GNOME

GNOME () is a free and open-source desktop environment for Unix-like operating systems. GNOME was originally an acronym for "GNU Network Object Model Environment", but the acronym was dropped because it no longer reflected the vision of the GNOME project.
GNOME is developed by The GNOME Project, which is composed of both volunteers and paid contributors, the largest corporate contributor being Red Hat. It is an international project that aims to develop software frameworks for the development of software, to program end-user applications based on these frameworks, and to coordinate efforts for internationalization and localization and accessibility of that software.
GNOME 3 is the default desktop environment on many major Linux distributions including Fedora, Debian, Ubuntu, SUSE Linux Enterprise (exclusively), Red Hat Enterprise Linux, CentOS, Pop!_OS, Oracle Linux, SteamOS, Tails and Endless OS, as well as Solaris, a major Unix operating system; and is provided as an official edition by Manjaro. The continued fork of the last GNOME 2 release, called MATE, is default on many Linux distros that target low usage of system resources.
History.
GNOME 1.
GNOME was started on 15 August 1997 by Miguel de Icaza and as a free software project to develop a desktop environment and applications for it. It was founded in part because K Desktop Environment, which was growing in popularity, relied on the Qt widget toolkit which used a proprietary software license until version 2.0 (June 1999). In place of Qt, GTK (GNOME Toolkit, at that time called GIMP Toolkit) was chosen as the base of GNOME. GTK uses the GNU Lesser General Public License (LGPL), a free software license that allows software linking to it to use a much wider set of licenses, including proprietary software licenses. GNOME itself is licensed under the LGPL for its libraries, and the GNU General Public License (GPL) for its applications.
GNOME has historically been part of the GNU Project. However, it is no longer part of that project. The name "GNOME" was initially an acronym of "GNU Network Object Model Environment", referring to the original intention of creating a distributed object framework similar to Microsoft's OLE, but the acronym was eventually dropped because it no longer reflected the vision of the GNOME project.
The California startup Eazel developed the Nautilus file manager from 1999 to 2001. De Icaza and Nat Friedman founded Helix Code (later Ximian) in 1999 in Massachusetts; this company developed GNOME's infrastructure and applications, and in 2003 was purchased by Novell.
 During the transition to GNOME 2 around the year 2001 and shortly thereafter there were brief talks about creating a "GNOME Office" suite. On 15 September 2003 GNOME-Office 1.0, consisting of AbiWord 2.0, GNOME-DB 1.0 and Gnumeric 1.2.0 was released. Although some release planning for GNOME Office 1.2 was happening on gnome-office mailing list, and Gnumeric 1.4 was announced as a part of it, the 1.2 release of the suite itself never materialized. GNOME wiki only mentions "GNOME/Gtk applications that are useful in an office environment".
GNOME 2.
GNOME 2 was very similar to a conventional desktop interface, featuring a simple desktop in which users could interact with virtual objects, such as windows, icons, and files. GNOME 2 started out with Sawfish, but later switched to Metacity as its default window manager. The handling of windows, applications, and files in GNOME 2 is similar to that of contemporary desktop operating systems. In the default configuration of GNOME 2, the desktop has a launcher menu for quick access to installed programs and file locations; open windows may be accessed by a taskbar along the bottom of the screen, and the top-right corner features a notification area for programs to display notices while running in the background. However, these features can be moved to almost any position or orientation the user desires, replaced with other functions or removed altogether.
As of 2009, GNOME 2 was the default desktop for OpenSolaris. The MATE desktop environment is a fork of the GNOME 2 codebase (see Criticism, below.)
GNOME 3.
In 2008, an increasing discontent among community and developers about the lack of project direction and technical progress has prompted the announcement of GNOME 3.0. Originally, the plan was to make only incremental changes and avoid disruption for users. This has changed, when the efforts led to creation of the GNOME Shell.
