Windows XP is a personal computer operating system produced by Microsoft as part of the Windows NT family of operating systems. It was released to manufacturing on August 24, 2001, broadly released for retail sale on October 25, 2001. Development of Windows XP began in the late 1990s as "Neptune", an operating system built on the Windows NT kernel, intended for mainstream consumer use. An updated version of Windows 2000 was originally planned for the business market; as such, Windows XP was the first consumer edition of Windows not to be based on MS-DOS. Upon its release, Windows XP received positive reviews, with critics noting increased performance and stability, a more intuitive user interface, improved hardware support, expanded multimedia capabilities. However, some industry reviewers were concerned by the new licensing model and product activation system. Extended support for Windows XP ended on April 8, 2014, after which the operating system ceased receiving further support or security updates to most users.
As of March 2019, 1.75% of Windows PCs run Windows XP, the OS is still most popular in some countries with up to 38% of the Windows share. In the late 1990s, initial development of what would become Windows XP was focused on two individual products. However, the projects proved to be too ambitious. In January 2000, shortly prior to the official release of Windows 2000, technology writer Paul Thurrott reported that Microsoft had shelved both Neptune and Odyssey in favor of a new product codenamed "Whistler", after Whistler, British Columbia, as many Microsoft employees skied at the Whistler-Blackcomb ski resort; the goal of Whistler was to unify both the consumer and business-oriented Windows lines under a single, Windows NT platform: Thurrott stated that Neptune had become "a black hole when all the features that were cut from were re-tagged as Neptune features. And since Neptune and Odyssey would be based on the same code-base anyway, it made sense to combine them into a single project". At PDC on July 13, 2000, Microsoft announced that Whistler would be released during the second half of 2001, unveiled the first preview build, 2250.
The build notably introduced an early version of Windows XP's visual styles system. Microsoft released the first beta build of Whistler, build 2296, on October 31, 2000. Subsequent builds introduced features that users of the release version of Windows XP would recognise, such as Internet Explorer 6.0, the Microsoft Product Activation system and the Bliss desktop background. On February 5, 2001, Microsoft announced that Whistler would be known as Windows XP, where XP stands for "eXPerience". In June 2001, Microsoft indicated that it was planning to, in conjunction with Intel and other PC makers, spend at least 1 billion US dollars on marketing and promoting Windows XP; the theme of the campaign, "Yes You Can", was designed to emphasize the platform's overall capabilities. Microsoft had planned to use the slogan "Prepare to Fly", but it was replaced due to sensitivity issues in the wake of the September 11 attacks. On August 24, 2001, Windows XP build. During a ceremonial media event at Microsoft Redmond Campus, copies of the RTM build were given to representatives of several major PC manufacturers in briefcases, who flew off on decorated helicopters.
While PC manufacturers would be able to release devices running XP beginning on September 24, 2001, XP was expected to reach general, retail availability on October 25, 2001. On the same day, Microsoft announced the final retail pricing of XP's two main editions, "Home" and "Professional". While retaining some similarities to previous versions, Windows XP's interface was overhauled with a new visual appearance, with an increased use of alpha compositing effects, drop shadows, "visual styles", which changed the appearance of the operating system; the number of effects enabled are determined by the operating system based on the computer's processing power, can be enabled or disabled on a case-by-case basis. XP added ClearType, a new subpixel rendering system designed to improve the appearance of fonts on liquid-crystal displays. A new set of system icons was introduced; the default wallpaper, Bliss, is a photo of a landscape in the Napa Valley outside Napa, with rolling green hills and a blue sky with stratocumulus and cirrus clouds.
