|Ken Thompson , Dennis Ritchie , Douglas McIlroy, and others. a. at Bell Laboratories
|until 1981: none (free)
from 1981: proprietary ( AT&T , Novell )
from 2005 free ( CDDL ) Sun Microsystems
|UNIX (no ancestors)
Unix ( English [ juːnɪks ]) is a multi-user - the operating system for computers . It was developed by Bell Laboratories in August 1969 to support software development. Today Unix generally stands for operating systems that either have their origin in the Unix system from AT&T (originally Bell Laboratories) or implement its concepts. Together with its variants and further developments - often under other names better known to the public - it is one of the most widespread and influential operating systems in computer history. Until the 1990s, Unix was mainly used in specialized application areas such as workstations and servers , especially at universities and research institutions . Today's mass application in almost all areas of computer technology did not begin until around the 2000s.
The main developers of Unix were Ken Thompson and Dennis Ritchie , who first wrote it in assembly language and then in the C programming language developed by Ritchie . With Unix some relevant concepts were information technology first introduced, such as the hierarchical , tree-like structured file system with file structure. The early developers also defined a set of concepts and rules for software development that came to be known as the Unix philosophy . Until the 1980s, Unix was further developed as an open source operating system, primarily at US universities, and had a considerable influence on the hacker culture .
In the 1980s it was commercialized by AT&T, which led to a number of independent further developments and spin-offs and resulted in the so-called " Unix Wars " between different systems and manufacturers. The various operating systems based on or derived from Unix are taken together the most widely used operating systems for computers and for many types of electronic devices that contain a computer. The range of uses extends from mobile devices such as smartphones to personal computers and web servers to the largest supercomputers . Furthermore, the Unix-like Linux in particular is also used as an embedded system in industrial measuring and control devices , in medical technology devices , entertainment electronics and electronically controlled objects such as household appliances , motor vehicles or WLAN routers . The most widespread commercial, proprietary Unix variant today is macOS from Apple or its mobile variant iOS , the most widespread Unix-like open source variant is Linux or the Android derived from it .
Typology of the variants
Since the term “UNIX” in capital letters or “U NIX ” in small caps is a registered trademark of the Open Group , only certified systems are allowed to use the name UNIX. Accordingly, “UNIX” is usually used in the specialist literature to identify certified systems, while “Unix” is used to denote all Unix-like systems.
Unix-like systems in UNIX derivatives and Unix-like systems are classified. The UNIX derivatives include z. B. the BSD systems, HP-UX (Hewlett-Packard), DG / UX (Data General), AIX (IBM), IRIX (Silicon Graphics), UnixWare ( SCO Group ), 386 / ix (first Eastman Kodak , later SunSoft ), Solaris (Oracle), AMIX (Commodore) and macOS (Apple).
Other systems such as Linux or QNX , however, are not based on the original Unix source code , but were developed separately. They are referred to as “Unix systems” because they also implement part of the operating system functions ( POSIX ) that are standardized for Unix . BSD is a special case , which was originally based on Bell Labs source code, but has been completely rewritten by a loose community of programmers since the mid-1990s, so that it is now free of the original, proprietary program code.
Originally mainly used in universities, it was mainly used in professional workstations and on servers from the 1980s and 1990s . With Linux, macOS (until 2016 OS X and originally, until 2012, Mac OS X) and as the basis of several common operating systems for mobile devices , it also reached the mass market for private users from around the 2000s. The two most widespread operating systems for smartphones and tablet computers , iOS and Android , are based on BSD (iOS) and Linux (Android) on Unix-like operating systems. In September 2013 alone, over a billion Android devices were activated worldwide. For 2013, the market research company Gartner Group forecast that for the first time more Android-based systems than PCs with Windows would be sold. In addition, Linux gained greater importance as an open-source operating system for corporate applications and as an embedded system for electronic devices such as WLAN routers or entertainment electronics devices .
Since Unix-like Linux can be adapted and optimized very flexibly, it has also spread widely in data centers in which specially adapted versions run on mainframes , computer clusters (see Beowulf ) or supercomputers . The systems listed in the TOP500 list of the fastest computer systems are currently (as of November 2018) operated exclusively under Linux. Windows' biggest competitor in the desktop area does not play a role in the high-performance computers.
