Unix – Flickroom

Unix ( ; trademarked as UNIX ) is a family of multitasking, multiuser calculator operating systems that derive from the original AT & T Unix, whose growth started in 1969 [ 1 ] at the Bell Labs research center by Ken Thompson, Dennis Ritchie, and others. [ 3 ] 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. [ 4 ] The UNIX trademark passed to The Open Group, an industry consortium founded in 1996, which allows the practice of the tag 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 operate system should provide a place of simple tools, each of which performs a limited, chiseled routine. [ 5 ] A unite and inode -based filesystem ( the Unix filesystem ) and an inter-process communication mechanism known as “ pipes “ serve as the main means of communication, [ 3 ] and a shell script and command lyric ( the Unix shell ) is used to combine the tools to perform complex workflows. Unix distinguishes itself from its predecessors as the first portable function organization : about the entire operate system is written in the C program language, which allows Unix to operate on numerous platforms. [ 6 ]

overview

Unix was in the first place meant to be a commodious platform for programmers developing software to be run on it and on other systems, quite than for non-programmers. [ 7 ] [ 8 ] [ 9 ] The system grew larger as the operate system started spreading in academic circles, and as users added their own tools to the system and shared them with colleagues. [ 10 ] At first, Unix was not designed to be portable [ 6 ] or for multi-tasking. [ 11 ] Later, Unix gradually gained portability, multi-tasking and multi-user capabilities in a time-sharing shape. Unix systems are characterized by diverse concepts : the use of plain textbook for storing data ; a hierarchical charge system ; treating devices and certain types of inter-process communication ( IPC ) as files ; and the consumption of a bombastic numeral of software tools, small programs that can be strung together through a command-line interpreter using pipes, as opposed to using a unmarried massive program that includes all of the like functionality. These concepts are jointly known as the “ Unix doctrine “. Brian Kernighan and Rob Pike summarize this in The Unix Programming Environment as “ the mind that the office of a organization comes more from the relationships among programs than from the programs themselves ”. [ 12 ] By the early on 1980s, users began seeing Unix as a likely universal operating system, suitable for computers of all sizes. [ 13 ] [ 14 ] The Unix environment and the client–server program model were all-important elements in the development of the Internet and the reshape of computing as centered in networks rather than in person computers. Both Unix and the C program linguistic process 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 engage system. The Unix operating system consists of many libraries and utilities along with the master control broadcast, the kernel. The kernel provides services to start and stop programs, handles the file system and other common “ subordinate ” tasks that most programs plowshare, 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 drug user space, the latter being a priority kingdom where most application programs operate .

history

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 engage system for the GE-645 central processing unit computer. [ 15 ] Multics featured several innovations, but besides presented austere problems. Frustrated by the size and complexity of Multics, but not by its goals, individual researchers at Bell Labs started withdrawing from the visualize. The concluding to leave were Ken Thompson, Dennis Ritchie, Douglas McIlroy, and Joe Ossanna, [ 11 ] who decided to reimplement their experiences in a modern undertaking of smaller scale. This modern operate system was initially without organizational back, and besides without a name. The new engage system was a single-tasking system. [ 11 ] In 1970, the group coined the mention 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 theme, but adds that “ no one can remember ” the lineage of the final spell Unix. [ 16 ] Dennis Ritchie, [ 11 ] Doug McIlroy, [ 1 ] and Peter G. Neumann [ 17 ] besides credit Kernighan. The operate on system was primitively written in assembly lyric, but in 1973, Version 4 Unix was rewritten in C. [ 11 ] Version 4 Unix, however, still had many PDP-11 dependant codes, and was not desirable for porting. The first gear port to another platform was made five years belated ( 1978 ) for the Interdata 8/32. [ 18 ] In 1974, Ken Robinson of the Department of Computer Science at University of New South Wales ( UNSW ) in Australia requested a imitate of Unix for their PDP-11/40 minicomputer from Dennis Ritchie at Bell Labs. This 1975 facility made UNSW the first university outside the United States to run Unix. [ 19 ] Bell Labs produced several versions of Unix that are jointly 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 ). [ 20 ] UIUC calibrate student Greg Chesson, who had worked on the Unix kernel at Bell Labs, was implemental in negotiating the terms of the license. [ 21 ] During the late 1970s and early on 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, exchangeable but much 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 operate system of option for over 90 % of the world ‘s top 500 fastest supercomputers, [ 22 ] as BSD and Linux distributions were developed through collaboration by a cosmopolitan network of programmers. In 2000, Apple released Darwin, besides a Unix system, which became the core of the Mac OS X operating organization, belated renamed macOS. [ 23 ] Unix operating systems are wide used in modern servers, workstations, and mobile devices. [ 24 ]

