1.
X86
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X86 is a family of backward-compatible instruction set architectures based on the Intel 8086 CPU and its Intel 8088 variant. The term x86 came into being because the names of several successors to Intels 8086 processor end in 86, many additions and extensions have been added to the x86 instruction set over the years, almost consistently with full backward compatibility. The architecture has been implemented in processors from Intel, Cyrix, AMD, VIA and many companies, there are also open implementations. In the 1980s and early 1990s, when the 8088 and 80286 were still in common use, today, however, x86 usually implies a binary compatibility also with the 32-bit instruction set of the 80386. An 8086 system, including such as 8087 and 8089. There were also terms iRMX, iSBC, and iSBX – all together under the heading Microsystem 80, however, this naming scheme was quite temporary, lasting for a few years during the early 1980s. Today, x86 is ubiquitous in both stationary and portable computers, and is also used in midrange computers, workstations, servers. A large amount of software, including operating systems such as DOS, Windows, Linux, BSD, Solaris and macOS, functions with x86-based hardware. There have been attempts, including by Intel itself, to end the market dominance of the inelegant x86 architecture designed directly from the first simple 8-bit microprocessors. Examples of this are the iAPX432, the Intel 960, Intel 860, however, the continuous refinement of x86 microarchitectures, circuitry and semiconductor manufacturing would make it hard to replace x86 in many segments. The table below lists processor models and model series implementing variations of the x86 instruction set, each line item is characterized by significantly improved or commercially successful processor microarchitecture designs. Such x86 implementations are seldom simple copies but often employ different internal microarchitectures as well as different solutions at the electronic, quite naturally, early compatible microprocessors were 16-bit, while 32-bit designs were developed much later. For the personal computer market, real quantities started to appear around 1990 with i386 and i486 compatible processors, other companies, which designed or manufactured x86 or x87 processors, include ITT Corporation, National Semiconductor, ULSI System Technology, and Weitek. Some early versions of these microprocessors had heat dissipation problems, AMD later managed to establish itself as a serious contender with the K6 set of processors, which gave way to the very successful Athlon and Opteron. There were also other contenders, such as Centaur Technology, Rise Technology, VIA Technologies energy efficient C3 and C7 processors, which were designed by the Centaur company, have been sold for many years. Centaurs newest design, the VIA Nano, is their first processor with superscalar and it was, perhaps interestingly, introduced at about the same time as Intels first in-order processor since the P5 Pentium, the Intel Atom. The instruction set architecture has twice been extended to a word size. In 1999-2003, AMD extended this 32-bit architecture to 64 bits and referred to it as x86-64 in early documents, Intel soon adopted AMDs architectural extensions under the name IA-32e, later using the name EM64T and finally using Intel 64
2.
IBM PC compatible
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IBM PC compatible computers are those similar to the original IBM PC, XT, and AT, able to run the same software and support the same expansion cards as those. Such computers used to be referred to as PC clones, or IBM clones, Columbia Data Products built the first clone of the IBM personal computer by a clean room implementation of its BIOS. Early IBM PC compatibles used the computer bus as the original PC. The IBM AT compatible bus was named the Industry Standard Architecture bus by manufacturers of compatible computers. The term IBM PC compatible is now a historical description only, only the Apple Macintosh classic Mac OS and macOS kept significant market share without compatibility with the IBM personal computer, so consumers are typically identified as being a PC or Mac user. IBM decided in 1980 to market a low-cost single-user computer as quickly as possible in response to Apple Computers success in the microcomputer market. On 12 August 1981, the first IBM PC went on sale, there were three operating systems available for it. The least expensive and most popular was PC DOS made by Microsoft, in a crucial concession, IBMs agreement allowed Microsoft to sell its own version, MS-DOS, for non-IBM computers. The only component of the original PC architecture exclusive to IBM was the BIOS and this software would run on any machine using MS-DOS or PC-DOS. Software that directly addressed the hardware instead of making standard calls was faster, however, software addressing IBM PC hardware in this way would not run on MS-DOS machines with different hardware. The 808x computer marketplace rapidly excluded all machines which were not hardware-, the 640 KB barrier on conventional system memory available to MS-DOS is a legacy of that period, other non-clone machines, while subject to a limit, could exceed 640 kB. Rumors of lookalike, compatible computers, created without IBMs approval, by June 1983 PC Magazine defined PC clone as a computer accommodate the user who takes a disk home from an IBM PC, walks across the room, and plugs it into the foreign machine. Because of a shortage of IBM PCs that year, many customers purchased clones instead, Columbia Data Products produced the first computer more or less compatible to the IBM PC standard during June 1982, soon followed by Eagle Computer. Compaq announced its first IBM PC compatible in November 1982, the Compaq Portable, the Compaq was the first sewing machine-sized portable computer that was essentially 100% PC-compatible. The company could not copy the BIOS directly as a result of the decision in Apple v. Franklin. Each computer would have its own Original Equipment Manufacturer version of MS-DOS, any software written for MS-DOS would operate on any MS-DOS computer, despite variations in hardware design. This expectation seemed reasonable in the marketplace of the time. Until then Microsoft was based primarily on computer languages such as BASIC, the established small system operating software was CP/M from Digital Research which was in use both at the hobbyist level and by the more professional of those using microcomputers
3.
