Dropbox is a file hosting service operated by the American company Dropbox, Inc. headquartered in San Francisco, that offers cloud storage, file synchronization, personal cloud, client software. Dropbox was founded in 2007 by MIT students Drew Houston and Arash Ferdowsi as a startup company, with initial funding from seed accelerator Y Combinator. Dropbox can create a special folder on the user's computer, the contents of which are synchronized to Dropbox's servers and to other computers and devices where the user has installed Dropbox, keeping the same files up-to-date on all devices. Dropbox uses a freemium business model, where users are offered a free account with a set storage size, with paid subscriptions available that offer more capacity and additional features. Dropbox Basic users are given two gigabytes of free storage space. Dropbox Plus users are given one terabyte of storage space, as well as additional features, including advanced sharing controls, remote wipe, an optional Extended Version History add-on.
Dropbox offers computer apps for Microsoft Windows, Apple macOS, Linux computers, mobile apps for iOS, Windows Phone smartphones and tablets. In March 2013, the company acquired Mailbox, a popular email app, in April 2014, the company introduced Dropbox Carousel, a photo and video gallery app. Both Mailbox and Carousel were shut down in December 2015, with key features from both apps implemented into the regular Dropbox service. In October 2015, it announced Dropbox Paper, its collaborative document editor, in a reported effort to expand its operations towards businesses; as of March 2016, Dropbox has 500 million users. Dropbox has received praise, including the Crunchie Award in 2010 for Best Internet Application, Macworld's 2009 Editor's Choice Award for Software, it has been ranked as one of the most valuable startups in the US and the world, with a valuation of over US$10 billion, it has been described as one of Y Combinator's most successful investments to date. However, Dropbox has experienced criticism and generated controversy for issues including security breaches and privacy concerns.
Dropbox has been blocked in China since 2014. It has a five star privacy rating from the Electronic Frontier Foundation. Dropbox founder Drew Houston conceived the Dropbox concept after forgetting his USB flash drive while he was a student at MIT. In a 2009 "Meet the Team" post on the Dropbox blog, he wrote that existing services at the time "suffered problems with Internet latency, large files, bugs, or just made me think too much", he began making something for his personal use, but realized that it could benefit others with the same problems. Houston founded Evenflow, Inc. in May 2007 as the company behind Dropbox, shortly thereafter secured seed funding from Y Combinator. Dropbox launched at 2008's TechCrunch Disrupt, an annual technology conference. Owing to trademark disputes between Proxy, Inc. and Evenflow, Dropbox's official domain name was "getdropbox.com" until October 2009, when it acquired its current domain, "dropbox.com". In October 2009, Inc. was renamed to Dropbox, Inc. In an interview with TechCrunch's "Founder Stories" in October 2011, Houston explained that a demo video was released during Dropbox's early days, with one viewer being Arash Ferdowsi.
Ferdowsi was "so impressed". In regards to competition, Houston stated that "It is easy for me to explain the idea, it is really hard to do it." Dropbox has seen steady user growth since its inception. It surpassed the 1 million registered users milestone in April 2009, followed by 2 million in September, 3 million in November, it passed 50 million users in October 2011, 100 million in November 2012, 200 million in November 2013, 400 million in June 2015, 500 million in March 2016. In July 2012, Dropbox acquired TapEngage, a startup that "enables advertisers and publishers to collaborate on tablet-optimized advertising"; the following December, Dropbox acquired two companies. In July 2013, Dropbox acquired Endorse, a "mobile coupon startup". In May 2014, Dropbox acquired Bubbli, a startup that has "built some innovative ways of incorporating 3D technology into 2D views, packaging it in a mobile app". In January 2015, Dropbox acquired CloudOn, a company that provided mobile applications for document editing and creation.