Standards

In the recently 1980s, an open manoeuver system calibration effort now known as POSIX provided a common baseline for all function systems ; IEEE based POSIX around the common social organization of the major competing variants of the Unix system, publishing the first POSIX standard in 1988. In the early 1990s, a break but very similar attempt was started by an industry consortium, the Common Open Software Environment ( COSE ) inaugural, which finally 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 campaign towards compatibility, respective Unix system vendors agreed on SVR4 ‘s feasible 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 computer architecture. The Filesystem Hierarchy Standard was created to provide a address directory layout for Unix-like operating systems ; it has chiefly been used in Linux .

Components

The Unix system is composed of respective components that were primitively packaged together. By including the development environment, libraries, documents and the portable, modifiable source code for all of these components, in addition to the kernel of an operating system, Unix was a self-contained software system. This was one of the key reasons it emerged as an important teach and learning creature and has had such a broad influence. [ according to whom? ] The inclusion of these components did not make the system large – the original V7 UNIX distribution, consisting of copies of all of the compile binaries plus all of the source code and documentation occupied less than 10 MB and arrived on a unmarried nine-track magnetic tape. The print documentation, typeset from the on-line sources, was contained in two volumes. The names and filesystem locations of the Unix components have changed substantially across the history of the system. however, the V7 execution is considered by many [ who? ] to have the canonic early structure :

• Kernel – source code in /usr/sys, composed of several sub-components:
  • conf – configuration and machine-dependent parts, including boot code
  • dev – device drivers for control of hardware (and some pseudo-hardware)
  • sys – operating system “kernel”, handling memory management, process scheduling, system calls, etc.
  • h – header files, defining key structures within the system and important system-specific invariables
• Development environment – early versions of Unix contained a development environment sufficient to recreate the entire system from source code:
  • ed – text editor, for creating source code files
  • cc – C language compiler (first appeared in V3 Unix)
  • as – machine-language assembler for the machine
  • ld – linker, for combining object files
  • lib – object-code libraries (installed in /lib or /usr/lib). libc, the system library with C run-time support, was the primary library, but there have always been additional libraries for things such as mathematical functions (libm) or database access. V7 Unix introduced the first version of the modern “Standard I/O” library stdio as part of the system library. Later implementations increased the number of libraries significantly.
  • make – build manager (introduced in PWB/UNIX), for effectively automating the build process
  • include – header files for software development, defining standard interfaces and system invariants
  • Other languages – V7 Unix contained a Fortran-77 compiler, a programmable arbitrary-precision calculator (bc, dc), and the awk scripting language; later versions and implementations contain many other language compilers and toolsets. Early BSD releases included Pascal tools, and many modern Unix systems also include the GNU Compiler Collection as well as or instead of a proprietary compiler system.
  • Other tools – including an object-code archive manager (ar), symbol-table lister (nm), compiler-development tools (e.g. lex & yacc), and debugging tools.
• Commands – Unix makes little distinction between commands (user-level programs) for system operation and maintenance (e.g. cron), commands of general utility (e.g. grep), and more general-purpose applications such as the text formatting and typesetting package. Nonetheless, some major categories are:
  • sh – the “shell” programmable command-line interpreter, the primary user interface on Unix before window systems appeared, and even afterward (within a “command window”).
  • Utilities – the core toolkit of the Unix command set, including cp, ls, grep, find and many others. Subcategories include:
    • System utilities – administrative tools such as mkfs, fsck, and many others.
    • User utilities – environment management tools such as passwd, kill, and others.
  • Document formatting – Unix systems were used from the outset for document preparation and typesetting systems, and included many related programs such as nroff, troff, tbl, eqn, refer, and pic. Some modern Unix systems also include packages such as TeX and Ghostscript.
  • Graphics – the plot subsystem provided facilities for producing simple vector plots in a device-independent format, with device-specific interpreters to display such files. Modern Unix systems also generally include X11 as a standard windowing system and GUI, and many support OpenGL.
  • Communications – early Unix systems contained no inter-system communication, but did include the inter-user communication programs mail and write. V7 introduced the early inter-system communication system UUCP, and systems beginning with BSD release 4.1c included TCP/IP utilities.
• Documentation – Unix was the first[ citation needed] operating system to include all of its documentation online in machine-readable form. The documentation included:
  • man – manual pages for each command, library component, system call, header file, etc.
  • doc – longer documents detailing major subsystems, such as the C language and troff