GNOME 3 was released in 2011. While GNOME 1 and 2 interfaces followed the traditional desktop metaphor, the GNOME Shell adopted a more abstract metaphor with streamlined window management workflow (where switching between different tasks and virtual desktops took place in a separate area called "the""overview"), unified "header bar" (replacing menu bar, taskbar, and toolbar), and "minimize" and "maximize" buttons hidden by default (via Client-side decoration mechanism).
GNOME 3 brought many enhancements to core software. Many GNOME Core Applications also went through redesigns to provide a more consistent user experience. Mutter replaced Metacity as the default window manager. "Adwaita" replaced Clearlooks as the default theme. 
Criticism.
The release of GNOME 3 has caused considerable controversy in the GNU and Linux communities. Projects aim to provide an easy-to-use and uncluttered user experience has led to some criticized design decisions, like removal of "minimize" and "maximize" buttons, oversimplification of configuration options and visual clues which could lead to confusion.
A few projects have been initiated to continue development of GNOME 2.x or to modify GNOME 3.x to be more like the 2.x releases. The MATE desktop environment was forked from the GNOME 2 code-base with the intent of retaining the traditional GNOME 2 interface, whilst keeping compatibility with modern Linux technology, such as GTK 3. The Linux Mint team addressed the issue by developing the "Mint GNOME Shell Extensions" that ran on top of GNOME Shell and allowed it to be used via the traditional desktop metaphor. This eventually led to the creation of the Cinnamon user interface, which was forked from the GNOME 3 codebase. Audacious migrated to Qt, noting the restrictions of GTK+ 3 as a reason. The LXDE Project, which was experimenting with a Qt port at the time, joined the Razor-qt Team and became LXQt.
Among those critical of the early releases of GNOME 3 is Linus Torvalds, the creator of the Linux kernel. Torvalds abandoned GNOME for a while after the release of GNOME 3.0, saying "The developers have apparently decided that it's 'too complicated' to actually do real work on your desktop, and have decided to make it really annoying to do".
Over time, the critical reception has grown more positive. In 2013, Torvalds resumed using GNOME, noting that "they have extensions now that are still much too hard to find; but with extensions you can make your desktop look almost as good as it used to look two years ago". Debian, a Linux distribution that had historically used GNOME 2, switched to Xfce when GNOME 3 was released but readopted GNOME 3 in time for the release of Debian 8 "Jessie".
GNOME 40.
GNOME 40 was released on 24 March 2021. It is a major new version, the first to adopt a new versioning scheme. Instead of using a vertical design in its activities overview, GNOME 40 organizes workspaces and the dash in a horizontal fashion. The release also brings new touchpad gestures.
Releases.
Release cycle.
Each of the component software products in the GNOME project has its own version number and release schedule. However, individual module maintainers coordinate their efforts to create a full GNOME stable release on an approximately six-month schedule, alongside its underlying libraries such as GTK and GLib. Some experimental projects are excluded from these releases.
Before GNOME 40, GNOME version numbers followed the scheme "v.xx.yy". Here, "v" is a major version, which can include large changes such as ABI breakage; these have no regular schedule and occur in response to requirements for large-scale changes. "xx" is a minor version, released on the above schedule of approximately every 6 months, in which the 1- or 2-digit number's parity indicates the type of release: if "xx" is even (e.g. 3.20) the release is considered stable, whereas if "xx" is odd, it represents a current development snapshot (e.g. 3.21) that will eventually evolve into the next stable release. "yy" indicates a point release, e.g. 3.20.6; these are made on a frequency of weeks in order to fix issues, add non-breaking enhancements, etc.
GNOME 40 started a new versioning scheme in which a single number is incremented each biannual release. The number is followed by a dot and then "alpha", "beta", or "rc" for a development release or another integer for minor stable releases (much like the "yy" mentioned previously).