Intel 80386
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The Intel 80386, also known as i386 or just 386, is a 32-bit microprocessor introduced in 1985. The first versions had 275,000 transistors and were the CPU of many workstations, the 32-bit 80386 can correctly execute most code intended for the earlier 16-bit processors such as 8088 and 80286 that were ubiquitous in early PCs. Over the years, successively newer implementations of the architecture have become several hundreds of times faster than the original 80386. A33 MHz 80386 was reportedly measured to operate at about 11.4 MIPS, the 80386 was introduced in October 1985, while manufacturing of the chips in significant quantities commenced in June 1986. Mainboards for 80386-based computer systems were cumbersome and expensive at first, in May 2006, Intel announced that 80386 production would stop at the end of September 2007. Although it had long been obsolete as a personal computer CPU, Intel, such systems using an 80386 or one of many derivatives are common in aerospace technology and electronic musical instruments, among others. Some mobile phones used the 80386 processor, such as BlackBerry 950. The processor was a significant evolution in the x86 architecture, the predecessor of the 80386 was the Intel 80286, a 16-bit processor with a segment-based memory management and protection system. The 80386 added a 32-bit architecture and a translation unit. It also offered support for register debugging, the 80386 featured three operating modes, real mode, protected mode and virtual mode. The protected mode which debuted in the 286 was extended to allow the 386 to address up to 4 GB of memory, the all new virtual 8086 mode made it possible to run one or more real mode programs in a protected environment, although some programs were not compatible. Several new instructions have been added to 386, BSF, BSR, BT, BTS, BTR, BTC, CDQ, CWDE, LFS, LGS, LSS, MOVSX, MOVZX, SETcc, SHLD, SHRD. Two new segment registers have been added for general purpose programs, debug registers DR0-DR7 were added for hardware breakpoints. New forms of MOV instruction are used to access them, chief architect in the development of the 80386 was John H. Crawford. He was responsible for extending the 80286 architecture and instruction set to 32-bit, the 80486 and P5 Pentium line of processors were descendants of the 80386 design. The following data types are supported and thus implemented by one or more 80386 machine instructions. Bit, bit field and bit string, 8-bit integer, either signed or unsigned. 16-bit integer, either signed or unsigned, 32-bit integer, either signed or unsigned
4.