impact

The Unix system had a meaning shock on other operating systems. It achieved its reputation by its interactivity, by providing the software at a noun phrase fee for educational practice, by running on cheap hardware, and by being easy to adapt and move to different machines. Unix was primitively written in assembly language, but was soon rewritten in C, a high-level scheduling speech. [ 25 ] Although this followed the leave of Multics and Burroughs MCP, it was Unix that popularized the idea. Unix had a drastically simplified charge model compared to many contemporary operating systems : treating all kinds of files as simpleton byte arrays. The file system hierarchy contained machine services and devices ( such as printers, terminals, or disk drives ), providing a consistent interface, but at the expense of occasionally requiring extra mechanisms such as ioctl and manner flags to access features of the hardware that did not fit the simple “ current of bytes ” model. The plan 9 operate on organization pushed this model even further and eliminated the need for extra mechanisms. Unix besides popularized the hierarchical charge system with randomly nested subdirectories, originally introduced by Multics. early common operating systems of the earned run average had ways to divide a storehouse device into multiple directories or sections, but they had a fasten number of levels, frequently entirely one horizontal surface. respective major proprietary operating systems finally added recursive subdirectory capabilities besides patterned after Multics. DEC ‘s RSX-11M ‘s “ group, drug user ” hierarchy evolved into OpenVMS directories, CP/M ‘s volumes evolved into MS-DOS 2.0+ subdirectories, and HP ‘s MPE group.account hierarchy and IBM ‘s SSP and OS/400 library systems were folded into broader POSIX file systems. Making the command interpreter an ordinary user-level course of study, with extra commands provided as break programs, was another Multics invention popularized by Unix. The Unix shell used the same lyric for interactional commands as for scripting ( shell scripts – there was no separate job control language like IBM ‘s JCL ). Since the carapace and OS commands were “ just another program ”, the exploiter could choose ( or even write ) their own blast. New commands could be added without changing the carapace itself. Unix ‘s innovative command-line syntax for creating modular chains of producer-consumer processes ( pipelines ) made a powerful program prototype ( coroutines ) wide available. many later command-line interpreters have been inspired by the Unix carapace. A fundamental simplify assumption of Unix was its concenter on newline – delimited text for closely all file formats. There were no “ binary ” editors in the master translation of Unix – the stallion system was configured using textual shell instruction scripts. The common denominator in the I/O system was the byte – unlike “ record-based ” file systems. The focus on textbook for representing about everything made Unix pipes specially utilitarian and encouraged the development of childlike, general tools that could be easily combined to perform more complicated ad hoc tasks. The focus on text and bytes made the organization far more scalable and portable than other systems. Over clock time, text-based applications have besides proven popular in lotion areas, such as print languages ( PostScript, ODF ), and at the application layer of the Internet protocols, for example, FTP, SMTP, HTTP, SOAP, and SIP. Unix popularized a syntax for regular expressions that found widespread use. The Unix programming interface became the footing for a widely implemented operating system interface standard ( POSIX, see above ). The C scheduling linguistic process soon spread beyond Unix, and is now omnipresent in systems and applications program. early Unix developers were crucial in bringing the concepts of modularity and reusability into software technology practice, spawning a “ software tools ” apparent motion. Over time, the leading developers of Unix ( and programs that ran on it ) established a set of cultural norms for developing software, norms which became as important and influential as the technology of Unix itself ; this has been termed the Unix doctrine.

