVR3 derivative.

SVR4

System V Release 4.0 was announced on October 18, 1988 and was incorporated into a variety of commercial Unix products from early 1989 onwards. A joint project of AT&T Unix System Laboratories and

, it combined technology from: * SVR3 * 4.3BSD *

New features included: * From BSD: **

TCP/IP The Internet protocol suite, commonly known as TCP/IP, is a framework for organizing the set of communication protocols used in the Internet and similar computer networks according to functional criteria. The foundational protocols in the suit ...

support ** Sockets ** UFS ** Support for multiple groups **

C shell The C shell (csh or the improved version, tcsh) is a Unix shell created by Bill Joy while he was a graduate student at University of California, Berkeley in the late 1970s. It has been widely distributed, beginning with the 2BSD release of the ...

* From SunOS: **

Virtual file system A virtual file system (VFS) or virtual filesystem switch is an abstract layer on top of a more concrete file system. The purpose of a VFS is to allow client applications to access different types of concrete file systems in a uniform way. A VFS ...

interface (replacing File System Switch in System V Release 3) ** NFS ** New virtual memory system including support for

memory mapped In computer science, a memory map is a structure of data (which usually resides in memory itself) that indicates how memory is laid out. The term "memory map" can have different meanings in different contexts. *It is the fastest and most flexible ...

files ** Improved shared library system based on the SunOS 4.x model **

OpenWindows OpenWindows is a discontinued desktop environment for Sun Microsystems workstations which combined SunView, NeWS, and X Window System protocols. OpenWindows was included in later releases of the SunOS 4 and Solaris (operating system), Solaris ope ...

GUI The GUI ( "UI" by itself is still usually pronounced . or ), graphical user interface, is a form of user interface that allows users to interact with electronic devices through graphical icons and audio indicator such as primary notation, inste ...

environment ** External Data Representation (XDR) and ONC RPC * From Xenix: ** x86

device driver In computing, a device driver is a computer program that operates or controls a particular type of device that is attached to a computer or automaton. A driver provides a software interface to hardware devices, enabling operating systems and ot ...

s ** Binary compatibility with Xenix (in the x86 version of System V) *

KornShell KornShell (ksh) is a Unix shell which was developed by David Korn at Bell Labs in the early 1980s and announced at USENIX on July 14, 1983. The initial development was based on Bourne shell source code. Other early contributors were Bell ...

* ANSI X3J11 C compatibility * Multi-National Language Support (MNLS) * Better

internationalization In economics, internationalization or internationalisation is the process of increasing involvement of enterprises in international markets, although there is no agreed definition of internationalization. Internationalization is a crucial strateg ...

support * An

application binary interface In computer software, an application binary interface (ABI) is an interface between two binary program modules. Often, one of these modules is a library or operating system facility, and the other is a program that is being run by a user. An ' ...

(ABI) based on

Executable and Linkable Format In computing, the Executable and Linkable FormatTool Interface Standard (TIS) Portable Formats SpecificationVersion 1.1'' (October 1993) (ELF, formerly named Extensible Linking Format), is a common standard file format for executable files, obj ...

(ELF) * Support for standards such as

and

X/Open X/Open group (also known as the Open Group for Unix Systems and incorporated in 1987 as X/Open Company, Ltd.) was a consortium founded by several European UNIX systems manufacturers in 1984 to identify and promote open standards in the field of info ...

Many companies licensed SVR4 and bundled it with computer systems such as

workstation A workstation is a special computer designed for technical or scientific applications. Intended primarily to be used by a single user, they are commonly connected to a local area network and run multi-user operating systems. The term ''workstat ...

s and

network server In computing, a server is a piece of computer hardware or software (computer program) that provides functionality for other programs or devices, called " clients". This architecture is called the client–server model. Servers can provide variou ...

s. SVR4 systems vendors included

Atari Atari () is a brand name that has been owned by several entities since its inception in 1972. It is currently owned by French publisher Atari SA through a subsidiary named Atari Interactive. The original Atari, Inc. (1972–1992), Atari, Inc., ...

