1.
Unix
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Among these is Apples macOS, which is the Unix version with the largest installed base as of 2014. Many Unix-like operating systems have arisen over the years, of which Linux is the most popular, 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-programmer users. The system grew larger as the system started spreading in academic circles, as users added their own tools to the system. Unix was designed to be portable, multi-tasking and multi-user in a time-sharing configuration and these concepts are collectively known as the Unix philosophy. By the early 1980s users began seeing Unix as a universal operating system. Under Unix, the system consists of many utilities along with the master control program. To mediate such access, the kernel has special rights, reflected in the division between user space and kernel space, the microkernel concept was introduced in an effort to reverse the trend towards larger kernels and return to a system in which most tasks were completed by smaller utilities. In an era when a standard computer consisted of a disk for storage and a data terminal for input and output. However, modern systems include networking and other new devices, as graphical user interfaces developed, the file model proved inadequate to the task of handling asynchronous events such as those generated by a mouse. In the 1980s, non-blocking I/O and the set of inter-process communication mechanisms were augmented with Unix domain sockets, shared memory, message queues, and semaphores. In microkernel implementations, functions such as network protocols could be moved out of the kernel, Multics introduced many innovations, but had many problems. Frustrated by the size and complexity of Multics but not by the aims and their last researchers to leave Multics, Ken Thompson, Dennis Ritchie, M. D. McIlroy, and J. F. Ossanna, decided to redo the work on a much smaller scale. The name Unics, a pun on Multics, was suggested for the project in 1970. Peter H. Salus credits Peter Neumann with the pun, while Brian Kernighan claims the coining for himself, in 1972, Unix was rewritten in the C programming language. Bell Labs produced several versions of Unix that are referred to as Research Unix. In 1975, the first source license for UNIX was sold to faculty at the University of Illinois Department of Computer Science, UIUC graduate student Greg Chesson was instrumental in negotiating the terms of this license. During the late 1970s and early 1980s, the influence of Unix in academic circles led to adoption of Unix by commercial startups, including Sequent, HP-UX, Solaris, AIX. In the late 1980s, AT&T Unix System Laboratories and Sun Microsystems developed System V Release 4, in the 1990s, Unix-like systems grew in popularity as Linux and BSD distributions were developed through collaboration by a worldwide network of programmers
2.
Unix-like
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A Unix-like operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Unix-like application is one that behaves like the corresponding Unix command or shell, there is no standard for defining the term, and some difference of opinion is possible as to the degree to which a given operating system or application is Unix-like. The Open Group owns the UNIX trademark and administers the Single UNIX Specification and they do not approve of the construction Unix-like, and consider it a misuse of their trademark. Other parties frequently treat Unix as a genericized trademark, in 2007, Wayne R. Gray sued to dispute the status of UNIX as a trademark, but lost his case, and lost again on appeal, with the court upholding the trademark and its ownership. Unix-like systems started to appear in the late 1970s and early 1980s, many proprietary versions, such as Idris, UNOS, Coherent, and UniFlex, aimed to provide businesses with the functionality available to academic users of UNIX. These largely displaced the proprietary clones, growing incompatibility among these systems led to the creation of interoperability standards, including POSIX and the Single UNIX Specification. Various free, low-cost, and unrestricted substitutes for UNIX emerged in the 1980s and 1990s, including 4. 4BSD, Linux, some of these have in turn been the basis for commercial Unix-like systems, such as BSD/OS and OS X. The various BSD variants are notable in that they are in fact descendants of UNIX, however, the BSD code base has evolved since then, replacing all of the AT&T code. Since the BSD variants are not certified as compliant with the Single UNIX Specification, dennis Ritchie, one of the original creators of Unix, expressed his opinion that Unix-like systems such as Linux are de facto Unix systems. Eric S. Raymond and Rob Landley have suggested there are three kinds of Unix-like systems, Genetic UNIX Those systems with a historical connection to the AT&T codebase. Most commercial UNIX systems fall into this category, so do the BSD systems, which are descendants of work done at the University of California, Berkeley in the late 1970s and early 1980s. Some of these systems have no original AT&T code but can trace their ancestry to AT&T designs. Trademark or branded UNIX These systems—largely commercial in nature—have been determined by the Open Group to meet the Single UNIX Specification and are allowed to carry the UNIX name, many ancient UNIX systems no longer meet this definition. Around 2001, Linux was given the opportunity to get a certification including free help from the POSIX chair Andrew Josey for the price of one dollar. Some non-Unix-like operating systems provide a Unix-like compatibility layer, with degrees of Unix-like functionality. IBM z/OSs UNIX System Services is sufficiently complete to be certified as trademark UNIX, cygwin and MSYS both provide a GNU environment on top of the Microsoft Windows user API, sufficient for most common open source software to be compiled and run. Subsystem for Unix-based Applications provides Unix-like functionality as a Windows NT subsystem, Windows Subsystem for Linux provides a Linux-compatible kernel interface developed by Microsoft and containing no Linux code, with Ubuntu user-mode binaries running on top of it
3.
Linux
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Linux is a Unix-like computer operating system assembled under the model of free and open-source software development and distribution. The defining component of Linux is the Linux kernel, an operating system kernel first released on September 17,1991 by Linus Torvalds, the Free Software Foundation uses the name GNU/Linux to describe the operating system, which has led to some controversy. Linux was originally developed for computers based on the Intel x86 architecture. Because of the dominance of Android on smartphones, Linux has the largest installed base of all operating systems. Linux is also the operating system on servers and other big iron systems such as mainframe computers. It is used by around 2. 3% of desktop computers, the Chromebook, which runs on Chrome OS, dominates the US K–12 education market and represents nearly 20% of the sub-$300 notebook sales in the US. Linux also runs on embedded systems – devices whose operating system is built into the firmware and is highly tailored to the system. This includes TiVo and similar DVR devices, network routers, facility automation controls, televisions, many smartphones and tablet computers run Android and other Linux derivatives. The development of Linux is one of the most prominent examples of free, the underlying source code may be used, modified and distributed—commercially or non-commercially—by anyone under the terms of its respective licenses, such as the GNU General Public License. Typically, Linux is packaged in a known as a Linux distribution for both desktop and server use. Distributions intended to run on servers may omit all graphical environments from the standard install, because Linux is freely redistributable, anyone may create a distribution for any intended use. The Unix operating system was conceived and implemented in 1969 at AT&Ts Bell Laboratories in the United States by Ken Thompson, Dennis Ritchie, Douglas McIlroy, first released in 1971, Unix was written entirely in assembly language, as was common practice at the time. Later, in a key pioneering approach in 1973, it was rewritten in the C programming language by Dennis Ritchie, the availability of a high-level language implementation of Unix made its porting to different computer platforms easier. Due to an earlier antitrust case forbidding it from entering the computer business, as a result, Unix grew quickly and became widely adopted by academic institutions and businesses. In 1984, AT&T divested itself of Bell Labs, freed of the legal obligation requiring free licensing, the GNU Project, started in 1983 by Richard Stallman, has the goal of creating a complete Unix-compatible software system composed entirely of free software. Later, in 1985, Stallman started the Free Software Foundation, by the early 1990s, many of the programs required in an operating system were completed, although low-level elements such as device drivers, daemons, and the kernel were stalled and incomplete. Linus Torvalds has stated that if the GNU kernel had been available at the time, although not released until 1992 due to legal complications, development of 386BSD, from which NetBSD, OpenBSD and FreeBSD descended, predated that of Linux. Torvalds has also stated that if 386BSD had been available at the time, although the complete source code of MINIX was freely available, the licensing terms prevented it from being free software until the licensing changed in April 2000
4.
