The KDE Software Compilation (KDE SC) was an umbrella term for the

desktop environment In computing, a desktop environment (DE) is an implementation of the desktop metaphor made of a bundle of programs running on top of a computer operating system that share a common graphical user interface (GUI), sometimes described as a graphi ...

plus a range of included applications produced by

KDE KDE is an international free software community that develops free and open-source software. As a central development hub, it provides tools and resources that enable collaborative work on its projects. Its products include the KDE Plasma gra ...

. From its 1.0 release in July 1998 until the release of version 4.4 in February 2010, the Software Compilation was simply known as KDE, which stood for K Desktop Environment until the rebrand. The then called KDE SC was used from 4.4 onward until the final release 4.14 in July 2014. It consisted of the

KDE Plasma 4 KDE Plasma 4 is the fourth generation of the KDE workspace environments. It consists of three workspaces, each targeting a certain platform: ''Plasma Desktop'' for traditional desktop PCs and Notebook (computer), notebooks, ''Plasma Netbook'' for ...

desktop and those KDE applications, whose development teams chose to follow the Software Compilation's release schedule. After that, the KDE SC was split into three separate product entities:

KDE Plasma KDE Plasma is a Shell (computing), graphical shell developed by the KDE community for Unix-like operating systems. It serves as the interface layer between the user and the operating system, providing a graphical user interface (GUI) and workspa ...

KDE Frameworks KDE Frameworks is a collection of Library (computing), libraries and software frameworks readily available to any Qt (software), Qt-based software stacks or applications on multiple operating systems. Featuring frequently needed functionality sol ...

and

KDE Applications The KDE Gear is a set of applications and supporting libraries that are developed by the KDE community, primarily used on Linux-based operating systems but mostly multiplatform, and released on a common release schedule. The bundle is compos ...

, each with their own independent release schedules.

History

Origins

KDE was founded in 1996 by

Matthias Ettrich Matthias Ettrich (born 14 June 1972) is a German computer scientist and founder of the KDE and LyX projects. Early life Ettrich was born in Bietigheim-Bissingen, Baden-Württemberg, West Germany, and went to school in Beilstein, Württemberg, ...

, who was then a student at the

University of Tübingen The University of Tübingen, officially the Eberhard Karl University of Tübingen (; ), is a public research university located in the city of Tübingen, Baden-Württemberg, Germany. The University of Tübingen is one of eleven German Excellenc ...

. At the time, he was troubled by certain aspects of the

Unix Unix (, ; trademarked as UNIX) is a family of multitasking, multi-user computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, a ...

desktop. Among his qualms was that none of the

applications Application may refer to: Mathematics and computing * Application software, computer software designed to help the user to perform specific tasks ** Application layer, an abstraction layer that specifies protocols and interface methods used in a ...

looked, felt, or worked alike. He proposed the formation of not only a set of applications, but, rather, a

, in which users could expect things to look, feel and work consistently. He also wanted to make this desktop easy to use; one of his complaints with desktop applications of the time was that his girlfriend could not use them. His initial

Usenet Usenet (), a portmanteau of User's Network, is a worldwide distributed discussion system available on computers. It was developed from the general-purpose UUCP, Unix-to-Unix Copy (UUCP) dial-up network architecture. Tom Truscott and Jim Elli ...

post spurred a lot of interest, and the KDE project was born. Ettrich chose to use Trolltech's Qt framework for the KDE project. Other programmers quickly started developing KDE/Qt applications, and by early 1997, a few applications were being released.

First series

On 12 July 1998, '' K Desktop Environment 1.0'' was released. In November 1998, the Qt toolkit was dual-licensed under the free/

open source Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use and view the source code, design documents, or content of the product. The open source model is a decentrali ...

Q Public License (QPL) and a proprietary license for proprietary software developers. Debate continued about compatibility with the

GNU General Public License The GNU General Public Licenses (GNU GPL or simply GPL) are a series of widely used free software licenses, or ''copyleft'' licenses, that guarantee end users the freedom to run, study, share, or modify the software. The GPL was the first ...