(

Atari System V The Atari TT030 is a member of the Atari ST family, released in 1990. It was originally intended to be a high-end Unix workstation, but Atari took two years to release a port of Unix SVR4 for the TT, which prevented the TT from ever being serio ...

Commodore Commodore may refer to: Ranks * Commodore (rank), a naval rank ** Commodore (Royal Navy), in the United Kingdom ** Commodore (United States) ** Commodore (Canada) ** Commodore (Finland) ** Commodore (Germany) or ''Kommodore'' * Air commodore ...

( Amiga Unix),

Data General Data General Corporation was one of the first minicomputer firms of the late 1960s. Three of the four founders were former employees of Digital Equipment Corporation (DEC). Their first product, 1969's Data General Nova, was a 16-bit minicomputer ...

(

DG/UX DG/UX is a discontinued Unix operating system developed by Data General for its Eclipse MV minicomputer line, and later the AViiON workstation and server line (both Motorola 88000 and Intel IA-32-based variants). Overview DG/UX 1.00, released in ...

Fujitsu is a Japanese multinational information and communications technology equipment and services corporation, established in 1935 and headquartered in Tokyo. Fujitsu is the world's sixth-largest IT services provider by annual revenue, and the la ...

( UXP/DS),

Hitachi () is a Japanese multinational corporation, multinational Conglomerate (company), conglomerate corporation headquartered in Chiyoda, Tokyo, Japan. It is the parent company of the Hitachi Group (''Hitachi Gurūpu'') and had formed part of the Ni ...

(HI-UX), Hewlett-Packard (HP-UX), NCR ( Unix/NS),

NEC is a Japanese multinational information technology and electronics corporation, headquartered in Minato, Tokyo. The company was known as the Nippon Electric Company, Limited, before rebranding in 1983 as NEC. It provides IT and network soluti ...

(

EWS-UX EWS-UX is a Unix operating system used by NEC Corporation for its EWS-4800 line of engineering workstations. EWS-UX is based largely on versions of Unix System V supplemented with BSD software. It was widely used from the late 1980s to around 2 ...

, UP-UX, UX/4800,

SUPER-UX SUPER-UX is a version of the Unix operating system from NEC that is used on its SX series of supercomputers. History The initial version of SUPER-UX was based on UNIX System V version 3.1 with features from BSD 4.3. The version for the NEC SX- ...

OKI Oki or Ōki may refer to: Places *Oki District, Shimane, a district in Shimane Prefecture, Japan *Oki Islands, an archipelago in the Sea of Japan *Oki Province, a former province of Japan *Ōki, Fukuoka, a town in southern Japan *Oki Airport, the ...

(OKI System V),

Pyramid Technology Pyramid Technology Corporation was a computer company that produced a number of RISC-based minicomputers at the upper end of the performance range. It was based in the San Francisco Bay Area of California They also became the second company to s ...

( DC/OSx),

SGI SGI may refer to: Companies *Saskatchewan Government Insurance *Scientific Games International, a gambling company *Silicon Graphics, Inc., a former manufacturer of high-performance computing products *Silicon Graphics International, formerly Rac ...

(

IRIX IRIX ( ) is a discontinued operating system developed by Silicon Graphics (SGI) to run on the company's proprietary MIPS workstations and servers. It is based on UNIX System V with BSD extensions. In IRIX, SGI originated the XFS file system and ...

Siemens Siemens AG ( ) is a German multinational conglomerate corporation and the largest industrial manufacturing company in Europe headquartered in Munich with branch offices abroad. The principal divisions of the corporation are ''Industry'', '' ...

(

SINIX Sinix may refer to: * SINIX, computer operating system * Şınıx, Azerbaijan {{dab 1983 software