Standardization
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It can also facilitate commoditization of formerly custom processes. This view includes the case of spontaneous standardization processes, to de facto standards. Standard weights and measures were developed by the Indus Valley Civilisation, weights existed in multiples of a standard weight and in categories. Technical standardisation enabled gauging devices to be used in angular measurement and measurement for construction. Uniform units of length were used in the planning of such as Lothal, Surkotada, Kalibangan, Dolavira, Harappa. The weights and measures of the Indus civilisation also reached Persia and Central Asia, Standardisation is also related to Processes. In view of large variations in units related to Civil, Electrical and other Engineering streams, engineers united to overcome the situation and this association later on gave birth to ISO in 1950. ISO stands for International Organisation for Standardisation and this voluntary organisation is solely dedicated to standardisation and makes standards related to it. Certification as per ISO norms is popular all across world, henry Maudslay developed the first industrially practical screw-cutting lathe in 1800. This allowed for the standardisation of screw thread sizes for the first time, before this, screw threads were usually made by chipping and filing. Nuts were rare, metal screws, when made at all, were usually for use in wood, metal bolts passing through wood framing to a metal fastening on the other side were usually fastened in non-threaded ways. This was an advance in workshop technology. Maudslays work, as well as the contributions of other engineers, accomplished a modest amount of industry standardization, joseph Whitworths screw thread measurements were adopted as the first national standard by companies around the country in 1841. It came to be known as the British Standard Whitworth, and was adopted in other countries. This new standard specified a 55° thread angle and a depth of 0. 640327p and a radius of 0. 137329p. The thread pitch increased with diameter in steps specified on a chart, an example of the use of the Whitworth thread is the Royal Navys Crimean War gunboats. These were the first instance of mass-production techniques being applied to marine engineering, American Unified Coarse was originally based on almost the same imperial fractions. The Unified thread angle is 60° and has flattened crests, thread pitch is the same in both systems except that the thread pitch for the 1⁄2 in bolt is 12 threads per inch in BSW versus 13 tpi in the UNC
5.
IEEE Computer Society
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IEEE Computer Society is a professional society of IEEE. Its purpose and scope is to advance the theory, practice, and application of computer and information processing science and technology, the CS is the largest of 39 technical societies organized under the IEEE Technical Activities Board. The Computer Society sponsors workshops and conferences, publishes a variety of peer-reviewed literature, operates technical committees, the IEEE Computer Society is also a member organization of the Federation of Enterprise Architecture Professional Organizations. When the AIEE merged with the IRE in 1963 to form the Institute of Electrical and Electronics Engineers, the group established its own constitution and bylaws in 1971 to become the IEEE Computer Society. The CS maintains its headquarters in Washington, D. C. and additional offices in California, the Computer Society maintains volunteer boards in six program areas, education, membership, professional activities, publications, standards, and technical and conference activities. In addition,12 standing committees administer activities such as the CS elections, the Computer Society participates in ongoing development of college computing curricula, jointly with the Association for Computing Machinery. Other educational activities include software development certification programs and online access to e-learning courseware, the Computer Society is a leading publisher of technical material in computing. Its publications include 13 peer-reviewed technical magazines and 20 scholarly journals called Transactions as well as conference proceedings, books, the Computer Society Digital Library provides subscriber access to all CS publications. In 2008, the Computer Society launched Computing Now, a Web portal featuring free access to a rotation of CSDL articles, along with news, CS blogs. As most publications are delivered digitally in 2014, computer society launched complementary monthly digest Computing Edge magazine, the Computer Society sponsors more than 170 technical conferences each year and coordinates the operation of several technical committees, councils, and task forces. The CS also maintains 12 standards committees to develop IEEE standards in areas of computer. In 2010 the CS introduced Special Technical Communities as a new way for members to develop communities focusing on selected technical areas, iEEE-CS currently has 26 technical committees and 2 technical councils. A technical council is essentially a large technical committee
6.
Operating system
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An operating system is system software that manages computer hardware and software resources and provides common services for computer programs. All computer programs, excluding firmware, require a system to function. Operating systems are found on many devices that contain a computer – from cellular phones, the dominant desktop operating system is Microsoft Windows with a market share of around 83. 3%. MacOS by Apple Inc. is in place, and the varieties of Linux is in third position. Linux distributions are dominant in the server and supercomputing sectors, other specialized classes of operating systems, such as embedded and real-time systems, exist for many applications. A single-tasking system can run one program at a time. Multi-tasking may be characterized in preemptive and co-operative types, in preemptive multitasking, the operating system slices the CPU time and dedicates a slot to each of the programs. Unix-like operating systems, e. g. Solaris, Linux, cooperative multitasking is achieved by relying on each process to provide time to the other processes in a defined manner. 16-bit versions of Microsoft Windows used cooperative multi-tasking, 32-bit versions of both Windows NT and Win9x, used preemptive multi-tasking. Single-user operating systems have no facilities to distinguish users, but may allow multiple programs to run in tandem, a distributed operating system manages a group of distinct computers and makes them appear to be a single computer. The development of networked computers that could be linked and communicate with each other gave rise to distributed computing, distributed computations are carried out on more than one machine. When computers in a work in cooperation, they form a distributed system. The technique is used both in virtualization and cloud computing management, and is common in large server warehouses, embedded operating systems are designed to be used in embedded computer systems. They are designed to operate on small machines like PDAs with less autonomy and they are able to operate with a limited number of resources. They are very compact and extremely efficient by design, Windows CE and Minix 3 are some examples of embedded operating systems. A real-time operating system is a system that guarantees to process events or data by a specific moment in time. A real-time operating system may be single- or multi-tasking, but when multitasking, early computers were built to perform a series of single tasks, like a calculator. Basic operating system features were developed in the 1950s, such as resident monitor functions that could run different programs in succession to speed up processing
7.