(GPL), so in September 2000, Trolltech made the Unix version of the Qt libraries available under the GPL, in addition to the QPL. Trolltech continued to require licenses for developing

proprietary software Proprietary software is computer software, software that grants its creator, publisher, or other rightsholder or rightsholder partner a legal monopoly by modern copyright and intellectual property law to exclude the recipient from freely sharing t ...

with Qt. The core libraries of KDE are collectively licensed under the GNU LGPL, but the only way for proprietary software to make use of them was to be developed under the terms of the Qt proprietary license.

Second series

Beginning 23 October 2000, the second series of releases, '' K Desktop Environment 2'', introduced significant technological improvements.KDE 2.0 Release Announcement
/ref> These included DCOP (Desktop COmmunication Protocol),

KIO KIO (KDE Input/Output) is a system library incorporated into KDE Frameworks and KDE Software Compilation 4. It provides access to files, web sites and other resources through a single consistent API. Applications, such as Konqueror and Dolph ...

(an application I/O library), KParts (a

component object model Component Object Model (COM) is a binary-interface technology for software components from Microsoft that enables using objects in a language-neutral way between different programming languages, programming contexts, processes and machines ...

, which allows an application to embed another within itself), and

KHTML KHTML is a discontinued browser engine that was developed by the KDE project. It originated as the engine of the Konqueror browser in the late 1990s, but active development ceased in 2016. It was officially discontinued in 2023. Built on the ...

(an

HTML Hypertext Markup Language (HTML) is the standard markup language for documents designed to be displayed in a web browser. It defines the content and structure of web content. It is often assisted by technologies such as Cascading Style Sheets ( ...

rendering and drawing engine).

Pre-fourth series

The third series was much larger than previous series, consisting of six major releases starting on 3 April 2002. The API changes between ''K Desktop Environment 2'' and ''K Desktop Environment 3'' were comparatively minor, meaning that the KDE 3 can be seen as largely a continuation of the ''K Desktop Environment 2'' series. All releases of ''K Desktop Environment 3'' were built upon Qt 3, which was only released under the GPL for Linux and Unix-like operating systems, including

Mac OS X macOS, previously OS X and originally Mac OS X, is a Unix, Unix-based operating system developed and marketed by Apple Inc., Apple since 2001. It is the current operating system for Apple's Mac (computer), Mac computers. With ...

. It is marked stable running on Mac OS X since 2008. Unlike KDE SC 4, however, it requires an X11 server to operate. In 2002, members of the KDE on Cygwin project began porting the GPL licensed Qt/X11 code base to Windows.

Fourth series

KDE Software Compilation 4 KDE Software Compilation 4 (KDE SC 4) was the only series of the so-called KDE Software Compilation (KDE SC), first released in January 2008. The final release was version 4.14.3 in November 2014. It was the follow-up to K Desktop Environment 3 ...

, first released on 11 January 2008, is based on Qt 4, which is also released under the GPL for Windows and Mac OS X. Therefore, KDE SC 4 applications can be compiled and run natively on these operating systems as well. KDE Software Compilation 4 on Mac OS X is currently considered beta, while on Windows it is not in the final state, so applications can be unsuitable for day to day use. KDE SC 4 includes many new technologies and technical changes. The centerpiece is a redesigned desktop and panels collectively called Plasma, which replaces Kicker, KDesktop, and SuperKaramba by integrating their functionality into one piece of technology; Plasma is intended to be more configurable for those wanting to update the decades-old

desktop metaphor In computing, the desktop metaphor is an interface metaphor which is a set of unifying concepts used by graphical user interfaces to help users interact more easily with the computer. The desktop metaphor treats the computer monitor as if it is ...