At the same time, Dropbox told TechCrunch that CloudOn's base in Herzliya would become the first Dropbox office in Israel. In July, Dropbox acquired an enterprise communication service. In April 2014, Dropbox acquired photo-sharing company Loom, document-sharing startup Hackpad. Dropbox announced in April 2017 that Hackpad would be shut down on July 19, with all notes being migrated to Dropbox Paper. In January 2019 Dropbox expressed its intention to buy HelloSign startup, which deals with document workflows and e-signatures; the transaction amounted $230 million. Dropbox has computer apps for Microsoft Windows, Apple macOS, Linux computers, mobile apps for iOS, Windows Phone smartphones and tablets, it offers a website interface. As part of its partnership with Microsoft, Dropbox announced a universal Windows 10 app in January 2016. Dropbox's apps offer an automatic photo uploading feature, allowing users to automatically upload photos or videos from cameras, tablets, SD ca
MacOS is a series of graphical operating systems developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac family of computers. Within the market of desktop and home computers, by web usage, it is the second most used desktop OS, after Microsoft Windows.macOS is the second major series of Macintosh operating systems. The first is colloquially called the "classic" Mac OS, introduced in 1984, the final release of, Mac OS 9 in 1999; the first desktop version, Mac OS X 10.0, was released in March 2001, with its first update, 10.1, arriving that year. After this, Apple began naming its releases after big cats, which lasted until OS X 10.8 Mountain Lion. Since OS X 10.9 Mavericks, releases have been named after locations in California. Apple shortened the name to "OS X" in 2012 and changed it to "macOS" in 2016, adopting the nomenclature that they were using for their other operating systems, iOS, watchOS, tvOS; the latest version is macOS Mojave, publicly released in September 2018.
Between 1999 and 2009, Apple sold. The initial version, Mac OS X Server 1.0, was released in 1999 with a user interface similar to Mac OS 8.5. After this, new versions were introduced concurrently with the desktop version of Mac OS X. Beginning with Mac OS X 10.7 Lion, the server functions were made available as a separate package on the Mac App Store.macOS is based on technologies developed between 1985 and 1997 at NeXT, a company that Apple co-founder Steve Jobs created after leaving the company. The "X" in Mac OS X and OS X is pronounced as such; the X was a prominent part of the operating system's brand identity and marketing in its early years, but receded in prominence since the release of Snow Leopard in 2009. UNIX 03 certification was achieved for the Intel version of Mac OS X 10.5 Leopard and all releases from Mac OS X 10.6 Snow Leopard up to the current version have UNIX 03 certification. MacOS shares its Unix-based core, named Darwin, many of its frameworks with iOS, tvOS and watchOS.
A modified version of Mac OS X 10.4 Tiger was used for the first-generation Apple TV. Releases of Mac OS X from 1999 to 2005 ran on the PowerPC-based Macs of that period. After Apple announced that they were switching to Intel CPUs from 2006 onwards, versions were released for 32-bit and 64-bit Intel-based Macs. Versions from Mac OS X 10.7 Lion run on 64-bit Intel CPUs, in contrast to the ARM architecture used on iOS and watchOS devices, do not support PowerPC applications. The heritage of what would become macOS had originated at NeXT, a company founded by Steve Jobs following his departure from Apple in 1985. There, the Unix-like NeXTSTEP operating system was developed, launched in 1989; the kernel of NeXTSTEP is based upon the Mach kernel, developed at Carnegie Mellon University, with additional kernel layers and low-level user space code derived from parts of BSD. Its graphical user interface was built on top of an object-oriented GUI toolkit using the Objective-C programming language. Throughout the early 1990s, Apple had tried to create a "next-generation" OS to succeed its classic Mac OS through the Taligent and Gershwin projects, but all of them were abandoned.
This led Apple to purchase NeXT in 1996, allowing NeXTSTEP called OPENSTEP, to serve as the basis for Apple's next generation operating system. This purchase led to Steve Jobs returning to Apple as an interim, the permanent CEO, shepherding the transformation of the programmer-friendly OPENSTEP into a system that would be adopted by Apple's primary market of home users and creative professionals; the project was first code named "Rhapsody" and officially named Mac OS X. Mac OS X was presented as the tenth major version of Apple's operating system for Macintosh computers. Previous Macintosh operating systems were named using Arabic numerals, as with Mac OS 8 and Mac OS 9; the letter "X" in Mac OS X's name refers to a Roman numeral. It is therefore pronounced "ten" in this context. However, it is commonly pronounced like the letter "X"; the first version of Mac OS X, Mac OS X Server 1.0, was a transitional product, featuring an interface resembling the classic Mac OS, though it was not compatible with software designed for the older system.