GNOME releases are made to the main FTP server in the form of source code with configure scripts, which are compiled by operating system vendors and integrated with the rest of their systems before distribution. Most vendors only use stable and tested versions of GNOME, and provide it in the form of easily installed, pre-compiled packages. The source code of every stable and development version of GNOME is stored in the GNOME git source code repository. Interested users can always obtain a snapshot of the _master_ development branch or any other branch/tag and build a cutting-edge version for their own use.
A number of build-scripts (such as JHBuild or formerly GARNOME) are available to help automate the process of compiling the source code.
Features.
User interface design.
Since GNOME 2, productivity has been a key focus for GNOME. To meet this end, the GNOME Human Interface Guidelines (HIG) were created. All GNOME programs share a coherent style of graphical user interface (GUI) but are not limited to the employment of the same GUI widgets. Rather, the design of the GNOME GUI is guided by concepts described in the GNOME HIG, itself relying on insights from cognitive ergonomics. Following the HIG, developers can create high-quality, consistent, and usable GUI programs, as it addresses everything from GUI design to recommended pixel-based layout of widgets.
During the GNOME 2 rewrite, many settings deemed of little value to the majority of users were removed. Havoc Pennington summarized the usability work in his 2002 essay "Free Software UI", emphasizing the idea that all preferences have a cost, and it is better to make software behave correctly by default than to add a UI preference to get the desired behavior:
Accessibility.
GNOME aims to make and keep the desktop environment physically and cognitively ergonomic for people with disabilities. The GNOME HIG tries to take this into account as far as possible but specific issues are solved by special software.
GNOME addresses computer accessibility issues by using the Accessibility Toolkit (ATK) application programming interface, which allows enhancing user experience by using special input methods and speech synthesis and speech recognition software. Particular utilities are registered with ATK using Assistive Technology Service Provider Interface (AT-SPI), and become globally used throughout the desktop. Several assistive technology providers, including Orca screen reader and Dasher input method, were developed specifically for use with GNOME.
Internationalization and localization.
The internationalization and localization of GNOME software relies on locale. 
Desktop.
GNOME provides three different login sessions for desktop:
GNOME Classic.
Beginning with GNOME 3.8, GNOME provides a suite of officially supported GNOME Shell extensions that provide Applications menu (a basic start menu) and "Places menu" on the top bar, and a panel with windows list at the bottom of the screen that lets quickly minimize and restore open windows, a "Show Desktop" button in the bottom left and virtual desktops in the bottom right corner.
GNOME Flashback.
"GNOME Flashback" is an official session for GNOME 3. It is based on GNOME Panel and Metacity (window manager), it is lightweight, has lower hardware requirements and uses less system resources (memory and CPU) than GNOME Shell. It provides a traditional and highly customizable taskbar (panel) with many plug-ins bundled in one package (gnome-applets) including a customizable start menu. It provides a similar user experience to the GNOME 2.x series and has customization capacities as built-in.
GNOME Flashback consists of the following components:
GNOME Shell.
This session is based on GNOME Shell and Mutter (window manager). It is default and offers a mobile-like paradigm for launching applications and accessing open windows and virtual desktops, but through the use of extensions it is possible for the appearance to be that of a traditional taskbar and provide a basic start menu. This session uses more RAM and CPU due to use of JavaScript for GNOME Shell and all of its extensions, and requiring 3D acceleration.
GNOME Shell is the default graphical shell of GNOME. It features a top bar holding (from left to right) an Activities button, an application menu, a clock and an integrated system status menu. The application menu displays the name of the application in focus and provides access to functions such as accessing the application's preferences, closing the application, or creating a new application window. The status menu holds various system status indicators, shortcuts to system settings, and session actions including logging out, switching users, locking the screen, and suspending the computer.
Clicking on the Activities button, moving the mouse to the top-left hot corner or pressing the Super key brings up the Overview. The Overview gives users an overview of current activities and provides a way to switch between windows and workspaces and to launch applications. The Dash on the left houses shortcuts to favorite applications and open windows and an application picker button to show a list of all installed applications. A search bar appears at the top and a workspace list for switching between workspaces is on the right. Notifications appear from the bottom of the screen.