Unix shell
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A Unix shell is a command-line interpreter or shell that provides a traditional Unix-like command line user interface. Users direct the operation of the computer by entering commands as text for a command line interpreter to execute, users typically interact with a Unix shell using a terminal emulator, however, direct operation via serial hardware connections, or networking session, are common for server systems. All Unix shells provide filename wildcarding, piping, here documents, command substitution, variables and control structures for condition-testing, the most generic sense of the term shell means any program that users employ to type commands. In Unix-like operating systems, users typically have many choices of command-line interpreters for interactive sessions, when a user logs in to the system interactively, a shell program is automatically executed for the duration of the session. The Unix shell is both a command language as well as a scripting programming language, and is used by the operating system as the facility to control the execution of the system. Shells created for operating systems often provide similar functionality. On hosts with a system, like macOS, some users may never use the shell directly. However, some vendors have replaced the traditional shell-based startup system with different approaches. The first Unix shell was the Thompson shell, sh, written by Ken Thompson at Bell Labs and distributed with Versions 1 through 6 of Unix, though not in current use, it is still available as part of some Ancient UNIX Systems. It was modeled after the Multics shell, itself modeled after the RUNCOM program Louis Pouzin showed to the Multics Team, the rc suffix on some Unix configuration files, is a remnant of the RUNCOM ancestry of Unix shells. The PWB shell or Mashey shell, sh, was a version of the Thompson shell, augmented by John Mashey and others and distributed with the Programmers Workbench UNIX. It focused on making shell programming practical, especially in large shared computing centers and it added shell variables, user-executable shell scripts, and interrupt-handling. Control structures were extended from if/goto to if/then/else/endif, switch/breaksw/endsw, as shell programming became widespread, these external commands were incorporated into the shell itself for performance. But the most widely distributed and influential of the early Unix shells were the Bourne shell, both shells have been used as the coding base and model for many derivative and work-alike shells with extended feature sets. The Bourne shell, sh, was a rewrite by Stephen Bourne at Bell Labs. The language, including the use of a keyword to mark the end of a block, was influenced by ALGOL68. Traditionally, the Bourne shell program name is sh and its path in the Unix file system hierarchy is /bin/sh, but a number of compatible work-alikes are also available with various improvements and additional features. The sh of FreeBSD, NetBSD are based on ash that has enhanced to be POSIX conformant for the occasion
8.
International Organization for Standardization
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The International Organization for Standardization is an international standard-setting body composed of representatives from various national standards organizations. Founded on 23 February 1947, the organization promotes worldwide proprietary and it is headquartered in Geneva, Switzerland, and as of March 2017 works in 162 countries. It was one of the first organizations granted general consultative status with the United Nations Economic, ISO, the International Organization for Standardization, is an independent, non-governmental organization, the members of which are the standards organizations of the 162 member countries. It is the worlds largest developer of international standards and facilitates world trade by providing common standards between nations. Nearly twenty thousand standards have been set covering everything from manufactured products and technology to food safety, use of the standards aids in the creation of products and services that are safe, reliable and of good quality. The standards help businesses increase productivity while minimizing errors and waste, by enabling products from different markets to be directly compared, they facilitate companies in entering new markets and assist in the development of global trade on a fair basis. The standards also serve to safeguard consumers and the end-users of products and services, the three official languages of the ISO are English, French, and Russian. The name of the organization in French is Organisation internationale de normalisation, according to the ISO, as its name in different languages would have different abbreviations, the organization adopted ISO as its abbreviated name in reference to the Greek word isos. However, during the meetings of the new organization, this Greek word was not invoked. Both the name ISO and the logo are registered trademarks, the organization today known as ISO began in 1926 as the International Federation of the National Standardizing Associations. ISO is an organization whose members are recognized authorities on standards. Members meet annually at a General Assembly to discuss ISOs strategic objectives, the organization is coordinated by a Central Secretariat based in Geneva. A Council with a membership of 20 member bodies provides guidance and governance. The Technical Management Board is responsible for over 250 technical committees, ISO has formed joint committees with the International Electrotechnical Commission to develop standards and terminology in the areas of electrical and electronic related technologies. Information technology ISO/IEC Joint Technical Committee 1 was created in 1987 to evelop, maintain, ISO has three membership categories, Member bodies are national bodies considered the most representative standards body in each country. These are the members of ISO that have voting rights. Correspondent members are countries that do not have their own standards organization and these members are informed about ISOs work, but do not participate in standards promulgation. Subscriber members are countries with small economies and they pay reduced membership fees, but can follow the development of standards
9.
International Electrotechnical Commission
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The IEC also manages three global conformity assessment systems that certify whether equipment, system or components conform to its International Standards. The first International Electrical Congress took place in 1881 at the International Exposition of Electricity, at that time the International System of Electrical and Magnetic Units was agreed to. The IEC was instrumental in developing and distributing standards for units of measurement, particularly Gauss, Hertz and it also first proposed a system of standards, the Giorgi System, which ultimately became the SI, or Système International d’unités. In 1938, it published a multilingual international vocabulary to unify terminology relating to electrical, electronic and this effort continues, and the International Electrotechnical Vocabulary remains an important work in the electrical and electronic industries. The CISPR – in English, the International Special Committee on Radio Interference – is one of the groups founded by the IEC, originally located in London, the commission moved to its current headquarters in Geneva in 1948. It has regional centres in Asia-Pacific, Latin America and North America, today, the IEC is the worlds leading international organization in its field, and its standards are adopted as national standards by its members. The work is done by some 10,000 electrical and electronics experts from industry, government, academia, test labs, IEC standards have numbers in the range 60000–79999 and their titles take a form such as IEC60417, Graphical symbols for use on equipment. Following the Dresden Agreement with CENELEC the numbers of older IEC standards were converted in 1997 by adding 60000, for example IEC27 became IEC60027. Standards of the 60000 series are also preceded by EN to indicate that the IEC standard is also adopted by CENELEC as a European standard. The IEC cooperates closely with the International Organization for Standardization and the International Telecommunication Union, Standards developed jointly with ISO such as ISO/IEC26300, ISO/IEC27001, and CASCO ISO/IEC17000 series, carry the acronym of both organizations. The use of the ISO/IEC prefix covers publications from ISO/IEC Joint Technical Committee 1 - Information Technology, as well as conformity assessment standards developed by ISO CASCO, other standards developed in cooperation between IEC and ISO are assigned numbers in the 80000 series, such as IEC 82045-1. IEC standards are also being adopted by other certifying bodies such as BSI, CSA, UL & ANSI/INCITS, SABS, SAI, SPC/GB, IEC standards adopted by other certifying bodies may have some noted differences from the original IEC standard. The IEC is made up of members, called national committees, national committees are constituted in different ways. Some NCs are public sector only, some are a combination of public and private sector, about 90% of those who prepare IEC standards work in industry
10.