Microprocessor
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A microprocessor is a computer processor which incorporates the functions of a computers central processing unit on a single integrated circuit, or at most a few integrated circuits. Microprocessors contain both combinational logic and sequential digital logic, Microprocessors operate on numbers and symbols represented in the binary numeral system. The integration of a whole CPU onto a chip or on a few chips greatly reduced the cost of processing power. Integrated circuit processors are produced in numbers by highly automated processes resulting in a low per unit cost. Single-chip processors increase reliability as there are many electrical connections to fail. As microprocessor designs get better, the cost of manufacturing a chip generally stays the same, before microprocessors, small computers had been built using racks of circuit boards with many medium- and small-scale integrated circuits. Microprocessors combined this into one or a few large-scale ICs, the internal arrangement of a microprocessor varies depending on the age of the design and the intended purposes of the microprocessor. Advancing technology makes more complex and powerful chips feasible to manufacture, a minimal hypothetical microprocessor might only include an arithmetic logic unit and a control logic section. The ALU performs operations such as addition, subtraction, and operations such as AND or OR, each operation of the ALU sets one or more flags in a status register, which indicate the results of the last operation. The control logic retrieves instruction codes from memory and initiates the sequence of operations required for the ALU to carry out the instruction, a single operation code might affect many individual data paths, registers, and other elements of the processor. As integrated circuit technology advanced, it was feasible to manufacture more and more complex processors on a single chip, the size of data objects became larger, allowing more transistors on a chip allowed word sizes to increase from 4- and 8-bit words up to todays 64-bit words. Additional features were added to the architecture, more on-chip registers sped up programs. Floating-point arithmetic, for example, was not available on 8-bit microprocessors. Integration of the point unit first as a separate integrated circuit and then as part of the same microprocessor chip. Occasionally, physical limitations of integrated circuits made such practices as a bit slice approach necessary, instead of processing all of a long word on one integrated circuit, multiple circuits in parallel processed subsets of each data word. With the ability to put large numbers of transistors on one chip and this CPU cache has the advantage of faster access than off-chip memory, and increases the processing speed of the system for many applications. Processor clock frequency has increased more rapidly than external memory speed, except in the recent past, a microprocessor is a general purpose system. Several specialized processing devices have followed from the technology, A digital signal processor is specialized for signal processing, graphics processing units are processors designed primarily for realtime rendering of 3D images
5.
History of Unix
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Multics introduced many innovations, but had many problems. Bell Labs, frustrated by the size and complexity of Multics but not the aims and their last researchers to leave Multics, Ken Thompson, Dennis Ritchie, Doug McIlroy, and Joe Ossanna among others, decided to redo the work on a much smaller scale. In 1979, Dennis Ritchie described their vision for Unix, What we wanted to preserve was not just a good environment in which to do programming, dissatisfied with the projects progress, Bell Labs management ultimately withdrew. Ken Thompson, a programmer in the Labs computing research department, had worked on Multics and he decided to write his own operating system. While he still had access to the Multics environment, he wrote simulations for the new file and he also programmed a game called Space Travel, but it needed a more efficient and less expensive machine to run on, and eventually he found a little-used PDP-7 at Bell Labs. The resulting system, much smaller than the envisioned Multics system, was to become Unix, in about a months time, Thompson had implemented a self-hosting operating system with an assembler, editor and shell, using a GECOS machine for bootstrapping. The new operating system was initially without organizational backing, and also without a name, in 1970, Peter G. Neumann coined the project name Unics as a pun on Multics, the new operating system was an emasculated Multics. McIlroy attributes Unix to Brian W. Kernighan, as well as popularizing Thompsons Unix philosophy, for the first time in 1970, the Unix operating system was officially named and ran on the PDP-11/20. A text formatting program called roff and a text editor were added, all three were written in PDP-11/20 assembly language. Bell Labs used this initial text processing system, consisting of Unix, roff, roff soon evolved into troff, the first electronic publishing program with full typesetting capability. As the system grew in complexity and the team wanted more users. After other Bell Labs departments purchased PDP-11s, they chose to run Unix instead of DECs own operating system. By Version 4 it was used within the laboratory and a Unix Support Group was formed. The C language appeared as part of Version 2, the Unix operating system was first presented formally to the outside world at the 1973 Symposium on Operating Systems Principles, where Ritchie and Thompson delivered a paper. Unix could not, therefore, be turned into a product, Bell Labs instead shipped the system for the cost of media and shipping. Ken Thompson quietly began answering requests by shipping out tapes and disks, each accompanied by – according to legend – a note signed, Love, Ken”. In 1973, AT&T released Version 5 Unix and licensed it to educational institutions, while commercial users were rare because of the US$20,000 cost, the latter was the most widely used version into the early 1980s. Anyone could purchase a license, but the terms were very restrictive, licensees only received the source code, the licenses also included the machine-dependent parts of the kernel, written in PDP-11 assembly language
6.
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
7.
Apple Inc.
