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UNIX System V

unix system v, unix system v release 4
UNIX System V pronounced: "System Five" is one of the first commercial versions of the Unix operating system It was originally developed by AT&T and first released in 1983 Four major versions of System V were released, numbered 1, 2, 3, and 4 System V Release 4, or 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

As of 2012update, the Unix market is divided between three System V variants: IBM's AIX, Hewlett-Packard's HP-UX and Oracle's Solaris1


  • 1 Overview
    • 11 Introduction
    • 12 AT&T support
    • 13 Rivalry with BSD
  • 2 Releases
    • 21 SVR1
    • 22 SVR2
    • 23 SVR3
    • 24 SVR4
    • 25 SVR42 / UnixWare
    • 26 SVR5 / UnixWare 7
    • 27 SVR6 canceled
  • 3 Market position
    • 31 Availability during 90's on x86 platforms
    • 32 Project Monterey
    • 33 System V and the Unix market
    • 34 OpenSolaris and illumos distributions
    • 35 System V compatibility
  • 4 References
  • 5 External links



Unix history tree AT&T System V license plate

System V was the successor to 1982's UNIX System III While AT&T sold their own hardware that ran System V, most customers instead ran a version from a reseller, based on AT&T's reference implementation A standards document called the System V Interface Definition outlined the default features and behavior of implementations

AT&T supportedit

During its formative years, AT&T 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 USL

Rivalry with BSDedit

Main article: Unix wars

In the 1980s and early-1990s, System V was considered one of the two major versions of UNIX, the other being the Berkeley Software Distribution BSD Historically, BSD was also commonly called "BSD Unix" or "Berkeley Unix"2 Eric S Raymond summarizes the longstanding relationship and rivalry between System V and BSD during the early period:3

In fact, for years after divestiture the Unix community was preoccupied with the first phase of the Unix wars – an internal dispute, the rivalry between System V Unix and BSD Unix The dispute had several levels, some technical sockets vs streams, BSD tty vs System V termio and some cultural The divide was roughly between longhairs and shorthairs; programmers and technical people tended to line up with Berkeley and BSD, more business-oriented types with AT&T and System V

While HP, IBM and others chose System V as the basis for their Unix offerings, other vendors such as Sun Microsystems and DEC extended BSD Throughout its development, though, System V was infused with features from BSD, while BSD variants such as DEC's Ultrix received System V features Since the early 1990s, due to standardization efforts such as POSIX and the commercial success of Linux, the division between System V and BSD has become less important


DMD 5620 Blit terminal connected to a SVR3 host, showing the Layers interface


System V, known inside Bell Labs as Unix 50, succeeded AT&T's previous commercial Unix called System III in January, 19834 There was never an external release of Unix 40, which would have been System IV567 This first release of System V called System V0, 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 50

System V also included features such as the vi editor and curses from 41 BSD, developed at the University of California, Berkeley; it also improved performance by adding buffer and inode caches It also added support for inter-process communication using messages, semaphores, and shared memory, developed earlier for the Bell-internal CB UNIX8

SVR1 ran on DEC PDP-11 and VAX minicomputers


The DEC VAX-11/780 was the porting base for SVR2

System V Release 2 was released in April, 19844 It added shell functions and the SVID New kernel features included record and file locking, demand paging, and copy on write9

The concept of the "porting base" was formalized, and the DEC VAX-11/780 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 CPU10

Apple Computer's A/UX operating system was initially based on this release Xenix 50 also used SVR2 as its basis The first release of HP-UX was also an SVR2 derivative11:33

Maurice J Bach's book, The Design of the UNIX Operating System, is the definitive description of the SVR2 kernel12


The AT&T 3B2 line of minicomputers was the porting base for SVR3

System V Release 3 was released in 1986413 It included STREAMS, the Remote File System RFS, the File System Switch FSS virtual file system mechanism, a restricted form of shared libraries, and the Transport Layer Interface TLI network API The final version was Release 32 in 1988, which added binary compatibility to Xenix on Intel platforms see Intel Binary Compatibility Standard

User interface improvements included the "layers" windowing system for the DMD 5620 graphics terminal, and the SVR32 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 was based upon SVR32, as was ISC 386/ix Among the more obscure distributions of SVR32 for the 386 were ESIX 32 by Everex and "System V, Release 32" sold by Intel themselves; these two shipped "plain vanilla" AT&T's codebase14