Richard Stallman
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Richard Matthew Stallman, often known by his initials, rms, is an American software freedom activist and programmer. He campaigns for software to be distributed in a such that its users receive the freedoms to use, study, distribute. Software that ensures these freedoms is termed free software, Stallman launched the GNU Project, founded the Free Software Foundation, developed the GNU Compiler Collection and GNU Emacs, and wrote the GNU General Public License. Stallman launched the GNU Project in September 1983 to create a Unix-like computer operating system composed entirely of free software, with this, he also launched the free software movement. In October 1985 he founded the Free Software Foundation, in 1989 he co-founded the League for Programming Freedom. This has included software license agreements, non-disclosure agreements, activation keys, dongles, copy restriction, proprietary formats, as of 2016, he has received fifteen honorary doctorates and professorships. Stallman was born to Alice Lippman, a teacher, and Daniel Stallman. He was interested in computers at an age, when Stallman was a pre-teen at a summer camp. From 1967 to 1969, Stallman attended a Columbia University Saturday program for school students. Stallman was also a laboratory assistant in the biology department at Rockefeller University. Although he was interested in mathematics and physics, his professor at Rockefeller thought he showed promise as a biologist. His first experience with computers was at the IBM New York Scientific Center when he was in high school. He was hired for the summer in 1970, following his year of high school. He completed the task after a couple of weeks and spent the rest of the writing a text editor in APL. As a first-year student at Harvard University in fall 1970, Stallman was known for his performance in Math 55. He was happy, For the first time in my life, Stallman graduated from Harvard magna cum laude earning a bachelors degree in Physics in 1974. Stallman considered staying on at Harvard, but instead he decided to enroll as a student at MIT. He pursued a doctorate in physics for one year, but left that program to focus on his programming at the MIT AI Laboratory
11.
Command-line interface
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A program which handles the interface is called a command language interpreter or shell. The interface is implemented with a command line shell, which is a program that accepts commands as text input. Command-line interfaces to computer operating systems are widely used by casual computer users. Alternatives to the line include, but are not limited to text user interface menus, keyboard shortcuts. Examples of this include the Windows versions 1,2,3,3.1, and 3.11, DosShell, and Mouse Systems PowerPanel. Command-line interfaces are preferred by more advanced computer users, as they often provide a more concise. Programs with command-line interfaces are generally easier to automate via scripting, a program that implements such a text interface is often called a command-line interpreter, command processor or shell. Under most operating systems, it is possible to replace the shell program with alternatives, examples include 4DOS for DOS, 4OS2 for OS/2. For example, the default Windows GUI is a program named EXPLORER. EXE. These programs are shells, but not CLIs, application programs may also have command line interfaces. When a program is launched from an OS command line shell, interactive command line sessions, After launch, a program may provide an operator with an independent means to enter commands in the form of text. OS inter-process communication, Most operating systems support means of inter-process communication, Command lines from client processes may be redirected to a CLI program by one of these methods. Some applications support only a CLI, presenting a CLI prompt to the user, Some examples of CLI-only applications are, DEBUG Diskpart Ed Edlin Fdisk Ping Some computer programs support both a CLI and a GUI. In some cases, a GUI is simply a wrapper around a separate CLI executable file, in other cases, a program may provide a CLI as an optional alternative to its GUI. CLIs and GUIs often support different functionality, for example, all features of MATLAB, a numerical analysis computer program, are available via the CLI, whereas the MATLAB GUI exposes only a subset of features. The early Sierra games, like the first three Kings Quest games, used commands from a command line to move the character around in the graphic window. Early computer systems often used teleprinter machines as the means of interaction with a human operator, the computer became one end of the human-to-human teleprinter model. So instead of a human communicating with another human over a teleprinter, in time, the actual mechanical teleprinter was replaced by a glass tty, and then by a smart terminal
12.
UNIX System V
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UNIX System V 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. It was the source of common commercial Unix features. System V is sometimes abbreviated to SysV, as of 2012, the Unix market is divided between three System V variants, IBMs AIX, Hewlett-Packards HP-UX and Oracles Solaris. System V was the successor to 1982s 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&Ts reference implementation. A standards document called the System V Interface Definition outlined the default features, 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. Historically, BSD was also commonly called BSD Unix or Berkeley Unix, the dispute had several levels, some technical 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 such as Sun Microsystems. Throughout its development, though, System V was infused with features from BSD, 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. System V, known inside Bell Labs as Unix 5.0, there was never an external release of Unix 4.0, which would have been System IV. This first release of System V was developed by AT&Ts UNIX Support Group, System V also included features such as the vi editor and curses from 4.1 BSD, developed at the University of California, Berkeley, it also improved performance by adding buffer and inode caches. It also added support for communication using messages, semaphores. SVR1 ran on DEC PDP-11 and VAX minicomputers, System V Release 2 was released in April,1984. It added shell functions and the SVID, new kernel features included record and file locking, demand paging, and copy on write. The concept of the base was formalized, and the DEC VAX-11/780 was chosen for this release. The porting base is the original version of a release. Educational source licenses for SVR2 were offered by AT&T for US$800 for the first CPU, a commercial source license was offered for $43,000, with three months of support, and a $16,000 price per additional CPU
13.
Computer file
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A computer file is a computer resource for recording data discretely in a computer storage device. Just as words can be written to paper, so can information be written to a computer file, there are different types of computer files, designed for different purposes. A file may be designed to store a picture, a message, a video. Some types of files can store different several types of information at once, by using computer programs, a person can open, read, change, and close a computer file. Computer files may be reopened, modified, and copied a number of times. Typically, computer files are organised in a system, which keeps track of where the files are. The word file derives from the Latin filum, such a file now exists in a memory tube developed at RCA Laboratories. Electronically it retains figures fed into calculating machines, holds them in storage while it memorizes new ones - speeds intelligent solutions through mazes of mathematics, in 1952, file denoted, inter alia, information stored on punched cards. In early use, the hardware, rather than the contents stored on it, was denominated a file. For example, the IBM350 disk drives were denominated disk files, although the contemporary register file demonstrates the early concept of files, its use has greatly decreased. On most modern operating systems, files are organized into one-dimensional arrays of bytes, for example, the bytes of a plain text file are associated with either ASCII or UTF-8 characters, while the bytes of image, video, and audio files are interpreted otherwise. Most file types also allocate a few bytes for metadata, which allows a file to some basic information about itself. Some file systems can store arbitrary file-specific data outside of the file format, on other file systems this can be done via sidecar files or software-specific databases. All those methods, however, are susceptible to loss of metadata than are container. At any instant in time, a file might have a size, normally expressed as number of bytes, in most modern operating systems the size can be any non-negative whole number of bytes up to a system limit. Many older operating systems kept track only of the number of blocks or tracks occupied by a file on a storage device. In such systems, software employed other methods to track the exact byte count, the general definition of a file does not require that its size have any real meaning, however, unless the data within the file happens to correspond to data within a pool of persistent storage. A special case is a zero byte file, these files can be newly created files that have not yet had any data written to them, or may serve as some kind of flag in the file system, or are accidents
14.