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Apple is an American multinational technology company headquartered in Cupertino, California that designs, develops, and sells consumer electronics, computer software, and online services. Apples consumer software includes the macOS and iOS operating systems, the media player, the Safari web browser. Its online services include the iTunes Store, the iOS App Store and Mac App Store, Apple Music, Apple was founded by Steve Jobs, Steve Wozniak, and Ronald Wayne in April 1976 to develop and sell personal computers. It was incorporated as Apple Computer, Inc. in January 1977, Apple joined the Dow Jones Industrial Average in March 2015. In November 2014, Apple became the first U. S. company to be valued at over US$700 billion in addition to being the largest publicly traded corporation in the world by market capitalization. The company employs 115,000 full-time employees as of July 2015 and it operates the online Apple Store and iTunes Store, the latter of which is the worlds largest music retailer. Consumers use more than one billion Apple products worldwide as of March 2016, Apples worldwide annual revenue totaled $233 billion for the fiscal year ending in September 2015. This revenue accounts for approximately 1. 25% of the total United States GDP.1 billion, the corporation receives significant criticism regarding the labor practices of its contractors and its environmental and business practices, including the origins of source materials. Apple was founded on April 1,1976, by Steve Jobs, Steve Wozniak, the Apple I kits were computers single-handedly designed and hand-built by Wozniak and first shown to the public at the Homebrew Computer Club. The Apple I was sold as a motherboard, which was less than what is now considered a personal computer. The Apple I went on sale in July 1976 and was market-priced at $666.66, Apple was incorporated January 3,1977, without Wayne, who sold his share of the company back to Jobs and Wozniak for $800. Multimillionaire Mike Markkula provided essential business expertise and funding of $250,000 during the incorporation of Apple, during the first five years of operations revenues grew exponentially, doubling about every four months. Between September 1977 and September 1980 yearly sales grew from $775,000 to $118m, the Apple II, also invented by Wozniak, was introduced on April 16,1977, at the first West Coast Computer Faire. It differed from its rivals, the TRS-80 and Commodore PET, because of its character cell-based color graphics. While early Apple II models used ordinary cassette tapes as storage devices, they were superseded by the introduction of a 5 1/4 inch floppy disk drive and interface called the Disk II. The Apple II was chosen to be the platform for the first killer app of the business world, VisiCalc. VisiCalc created a market for the Apple II and gave home users an additional reason to buy an Apple II. Before VisiCalc, Apple had been a distant third place competitor to Commodore, by the end of the 1970s, Apple had a staff of computer designers and a production line
8.
Berkeley Software Distribution
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Berkeley Software Distribution is a Unix operating system derivative developed and distributed by the Computer Systems Research Group of the University of California, Berkeley, from 1977 to 1995. Today the term BSD is often used non-specifically to refer to any of the BSD descendants which together form a branch of the family of Unix-like operating systems, operating systems derived from the original BSD code remain actively developed and widely used. Historically, BSD has been considered a branch of Unix, Berkeley Unix, because it shared the initial codebase, in the 1980s, BSD was widely adopted by vendors of workstation-class systems in the form of proprietary Unix variants such as DEC ULTRIX and Sun Microsystems SunOS. This can be attributed to the ease with which it could be licensed, FreeBSD, OpenBSD, NetBSD, Darwin, and PC-BSD. The earliest distributions of Unix from Bell Labs in the 1970s included the source code to the system, allowing researchers at universities to modify. A larger PDP-11/70 was installed at Berkeley the following year, using money from the Ingres database project, also in 1975, Ken Thompson took a sabbatical from Bell Labs and came to Berkeley as a visiting professor. He helped to install Version 6 Unix and started working on a Pascal implementation for the system, graduate students Chuck Haley and Bill Joy improved Thompsons Pascal and implemented an improved text editor, ex. Other universities became interested in the software at Berkeley, and so in 1977 Joy started compiling the first Berkeley Software Distribution, 1BSD was an add-on to Version 6 Unix rather than a complete operating system in its own right. Some thirty copies were sent out, some 75 copies of 2BSD were sent out by Bill Joy. 2. 9BSD from 1983 included code from 4. 1cBSD, the most recent release,2. 11BSD, was first issued in 1992. As of 2008, maintenance updates from volunteers are still continuing, a VAX computer was installed at Berkeley in 1978, but the port of Unix to the VAX architecture, UNIX/32V, did not take advantage of the VAXs virtual memory capabilities. 3BSD was also alternatively called Virtual VAX/UNIX or VMUNIX, and BSD kernel images were normally called /vmunix until 4. 4BSD, 4BSD offered a number of enhancements over 3BSD, notably job control in the previously released csh, delivermail, reliable signals, and the Curses programming library. In a 1985 review of BSD releases, John Quarterman et al, many installations inside the Bell System ran 4. 1BSD. 4. 1BSD was a response to criticisms of BSDs performance relative to the dominant VAX operating system, the 4. 1BSD kernel was systematically tuned up by Bill Joy until it could perform as well as VMS on several benchmarks. Back at Bell Labs,4. 1cBSD became the basis of the 8th Edition of Research Unix, to guide the design of 4. The committee met from April 1981 to June 1983, apart from the Fast File System, several features from outside contributors were accepted, including disk quotas and job control. Sun Microsystems provided testing on its Motorola 68000 machines prior to release, the official 4. 2BSD release came in August 1983. On a lighter note, it marked the debut of BSDs daemon mascot in a drawing by John Lasseter that appeared on the cover of the printed manuals distributed by USENIX
9.