The Start menu received its first major overhaul in XP, switching to a two-column layout with the ability to list and display used applications opened documents, the traditional cascading "All Programs" menu. The taskbar can now group windows opened by a single application into one taskbar button, with a popup menu listing the individual windows; the notification area hides "inactive" icons by default. A "common tasks" list was added, Windows Explorer's sidebar was updated to use a new task-based design with lists of common actions. Fast user switching allows additional users to log into a Windows XP machine without existing users having to close their programs and loggin
NetBSD is a free and open-source Unix-like operating system based on the Berkeley Software Distribution. It was the first open-source BSD descendant released after 386BSD was forked, it continues to be developed and is available for many platforms, including servers, handheld devices, embedded systems. The NetBSD project focuses on code clarity, careful design, portability across many computer architectures, its source code is permissively licensed. NetBSD was derived from the 4.3BSD-Reno release of the Berkeley Software Distribution from the Computer Systems Research Group of the University of California, via their Net/2 source code release and the 386BSD project. The NetBSD project began as a result of frustration within the 386BSD developer community with the pace and direction of the operating system's development; the four founders of the NetBSD project, Chris Demetriou, Theo de Raadt, Adam Glass, Charles Hannum, felt that a more open development model would benefit the project: one centered on portable, correct code.
They aimed to produce a multi-platform, production-quality, BSD-based operating system. The name "NetBSD" was suggested by De Raadt, based on the importance and growth of networks such as the Internet at that time, the distributed, collaborative nature of its development; the NetBSD source code repository was established on 21 March 1993 and the first official release, NetBSD 0.8, was made on 19 April 1993. This was derived from 386BSD 0.1 plus the version 0.2.2 unofficial patchkit, with several programs from the Net/2 release missing from 386BSD re-integrated, various other improvements. The first multi-platform release, NetBSD 1.0, was made in October 1994, being updated with 4.4BSD-Lite sources, it was free of all encumbered 4.3BSD Net/2 code. In 1994, for disputed reasons, one of the founders, Theo de Raadt, was removed from the project, he founded a new project, OpenBSD, from a forked version of NetBSD 1.0 near the end of 1995. In 1998, NetBSD 1.3 introduced the pkgsrc packages collection.
Until 2004, NetBSD 1.x releases were made at annual intervals, with minor "patch" releases in between. From release 2.0 onwards, NetBSD uses semantic versioning, each major NetBSD release corresponds to an incremented major version number, i.e. the major releases following 2.0 are 3.0, 4.0 and so on. The previous minor releases are now divided into two categories: x.y "stable" maintenance releases and x.y.z releases containing only security and critical fixes. As the project's motto suggests, NetBSD has been ported to a large number of 32- and 64-bit architectures; these range from VAX minicomputers to Pocket PC PDAs. As of 2009, NetBSD supports 57 hardware platforms; the kernel and userland for these platforms are all built from a central unified source-code tree managed by CVS. Unlike other kernels such as μClinux, the NetBSD kernel requires the presence of an MMU in any given target architecture. NetBSD's portability is aided by the use of hardware abstraction layer interfaces for low-level hardware access such as bus input/output or DMA.
Using this portability layer, device drivers can be split into "machine-independent" and "machine-dependent" components. This makes a single driver usable on several platforms by hiding hardware access details, reduces the work to port it to a new system; this permits a particular device driver for a PCI card to work without modifications, whether it is in a PCI slot on an IA-32, PowerPC, SPARC, or other architecture with a PCI bus. A single driver for a specific device can operate via several different buses, like ISA, PCI, or PC Card. In comparison, Linux device driver code must be reworked for each new architecture; as a consequence, in porting efforts by NetBSD and Linux developers, NetBSD has taken much less time to port to new hardware. This platform independence aids the development of embedded systems since NetBSD 1.6, when the entire toolchain of compilers, assemblers and other tools support cross-compiling. In 2005, as a demonstration of NetBSD's portability and suitability for embedded applications, Technologic Systems, a vendor of embedded systems hardware and demonstrated a NetBSD-powered kitchen toaster.