Consumer releases of Mac OS X included more backward compatibility. Mac OS applications could be rewritten to run natively via the Carbon API; the consumer version of Mac OS X was launched in 2001 with Mac OS X 10.0. Reviews were variable, with extensive praise for its sophisticated, glossy Aqua interface but criticizing it for sluggish performance. With Apple's popularity at a low, the makers of several classic Mac applications such as FrameMaker and PageMaker declined to develop new versions of their software for Mac OS X. Ars Technica columnist John Siracusa, who reviewed every major OS X release up to 10.10, described the early releases in retrospect as'dog-slow, feature poor' and Aqua as'unbearably slow and a huge resource hog'. Apple developed several new releases of Mac OS X. Siracusa's review of version 10.3, noted "It's strange to have gone from years of uncertainty and vaporware to a steady annual supply of major new operating system releases." Version 10.4, Tiger shocked executives at Microsoft by offering a number of features, such as fast file s
GNU General Public License
The GNU General Public License is a widely-used free software license, which guarantees end users the freedom to run, study and modify the software. The license was written by Richard Stallman of the Free Software Foundation for the GNU Project, grants the recipients of a computer program the rights of the Free Software Definition; the GPL is a copyleft license, which means that derivative work can only be distributed under the same license terms. This is in distinction to permissive free software licenses, of which the BSD licenses and the MIT License are widely-used examples. GPL was the first copyleft license for general use; the GPL license family has been one of the most popular software licenses in the free and open-source software domain. Prominent free-software programs licensed under the GPL include the Linux kernel and the GNU Compiler Collection. David A. Wheeler argues that the copyleft provided by the GPL was crucial to the success of Linux-based systems, giving the programmers who contributed to the kernel the assurance that their work would benefit the whole world and remain free, rather than being exploited by software companies that would not have to give anything back to the community.
In 2007, the third version of the license was released to address some perceived problems with the second version that were discovered during its long-time usage. To keep the license up to date, the GPL license includes an optional "any version" clause, allowing users to choose between the original terms or the terms in new versions as updated by the FSF. Developers can omit it; the GPL was written by Richard Stallman in 1989, for use with programs released as part of the GNU project. The original GPL was based on a unification of similar licenses used for early versions of GNU Emacs, the GNU Debugger and the GNU C Compiler; these licenses contained similar provisions to the modern GPL, but were specific to each program, rendering them incompatible, despite being the same license. Stallman's goal was to produce one license that could be used for any project, thus making it possible for many projects to share code; the second version of the license, version 2, was released in 1991. Over the following 15 years, members of the free software community became concerned over problems in the GPLv2 license that could let someone exploit GPL-licensed software in ways contrary to the license's intent.
These problems included tivoization, compatibility issues similar to those of the Affero General Public License—and patent deals between Microsoft and distributors of free and open-source software, which some viewed as an attempt to use patents as a weapon against the free software community. Version 3 was developed to attempt to address these concerns and was released on 29 June 2007. Version 1 of the GNU GPL, released on 25 February 1989, prevented what were the two main ways that software distributors restricted the freedoms that define free software; the first problem was that distributors may publish binary files only—executable, but not readable or modifiable by humans. To prevent this, GPLv1 stated that copying and distributing copies or any portion of the program must make the human-readable source code available under the same licensing terms; the second problem was that distributors might add restrictions, either to the license, or by combining the software with other software that had other restrictions on distribution.
The union of two sets of restrictions would apply to the combined work, thus adding unacceptable restrictions. To prevent this, GPLv1 stated that modified versions, as a whole, had to be distributed under the terms in GPLv1. Therefore, software distributed under the terms of GPLv1 could be combined with software under more permissive terms, as this would not change the terms under which the whole could be distributed. However, software distributed under GPLv1 could not be combined with software distributed under a more restrictive license, as this would conflict with the requirement that the whole be distributable under the terms of GPLv1. According to Richard Stallman, the major change in GPLv2 was the "Liberty or Death" clause, as he calls it – Section 7; the section says that licensees may distribute a GPL-covered work only if they can satisfy all of the license's obligations, despite any other legal obligations they might have. In other words, the obligations of the license may not be severed due to conflicting obligations.