IBM's AIX operating system is an SVR3 derivative


HP 9000 C110 running HP-UX in console mode OpenWindows, an early desktop environment for SVR4 HP 9000 735 running HP-UX with the Common Desktop Environment CDE A modern GNOME-based OpenSolaris desktop Sun Ultra 20 with Solaris 10

System V Release 40 was announced on October 18, 198815 and was incorporated into a variety of commercial Unix products from early 1989 onwards4 A joint project of AT&T Unix System Laboratories and Sun Microsystems, it combined technology from:

  • SVR3
  • 43BSD
  • Xenix
  • SunOS

New features included:

  • From BSD: TCP/IP support, sockets, UFS, support for multiple groups, C shell
  • From SunOS: the virtual file system interface replacing the File System Switch in System V release 3, NFS, new virtual memory system including support for memory mapped files, an improved shared library system based on the SunOS 4x model,16 the OpenWindows GUI environment, External Data Representation XDR and ONC RPC
  • From Xenix: x86 device drivers, binary compatibility with Xenix in the x86 version of System V
  • Korn shell
  • ANSI X3J11 C compatibility
  • Multi-National Language Support MNLS
  • Better internationalization support
  • An application binary interface ABI based on Executable and Linkable Format ELF
  • Support for standards such as POSIX and X/Open

Many companies licensed SVR4 and bundled it with computer systems such as workstations and network servers SVR4 systems vendors included Atari Atari System V, Commodore Amiga Unix, Data General DG/UX, Fujitsu UXP/DS, Hitachi HI-UX, Hewlett-Packard HP-UX, NCR Unix/NS, NEC EWS-UX, UP-UX, UX/4800, OKI OKI System V, Pyramid Technology DC/OSx, SGI IRIX, Siemens SINIX, Sony NEWS-OS, Sumitomo Electric Industries SEIUX, and Sun Microsystems Solaris with illumos in 2010's as the only open-source platform

Software porting houses also sold enhanced and supported Intel x86 versions SVR4 software vendors included Dell Dell UNIX,17 Everex ESIX, Micro Station Technology SVR4, Microport SVR4, and UHC SVR418

The primary platforms for SVR4 were Intel x86 and SPARC; the SPARC version, called Solaris 2 or, internally, SunOS 5x, was developed by Sun The relationship between Sun and AT&T was terminated after the release of SVR4, meaning that later versions of Solaris did not inherit features of later SVR4x releases Sun would in 2005 release most of the source code for Solaris 10 SunOS 510 as the open-source OpenSolaris project, creating, with its forks, the only open-source albeit heavily modified System V implementation available After Oracle took over Sun, Solaris was forked into proprietary release, but illumos as the continuation project is being developed in open-source

A consortium of Intel-based resellers including Unisys, ICL, NCR Corporation, and Olivetti developed SVR40MP with multiprocessing capability allowing system calls to be processed from any processor, but interrupt servicing only from a "master" processor19

Release 41 ES Enhanced Security added security features required for Orange Book B2 compliance and Access Control Lists and support for dynamic loading of kernel modules2021

SVR42 / UnixWareedit

In 1992, AT&T USL engaged in a joint venture with Novell, called Univel That year saw the release System V42 as Univel UnixWare, featuring the VERITAS File System Other vendors included UHC and Consensys Release 42MP, completed late 1993, added support for multiprocessing and it was released as UnixWare 2 in 199522

Eric S Raymond warned prospective buyers about SVR42 versions, as they often did not include on-line man pages In his 1994 buyers guide, he attributes this change in policy to Unix System Laboratories23

SVR5 / UnixWare 7edit

The Santa Cruz Operation SCO, owners of Xenix, eventually acquired the UnixWare trademark and the distribution rights to the System V Release 42 codebase from Novell, while other vendors Sun, IBM, HP continued to use and extend System V Release 4 Novell transferred ownership of the Unix trademark to The Open Group Any operating system that meets the Single Unix Specification SUS, effectively a successor to the System V Interface Definition, may be granted Unix rights The SUS is met by Apple's Mac OS X, a BSD derivative, as well as several other operating systems not derived from either BSD or System V

System V Release 5 was developed in 1997 by the Santa Cruz Operation SCO as a merger of SCO OpenServer an SVR3-derivative and UnixWare, with a focus on large-scale servers11:23,32 It was released as SCO UnixWare 7 SCO's successor, The SCO Group, also based SCO OpenServer 6 on SVR5, but the codebase is not used by any other major developer or reseller