Commercial ports to embedded platforms, including the AMD Geode LX800, Freescale PowerQUICC processors, Marvell Orion, AMCC 405 family of PowerPC processors, Intel XScale IOP and IXP series, were available from and supported by Wasabi Systems. The NetBSD cross-compiling framework lets a developer build a complete NetBSD system for an architecture from a more powerful system of different architecture, including on a different operating system. Several embedded systems using NetBSD have required no additional software development other than toolchain and target rehost. NetBSD features pkgsrc, a framework for building and managing third-party application software packages; the pkgsrc collection consists of more than 18,000 packages as of April 2018. Building and installing packages such as KDE, GNOME, the Apache HTTP Server or Perl is performed through the use of a system of makefiles; this can automatically fetch the source code, patch, configure and install the package such that it can be removed again later.
An alternative to compiling from source is to use a precompiled binary package. In either case, any prerequisites/dependencies will be installed automatically by the package system, without need for manual intervention. Pkgsrc supports not only NetBSD, but several other BSD variants like
Carnegie Mellon University
Carnegie Mellon University is a private research university based in Pittsburgh, Pennsylvania. Founded in 1900 by Andrew Carnegie as the Carnegie Technical Schools, the university became the Carnegie Institute of Technology in 1912 and began granting four-year degrees. In 1967, the Carnegie Institute of Technology merged with the Mellon Institute of Industrial Research to form Carnegie Mellon University. With its main campus located 3 miles from Downtown Pittsburgh, Carnegie Mellon has grown into an international university with over a dozen degree-granting locations in six continents, including campuses in Qatar and Silicon Valley, more than 20 research partnerships; the university has seven colleges and independent schools which all offer interdisciplinary programs: the College of Engineering, College of Fine Arts, Dietrich College of Humanities and Social Sciences, Mellon College of Science, Tepper School of Business, H. John Heinz III College of Information Systems and Public Policy, the School of Computer Science.
Carnegie Mellon counts 13,961 students from 109 countries, over 105,000 living alumni, over 5,000 faculty and staff. Past and present faculty and alumni include 20 Nobel Prize laureates, 13 Turing Award winners, 23 Members of the American Academy of Arts and Sciences, 22 Fellows of the American Association for the Advancement of Science, 79 Members of the National Academies, 124 Emmy Award winners, 47 Tony Award laureates, 10 Academy Award winners; the Carnegie Technical Schools were founded in 1900 in Pittsburgh by the Scottish American industrialist and philanthropist Andrew Carnegie, who wrote the time-honored words "My heart is in the work", when he donated the funds to create the institution. Carnegie's vision was to open a vocational training school for the sons and daughters of working-class Pittsburghers. Carnegie was inspired for the design of his school by the Pratt Institute in Brooklyn, New York founded by industrialist Charles Pratt in 1887. In 1912, the institution changed its name to Carnegie Institute of Technology and began offering four-year degrees.
During this time, CIT consisted of four constituent schools: the School of Fine and Applied Arts, the School of Apprentices and Journeymen, the School of Science and Technology, the Margaret Morrison Carnegie School for Women. The Mellon Institute of Industrial Research was founded in 1913 by a banker and industrialist brothers Andrew and Richard B. Mellon in honor of their father, Thomas Mellon, the patriarch of the Mellon family; the Institute began as a research organization which performed work for government and industry on a contract and was established as a department within the University of Pittsburgh. In 1927, the Mellon Institute incorporated as an independent nonprofit. In 1938, the Mellon Institute's iconic building was completed and it moved to its new, current, location on Fifth Avenue. In 1967, with support from Paul Mellon, Carnegie Tech merged with the Mellon Institute of Industrial Research to become Carnegie Mellon University. Carnegie Mellon's coordinate women's college, the Margaret Morrison Carnegie College closed in 1973 and merged its academic programs with the rest of the university.
The industrial research mission of the Mellon Institute survived the merger as the Carnegie Mellon Research Institute and continued doing work on contract to industry and government. CMRI closed in 2001 and its programs were subsumed by other parts of the university or spun off into autonomous entities. Carnegie Mellon's 140-acre main campus is three miles from downtown Pittsburgh, between Schenley Park and the Squirrel Hill and Oakland neighborhoods. Carnegie Mellon is bordered to the west by the campus of the University of Pittsburgh. Carnegie Mellon owns 81 buildings in the Squirrel Hill neighborhoods of Pittsburgh. For decades the center of student life on campus was the University's student union. Built in the 1950s, Skibo Hall's design was typical of Mid-Century Modern architecture, but was poorly equipped to deal with advances in computer and internet connectivity; the original Skibo was razed in the summer of 1994 and replaced by a new student union, wi-fi enabled. Known as University Center, the building was dedicated in 1996.