This provision is intended to discourage any party from using a patent infringement claim or other litigation to impair users' freedom under the license. By 1990, it was becoming apparent that a less restrictive license would be strategically useful for the C library and for software libraries that did the job of existing proprietary ones; the version numbers diverged in 1999 when version 2.1 of the LGPL was released, which renamed it the GNU Lesser General Public License to reflect its place in the philosophy. Most "GPLv2 or any version" is stated by users of the license, to allow upgrading to GPLv3. In late 2005, the Free Software Foundation announced work on version 3 of the GPL. On 16 January 2006, the first "discussion draft" of GPLv3 was published, the public consultation began; the public consultation was planned for ni
A control element in a graphical user interface is an element of interaction, such as a button or a scroll bar. Controls are software components that a computer user interacts with through direct manipulation to read or edit information about an application. User interface libraries such as Windows Presentation Foundation, GTK+, Cocoa, contain a collection of controls and the logic to render these; each widget facilitates a specific type of user-computer interaction, appears as a visible part of the application's GUI as defined by the theme and rendered by the rendering engine. The theme makes all widgets adhere to a unified aesthetic design and creates a sense of overall cohesion; some widgets support interaction with the user, for example labels and check boxes. Others act as containers that group the widgets added to them, for example windows and tabs. Structuring a user interface with widget toolkits allows developers to reuse code for similar tasks, provides users with a common language for interaction, maintaining consistency throughout the whole information system.
Graphical user interface builders facilitate the authoring of GUIs in a WYSIWYG manner employing a user interface markup language. They automatically generate all the source code for a widget from general descriptions provided by the developer through direct manipulation. Any widget displays an information arrangement changeable by the user, such as a window or a text box; the defining characteristic of a widget is to provide a single interaction point for the direct manipulation of a given kind of data. In other words, widgets are basic visual building blocks which, combined in an application, hold all the data processed by the application and the available interactions on this data. GUI widgets are graphical elements used to build the human-machine-interface of a program. GUI widgets are implemented like software components. Widget toolkits and software frameworks, like e.g. GTK+ or Qt, contain them in software libraries so that programmers can use them to build GUIs for their programs. A family of common reusable widgets has evolved for holding general information based on the Palo Alto Research Center Inc. research for the Xerox Alto User Interface.
Various implementations of these generic widgets are packaged together in widget toolkits, which programmers use to build graphical user interfaces. Most operating systems include a set of ready-to-tailor widgets that a programmer can incorporate in an application, specifying how it is to behave; each type of widget is defined as a class by object-oriented programming. Therefore, many widgets are derived from class inheritance. In the context of an application, a widget may be disabled at a given point in time. An enabled widget has the capacity to respond to events, such as keystrokes or mouse actions. A widget that cannot respond to such events is considered disabled; the appearance of a widget differs depending on whether it is enabled or disabled. See the adjacent image for an example. Widgets are sometimes qualified as virtual to distinguish them from their physical counterparts, e.g. virtual buttons that can be clicked with a pointer, vs. physical buttons that can be pressed with a finger.
A related concept is the desktop widget, a small specialized GUI application that provides some visual information and/or easy access to used functions such as clocks, news aggregators and desktop notes. These kinds of widgets are hosted by a widget engine. “Widget” entered American English around 1920, as a generic term for any useful device a product manufactured for sale. In computer use it has been borrowed as a shortened form of “window gadget,” and was first applied to user interface elements during Project Athena in 1988; the word was chosen because "all other common terms were overloaded with inappropriate connotations" – since the project's Intrinsics toolkit associated each widget with a window of the underlying X Window System – and because of the common prefix with the word window. Selection and display of collections Button – control which can be clicked upon to perform an action. An equivalent to a push-button as found on electronic instruments. Radio button – control which can be clicked upon to select one option from a selection of options, similar to selecting a radio station from a group of buttons dedicated to radio tuning.