Computer terminal
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A computer terminal is an electronic or electromechanical hardware device that is used for entering data into, and displaying data from, a computer or a computing system. The function of a terminal is confined to display and input of data, a terminal that depends on the host computer for its processing power is called a dumb terminal or thin client. A personal computer can run terminal emulator software that replicates the function of a terminal, sometimes allowing concurrent use of local programs and access to a distant terminal host system. The terminal of the first working programmable, fully automatic digital Turing-complete computer, the Z3, had a keyboard, early user terminals connected to computers were electromechanical teleprinters/teletypewriters, such as the Teletype Model 33 ASR, originally used for telegraphy or the Friden Flexowriter. Later printing terminals such as the DECwriter LA30 were developed, however printing terminals were limited by the speed at which paper could be printed, and for interactive use the paper record was unnecessary. The problem was that the amount of memory needed to store the information on a page of text was comparable to the memory in low end minicomputers then in use. Displaying the information at video speeds was also a challenge and the control logic took up a rack worth of pre-integrated circuit electronics. Another approach involved the use of the tube, a specialized CRT developed by Tektronix that retained information written on it without the need to refresh. The Datapoint 3300 from Computer Terminal Corporation was announced in 1967 and shipped in 1969 and it solved the memory space issue mentioned above by using a digital shift-register design, and using only 72 columns rather than the later more common choice of 80. Some type of blinking cursor that can be positioned, the term intelligent in this context dates from 1969. Notable examples include the IBM2250 and IBM2260, predecessors to the IBM3270, providing even more processing possibilities, workstations like the Televideo TS-800 could run CP/M-86, blurring the distinction between terminal and Personal Computer. Most terminals were connected to minicomputers or mainframe computers and often had a green or amber screen, typically terminals communicate with the computer via a serial port via a null modem cable, often using an EIA RS-232 or RS-422 or RS-423 or a current loop serial interface. In fact, the design for the Intel 8008 was originally conceived at Computer Terminal Corporation as the processor for the Datapoint 2200. While early IBM PCs had single color green screens, these screens were not terminals. The screen of a PC did not contain any character generation hardware, all signals and video formatting were generated by the video display card in the PC, or by the CPU. An IBM PC monitor, whether it was the monochrome display or the 16-color display, was technically much more similar to an analog TV set than to a terminal. With suitable software a PC could, however, emulate a terminal, the Data General One could be booted into terminal emulator mode from its ROM. Since the advent and subsequent popularization of the computer, few genuine hardware terminals are used to interface with computers today
15.
Computer network
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A computer network or data network is a telecommunications network which allows nodes to share resources. In computer networks, networked computing devices exchange data with other using a data link. The connections between nodes are established using either cable media or wireless media, the best-known computer network is the Internet. Network computer devices that originate, route and terminate the data are called network nodes, nodes can include hosts such as personal computers, phones, servers as well as networking hardware. Two such devices can be said to be networked together when one device is able to exchange information with the other device, Computer networks differ in the transmission medium used to carry their signals, communications protocols to organize network traffic, the networks size, topology and organizational intent. In most cases, application-specific communications protocols are layered over other more general communications protocols and this formidable collection of information technology requires skilled network management to keep it all running reliably. The chronology of significant computer-network developments includes, In the late 1950s, in 1960, the commercial airline reservation system semi-automatic business research environment went online with two connected mainframes. Licklider developed a group he called the Intergalactic Computer Network. In 1964, researchers at Dartmouth College developed the Dartmouth Time Sharing System for distributed users of computer systems. The same year, at Massachusetts Institute of Technology, a group supported by General Electric and Bell Labs used a computer to route. Throughout the 1960s, Leonard Kleinrock, Paul Baran, and Donald Davies independently developed network systems that used packets to transfer information between computers over a network, in 1965, Thomas Marill and Lawrence G. Roberts created the first wide area network. This was an precursor to the ARPANET, of which Roberts became program manager. Also in 1965, Western Electric introduced the first widely used telephone switch that implemented true computer control, in 1972, commercial services using X.25 were deployed, and later used as an underlying infrastructure for expanding TCP/IP networks. In July 1976, Robert Metcalfe and David Boggs published their paper Ethernet, Distributed Packet Switching for Local Computer Networks, in 1979, Robert Metcalfe pursued making Ethernet an open standard. In 1976, John Murphy of Datapoint Corporation created ARCNET, a network first used to share storage devices. In 1995, the transmission speed capacity for Ethernet increased from 10 Mbit/s to 100 Mbit/s, by 1998, Ethernet supported transmission speeds of a Gigabit. Subsequently, higher speeds of up to 100 Gbit/s were added, the ability of Ethernet to scale easily is a contributing factor to its continued use. Providing access to information on shared storage devices is an important feature of many networks, a network allows sharing of files, data, and other types of information giving authorized users the ability to access information stored on other computers on the network
16.
Thread (computing)
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In computer science, a thread of execution is the smallest sequence of programmed instructions that can be managed independently by a scheduler, which is typically a part of the operating system. The implementation of threads and processes differs between operating systems, but in most cases a thread is a component of a process, multiple threads can exist within one process, executing concurrently and sharing resources such as memory, while different processes do not share these resources. In particular, the threads of a process share its executable code, systems with a single processor generally implement multithreading by time slicing, the central processing unit switches between different software threads. This context switching generally happens very often and rapidly enough that users perceive the threads or tasks as running in parallel, Threads made an early appearance in OS/360 Multiprogramming with a Variable Number of Tasks in 1967, in which context they were called tasks. The term thread has been attributed to Victor A. Vyssotsky, some threading implementations are called kernel threads, whereas light-weight processes are a specific type of kernel thread that share the same state and information. Furthermore, programs can have user-space threads when threading with timers, signals, or other methods to interrupt their own execution, in computer programming, single-threading is the processing of one command at a time. The opposite of single-threading is multithreading, while it has been suggested that the term single-threading is misleading, the term has been widely accepted within the functional programming community. Multithreading is mainly found in multitasking operating systems, multithreading is a widespread programming and execution model that allows multiple threads to exist within the context of one process. These threads share the resources, but are able to execute independently. The threaded programming model provides developers with an abstraction of concurrent execution. Multithreading can also be applied to one process to enable parallel execution on a multiprocessing system, multithreaded applications have the following advantages, Responsiveness, multithreading can allow an application to remain responsive to input. In a one-thread program, if the main execution thread blocks on a long-running task, on the other hand, in most cases multithreading is not the only way to keep a program responsive, with non-blocking I/O and/or Unix signals being available for gaining similar results. Lower resource consumption, using threads, an application can serve multiple clients concurrently using fewer resources than it would need when using multiple copies of itself. For example, the Apache HTTP server uses thread pools, a pool of threads for listening to incoming requests. GPU computing environments like CUDA and OpenCL use the model where dozens to hundreds of threads run in parallel across data on a large number of cores. Multithreading has the drawbacks, Synchronization, since threads share the same address space. In order for data to be manipulated, threads will often need to rendezvous in time in order to process the data in the correct order. Threads may also require mutually exclusive operations in order to prevent common data from being simultaneously modified or read while in the process of being modified, careless use of such primitives can lead to deadlocks
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ANSI C
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Historically, the names referred specifically to the original and best-supported version of the standard. Software developers writing in C are encouraged to conform to the standards, the first standard for C was published by ANSI. While some software developers use the term ISO C, others are standards body–neutral, in 1983, the American National Standards Institute formed a committee, X3J11, to establish a standard specification of C. The standard was completed in 1989 and ratified as ANSI X3. 159-1989 Programming Language C and this version of the language is often referred to as ANSI C. Later on sometimes the label C89 is used to distinguish it from C99, the same standard as C89 was ratified by the International Organization for Standardization as ISO/IEC9899,1990, with only formatting changes, which is sometimes referred to as C90. Therefore, the terms C89 and C90 refer to essentially the same language and this standard has been withdrawn by both ANSI/INCITS and ISO/IEC. In 1995, the ISO published an extension, called Amendment 1 and its full name finally was ISO/IEC 9899/AMD1,1995 or nicknamed C95. C11 is the current standard for the C programming language, ANSI C is now supported by almost all the widely used compilers. Most of the C code being written nowadays is based on ANSI C, any program written only in standard C and without any hardware dependent assumptions is virtually guaranteed to compile correctly on any platform with a conforming C implementation. To mitigate the differences between K&R C and the ANSI C standard, the macro can be used to split code into ANSI. In the above example, a prototype is used in a declaration for ANSI compliant implementations. Those are still ANSI-compliant as of C99, note how this code checks both definition and evaluation, this is because some implementations may set __STDC__ to zero to indicate non-ANSI compliance. ISO/IEC9899,1999 Programming Languages -- C, ANSI Standards Action Vol.36, #48
18.