In 2014, Carnegie Mellon re-dedicated the University Center as the Cohon University Center in recognition of the eighth president of the university, Jared Cohon. A large grassy area known as "the Cut" forms the backbone of the campus, with a separate grassy area known as "the Mall" running perpendicular; the Cut was formed by filling in a ravine with soil from a nearby hill, leveled to build the College of Fine Arts building. The northwestern part of the campus was acquired from the United States Bureau of Mines in the 1980s. In 2006, Carnegie Mellon Trustee Jill Gansman Kraus donated the 80-foot -tall sculpture Walking to the Sky, placed on the lawn facing Forbes Ave between the Cohon University Center and Warner Hall; the sculpture was controversial for its placement, the general lack of input that the campus community had, its aesthetic appeal. In April 2015, Carnegie Mellon University, in collaboration with Jones Lang LaSalle, announced the planning of a second office space structure, alongside the Robert Mehrabian Collaborative Innovation Center, an upscale and full-service hotel, retail and dining development along Forbes Avenue.
This complex will connect to the Tepper Quadrangle, the Heinz College, the Tata Consultancy Services Building, the Gates-Hillman Center to create an innovation corridor on the university campus. The eff
In Unix and operating systems inspired by it, the file system is considered a central component of the operating system. It was one of the first parts of the system to be designed and implemented by Ken Thompson in the first experimental version of Unix, dated 1969; as in other operating systems, the filesystem provides information storage and retrieval, one of several forms of interprocess communication, in that the many small programs that traditionally form a Unix system can store information in files so that other programs can read them, although pipes complemented it in this role starting with the Third Edition. The filesystem provides access to other resources through so-called device files that are entry points to terminals and mice; the rest of this article uses Unix as a generic name to refer to both the original Unix operating system and its many workalikes. The filesystem appears as one rooted tree of directories. Instead of addressing separate volumes such as disk partitions, removable media, network shares as separate trees, such volumes can be mounted on a directory, causing the volume's file system tree to appear as that directory in the larger tree.
The root of the entire tree is denoted /. In the original Bell Labs Unix, a two-disk setup was customary, where the first disk contained startup programs, while the second contained users' files and programs; this second disk was mounted at the empty directory named usr on the first disk, causing the two disks to appear as one filesystem, with the second's disks contents viewable at /usr. Unix directories do not contain files. Instead, they contain the names of files paired with references to so-called inodes, which in turn contain both the file and its metadata. Multiple names in the file system may refer to the same file, a feature termed a hard link; the mathematical traits of hard links make the file system a limited type of directed acyclic graph, although the directories still form a tree, as they may not be hard-linked. The original Unix file system supported three types of files: ordinary files, "special files" termed device files; the Berkeley Software Distribution and System V each added a file type to be used for interprocess communication: BSD added sockets, while System V added FIFO files.