. There are a number of new frameworks, including

Phonon A phonon is a collective excitation in a periodic, elastic arrangement of atoms or molecules in condensed matter, specifically in solids and some liquids. In the context of optically trapped objects, the quantized vibration mode can be defined a ...

(a new multimedia interface making KDE independent of any one specific media backend)

Solid Solid is a state of matter where molecules are closely packed and can not slide past each other. Solids resist compression, expansion, or external forces that would alter its shape, with the degree to which they are resisted dependent upon the ...

(an API for network and portable devices), and

Decibel The decibel (symbol: dB) is a relative unit of measurement equal to one tenth of a bel (B). It expresses the ratio of two values of a Power, root-power, and field quantities, power or root-power quantity on a logarithmic scale. Two signals whos ...

(a new communication framework to integrate all communication protocols into the desktop). Also featured is a metadata and search framework, incorporating Strigi as a full-text file indexing service, and

NEPOMUK Nepomuk (; ) is a town in Plzeň-South District in the Plzeň Region of the Czech Republic. It has about 3,600 inhabitants. It is known as the birthplace of Saint John of Nepomuk, who was born here around 1340. Administrative division Nepomuk ...

with KDE integration. Starting with Qt 4.5, Qt was also made available under the LGPL version 2.1, a major step for KDE adoption in corporate and proprietary environments, as the LGPL permits proprietary applications to link to libraries licensed under the LGPL.

Post-fourth series

As of August 2014, KDE no longer provides synchronized releases of the entire software compilation; instead the software is split into three parts: * KDE Frameworks 5, a collection of libraries and software frameworks (5.0 released on July 7, 2014, and new major releases are made monthly) *

KDE Plasma 5 KDE Plasma 5 is the fifth generation of the KDE Plasma graphical workspaces environment, created by KDE primarily for Linux systems. KDE Plasma 5 is the successor of KDE Plasma 4 and was first released on 15 July 2014. It was succeeded by KDE Pl ...

, a desktop environment (5.0 released on July 15, 2014, and new major releases are made every three months) *

, a bundle of applications and supporting libraries (14.12 was the first version incorporating Frameworks 5 based applications, and introduced date-based version numbers). Major changes include a move from Qt 4 to Qt 5, support for the next-generation display server protocol Wayland, support for the next-generation rendering API

Vulkan Vulkan is a cross-platform API and open standard for 3D graphics and computing. It was intended to address the shortcomings of OpenGL, and allow developers more control over the GPU. It is designed to support a wide variety of GPUs, CPUs and o ...

and modularization of the KDE core libraries. Initial releases of Frameworks 5 and Plasma 5 were made available in July 2014.

Development

Source code

KDE SC releases are made to the KDE FTP server in the form of

source code In computing, source code, or simply code or source, is a plain text computer program written in a programming language. A programmer writes the human readable source code to control the behavior of a computer. Since a computer, at base, only ...

with configure scripts, which are compiled by operating system vendors and integrated with the rest of their systems before distribution. Most vendors use only stable and tested versions of KDE SC, providing it in the form of easily installable, pre-compiled packages. The source code of every stable and development version of KDE SC is stored in the KDE source code repository, using

Git Git () is a distributed version control system that tracks versions of files. It is often used to control source code by programmers who are developing software collaboratively. Design goals of Git include speed, data integrity, and suppor ...

KDE Platform KDE Platform 4 was a collection of Library (computing), libraries and software frameworks by KDE that served as technological foundation for KDE Software Compilation 4 distributed under the GNU Lesser General Public License (LGPL). KDE Platform 4 ...

is licensed under the LGPL, BSD license,

MIT license The MIT License is a permissive software license originating at the Massachusetts Institute of Technology (MIT) in the late 1980s. As a permissive license, it puts very few restrictions on reuse and therefore has high license compatibility. Unl ...

, or X11 license. Applications also allow GPL. Documentation also allow FDL. CMake modules must be licensed under the BSD licence.