Radio buttons always appear in pairs or larger groups, only one option in the group can be selected at a time. Check box – control which can be clicked upon to enable or disable an option. Called a tick box; the box indicates an "on" or "off" state via a check mark/tick ☑ or a cross ☒. Can be shown in an intermediate state to indicate that various objects in a multiple selection have different values for the property represented by the check box. Multiple check boxes in a group may be selected, in contrast with radio buttons. Split button – control combining a button and a drop-down list with related, secondary actions Cycle button - a button that cycles its content through two or more values, thus enabling selection of one from a group of items. Slider – control with a handle that can be moved up and down or right and left on a bar to select a value; the bar allows users to make adjustments to a process throughout a range of allowed values. List box – a graphical control element that allows
In computing, a plug-in is a software component that adds a specific feature to an existing computer program. When a program supports plug-ins, it enables customization. Web browsers have allowed executables as plug-ins, though they are now deprecated. Two plug-in examples are the Adobe Flash Player for playing videos and a Java virtual machine for running applets. A theme or skin is a preset package containing additional or changed graphical appearance details, achieved by the use of a graphical user interface that can be applied to specific software and websites to suit the purpose, topic, or tastes of different users to customize the look and feel of a piece of computer software or an operating system front-end GUI. Applications support plug-ins for many reasons; some of the main reasons include: to enable third-party developers to create abilities which extend an application to support adding new features to reduce the size of an application to separate source code from an application because of incompatible software licenses.
Types of applications and why they use plug-ins: Audio editors use plug-ins to generate, process or analyze sound. Ardour and Audacity are examples of such editors. Digital audio workstations use plug-ins to process it. Examples include ProTools. Email clients use plug-ins to encrypt email. Pretty Good Privacy is an example of such plug-ins. Video game console emulators use plug-ins to modularize the separate subsystems of the devices they seek to emulate. For example, the PCSX2 emulator makes use of video, optical, etc. plug-ins for those respective components of the PlayStation 2. Graphics software use plug-ins to support file formats and process images. Media players use plug-ins to apply filters. Foobar2000, GStreamer, Quintessential, VST, Winamp, XMMS are examples of such media players. Packet sniffers use plug-ins to decode packet formats. OmniPeek is an example of such packet sniffers. Remote sensing applications use plug-ins to process data from different sensor types. Text editors and Integrated development environments use plug-ins to support programming languages or enhance development process e.g. Visual Studio, RAD Studio, IntelliJ IDEA, jEdit and MonoDevelop support plug-ins.
Visual Studio itself can be plugged into other applications via Visual Studio Tools for Office and Visual Studio Tools for Applications. Web browsers have used executables as plug-ins, though they are now deprecated. Examples include Java SE, QuickTime, Microsoft Silverlight and Unity; the host application provides services which the plug-in can use, including a way for plug-ins to register themselves with the host application and a protocol for the exchange of data with plug-ins. Plug-ins depend on the services provided by the host application and do not work by themselves. Conversely, the host application operates independently of the plug-ins, making it possible for end-users to add and update plug-ins dynamically without needing to make changes to the host application. Programmers implement plug-in functionality using shared libraries, which get dynamically loaded at run time, installed in a place prescribed by the host application. HyperCard supported a similar facility, but more included the plug-in code in the HyperCard documents themselves.
Thus the HyperCard stack became a self-contained application in its own right, distributable as a single entity that end-users could run without the need for additional installation-steps. Programs may implement plugins by loading a directory of simple script files written in a scripting language like Python or Lua. In Mozilla Foundation definitions, the words "add-on", "extension" and "plug-in" are not synonyms. "Add-on" can refer to anything. Extensions comprise a subtype, albeit the most powerful one. Mozilla applications come with integrated add-on managers that, similar to package managers, install and manage extensions; the term, "Plug-in", however refers to NPAPI-based web content renderers. Plug-ins are being deprecated. Plug-ins appeared as early as the mid 1970s, when the EDT text editor running on the Unisys VS/9 operating system using the UNIVAC Series 90 mainframe computers provided the ability to run a program from the editor and to allow such a program to access the editor buffer, thus allowing an external program to access an edit session in memory.