BSD added symbolic links to the range of file types, which are files that refer to other files, complement hard links. Symlinks were modeled after a similar feature in Multics, differ from hard links in that they may span filesystems and that their existence is independent of the target object. Other Unix systems may support additional types of files. Certain conventions exist for locating some kinds of files, such as programs, system configuration files, users' home directories; these were first documented in the hier man page since Version 7 Unix. The details of the directory layout have varied over time. Although the file system layout is not part of the Single UNIX Specification, several attempts exist to standardize it, such as the System V Application Binary Interface, the Intel Binary Compatibility Standard, the Common Operating System Environment, Linux Foundation's Filesystem Hierarchy Standard. Here is a generalized overview of common locations of files on a Unix operating system: This article incorporates material from the Citizendium article "Unix filesystem", licensed under the Creative Commons Attribution-ShareAlike 3.0 Unported License but not under the GFDL
Microsoft Windows is a group of several graphical operating system families, all of which are developed and sold by Microsoft. Each family caters to a certain sector of the computing industry. Active Windows families include Windows Embedded. Defunct Windows families include Windows Mobile and Windows Phone. Microsoft introduced an operating environment named Windows on November 20, 1985, as a graphical operating system shell for MS-DOS in response to the growing interest in graphical user interfaces. Microsoft Windows came to dominate the world's personal computer market with over 90% market share, overtaking Mac OS, introduced in 1984. Apple came to see Windows as an unfair encroachment on their innovation in GUI development as implemented on products such as the Lisa and Macintosh. On PCs, Windows is still the most popular operating system. However, in 2014, Microsoft admitted losing the majority of the overall operating system market to Android, because of the massive growth in sales of Android smartphones.
In 2014, the number of Windows devices sold was less than 25 %. This comparison however may not be relevant, as the two operating systems traditionally target different platforms. Still, numbers for server use of Windows show one third market share, similar to that for end user use; as of October 2018, the most recent version of Windows for PCs, tablets and embedded devices is Windows 10. The most recent versions for server computers is Windows Server 2019. A specialized version of Windows runs on the Xbox One video game console. Microsoft, the developer of Windows, has registered several trademarks, each of which denote a family of Windows operating systems that target a specific sector of the computing industry; as of 2014, the following Windows families are being developed: Windows NT: Started as a family of operating systems with Windows NT 3.1, an operating system for server computers and workstations. It now consists of three operating system subfamilies that are released at the same time and share the same kernel: Windows: The operating system for mainstream personal computers and smartphones.
The latest version is Windows 10. The main competitor of this family is macOS by Apple for personal computers and Android for mobile devices. Windows Server: The operating system for server computers; the latest version is Windows Server 2019. Unlike its client sibling, it has adopted a strong naming scheme; the main competitor of this family is Linux. Windows PE: A lightweight version of its Windows sibling, meant to operate as a live operating system, used for installing Windows on bare-metal computers, recovery or troubleshooting purposes; the latest version is Windows PE 10. Windows IoT: Initially, Microsoft developed Windows CE as a general-purpose operating system for every device, too resource-limited to be called a full-fledged computer. However, Windows CE was renamed Windows Embedded Compact and was folded under Windows Compact trademark which consists of Windows Embedded Industry, Windows Embedded Professional, Windows Embedded Standard, Windows Embedded Handheld and Windows Embedded Automotive.
The following Windows families are no longer being developed: Windows 9x: An operating system that targeted consumers market. Discontinued because of suboptimal performance. Microsoft now caters to the consumer market with Windows NT. Windows Mobile: The predecessor to Windows Phone, it was a mobile phone operating system; the first version was called Pocket PC 2000. The last version is Windows Mobile 6.5. Windows Phone: An operating system sold only to manufacturers of smartphones; the first version was Windows Phone 7, followed by Windows Phone 8, the last version Windows Phone 8.1. It was succeeded by Windows 10 Mobile; the term Windows collectively describes any or all of several generations of Microsoft operating system products. These products are categorized as follows: The history of Windows dates back to 1981, when Microsoft started work on a program called "Interface Manager", it was announced in November 1983 under the name "Windows", but Windows 1.0 was not released until November 1985.