Mobile.
The libhandy library can be used with GNOME Shell to create a responsive user interface that dynamically adapts to device form factor.
Development.
GNOME is developed by The GNOME Project. GNOME development is loosely managed. Discussion chiefly occurs on a number of public mailing lists. GNOME developers and users gather at an annual GUADEC meeting to discuss the current state and the future direction of GNOME. GNOME incorporates standards and programs from freedesktop.org to better support interoperability with other desktops.
GNOME is mainly written in C, XML, C++, C#, HTML, Vala, Python, JavaScript, CSS, and more. A number of language bindings are available.
Development platform.
The GLib data structures and utilities library, GObject object and type system and GTK widget toolkit comprise the central part of GNOME development platform. This foundation is further extended with D-Bus IPC framework, Cairo 2D vector-based drawing library, Clutter accelerated graphics library, Pango international text rendering library, PulseAudio low-level audio API, GStreamer multimedia framework, and several specialized libraries including NetworkManager, PackageKit, Telepathy (instant messaging), and WebKit.
Dependencies.
The GNOME desktop environment does not consist solely of the graphical control element library GTK and the core applications that make use of it. There are quite a few additional software packages that make up the GNOME desktop environment, such as the above.
Wayland or X Window System.
GNOME runs on Wayland and the X Window System. Wayland support was introduced in GNOME 3.10 and deemed "for the majority of users […] a usable day to day experience" by 3.20, at which point Wayland became the default user session. GNOME 3.24 will extend Wayland compatibility to Nvidia drivers. With GNOME 3.30, it is possible to run GNOME without X.Org Server, using only Wayland.
systemd.
In May 2011 Lennart Poettering proposed systemd as a GNOME dependency. 
As systemd is available only on Linux, the proposal led to a discussion of possibly dropping support for other platforms in future GNOME releases. Since GNOME 3.2 multiseat support has only been available on systems using systemd. 
In November 2012 the GNOME release team concluded there will be no compile time dependency on systemd for basic functionality, like session tracking. For non-basic functionality, like power management, compile time dependency is possible. For example, there is no concept of systemd inhibitors in alternatives like consolekit. A package manager may want to ensure that the system is not turned off while the upgrade is taking place.
Applications.
Core Applications.
There are a large number of GTK and Clutter-based programs written by various authors. Since the release of GNOME 3.0, The GNOME Project concentrates on developing a set of programs that accounts for the GNOME Core Applications. The commonalities of the GNOME Core Applications are the adherence to the current GNOME Human Interface Guidelines (HIG) as well as the tight integration with underlying GNOME layers like e.g. GVfs (GNOME virtual filesystem) and also with one another e.g. GOA (gnome-online-accounts) settings and GNOME Files with Google Drive and GNOME Photos with Google Photos. Some programs are simply existing programs with a new name and revamped user interface, while others have been written from scratch.
Games.
GNOME Games have the look and feel of the GNOME Core Applications and are released simultaneously with GNOME. All have been rewritten to conform to the current GNOME Human Interface Guidelines.
Development tools.
Programmers have written software to provide development tools consistent with the GNOME desktop and to facilitate the development of GNOME software.
GNOME Builder is the new integrated development environment, Anjuta is the older one. Glade Interface Designer software constructs graphical interfaces using the graphical control elements in GTK. Devhelp is an API browser, Accerciser an accessibility explorer.
There are several debugging tools, including Nemiver, GtkInspector, and Alleyoop, have also been provided to facilitate development of GNOME software.
Integration options for third-party development tools (e.g. NoFlo) also exist.
The libsoup library enables access to HTTP servers from GNOME applications.
BuildStream is a flexible and extensible framework for the modeling of build and CI pipelines in a declarative YAML format, written in Python. Its mascot is a Beaver, because beavers build things in a stream.