System functions and commands from Unix could originally only be called up by the user via keyboard input via a command line , although the concept of the graphical user interface with windows and mouse operation was already known at the time of its creation. For this reason there is no standardized graphical Unix user interface, but a number of later developed variants such as twm or CDE , Gnome and KDE , many of which are based on the X Window System . For many users such as professional programmers and system administrators , the command line is still the preferred operator interface. Unix descendants for mobile devices such as smartphones and tablet computers , including Apple iOS and Android, use their own operating concepts. Access to the command line and file system is usually completely (iOS) or partially (Android) blocked.
Structure and features
The Unix kernel only has access to the hardware via device drivers and manages processes . In addition, it provides the file system and, in modern versions, the network protocol stack . System calls from processes are used to start ( fork , exec system calls ) and control other processes as well as to communicate with the file system. Access to the device driver is mapped as access to "special files" (device files) in the file system. As a result, files and devices are standardized as far as possible from the point of view of the processes and thus of the application programs (system calls open , read , write , etc.).
A large number of programs including a C development system and a typesetting program ( troff ) complete the system.
The file system is organized as a hierarchical directory with any number of subdirectories. The concept that is considered the standard today was revolutionary at the time. The root directory of this hierarchy is the "/" directory. One of the basic concepts of UNIX is to also map floppy and CD drives, other hard disks on your own or third-party computers, terminals, tape devices and other special files in the file system (device files, files that appear to contain the data of a drive and when reading " output ”) instead of creating separate directory hierarchies under so-called“ drive letters ” like some other operating systems (including VMS , MS-DOS , Windows ). “ Everything is a file ” is a basic principle of Unix. This generalized file term belongs to the essence of UNIX and enables a simple, uniform interface for the most varied of applications. In some UNIX derivatives even processes and their properties are mapped to files ( proc file system ).
The command interpreter, the shell - under Unix a normal process without privileges - as well as numerous standard commands allow the user a simple input / output redirection in files , and communication between processes via pipes .
A large collection of simple commands, the UNIX toolbox , can thus be combined with the help of the programming options of the command interpreter and take on complicated tasks. The ability to combine the mostly standardized tools often avoids having to write specialized programs for "one-off tasks" or simple administration work, as is often the case in other operating systems.
Among the important features of a typical Unix system include: high stability, multi-user , multi-tasking (now also multithreading ), memory protection and virtual memory (first implemented in the BSD line), IP - network support (also first in the BSD line), excellent scripting features , a full shell and a variety of tools (the Unix commands ) and daemons . Operating systems of Unix workstations and UNIX derivatives usually contain a graphical user interface based on X11 .
Unix is historically closely linked to the C programming language - both helped each other to breakthrough, and so C is still the preferred language among Unix systems today.
The name Unix
The system was originally named Unics by an employee , an acronym for Uniplexed Information and Computing Service and an allusion to Multics . It is unclear how the shorter notation of the end as a single letter "x" later came about.
Whether the spelling is Unix or UNIX instead has been debated for a long time. Historically, the spelling Unix is the older, the spelling UNIX only appeared later - for purely aesthetic reasons. Today they have different meanings: In the specialist literature, Unix is usually used as a term for Unix -like systems , while UNIX is used to identify certified systems. When plural is the German "Unixes" and the third declension of Latin ajar "Unixes" in use in English "Unixes" and also "Unixes" .
Ken Thompson created the first version of Unix in assembly language in 1969 on the DEC PDP-7 as an alternative to Multics . As one of the first programs for the new kernel, Thompson wrote the game Space Travel together with Dennis Ritchie to sound out which interfaces they need. 1972–1974 the operating system was completely re-implemented in C and distributed free of charge to various universities together with a C compiler (AT&T, as a state-controlled monopoly in the telecommunications industry, was not allowed to sell software). a. at the University of California at Berkeley , the BSD -line of Unix. It was not until the late 1970s that AT&T tried to market Unix profitably, from which the System V line from Unix emerged. In the 1980s, Unix became the dominant operating system at universities, and there was a plethora of different UNIX derivatives, all of which descended in some form from the two main lines BSD or System-V . In response, there was a call for standardization.
Each manufacturer changed and expanded the system according to their own ideas in the 1980s. Versions with different capabilities, commands, command options and program libraries developed. Around 1985 the IEEE began to standardize the interfaces for application programs. This led to the development of the IEEE 1003 standard, called POSIX at the suggestion of Richard Stallman . Today it consists of around fifteen documents that deal with all aspects of Unix systems such as the command line interpreter (POSIX defines its own shell, the POSIX shell , which is, however, identical to the Kornshell except for details ), the Unix commands and their Deal with options, input / output and other things.