Process (computing)
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In computing, a process is an instance of a computer program that is being executed. It contains the code and its current activity. Depending on the system, a process may be made up of multiple threads of execution that execute instructions concurrently. A computer program is a collection of instructions, while a process is the actual execution of those instructions. Several processes may be associated with the program, for example. Multitasking is a method to allow processes to share processors. Each CPU executes a task at a time. However, multitasking allows each processor to switch between tasks that are being executed without having to wait for each task to finish. Depending on the system implementation, switches could be performed when tasks perform input/output operations. A common form of multitasking is time-sharing, time-sharing is a method to allow fast response for interactive user applications. In time-sharing systems, context switches are performed rapidly, which makes it seem like multiple processes are being executed simultaneously on the same processor and this seeming execution of multiple processes simultaneously is called concurrency. In general, a system process consists of the following resources. Memory, which includes the code, process-specific data, a call stack. Operating system descriptors of resources that are allocated to the process, such as file descriptors or handles, security attributes, such as the process owner and the process set of permissions. Processor state, such as the content of registers and physical memory addressing, the state is typically stored in computer registers when the process is executing, and in memory otherwise. The operating system holds most of this information about processes in data structures called process control blocks. Any subset of the resources, typically at least the processor state, the operating system keeps its processes separate and allocates the resources they need, so that they are less likely to interfere with each other and cause system failures. The operating system may also provide mechanisms for communication to enable processes to interact in safe
19.
SIGSEGV
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On standard x86 computers this is a form of general protection fault. The OS kernel will, in response, usually perform some corrective action, segmentation faults are a common class of error in programs written in languages like C that provide low-level memory access. They arise primarily due to errors in use of pointers for virtual memory addressing, newer programming languages may employ mechanisms designed to avoid segmentation faults and improve memory safety. For example, the Rust programming language employs an Ownership based model to ensure memory safety. A segmentation fault occurs when a program attempts to access a location that it is not allowed to access. The term segmentation has various uses in computing, in the context of segmentation fault, thus attempting to read outside of the programs address space, or writing to a read-only segment of the address space, results in a segmentation fault, hence the name. On systems using only paging, a page fault generally leads to a segmentation fault. At the hardware level, the fault is initially raised by the management unit on illegal access, as part of its memory protection feature. If the problem is not a logical address but instead an invalid physical address. At the operating level, this fault is caught and a signal is passed on to the offending process. Different operating systems have different signal names to indicate that a fault has occurred. On Unix-like operating systems, a signal called SIGSEGV is sent to the offending process, on Microsoft Windows, the offending process receives a STATUS_ACCESS_VIOLATION exception. The proximate cause is an access violation, while the underlying cause is generally a software bug of some sort. In C code, segmentation faults most often occur because of errors in pointer use, the default action for a segmentation fault or bus error is abnormal termination of the process that triggered it. A core file may be generated to aid debugging, and other platform-dependent actions may also be performed, for example, Linux systems using the grsecurity patch may log SIGSEGV signals in order to monitor for possible intrusion attempts using buffer overflows. Writing to read-only memory raises a segmentation fault, at the level of code errors, this occurs when the program writes to part of its own code segment or the read-only portion of the data segment, as these are loaded by the OS into read-only memory. Here is an example of ANSI C code that will cause a segmentation fault on platforms with memory protection. It attempts to modify a string literal, which is undefined behavior according to the ANSI C standard, when loaded, the operating system places it with other strings and constant data in a read-only segment of memory
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SIGBUS
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On standard x86 computers this is a form of general protection fault. The OS kernel will, in response, usually perform some corrective action, segmentation faults are a common class of error in programs written in languages like C that provide low-level memory access. They arise primarily due to errors in use of pointers for virtual memory addressing, newer programming languages may employ mechanisms designed to avoid segmentation faults and improve memory safety. For example, the Rust programming language employs an Ownership based model to ensure memory safety. A segmentation fault occurs when a program attempts to access a location that it is not allowed to access. The term segmentation has various uses in computing, in the context of segmentation fault, thus attempting to read outside of the programs address space, or writing to a read-only segment of the address space, results in a segmentation fault, hence the name. On systems using only paging, a page fault generally leads to a segmentation fault. At the hardware level, the fault is initially raised by the management unit on illegal access, as part of its memory protection feature. If the problem is not a logical address but instead an invalid physical address. At the operating level, this fault is caught and a signal is passed on to the offending process. Different operating systems have different signal names to indicate that a fault has occurred. On Unix-like operating systems, a signal called SIGSEGV is sent to the offending process, on Microsoft Windows, the offending process receives a STATUS_ACCESS_VIOLATION exception. The proximate cause is an access violation, while the underlying cause is generally a software bug of some sort. In C code, segmentation faults most often occur because of errors in pointer use, the default action for a segmentation fault or bus error is abnormal termination of the process that triggered it. A core file may be generated to aid debugging, and other platform-dependent actions may also be performed, for example, Linux systems using the grsecurity patch may log SIGSEGV signals in order to monitor for possible intrusion attempts using buffer overflows. Writing to read-only memory raises a segmentation fault, at the level of code errors, this occurs when the program writes to part of its own code segment or the read-only portion of the data segment, as these are loaded by the OS into read-only memory. Here is an example of ANSI C code that will cause a segmentation fault on platforms with memory protection. It attempts to modify a string literal, which is undefined behavior according to the ANSI C standard, when loaded, the operating system places it with other strings and constant data in a read-only segment of memory
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Pipeline (Unix)
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In Unix-like computer operating systems, a pipeline is a sequence of processes chained together by their standard streams, so that the output of each process feeds directly as input to the next one. The concept of pipelines was championed by Douglas McIlroy at Unixs ancestral home of Bell Labs, during the development of Unix and it is named by analogy to a physical pipeline. The standard shell syntax for pipelines is to list multiple commands, each process takes input from the previous process and produces output for the next process via standard streams. Pipes are unidirectional, data flows through the pipeline from left to right, all widely used Unix shells have a special syntax construct for the creation of pipelines. In all usage one writes the commands in sequence, separated by the ASCII vertical bar character |, the shell starts the processes and arranges for the necessary connections between their standard streams. By default, the standard streams of the processes in a pipeline are not passed on through the pipe, instead. However, many shells have additional syntax for changing this behavior, in the csh shell, for instance, using |& instead of | signifies that the standard error stream should also be merged with the standard output and fed to the next process. The Bourne Shell can also merge standard error, using 2>&1, in the most commonly used simple pipelines the shell connects a series of sub-processes via pipes, and executes external commands within each sub-process. Thus the shell itself is doing no direct processing of the data flowing through the pipeline, however, its possible for the shell to perform processing directly, using a so-called mill, or pipemill. There are a couple of ways to avoid this behavior. First, some support an option to disable reading from stdin. Alternatively, if the drain does not need to read any input from stdin to do something useful, pipelines can be created under program control. The Unix pipe system call asks the operating system to construct a new anonymous pipe object and this results in two new, opened file descriptors in the process, the read-only end of the pipe, and the write-only end. The pipe ends appear to be normal, anonymous file descriptors, to avoid deadlock and exploit parallelism, the Unix process with one or more new pipes will then, generally, call fork to create new processes. Each process will then close the end of the pipe that it not be using before producing or consuming any data. Alternatively, a process might create a new thread and use the pipe to communicate between them, named pipes may also be created using mkfifo or mknod and then presented as the input or output file to programs as they are invoked. They allow multi-path pipes to be created, and are effective when combined with standard error redirection. Instead, the output of the program is held in the buffer
22.