Windows 1.0 was to achieved little popularity. Windows 1.0 is not a complete operating system. The shell of Windows 1.0 is a program known as the MS-DOS Executive. Components included Calculator, Cardfile, Clipboard viewer, Control Panel, Paint, Reversi and Write. Windows 1.0 does not allow overlapping windows. Instead all windows are tiled. Only modal dialog boxes may appear over other windows. Microsoft sold as included Windows Development libraries with the C development environment, which included numerous windows samples. Windows 2.0 was released in December 1987, was more popular than its predecessor. It features several improvements to the user memory management. Windows 2.03 changed the OS from tiled windows to overlapping windows. The result of this change led to Apple Computer filing a suit against Microsoft alleging infringement on Apple's copyrights. Windows 2.0
Mahadev Satyanarayanan is an experimental computer scientist, a founding pioneer in edge computing, mobile computing, pervasive computing, Internet of Things. He is the Carnegie Group Professor of Computer Science at Carnegie Mellon University. Satya obtained his Bachelor's and Master's degree from Indian Institute of Technology, Madras in 1975 and 1977, his Ph. D. in Computer Science from CMU in 1983. He is IEEE fellow, his work on the Andrew File System was recognized with the prestigious ACM Software System Award in 2016 and the ACM SIGOPS Hall of Fame Award in 2008 for its excellent engineering and long-lasting impact. His work on disconnected operation in Coda File System received the ACM SIGOPS Hall of Fame Award in 2015 and the inaugural ACM SIGMOBILE Test-of-Time Award in 2016, he served as the founding Program Chair of the IEEE/ACM Symposium on Edge Computing and the HotMobile workshops, the founding Editor-in-Chief of IEEE Pervasive Computing, the founding Area Editor for the Synthesis Series on Mobile and Pervasive Computing.
In addition, he was the founding director of Intel Research Pittsburgh and an advisor to the company Maginatics, acquired by EMC in 2014. In his research career, Satya has focused on the performance, scalability and trust challenges in computing systems that reach from the cloud to the mobile edge of the Internet, he has pioneered many advances in edge computing, distributed systems, mobile computing, pervasive computing, the Internet of Things. Below is a chronological summary of his primary research contributions. Satya was a principal architect and implementer of the Andrew File System, the technical forerunner of modern cloud-based storage systems. AFS has been continuously deployed at CMU at a scale of many thousands of users. From its conception in 1983 as the unifying campus-wide IT infrastructure for CMU, AFS evolved through versions AFS-1, AFS-2 and AFS-3. In mid-1989, AFS-3 was commercialized by Transarc Corporation and its evolution continued outside CMU. Transarc was acquired by IBM, AFS became an IBM product for a number of years.
In 2000, IBM released the code to the open source community as OpenAFS. Since its release as OpenAFS, the system has continued to be used in many enterprises all over the world. In the academic and research lab community, OpenAFS is in use at more than 30 sites in the United States and dozens of sites in Europe, New Zealand, South Korea. Many global companies have used OpenAFS including Morgan Stanley, Goldman Sachs, Qualcomm, IBM, United Airlines, Hitachi, InfoPrint, Pictage. Over a 30-year period, AFS has been a seminal influence on academic research and commercial practice in distributed data storage systems for unstructured data, its approach to native file system emulation, scalable file caching, access-control based security, scalable system administration have proved to be of enduring value in enterprise-scale information sharing. The design principles that were discovered and validated in the creation and evolution of AFS have influenced all modern commercial distributed file systems, including Microsoft DFS, Google File System, Lustre File System and NetApp ONTAP.
In addition, AFS inspired the creation of DropBox whose founders used AFS as part of Project Athena at MIT. It inspired the creation of Maginatics, a startup company advised by Satya that provides cloud-sourced network-attached storage for distributed environments; the NFS v4 network file system protocol standard has been extensively informed by the lessons of AFS. In 2016, AFS was honored with the prestigious ACM Software System Award. Earlier, ACM recognized the significance of AFS by inducting a key paper on it to the ACM SIGOPS Hall of Fame; the AFS papers in 1985 and 1987 received Outstanding Paper awards at the ACM Symposium on Operating System Principles. In 1987, Satya began work on the Coda File System to address a fundamental shortcoming of AFS-like systems. Extensive first-hand experience with the AFS deployment at CMU showed that users are impacted by server and network failures; this vulnerability is not just hypothetical, but indeed a fact of life in real-world deployments. Once users become critically dependent on files cached from servers, a server or network failure renders these files inaccessible and leaves clients crippled for the duration of the failure.