The IEEE prices for POSIX documentation are very high; publication is prohibited by copyright. In recent times, there has therefore been a tendency towards the Open Group's single UNIX specification . This standard is open, freely available on the Internet, and accepts suggestions from anyone.
UNIX derivatives and Unix-like operating systems
Until Unix V7 appeared in 1979, the Unix source code was distributed to universities in return for reimbursement of the cost of copying and data storage. Unix thus had the character of a free, portable operating system. The code was used in lectures and publications and could be changed and supplemented according to your own ideas. The University of Berkeley developed its own distribution with significant extensions, the Berkeley Software Distribution (BSD).
In the early 1980s, AT&T decided to market Unix; the AT&T source code could no longer be made publicly accessible from this point in time. Use in lectures etc. was also excluded. For systems based on BSD - since part of the code came from AT&T - high license fees were charged.
Many companies licensed the UNIX source code and brought their own variants onto the market, even Microsoft had a Unix on offer with Xenix for some time. Siemens adapted Xenix in 1984 to a German Unix called Sinix .
The unavailability of the source code caused Richard Stallman to launch the GNU project (" G NU’s N ot U nix ") in 1983 . The aim of the project was to create a free Unix-compatible operating system. By 1990 the project had developed all essential parts - including the GNU C compiler (gcc) - with the exception of the kernel.
Minix and Linux
In 1987 the Minix teaching system appeared , developed by Andrew S. Tanenbaum at the Free University of Amsterdam . Minix was a Unix clone with a microkernel , C compiler , text editor and many commands that, as a relatively undemanding system, ran on weak PC hardware. The source code was part of the scope of delivery. While it was commercial and proprietary, it came at a very low price. As previously Unix, this system served many as a starting point for their own experiments.
In 1991 the student Linus Torvalds worked on a terminal emulator with which he wanted to access a university computer. Over time, he built in file system access and many other useful features. He soon realized that he was programming more than one terminal emulator. He published the source code in the newsgroup comp.os.minix as a Minix-inspired kernel that should run on an Intel 386 PC. First his project should be called Freax . Since the university administrator assigned him “Linux” as the login for his FTP repository, he named the project after it. In the source code of version 0.01 of Linux the name Freax occurs ("Makefile for the FREAX kernel").
Free BSD derivatives
In 1992, Bill and Lynne Jolitz published 386BSD, another free system for 80386 processors. It consisted of a patch for the non-AT&T free parts of the BSD distribution and formed another free, very advanced operating system for Intel processors.
In 1994 Berkeley released 4.4BSDLite, the last version of their distribution, which has since been freed from AT&T source code.
macOS with Darwin
Apple macOS is a successor to OPENSTEP and NeXTStep and was introduced in 2001 under the name Mac OS X. It is based on a hybrid kernel called XNU , which consists of a Mach microkernel and parts of the FreeBSD kernel. The base system called Darwin also contains programs derived from other BSDs that are expected in a Unix environment. The development of Darwin was placed under the open source license Apple Public Source License , version 2.0 of which was recognized by the Free Software Foundation as a free software license . Together with proprietary, non-open source system parts - for example Aqua and many programming interfaces - Apple creates the proprietary operating systems macOS and iOS , tvOS , watchOS and audioOS . As of Mac OS X Leopard 10.5 (2007), the operating system is certified as UNIX 03 by the Open Group .
Since 2005, Solaris (Version 10) has also been available in its current version for free use. Solaris runs on 32-bit and 64-bit processors ( x86 / AMD64 , EM64T ) from AMD and Intel as well as on 64-bit systems with Sun's UltraSPARC . For access to sources and collaboration, including extensions, it is available in the OpenSolaris version, which does not differ functionally from the binary version.