The plug-in program could make calls to the editor to have it perform text-editing services upon the buffer that the editor shared with the plug-in. The Waterloo Fortran compiler used this feature to allow interactive compilation of Fortran programs edited by EDT. Early PC software applications to incorporate plug-in functionality included HyperCard and QuarkXPress on the Macintosh, both released in 1987. In 1988, Silicon Beach Software included plug-in functionality in Digital Darkroom and SuperPaint, Ed Bomke coined the term plug-in. Applet Browser extension
The United Kingdom the United Kingdom of Great Britain and Northern Ireland, sometimes referred to as Britain, is a sovereign country located off the north-western coast of the European mainland. The United Kingdom includes the island of Great Britain, the north-eastern part of the island of Ireland, many smaller islands. Northern Ireland is the only part of the United Kingdom that shares a land border with another sovereign state, the Republic of Ireland. Apart from this land border, the United Kingdom is surrounded by the Atlantic Ocean, with the North Sea to the east, the English Channel to the south and the Celtic Sea to the south-west, giving it the 12th-longest coastline in the world; the Irish Sea lies between Great Ireland. With an area of 242,500 square kilometres, the United Kingdom is the 78th-largest sovereign state in the world, it is the 22nd-most populous country, with an estimated 66.0 million inhabitants in 2017. The UK is constitutional monarchy; the current monarch is Queen Elizabeth II, who has reigned since 1952, making her the longest-serving current head of state.
The United Kingdom's capital and largest city is London, a global city and financial centre with an urban area population of 10.3 million. Other major urban areas in the UK include Greater Manchester, the West Midlands and West Yorkshire conurbations, Greater Glasgow and the Liverpool Built-up Area; the United Kingdom consists of four constituent countries: England, Scotland and Northern Ireland. Their capitals are London, Edinburgh and Belfast, respectively. Apart from England, the countries have their own devolved governments, each with varying powers, but such power is delegated by the Parliament of the United Kingdom, which may enact laws unilaterally altering or abolishing devolution; the nearby Isle of Man, Bailiwick of Guernsey and Bailiwick of Jersey are not part of the UK, being Crown dependencies with the British Government responsible for defence and international representation. The medieval conquest and subsequent annexation of Wales by the Kingdom of England, followed by the union between England and Scotland in 1707 to form the Kingdom of Great Britain, the union in 1801 of Great Britain with the Kingdom of Ireland created the United Kingdom of Great Britain and Ireland.
Five-sixths of Ireland seceded from the UK in 1922, leaving the present formulation of the United Kingdom of Great Britain and Northern Ireland. There are fourteen British Overseas Territories, the remnants of the British Empire which, at its height in the 1920s, encompassed a quarter of the world's land mass and was the largest empire in history. British influence can be observed in the language and political systems of many of its former colonies; the United Kingdom is a developed country and has the world's fifth-largest economy by nominal GDP and ninth-largest economy by purchasing power parity. It has a high-income economy and has a high Human Development Index rating, ranking 14th in the world, it was the world's first industrialised country and the world's foremost power during the 19th and early 20th centuries. The UK remains a great power, with considerable economic, military and political influence internationally, it is sixth in military expenditure in the world. It has been a permanent member of the United Nations Security Council since its first session in 1946.
It has been a leading member state of the European Union and its predecessor, the European Economic Community, since 1973. The United Kingdom is a member of the Commonwealth of Nations, the Council of Europe, the G7, the G20, NATO, the Organisation for Economic Co-operation and Development and the World Trade Organization; the 1707 Acts of Union declared that the kingdoms of England and Scotland were "United into One Kingdom by the Name of Great Britain". The term "United Kingdom" has been used as a description for the former kingdom of Great Britain, although its official name from 1707 to 1800 was "Great Britain"; the Acts of Union 1800 united the kingdom of Great Britain and the kingdom of Ireland in 1801, forming the United Kingdom of Great Britain and Ireland. Following the partition of Ireland and the independence of the Irish Free State in 1922, which left Northern Ireland as the only part of the island of Ireland within the United Kingdom, the name was changed to the "United Kingdom of Great Britain and Northern Ireland".