SVR6 cancelededit

System V Release 6 was announced by SCO to be released by the end of 2004, but was apparently cancelled24 It was supposed to support 64-bit systems25 See also: Smallfoot

Market positionedit

The GNOME desktop on OpenSolaris, an SVR4 derivative

Availability during 90's on x86 platformsedit

In the 1980s and 1990s, a variety of SVR4 versions of Unix were available commercially for the x86 PC platform However, the market for commercial Unix on PCs declined after Linux and BSD became widely available In late 1994, Eric S Raymond discontinued his PC-clone UNIX Software Buyer's Guide on USENET, stating, "The reason I am dropping this is that I run Linux now, and I no longer find the SVr4 market interesting or significant"26

In 1998, a confidential memo at Microsoft stated, "Linux is on track to eventually own the x86 UNIX market," and further predicted, "I believe that Linux – moreso than NT – will be the biggest threat to SCO in the near future"27

An InfoWorld article from 2001 characterized SCO UnixWare as having a "bleak outlook" due to being "trounced" in the market by Linux and Solaris, and IDC predicted that SCO would "continue to see a shrinking share of the market"28

Project Montereyedit

Project Monterey was started in 1998 to combine major features of existing commercial Unix platforms, as a joint project of Compaq, IBM, Intel, SCO, and Sequent Computer Systems The target platform was meant to be Intel's new IA-64 architecture and Itanium line of processors However, the project was abruptly canceled in 2001 after little progress29

System V and the Unix marketedit

By 2001, several major Unix variants such as SCO UnixWare, Compaq Tru64 UNIX, and SGI IRIX were all in decline28 The three major Unix versions doing well in the market were IBM AIX, Hewlett-Packard's HP-UX, and Sun Solaris28

In 2006, when SGI declared bankruptcy, analysts questioned whether Linux would replace proprietary Unix altogether In a 2006 article written for Computerworld by Mark Hall, the economics of Linux were cited as a major factor driving the migration from Unix to Linux:30

Linux's success in high-end, scientific and technical computing, like Unix's before it, preceded its success in your data center Once Linux proved itself by executing the most complex calculations possible, IT managers quickly grasped that it could easily serve Web pages and run payroll Naturally, it helps to be lucky: Free, downloadable Linux's star began to rise during one of the longest downturns in IT history With companies doing more with less, one thing they could dump was Unix

The article also cites trends in high-performance computing applications as evidence of a dramatic shift from Unix to Linux:30

A look at the Top500 list of supercomputers tells the tale best In 1998, Unix machines from Sun and SGI combined for 46% of the 500 fastest computers in the world Linux accounted for one 02% In 2005, Sun had 08% — or four systems — and SGI had 36%, while 72% of the Top500 ran Linux

In a November 2015 survey of the top 500 supercomputers, Unix was used by only 12% all running IBM AIX, while Linux was used by 988%31

System V derivatives continued to be deployed on some proprietary server platforms The principal variants of System V that remain in commercial use are AIX IBM, Solaris Oracle, and HP-UX HP According to a study done by IDC, in 2012 the worldwide Unix market was divided between IBM 56%, Oracle 192%, and HP 186% No other commercial Unix vendor had more than 2% of the market1 Industry analysts generally characterize proprietary Unix as having entered a period of slow but permanent decline32

OpenSolaris and illumos distributionsedit

OpenSolaris and its derivatives are the only SVR4 descendants that are open-source software Core system software continues to be developed as illumos used in illumos distributions such as SmartOS, OpenIndiana and others

System V compatibilityedit

The System V interprocess communication mechanisms are available in Unix-like operating systems not derived from System V; in particular, in Linux833 a reimplementation of Unix as well as the BSD derivative FreeBSD34 POSIX 2008 specifies a replacement for these interfaces8

FreeBSD maintains a binary compatibility layer for the COFF format, which allows FreeBSD to execute binaries compiled for some SVR32 derivatives such as SCO UNIX and Interactive UNIX35 Modern System V, Linux, and BSD platforms use the ELF file format for natively compiled binaries