Major releases

Major releases are releases that begin a series (version number X.0). These releases are allowed to break binary compatibility with the predecessor, or to put it differently, all following releases (X.1, X.2, ...) will guarantee binary portability (

API An application programming interface (API) is a connection between computers or between computer programs. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how to build ...

& ABI). This means, for instance, that software that was developed for KDE 3.0 will work on all (future) KDE 3 releases; however, an application developed for KDE 2 is not guaranteed to be able to make use of the KDE 3 libraries. KDE major version numbers follow the Qt release cycle, meaning that KDE SC 4 is based on Qt 4, while KDE 3 was based on Qt 3. Qt 5.0 was released 19 December 2012, Qt 5.2 12 December 2013. And for example KDE Frameworks 5.21.0 requires Qt >= 5.4, and no longer supports Qt 5.3 (cf. Qt version history).

Standard releases

There are two main types of standard releases: Feature releases and bugfix releases. Feature releases have two version numbers, for example 3.5 and contain new features. As soon as a feature release is ready and announced, work on the next feature release starts. A feature release needs several months to be finished and many bugs that are fixed during this time are backported to the stable branch, meaning that these fixes are incorporated into the last stable release by bugfix releases. During the KDE SC 4 series, KDE SC had a feature release roughly every six months. Since the split, KDE Plasma releases a new feature version roughly every 3–4 months. Bugfix releases have three version numbers, e.g. KDE 1.1.1, and focus on fixing bugs, minor glitches, and making small usability improvements. Bugfix releases in general do not allow new features, although some releases include small enhancements. A shortened release schedule is used. Starting with the KDE SC 4 series, KDE SC has a maintenance release roughly every month, except during the month of a feature release, while with Plasma 5, bugfix releases tend to happen even shorter like 2–3 weeks.

Release cycle

The KDE team releases new versions on a regular basis.

Lines of Code

* KDE 1.0 had LoC. * KDE 4.3 had LoC.

Implementation

Most KDE software uses Qt which runs on most Unix and

Unix-like A Unix-like (sometimes referred to as UN*X, *nix or *NIX) operating system is one that behaves in a manner similar to a Unix system, although not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Uni ...

systems (including Mac OS X), Android and Microsoft Windows. CMake serves as the build tool. This allows KDE to support a wider range of platforms, including Windows. GNU gettext is used for translation.

Doxygen Doxygen ( ) is a documentation generator that works with many programming languages. It extracts information from specially-formatted source code comments and saves the information in one of various supported formats. Doxygen supports static ...

is used to generate api documentation.

Overview

* KDE Software Compilation: KDE Software Compilation (KDE SC) is the coordinated releases of new software versions, gathering elements from the previous components to build an integrated core of software. The KDE SC is not a product as a single entity. * Calligra Suite: Integrated office suite. * KDEWebdev: Web development tools. * KDE-Extragear: Extragear is a collection of applications associated with KDE. Those applications are not part the official software compilation, but they are still part of the project. * KDE-Playground: This package contains pre-release and unstable software. It is a place for applications to mature.

Packages

The Software Compilation consists of the following packages: * KDE-Libs: A collection of

libraries A library is a collection of Book, books, and possibly other Document, materials and Media (communication), media, that is accessible for use by its members and members of allied institutions. Libraries provide physical (hard copies) or electron ...

that provides frameworks and functionality for developers. * KDE-Base: The base set of files, libraries and programs needed by the Software Compilation. KDE-Base is divided into three parts: ** Applications: Containing the applications that form the KDE desktop, like Konqueror, Dolphin, KWrite, and Konsole. ** Runtime: Applications required by KDE apps to function properly at runtime. ** Workspace: Provides the graphical environments. * KDE-Plasma-Addons: Additional Plasma widgets. * KDE-Network * KDE-Pim * KDE-Graphics * KDE-Multimedia *