Free software
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The right to study and modify software entails availability of the software source code to its users. This right is conditional on the person actually having a copy of the software. Richard Stallman used the existing term free software when he launched the GNU Project—a collaborative effort to create a freedom-respecting operating system—and the Free Software Foundation. The FSFs Free Software Definition states that users of software are free because they do not need to ask for permission to use the software. Free software thus differs from proprietary software, such as Microsoft Office, Google Docs, Sheets, and Slides or iWork from Apple, which users cannot study, change, freeware, which is a category of freedom-restricting proprietary software that does not require payment for use. For computer programs that are covered by law, software freedom is achieved with a software license. Software that is not covered by law, such as software in the public domain, is free if the source code is in the public domain. Proprietary software, including freeware, use restrictive software licences or EULAs, Users are thus prevented from changing the software, and this results in the user relying on the publisher to provide updates, help, and support. This situation is called vendor lock-in, Users often may not reverse engineer, modify, or redistribute proprietary software. Other legal and technical aspects, such as patents and digital rights management may restrict users in exercising their rights. Free software may be developed collaboratively by volunteer computer programmers or by corporations, as part of a commercial, from the 1950s up until the early 1970s, it was normal for computer users to have the software freedoms associated with free software, which was typically public domain software. Software was commonly shared by individuals who used computers and by manufacturers who welcomed the fact that people were making software that made their hardware useful. Organizations of users and suppliers, for example, SHARE, were formed to exchange of software. As software was written in an interpreted language such as BASIC. Software was also shared and distributed as printed source code in computer magazines and books, in United States vs. IBM, filed January 17,1969, the government charged that bundled software was anti-competitive. While some software might always be free, there would henceforth be an amount of software produced primarily for sale. In the 1970s and early 1980s, the industry began using technical measures to prevent computer users from being able to study or adapt the software as they saw fit. In 1980, copyright law was extended to computer programs, Software development for the GNU operating system began in January 1984, and the Free Software Foundation was founded in October 1985
10.