Although the United Kingdom is a sovereign country, Scotland and Northern Ireland are widely referred to as countries. The UK Prime Minister's website has used the phrase "countries within a country" to describe the United Kingdom; some statistical summaries, such as those for the twelve NUTS 1 regions of the United Kingdom refer to Scotland and Northern Ireland as "regions". Northern Ireland is referred to as a "province". With regard to Northern Ireland, the descriptive name used "can be controversial, with the choice revealing one's political preferences"; the term "Great Britain" conventionally refers to the island of Great Britain, or politically to England and Wales in combination. However, it is sometimes used as a loose synonym for the United Kingdom as a whole; the term "Britain" is used both as a synonym for Great Britain, as a synonym for the United Kingdom. Usage is mixed, with the BBC preferring to use Britain as shorthand only for Great Britain and the UK Government, while accepting that both terms refer to the United K
Linux is a family of free and open-source software operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991 by Linus Torvalds. Linux is packaged in a Linux distribution. Distributions include the Linux kernel and supporting system software and libraries, many of which are provided by the GNU Project. Many Linux distributions use the word "Linux" in their name, but the Free Software Foundation uses the name GNU/Linux to emphasize the importance of GNU software, causing some controversy. Popular Linux distributions include Debian and Ubuntu. Commercial distributions include SUSE Linux Enterprise Server. Desktop Linux distributions include a windowing system such as X11 or Wayland, a desktop environment such as GNOME or KDE Plasma. Distributions intended for servers may omit graphics altogether, include a solution stack such as LAMP; because Linux is redistributable, anyone may create a distribution for any purpose. Linux was developed for personal computers based on the Intel x86 architecture, but has since been ported to more platforms than any other operating system.
Linux is the leading operating system on servers and other big iron systems such as mainframe computers, the only OS used on TOP500 supercomputers. It is used by around 2.3 percent of desktop computers. The Chromebook, which runs the Linux kernel-based Chrome OS, dominates the US K–12 education market and represents nearly 20 percent of sub-$300 notebook sales in the US. Linux runs on embedded systems, i.e. devices whose operating system is built into the firmware and is tailored to the system. This includes routers, automation controls, digital video recorders, video game consoles, smartwatches. Many smartphones and tablet computers run other Linux derivatives; because of the dominance of Android on smartphones, Linux has the largest installed base of all general-purpose operating systems. Linux is one of the most prominent examples of open-source software collaboration; the source code may be used and distributed—commercially or non-commercially—by anyone under the terms of its respective licenses, such as the GNU General Public License.
The Unix operating system was conceived and implemented in 1969, at AT&T's Bell Laboratories in the United States by Ken Thompson, Dennis Ritchie, Douglas McIlroy, Joe Ossanna. First released in 1971, Unix was written in assembly language, as was common practice at the time. 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, AT&T was required to license the operating system's source code to anyone who asked; as a result, Unix grew and became adopted by academic institutions and businesses. In 1984, AT&T divested itself of Bell Labs; the GNU Project, started in 1983 by Richard Stallman, had the goal of creating a "complete Unix-compatible software system" composed of free software. Work began in 1984. In 1985, Stallman started the Free Software Foundation and wrote the GNU General Public License in 1989.
By the early 1990s, many of the programs required in an operating system were completed, although low-level elements such as device drivers and the kernel, called GNU/Hurd, were stalled and incomplete. Linus Torvalds has stated that if the GNU kernel had been available at the time, he would not have decided to write his own. 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 stated that if 386BSD had been available at the time, he would not have created Linux. MINIX was created by Andrew S. Tanenbaum, a computer science professor, released in 1987 as a minimal Unix-like operating system targeted at students and others who wanted to learn the operating system principles. Although the complete source code of MINIX was available, the licensing terms prevented it from being free software until the licensing changed in April 2000. In 1991, while attending the University of Helsinki, Torvalds became curious about operating systems.
Frustrated by the licensing of MINIX, which at the time limited it to educational use only, he began to work on his own operating system kernel, which became the Linux kernel. Torvalds began the development of the Linux kernel on MINIX and applications written for MINIX were used on Linux. Linux matured and further Linux kernel development took place on Linux systems. GNU applications replaced all MINIX components, because it was advantageous to use the available code from the GNU Project with the fledgling operating system. Torvalds initiated a switch from his original license, which prohibited commercial redistribution, to the GNU GPL. Developers worked to integrate GNU components with the Linux kernel, making a functional and free operating system. Linus Torvalds had wanted to call his invention "Freax", a portmant