Semaphore (programming)
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A trivial semaphore is a plain variable that is changed depending on programmer-defined conditions. The variable is used as a condition to control access to some system resource. Semaphores are a tool in the prevention of race conditions, however. The semaphore concept was invented by Dutch computer scientist Edsger Dijkstra in 1962 or 1963 and it has also been used as the control mechanism for I/O controllers, for example in the Electrologica X8 computer. Suppose a library has 10 identical study rooms, to be used by one student at a time, to prevent disputes, students must request a room from the front desk if they wish to make use of a study room. If no rooms are free, students wait at the desk until someone relinquishes a room, when a student has finished using a room, the student must return to the desk and indicate that one room has become free. When a student requests a room, the clerk decreases this number, when a student releases a room, the clerk increases this number. Once access to a room is granted, the room can be used for as long as desired, in this scenario the front desk count-holder represents a counting semaphore, the rooms are the resources, and the students represent processes. The value of the semaphore in this scenario is initially 10, when a student requests a room, they are granted access, and the value of the semaphore is changed to 9. After the next student comes, it drops to 8, then 7, If someone requests a room and the resulting value of the semaphore would be negative, they are forced to wait until a room is freed. When used to access to a pool of resources, a semaphore tracks only how many resources are free. Some other mechanism may be required to select a free resource. The paradigm is especially powerful because the count may serve as a useful trigger for a number of different actions. The librarian above may turn the lights off in the hall when there are no students remaining. The success of the protocol requires applications follow it correctly, fairness and safety are likely to be compromised if even a single process acts incorrectly. Counting semaphores are equipped with two operations, historically denoted as P and V, operation V increments the semaphore S, and operation P decrements it. The value of the semaphore S is the number of units of the resource that are currently available, the P operation wastes time or sleeps until a resource protected by the semaphore becomes available, at which time the resource is immediately claimed. The V operation is the inverse, it makes a resource available again after the process has finished using it, one important property of semaphore S is that its value cannot be changed except by using the V and P operations
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Shared memory
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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 programs, depending on context, programs may run on a single processor or on multiple separate processors. Using memory for communication inside a program, e. g. among its multiple threads, is also referred to as shared memory. In computer hardware, shared memory refers to a block of random access memory that can be accessed by several different central processing units in a computer system. A shared memory system is easy to program since all processors share a single view of data. Shared memory computers cannot scale very well, such cache coherence protocols can, when they work well, provide extremely high-performance access to shared information between multiple processors. On the other hand, they can become overloaded and become a bottleneck to performance. Technologies like crossbar switches, Omega networks, HyperTransport or front-side bus can be used to dampen the bottleneck-effects, the alternatives to shared memory are distributed memory and distributed shared memory, each having a similar set of issues. In computer software, shared memory is either a method of inter-process communication and this is most often used for shared libraries and for XIP. Since both processes can access the memory area like regular working memory, this is a very fast way of communication. POSIX provides a standardized API for using shared memory, POSIX Shared Memory and this uses the function shm_open from sys/mman. h. POSIX interprocess communication includes the shared-memory functions shmat, shmctl, shmdt, unix System V provides an API for shared memory as well. BSD systems provide anonymous mapped memory which can be used by several processes, the shared memory created by shm_open is persistent. It stays in the system until explicitly removed by a process and this has a drawback that if the process crashes and fails to clean up shared memory it will stay until system shutdown. POSIX also provides the mmap API for mapping files into memory, linux distributions based on the 2.6 kernel and later offer /dev/shm as shared memory in the form of a RAM disk, more specifically as a world-writable directory that is stored in memory. Both the RedHat and Debian based distributions include it by default, support for this type of RAM disk is completely optional within the kernel configuration file. On Windows the function CreateSharedMemory can be used to create a shared memory, alternatively one can use CreateFileMapping and MapViewOfFile functions to map a region of a file into memory in multiple processes. Some C++ libraries provide a portable and object-oriented access to shared memory functionality, for example, Boost contains Boost. Interprocess C++ Library
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Du (Unix)
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Du is a standard Unix program used to estimate file space usage—space used under a particular directory or files on a file system. The du utility first appeared in version 1 of AT&T UNIX, by default, the Single UNIX Specification specifies that du is to display the file space allocated to each file and directory contained in the current directory. Links will be displayed as the size of the file, not what is being linked to. As du reports allocation space and not absolute file space, the amount of space on a file system shown by du may vary from that shown by df if files have been deleted but their blocks not yet freed. Also the minfree setting that allocates datablocks for the filesystem and the super user processes creates a discrepancy between total blocks and the sum of used and available blocks, the minfree setting is usually set to about 5% of the total filesystem size. For more info see core utils faq. du takes an argument, specifying a pathname for du to work, if it is not specified. -d 0 sums at the current level, -d 1 sums at the subdirectory, -d 2 at sub-subdirectories, other Unix and Unix-like operating systems may add extra options. For example, BSD and GNU du specify a -h option, displaying disk usage in an easier to read by the user
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GNU