The TCP/IP network protocols were cursorily implemented on the Unix versions widely used on relatively cheap computers, which contributed to the Internet explosion of global real-time connectivity, and which formed the basis for implementations on many other platforms. The Unix policy of extensive on-line software documentation and ( for many years ) quick access to all system source code raised programmer expectations, and contributed to the launching of the free software apparent motion in 1983 .

spare Unix and Unix-like variants

In 1983, Richard Stallman announced the GNU ( short for “ GNU ‘s not Unix ” ) project, an ambitious attempt to create a exempt software Unix-like arrangement ; “ free ” in the sense that everyone who received a replicate would be free to use, study, modify, and redistribute it. The GNU project ‘s own kernel development project, GNU Hurd, had not however produced a work kernel, but in 1991 Linus Torvalds released the Linux kernel as free software under the GNU General Public License. In accession to their manipulation in the GNU engage system, many GNU packages – such as the GNU Compiler Collection ( and the rest of the GNU toolchain ), the GNU C library and the GNU congress of racial equality utilities – have gone on to play central roles in other barren Unix systems deoxyadenosine monophosphate well. Linux distributions, consisting of the Linux kernel and large collections of compatible software have become popular both with individual users and in business. popular distributions include Red Hat Enterprise Linux, Fedora, SUSE Linux Enterprise, openSUSE, Debian, Ubuntu, Linux Mint, Mandriva Linux, Slackware Linux, Arch Linux and Gentoo. [ 26 ] A release derivative of BSD Unix, 386BSD, was released in 1992 and led to the NetBSD and FreeBSD projects. With the 1994 colony of a lawsuit brought against the University of California and Berkeley Software Design Inc. ( USL v. BSDi ) by Unix System Laboratories, it was clarified that Berkeley had the right to distribute BSD Unix for dislodge if it sol desired. Since then, BSD Unix has been developed in respective different product branches, including OpenBSD and DragonFly BSD. Linux and BSD are increasingly filling the market needs traditionally served by proprietary Unix operating systems, american samoa well as expanding into newly markets such as the consumer desktop and mobile and embedded devices. Because of the modular design of the Unix model, sharing components is relatively common ; consequently, most or all Unix and Unix-like systems include at least some BSD code, and some systems besides include GNU utilities in their distributions. In a 1999 interview, Dennis Ritchie voiced his impression that Linux and BSD operating systems are a good continuation of the footing of the Unix design, and are derivatives of Unix : [ 27 ]

I think the Linux phenomenon is quite delightful, because it draws then powerfully on the basis that Unix provided. Linux seems to be the among the healthiest of the direct Unix derivatives, though there are besides the versatile BSD systems adenine good as the more official offerings from the workstation and mainframe manufacturers .

In the same interview, he states that he views both Unix and Linux as “ the good continuation of ideas that were started by Ken and me and many others, many years ago ”. [ 27 ] OpenSolaris was the release software counterpart to Solaris developed by Sun Microsystems, which included a CDDL -licensed kernel and a primarily GNU userland. however, Oracle discontinued the project upon their acquisition of Sun, which prompted a group of early Sun employees and members of the OpenSolaris residential district to fork OpenSolaris into the illumos kernel. As of 2014, illumos remains the only active open-source System V derivative .