* KDE-Accessibility: Accessibility applications. * KDE-Utilities * KDE-Edu * KDE-Games * KDE-Toys
KDE-Artwork
Additional icons, styles, etc. * KDE-Admin * KDE-SDK * KDE-Bindings

Base technologies

– HTML rendering engine, forked into

WebKit WebKit is a browser engine primarily used in Apple's Safari web browser, as well as all web browsers on iOS and iPadOS. WebKit is also used by the PlayStation consoles starting with the PS3, the Tizen mobile operating systems, the Amazon K ...

in 2004 * KJS

JavaScript engine The first engines for JavaScript were mere interpreters of the source code, but all relevant modern engines use just-in-time compilation for improved performance. JavaScript engines are typically developed by web browser vendors, and every maj ...

– Extensible network-transparent file access *

Kiosk Historically, a kiosk () was a small garden pavilion open on some or all sides common in Iran, Persia, the Indian subcontinent, and in the Ottoman Empire from the 13th century onward. Today, several examples of this type of kiosk still exist ...

– Allows disabling features within KDE to create a more controlled environment * KParts – Lightweight in-process graphical component framework *

KWin KWin is a window manager for the X Window System and a Wayland (display server protocol)#Wayland compositors, Wayland compositor. It is released as a part of KDE Plasma, for which it is the default window manager. KWin can also be used on its o ...

–

Window manager A window manager is system software that controls the placement and appearance of window (computing), windows within a windowing system in a graphical user interface. Most window managers are designed to help provide a desktop environment. They ...

* XMLGUI – Allows defining UI elements, such as menus and toolbars via

XML Extensible Markup Language (XML) is a markup language and file format for storing, transmitting, and reconstructing data. It defines a set of rules for encoding electronic document, documents in a format that is both human-readable and Machine-r ...

files *

–

Multimedia framework A multimedia framework is a software framework that handles Electronic media, media on a computer and through a network. A good multimedia framework offers an intuitive Application programming interface, API and a modular architecture to easily a ...

* Plasma – Desktop and panel widget engine *

– Device integration framework *

Sonnet A sonnet is a fixed poetic form with a structure traditionally consisting of fourteen lines adhering to a set Rhyme scheme, rhyming scheme. The term derives from the Italian word ''sonetto'' (, from the Latin word ''sonus'', ). Originating in ...

–

Spell checker In software, a spell checker (or spelling checker or spell check) is a software feature that checks for misspellings in a text. Spell-checking features are often embedded in software or services, such as a word processor, email client, electronic ...

* ThreadWeaver – Library to use

multiprocessor Multiprocessing (MP) is the use of two or more central processing units (CPUs) within a single computer system. The term also refers to the ability of a system to support more than one processor or the ability to allocate tasks between them. The ...

systems more effectively

Applications

Major applications by KDE Software Compilation include: * Ark – Archiving tool * Dragon Player – Media player. *

Dolphin A dolphin is an aquatic mammal in the cetacean clade Odontoceti (toothed whale). Dolphins belong to the families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), Pontopori ...

–

File manager A file manager or file browser is a computer program that provides a user interface to manage computer files, files and folder (computing), folders. The most common Computer file#Operations, operations performed on files or groups of files incl ...

* Falkon -

Web browser A web browser, often shortened to browser, is an application for accessing websites. When a user requests a web page from a particular website, the browser retrieves its files from a web server and then displays the page on the user's scr ...

* Gwenview – Image viewer *

Kate Kate may refer to: People and fictional characters * Kate (given name), a list of people and fictional characters with the given name or nickname * Gyula Káté (born 1982), Hungarian amateur boxer * Lauren Kate (born 1981), American author o ...

/ KWrite –

Text editor A text editor is a type of computer program that edits plain text. An example of such program is "notepad" software (e.g. Windows Notepad). Text editors are provided with operating systems and software development packages, and can be used to c ...

* Konsole –

Terminal emulator A terminal emulator, or terminal application, is a computer program that emulates a video terminal within some other display architecture. Though typically synonymous with a shell or text terminal, the term ''terminal'' covers all remote term ...