Open-source model
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Open-source software may be developed in a collaborative public manner. According to scientists who studied it, open-source software is a prominent example of open collaboration, a 2008 report by the Standish Group states that adoption of open-source software models has resulted in savings of about $60 billion per year to consumers. In the early days of computing, programmers and developers shared software in order to learn from each other, eventually the open source notion moved to the way side of commercialization of software in the years 1970-1980. In 1997, Eric Raymond published The Cathedral and the Bazaar and this source code subsequently became the basis behind SeaMonkey, Mozilla Firefox, Thunderbird and KompoZer. Netscapes act prompted Raymond and others to look into how to bring the Free Software Foundations free software ideas, the new term they chose was open source, which was soon adopted by Bruce Perens, publisher Tim OReilly, Linus Torvalds, and others. The Open Source Initiative was founded in February 1998 to encourage use of the new term, a Microsoft executive publicly stated in 2001 that open source is an intellectual property destroyer. I cant imagine something that could be worse than this for the software business, IBM, Oracle, Google and State Farm are just a few of the companies with a serious public stake in todays competitive open-source market. There has been a significant shift in the corporate philosophy concerning the development of FOSS, the free software movement was launched in 1983. In 1998, a group of individuals advocated that the free software should be replaced by open-source software as an expression which is less ambiguous. Software developers may want to publish their software with an open-source license, the Open Source Definition, notably, presents an open-source philosophy, and further defines the terms of usage, modification and redistribution of open-source software. Software licenses grant rights to users which would otherwise be reserved by law to the copyright holder. Several open-source software licenses have qualified within the boundaries of the Open Source Definition, the open source label came out of a strategy session held on April 7,1998 in Palo Alto in reaction to Netscapes January 1998 announcement of a source code release for Navigator. They used the opportunity before the release of Navigators source code to clarify a potential confusion caused by the ambiguity of the free in English. Many people claimed that the birth of the Internet, since 1969, started the open source movement, the Free Software Foundation, started in 1985, intended the word free to mean freedom to distribute and not freedom from cost. Since a great deal of free software already was free of charge, such software became associated with zero cost. The Open Source Initiative was formed in February 1998 by Eric Raymond and they sought to bring a higher profile to the practical benefits of freely available source code, and they wanted to bring major software businesses and other high-tech industries into open source. Perens attempted to open source as a service mark for the OSI. The Open Source Initiatives definition is recognized by governments internationally as the standard or de facto definition, OSI uses The Open Source Definition to determine whether it considers a software license open source
11.
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
12.
FreeBSD
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FreeBSD is a free and open source Unix-like operating system descended from Research Unix via the Berkeley Software Distribution. Although for legal reasons FreeBSD cannot use the Unix trademark, it is a descendant of BSD. FreeBSD has similarities with Linux, with two differences in scope and licensing, FreeBSD maintains a complete operating system, i. e. The FreeBSD project includes a security team overseeing all software shipped in the base distribution, a wide range of additional third-party applications may be installed using the pkgng package management system or the FreeBSD Ports, or by directly compiling source code. FreeBSDs roots go back to the University of California, Berkeley, the university acquired a UNIX source license from AT&T. The BSD project was founded in 1976 by Bill Joy, but since BSD contained code from AT&T Unix, all recipients had to get a license from AT&T first in order to use BSD. In June 1989, Networking Release 1 or simply Net-1 – the first public version of BSD – was released, after releasing Net-1, Keith Bostic, a developer of BSD, suggested replacing all AT&T code with freely-redistributable code under the original BSD license. Work on replacing AT&T code began and, after 18 months, however, six files containing AT&T code remained in the kernel. The BSD developers decided to release the Networking Release 2 without those six files and they released 386BSD via an anonymous FTP server. The first version of FreeBSD was released on November 1993, in the early days of the projects inception, a company named Walnut Creek CDROM, upon the suggestion of the two FreeBSD developers, agreed to release the operating system on CD-ROM. By 1997, FreeBSD was Walnut Creeks most successful product, the company itself later renamed to The FreeBSD Mall and later iXSystems. Today, FreeBSD is used by many IT companies such as IBM, Nokia, Juniper Networks, certain parts of Apples Mac OS X operating system are based on FreeBSD. The PlayStation 3 operating system also borrows certain components from FreeBSD, netflix, WhatsApp, and FlightAware are also examples of big, successful and heavily network-oriented companies which are running FreeBSD. 386BSD and FreeBSD were both derived from 1992s BSD release, in January 1992, BSDi started to release BSD/386, later called BSD/OS, an operating system similar to FreeBSD and based on 1992s BSD release. AT&T filed a lawsuit against BSDi and alleged distribution of AT&T source code in violation of license agreements, the lawsuit was settled out of court and the exact terms were not all disclosed. The only one that became public was that BSDi would migrate their source base to the newer 4. 4BSD-Lite sources, Although not involved in the litigation, it was suggested to FreeBSD that they should also move to 4. 4BSD-Lite. FreeBSD2.0, which was released on November 1994, was the first version of FreeBSD without any code from AT&T, Desktop Although FreeBSD does not install the X Window System by default, it is available in the FreeBSD ports collection. A number of Desktop environments such as GNOME, KDE and Xfce, embedded systems Although it explicitly focuses on the IA-32 and x86-64 platforms, FreeBSD also supports others such as ARM, PowerPC and MIPS to a lesser degree