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GNU /ɡnuː/ is an operating system and an extensive collection of computer software. GNU is composed wholly of free software, most of which is licensed under the GNU Projects own GPL, GNU is a recursive acronym for GNUs Not Unix. Chosen because GNUs design is Unix-like, but differs from Unix by being free software, the GNU project includes an operating system kernel, GNU HURD, which was the original focus of the Free Software Foundation. However, non-GNU kernels, most famously Linux, can also be used with GNU software, and since the kernel is the least mature part of GNU, the combination of GNU software and the Linux kernel is commonly known as Linux. Richard Stallman, the founder of the project, views GNU as a means to a social end. unix-wizards. Software development began on January 5,1984, when Stallman quit his job at the Lab so that they could not claim ownership or interfere with distributing GNU components as free software, Richard Stallman chose the name by using various plays on words, including the song The Gnu. The goal was to bring a free software operating system into existence. This philosophy was published as the GNU Manifesto in March 1985. It was thus decided that the development would be started using C and Lisp as system programming languages, at the time, Unix was already a popular proprietary operating system. The design of Unix was modular, so it could be reimplemented piece by piece, in October 1985, Stallman set up the Free Software Foundation. In the late 1980s and 1990s, the FSF hired software developers to write the software needed for GNU, as GNU gained prominence, interested businesses began contributing to development or selling GNU software and technical support. The most prominent and successful of these was Cygnus Solutions, now part of Red Hat, GNU developers have contributed to Linux ports of GNU applications and utilities, which are now also widely used on other operating systems such as BSD variants, Solaris and macOS. Many GNU programs have been ported to other operating systems, including proprietary platforms such as Microsoft Windows, GNU programs have been shown to be more reliable than their proprietary Unix counterparts. As of November 2015, there are a total of 466 GNU packages hosted on the official GNU development site. With the April 30,2015 release of the Debian GNU/HURD2015 distro, GNU OS now provides the components to assemble a system that users can install. This includes the GNU Hurd kernel, that is currently in a pre-production state, the Hurd status page states that it may not be ready for production use, as there are still some bugs and missing features. However, it should be a base for further development. Due to Hurd not being ready for use, in practice these operating systems are Linux distributions
26.
IBM AIX
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AIX is a series of proprietary Unix operating systems developed and sold by IBM for several of its computer platforms. AIX is based on UNIX System V with 4. 3BSD-compatible extensions and it is one of five commercial operating systems that have versions certified to The Open Groups UNIX03 standard. The AIX family of operating systems debuted in 1986, became the operating system for the RS/6000 series on its launch in 1990. It is currently supported on IBM Power Systems alongside IBM i, Unix started life at AT&Ts Bell Labs research center in the early 1970s, running on DEC minicomputers. By 1976, the system was in use at various academic institutions, including Princeton. This port would later grow out to become UTS, a mainframe Unix offering by IBMs competitor Amdahl Corporation, IBMs own involvement in Unix can be dated to 1979, when it assisted Bell Labs in doing its own Unix port to the 370. In the process, IBM made modifications to the TSS/370 hypervisor to better support Unix and it took until 1985 for IBM to offer its own Unix on the S/370 platform, IX/370, which was developed by Interactive Systems Corporation and intended by IBM to compete with Amdahl UTS. AIX Version 1, introduced in 1986 for the IBM6150 RT workstation, was based on UNIX System V Releases 1 and 2, in developing AIX, IBM and Interactive Systems Corporation also incorporated source code from 4.2 and 4.3 BSD UNIX. Among other variants, IBM later produced AIX Version 3, based on System V Release 3, since 1990, AIX has served as the primary operating system for the RS/6000 series. AIX Version 4, introduced in 1994, added symmetric multiprocessing with the introduction of the first RS/6000 SMP servers and continued to evolve through the 1990s, culminating with AIX4.3.3 in 1999. Version 4.1, in a modified form, was also the standard operating system for the Apple Network Server systems sold by Apple Computer to complement the Macintosh line. IBM maintains that their license was irrevocable, and continued to sell, AIX was a component of the 2003 SCO v. IBM lawsuit, in which the SCO Group filed a lawsuit against IBM, alleging IBM contributed SCOs intellectual property to the Linux codebase. The SCO Group, who argued they were the owners of the copyrights covering the Unix operating system. In March 2010, a jury returned a finding that Novell, not the SCO Group. AIX6 was announced in May 2007, and it ran as an open beta from June 2007 until the availability of AIX6.1 on November 9,2007. Major new features in AIX6.1 included full role-based access control, workload partitions, enhanced security, AIX7.1 was announced in April 2010, and an open beta ran until general availability of AIX7.1 in September 2010. Several new features, including better scalability, enhanced clustering and management capabilities were added, AIX7.1 includes a new built-in clustering capability called Cluster Aware AIX. AIX is able to organize multiple LPARs through the communications channel to neighboring CPUs
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HP-UX
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HP-UX is Hewlett Packard Enterprises proprietary implementation of the Unix operating system, based on UNIX System V and first released in 1984. Recent versions support the HP9000 series of systems, based on the PA-RISC instruction set architecture. HP-UX was the first Unix to offer access control lists for file access permissions as an alternative to the standard Unix permissions system, HP-UX was also among the first Unix systems to include a built-in logical volume manager. HP has had a partnership with Veritas Software, and uses VxFS as the primary file system. It is one of six operating systems that have versions certified to The Open Groups UNIX03 standard. HP-UX 11i offers a common root disk for its file system. HP Serviceguard is the solution for HP-UX. HPVM supports guests running on HP-UX 11i v3 hosts – guests can run Linux, Windows, HP supports online VM guest migration, where encryption can secure the guest contents during migration. A directory containing such files had its suid bit set and was hidden from both ordinary and root processes under normal use. Such a scheme was sometimes exploited by intruders to hide malicious programs or data, cDFs and the CDF filesystem were dropped with release 10.0. HP-UX operating systems supports a variety of PA-RISC systems, the 11.0 added support for Integrity-based servers for the transition from PA-RISC to Itanium. HP-UX 11i v1.5 is the first version that supported Itanium, on the introduction of HP-UX 11i v2 the operating system supported both of these architectures. HP-UX 11i supports HP Integrity Servers of HP BL server blade family and these servers use the Intel Itanium architecture. HP-UX 11i v2 and 11i v3 support HPs CX series servers, CX stands for carrier grade and is used mainly for telco industry with -48V DC support and is NEBS certified. Both of these systems contain Itanium Mad6M processors and are discontinued, HP-UX supports HPs RX series of servers. Prior to the release of HP-UX version 11.11, HP used a decimal version numbering scheme with the first number giving the major release, with 11.11, HP made a marketing decision to name their releases 11i followed by a v for the version. The i was intended to indicate the OS is Internet-enabled,1.0 First release for HP9000 Series 500. HP-UX for Series 500 was substantially different that HP-UX for any other HP machines, Support for the HP Integral PC
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