* Kontact –

Personal information manager A personal information manager (often referred to as a PIM tool or, more simply, a PIM) is a type of application software that functions as a personal organizer. The acronym PIM is now, more commonly, used in reference to personal information mana ...

featuring an

e-mail client An email client, email reader or, more formally, message user agent (MUA) or mail user agent is a computer program used to access and manage a user's email. A web app, web application which provides message management, composition, and receptio ...

, a

news client A newsreader is a software application that reads articles on Usenet distributed throughout newsgroups. Newsreaders act as clients which connect to a news server, via the Network News Transfer Protocol (NNTP), to download articles and post new ...

, a feed aggregator, to-do lists, etc. *

Konqueror Konqueror is a Free and open-source software, free and open-source web browser and file manager that provides World Wide Web, web access and file viewer, file-viewer functionality for file systems (such as local files, files on a remote FTP ser ...

–

and

file manager A file manager or file browser is a computer program that provides a user interface to manage computer files, files and folder (computing), folders. The most common Computer file#Operations, operations performed on files or groups of files incl ...

* Kopete – Instant messaging client * – a

remote desktop In computing, the term remote desktop refers to a software- or operating system feature that allows a personal computer's desktop environment to be run remotely from one system (usually a PC, but the concept applies equally to a server or a sma ...

client. Both the

Virtual Network Computing VNC (Virtual Network Computing) is a graphical desktop-sharing system that uses the RFB protocol, Remote Frame Buffer protocol (RFB) to remotely control another computer. It transmits the computer keyboard, keyboard and computer mouse, mouse in ...

(VNC) and

Remote Desktop Protocol Remote Desktop Protocol (RDP) is a proprietary protocol developed by Microsoft Corporation which provides a user with a graphical interface to connect to another computer over a network connection. The user employs RDP client software for this pu ...

(RDP) protocols are supported, so

and

Windows Windows is a Product lining, product line of Proprietary software, proprietary graphical user interface, graphical operating systems developed and marketed by Microsoft. It is grouped into families and subfamilies that cater to particular sec ...

PC can be accessed using this software. As part of the GSoC, project developers helped make Libvncserver compile on Windows platforms, allowing for a port to Windows.

Licensing

In November 1998, the Qt framework was dual-licensed under the

free and open-source Free and open-source software (FOSS) is software available under a Software license, license that grants users the right to use, modify, and distribute the software modified or not to everyone free of charge. FOSS is an inclusive umbrella term ...

Q Public License (QPL) and a commercial license for

developers. The same year, the KDE Free Qt foundation was created which guarantees that Qt would fall under a variant of the very liberal

BSD license BSD licenses are a family of permissive free software licenses, imposing minimal restrictions on the use and distribution of covered software. This is in contrast to copyleft licenses, which have share-alike requirements. The original BSD lic ...

should Trolltech cease to exist or no free version of Qt be released during 12 months. Debate continued about compatibility with the GNU General Public License (GPL), hence in September 2000 Trolltech made the Unix version of the Qt libraries available under the GPL in addition to the QPL which eliminated the concerns of the

Free Software Foundation The Free Software Foundation (FSF) is a 501(c)(3) non-profit organization founded by Richard Stallman on October 4, 1985. The organisation supports the free software movement, with the organization's preference for software being distributed ...

. Trolltech continued to require licenses for developing

with Qt. The core libraries of KDE are collectively licensed under the GNU

LGPL The GNU Lesser General Public License (LGPL) is a free-software license published by the Free Software Foundation (FSF). The license allows developers and companies to use and integrate a software component released under the LGPL into their own ...

but the only way for proprietary software to make use of them was to be developed under the terms of the Qt proprietary license. Starting with Qt 4.5, Qt was also made available under the LGPL version 2.1, now allowing proprietary applications to legally use the open source Qt version.