  1. ^ a b "The Last Days of Unix" Network World 19 August 2013 Retrieved 26 Jun 2014 
  2. ^ Garfinkel, Simson Spafford, Gene Schwartz, Alan Practical UNIX and Internet Security 2003 pp 15-20
  3. ^ Raymond, Eric S The Art of Unix Programming 2003 p 38
  4. ^ a b c d Lévénez, Éric "Unix History Unix Timeline" Archived from the original on 2010-12-29 Retrieved 2010-12-29 
  5. ^ Overview of the XENIX 286 Operating System PDF Intel Corporation November 1984 p 110 There was no System IV 
  6. ^ Dale Dejager 1984-01-16 "UNIX History" Newsgroup: netunix 
  7. ^ Tanenbaum, Andrew S 2001 Modern Operating Systems 2nd ed Upper Saddle River, NJ: Prentice Hall p 675 ISBN 0-13-031358-0 Whatever happened to System IV is one of the great unsolved mysteries of computer science 
  8. ^ a b c Kerrisk, Michael 2010 The Linux Programming Interface No Starch Press p 921 
  9. ^ Goodheart, Berny; Cox, James 1994, The Magic Garden Explained, Prentice Hall, p 11, ISBN 0-13-098138-9 
  10. ^ "UNIX System V and add on applications prices" PDF AT&T International 24 February 1983 Retrieved 27 April 2014 
  11. ^ a b Kenneth H Rosen 1999 UNIX: The Complete Reference McGraw-Hill Professional 
  12. ^ Bach, Maurice 1986, The Design of the UNIX Operating System, Prentice Hall, ISBN 0-13-201799-7 
  13. ^ Rargo, Stephan A April 10, 1993, UNIX System V Network Programming, Addison-Wesley Professional, ISBN 978-0-201-56318-4 
  14. ^ Jeff Tye 10 July 1989 Other OSs That Run Unix on a 386 InfoWorld p 62 ISSN 0199-6649 
  15. ^ "SEVERAL MAJOR COMPUTER AND SOFTWARE COMPANIES ANNOUNCE STRATEGIC COMMITMENT TO AT&T'S UNIX SYSTEM V, RELEASE 40" Press release Amdahl, Control Data Corporation, et al October 18, 1988 Retrieved 2007-01-01 
  16. ^ John R Levine 1999 Linkers and Loaders Morgan–Kauffman 
  17. ^ Technologists notes — A brief history of Dell UNIX, 10 January 2008, retrieved 2009-02-18 
  18. ^ Eric S Raymond, A buyer's guide to UNIX versions for PC-clone hardware, posted to Usenet November 16, 1994
  19. ^ Unix Internatl and USL release early version of SVR4 multiprocessing software, 17 June 1991, retrieved 2009-04-22 
  20. ^ William Fellows 13 August 1992 "Unix International reviews the Unix System V4 story so far" Computer Business Review Retrieved 2008-10-31 
  21. ^ Bishop, Matt December 2, 2002, Computer Security, Addison Wesley, p 505, ISBN 0-201-44099-7 
  22. ^ UnixWare 2 Product Announcement Questions& Answers, 1995 
  23. ^ Eric S Raymond 16 November 1994 "PC-clone UNIX Software Buyer's Guide" Retrieved 6 May 2014 
  24. ^ SCO updates Unix, OpenServer product plans InfoWorld, August 19, 2003
  25. ^ SCO UNIX Roadmap at Archiveis
  26. ^ Eric S Raymond 16 November 1994 "PC-clone UNIX Software Buyer's Guide" Retrieved 3 February 2014 
  27. ^ Vinod Valloppillil 11 August 1998 "Open Source Software: A New Development Methodology" Retrieved 3 February 2014 
  28. ^ a b c Tom Yager 19 November 2001 "Vital Signs for Unix" Computerworld Retrieved 5 June 2015 
  29. ^ Raymond, Eric S The Art of Unix Programming 2003 p 43
  30. ^ a b Mark Hall 15 May 2006, The End of Unix, retrieved 5 June 2015 
  31. ^ "TOP500 Supercomputer Sites - List Statistics" Retrieved 28 January 2016 
  32. ^ Patrick Thibodeau 12 December 2013 "As Unix fades away from data centers, it's unclear what's next" Retrieved 6 June 2015 
  33. ^ svipc7 – Linux Programmer's Manual – Overview, Conventions and Miscellanea
  34. ^ msgsnd2 – FreeBSD System Calls Manual
  35. ^ Lehey, Greg The Complete FreeBSD: Documentation from the Source 2003 pp 164-165

External linksedit

  • PC-clone UNIX Software Buyer's Guide by Eric S Raymond posted to USENET in 1994
  • Unix FAQ - history
  • A Unix History Diagram - The original and continuously updated version of the Unix history, as published by O'Reilly

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