ARPANET

In May 1975, RFC 681 described the development of Network Unix by the Center for Advanced Computation at the University of Illinois Urbana-Champaign. [ 28 ] The Unix system was said to “ stage respective interesting capabilities as an ARPANET mini-host ”. At the clock time, Unix required a license from Bell Telephone Laboratories that cost US $ 20,000 for non-university institutions, while universities could obtain a license for a noun phrase fee of $ 150. It was noted that Bell was “ open to suggestions ” for an ARPANET-wide license. The RFC specifically mentions that Unix “ offers herculean local serve facilities in terms of drug user programs, respective compilers, an editor based on QED, a versatile document planning system, and an effective file system featuring twist access control condition, mountable and de-mountable volumes, and a unify treatment of peripherals as particular files. ” The latter permitted the Network Control Program ( NCP ) to be integrated within the Unix file system, treating net connections as limited files that could be accessed through standard Unix I/O calls, which included the add benefit of closing all connections on program die, should the exploiter neglect to do so. The modular purpose of Unix allowed them “ to minimize the total of code added to the basic Unix kernel “, with much of the NCP code in a swappable user process, running entirely when needed .

Branding

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 ), [ 29 ] and in 1995 sold the relate business operations to Santa Cruz Operation ( SCO ). [ 30 ] Whether Novell besides sold the copyrights to the actual software was the subject of a union 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 test decisions, closing the casing. [ 31 ] Unix seller SCO Group Inc. accused Novell of defame of title. The present owner of the brand UNIX is The Open Group, an diligence standards consortium. only systems in full 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 course of operating systems than to a specific implementation of an operate 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 manoeuver arrangement ‘s seller pays a significant certificate fee and annual brand royalties to The Open Group. [ 32 ] Systems that have been licensed to use the UNIX trademark include AIX, [ 33 ] EulerOS, [ 34 ] HP-UX, [ 35 ] Inspur K-UX, [ 36 ] IRIX, [ 37 ] macOS, [ 38 ] Solaris, [ 39 ] Tru64 UNIX ( once “ Digital UNIX ”, or OSF/1 ), [ 40 ] and z/OS. [ 41 ] notably, EulerOS and Inspur K-UX are Linux distributions certified as UNIX 03 compliant. [ 42 ] [ 43 ] sometimes a theatrical performance like Un*x, *NIX, or *N?X is used to indicate all manoeuver systems exchangeable to Unix. This comes from the use of the asterisk ( * ) and the question chump characters as wildcard indicators in many utilities. This notation is besides 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 constantly used as an adjective followed by a generic term such as system to help avoid the creation of a genericized hallmark. Unix was the master format, [ disputed – discuss ] but the use of UNIX remains far-flung because it was once typeset in minor caps ( Unix ). According to Dennis Ritchie, when presenting the original Unix newspaper to the third base Operating Systems Symposium of the American Association for Computing Machinery ( ACM ), “ we had a new compositor and troff had fair been invented and we were intoxicated by being able to produce minor caps ”. [ 44 ] Many of the operate system ‘s predecessors and contemporaries used all-uppercase inscription, so many people wrote the name in upper lawsuit ascribable to force of habit. It is not an acronym. [ 45 ] Trademark names can be registered by different entities in unlike countries and hallmark laws in some countries allow the lapp brand diagnose to be controlled by two unlike entities if each entity uses the hallmark in easily distinct categories. The resultant role is that Unix has been used as a brand name for versatile products including bookshelves, ink pens, bottled glue, diapers, haircloth driers and food containers. [ 46 ] several plural forms of Unix are used casually to refer to multiple brands of Unix and Unix-like systems. Most coarse is the conventional Unixes, but Unices, treating Unix as a Latin noun of the third base declension, is besides democratic. The pseudo- Anglo-Saxon plural shape Unixen is not common, although occasionally seen. Sun Microsystems, developer of the Solaris form, has asserted that the term Unix is itself plural, referencing its many implementations. [ 47 ]

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