In a large enough system, unplanned outages of servers and network segments are impossible to avoid. Today's enthusiastic embrace of cloud computing rekindles many of these concerns because of increased dependence on centralized resources, The goal of the Coda project was to preserve the many strengths of AFS, while reducing its vulnerability to failures. Over 30+ years, research on Coda has proved to be fruitful in creating new insights and mechanisms for failure-resilient and secure read-write access to shared information by mobile and static users over wireless and wired networks. Coda was the first system to show how server replication could be combined with client caching to achieve good performance and high availability. Coda invented the concept of "disconnected operation", in which cached state on clients is used to mask network and server failures. Coda demonstrated bandwidth-adaptive weakly-connected operation over networks with low bandwidth, high latency or frequent failures. Coda's use of optimistic replication, trading consistency for availability, was controversial when introduced.
Today, it is a standard practice in all data storage systems for mobile environments. Coda pioneered the concept of translucent caching, which balances the full transparency of classic caching with the user visibility needed to achieve a good use
An operating system is system software that manages computer hardware and software resources and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may include accounting software for cost allocation of processor time, mass storage and other resources. For hardware functions such as input and output and memory allocation, the operating system acts as an intermediary between programs and the computer hardware, although the application code is executed directly by the hardware and makes system calls to an OS function or is interrupted by it. Operating systems are found on many devices that contain a computer – from cellular phones and video game consoles to web servers and supercomputers; the dominant desktop operating system is Microsoft Windows with a market share of around 82.74%. MacOS by Apple Inc. is in second place, the varieties of Linux are collectively in third place. In the mobile sector, use in 2017 is up to 70% of Google's Android and according to third quarter 2016 data, Android on smartphones is dominant with 87.5 percent and a growth rate 10.3 percent per year, followed by Apple's iOS with 12.1 percent and a per year decrease in market share of 5.2 percent, while other operating systems amount to just 0.3 percent.
Linux distributions are dominant in supercomputing sectors. Other specialized classes of operating systems, such as embedded and real-time systems, exist for many applications. A single-tasking system can only run one program at a time, while a multi-tasking operating system allows more than one program to be running in concurrency; this is achieved by time-sharing, where the available processor time is divided between multiple processes. These processes are each interrupted in time slices by a task-scheduling subsystem of the operating system. Multi-tasking may be characterized in 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, such as Solaris and Linux—as well as non-Unix-like, such as AmigaOS—support preemptive multitasking. 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 multi-user operating system extends the basic concept of multi-tasking with facilities that identify processes and resources, such as disk space, belonging to multiple users, the system permits multiple users to interact with the system at the same time. Time-sharing operating systems schedule tasks for efficient use of the system and may include accounting software for cost allocation of processor time, mass storage and other resources to multiple users. 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 group work in cooperation, they form a distributed system.
In an OS, distributed and cloud computing context, templating refers to creating a single virtual machine image as a guest operating system saving it as a tool for multiple running virtual machines. The technique is used both in virtualization and cloud computing management, 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. They are able to operate with a limited number of resources, they are compact and efficient by design. Windows CE and Minix 3 are some examples of embedded operating systems. A real-time operating system is an operating 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, it uses specialized scheduling algorithms so that a deterministic nature of behavior is achieved. An event-driven system switches between tasks based on their priorities or external events while time-sharing operating systems switch tasks based on clock interrupts.
A library operating system is one in which the services that a typical operating system provides, such as networking, are provided in the form of libraries and composed with the application and configuration code to construct a unikernel: a specialized, single address space, machine image that can be deployed to cloud or embedded environments. 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 automatically run different programs in succession to speed up processing. Operating systems did not exist in their more complex forms until the early 1960s. Hardware features were added, that enabled use of runtime libraries and parallel processing; when personal computers became popular in the 1980s, operating systems were made for them similar in concept to those used on larger computers. In the 1940s, the earliest electronic digital systems had no operating systems.
Electronic systems of this time were programmed on rows of mechanical switches or by jumper wires on plug boards. These were special-purpose systems that, for example, generated ballistics tables for the military or controlled the pri