The following list gives only a rough overview. Only the most important systems are mentioned. These each have their own versions and their own development history.
|Note / manufacturer
|PDP-7 version from Bell Laboratories
|3rd November 1971
|UNIX First Edition
|June 12, 1972
|UNIX Second Edition
|UNIX Third Edition
|UNIX Fourth Edition
|UNIX Fifth Edition
|UNIX Sixth Edition
|First Berkeley Software Distribution (BSD)
|Second Berkeley Software Distribution
|UNIX Seventh Edition
|UNIX / 32V
|Porting the UNIX V7 to VAX computers
|3BSD and 4BSD
|Berkeley port to VAX computers
|Unix version of the company Microsoft , later SCO continued
|UNIX System III
|first commercial version from Bell Labs
|Unix from Hewlett-Packard (HP)
|Sun UNIX 1.0
|Unix version from Sun Microsystems
|Start of the GNU project
|(GNU: Gnu is Not Unix - GNU is not Unix )
|UNIX System V
|Unix version from Digital Equipment Corporation (DEC)
|Unix version from Siemens
|unixoid system from the Mark Williams Company
|Start of the Mach microkernel project at Carnegie Mellon University ( California ).
|UNIX Eighth Edition
|UNIX Ninth Edition
|Unix version from IBM
|A / UX
|Unix version from Apple
|Unix clone from the Free University of Amsterdam
|Unix version from Silicon Graphics
|UNIX Tenth Edition
|Unix version from NeXT based on 4.3BSD and Mach 2.5 kernel
|Unix version from Siemens for real-time requirements
|OSF / 1
|Unix clone from the Open Software Foundation
|SVR4 for Commodore Amiga
|4.3BSD Net / 2
|BSD version without AT&T code, incomplete
|TT / X compatible with Unix System V Release 4
|Unix version from Atari
|oriented towards Minix
|Patch for BSD4.3 Net / 2 for Intel processors
|Sun Microsystems company
|Unix version of Univel ( AT&T & Novell )
|based on 386BSD
|based on 386BSD and 4.3BSD Net / 2 (shortly afterwards 2.0 to 4.4BSDLite)
|4.4BSDEncumbered and 4.4BSDLite
|(without Bell Labs code)
|Successor to OSF / 1
|Company Hewlett-Packard (HP)
|based on NetBSD 1.0
|AT & T is divided Bell Labs in the company Lucent Technologies , a
|Darwin , OpenDarwin
|Developed from NeXTSTEP by Apple (see macOS , XNU )
|starting from FreeBSD
|Sun Microsystems company
|A re-implementation of Unix Version 6 for the x86 and RISC-V platforms as an educationally suitable operating system for learning how an operating system works
- Dennis M. Ritchie, Ken Thompson: Unix Programmer's Manual , 2nd Edition, Bell Telephone Laboratories, Inc., 1972 (PDF; 7.4 MB)
- Dennis M. Ritchie, Ken Thompson: The UNIX Time-Sharing System . In: The Bell System Technical Journal , Vol. 57, July-August 1978, no. 6, Part 2, pp. 1897-2312
- Brian W. Kernighan, Rob Pike: The Unix Toolbox - Programming with UNIX (German translation). Hanser Verlag, Munich 1986, ISBN 3-446-14273-8
- E. Foxley: Unix for super users. Addison-Wesley, 1988, ISBN 3-925118-24-1
- Jürgen Gulbins, Karl Obermayr: UNIX System V.4. Terms, concepts, commands, interfaces. 4th edition 1995, ISBN 3-540-58864-7
- Jerry Peek, Grace Todino, John Strang: UNIX. A practical introduction. O'Reilly Verlag, 2002, ISBN 3-89721-157-2
- Arnold Willemer : How do I become a UNIX guru? - Introduction to UNIX, Linux and Co. Galileo Computing <openbook>, 2003, ISBN 978-3-89842-240-6
- Mark Ward: 40 years of Unix. BBC , accessed February 28, 2010 .
- Android becomes a candy bar . Golem.de
- According to Gartner, Android will overtake Windows in 2013. itespresso.de
- History and Timeline. Open Group, accessed February 24, 2013 .
- Peter Neumann's Home Page. SRI International , archived from the original on May 29, 2011 ; Retrieved February 24, 2013 .
- Susanne Nolte: word game. In: Heise online . August 8, 2009 ( iX 8/2009). Retrieved July 12, 2017.
- Unix , Jargon File
- Matthias Kremp: 40 years of Unix. Spiegel Online, August 18, 2009, accessed October 16, 2011 .
- Open Brand Certificate (PDF; 80 kB)
- https://pdos.csail.mit.edu/6.828/2019/xv6.html xv6 from MIT