KDE 4. KDE ( K Desktop Environment) (ˌkeɪdiːˈiː is a Free software project which aims to be a powerful system for an easy-to-use Desktop environment. 0

GNOME 2. A gnome is a Mythical creature characterized by its extremely small size and subterranean lifestyle 20

Xfce 4. Xfce ( ɛf siː iː is a Free software Desktop environment for Unix and other Unix-like platforms such as Linux, Solaris 4

In computing, the X Window System (commonly X11 or X) is a windowing system which implements the X display protocol and provides windowing on bitmap displays. Computing is usually defined like the activity of using and developing Computer technology Computer hardware and software. A windowing system (or window system) is a component of a Graphical user interface (GUI and more specifically of a Desktop environment, which supports In Computing, the X Window System (commonly X11 or X) is a network -transparent Windowing system for bitmap displays A windowing system (or window system) is a component of a Graphical user interface (GUI and more specifically of a Desktop environment, which supports In Computer graphics, a raster graphics image or bitmap, is a Data structure representing a generally rectangular grid of Pixels It provides the standard toolkit and protocol with which to build graphical user interfaces (GUIs) on most Unix-like operating systems and OpenVMS, and has been ported to many other contemporary general purpose operating systems. A Unix-like (sometimes shortened to *nix) Operating system is one that behaves in a manner similar to a Unix system while not necessarily conforming Open Virtual Memory System ( OpenVMS) initially known just as Virtual Memory System ( VMS) is the name of a High-end Computer server See also Software portability In Computer science, porting is the process of adapting software so that an executable program can be created

X provides the basic framework, or primitives, for building GUI environments: drawing and moving windows on the screen and interacting with a mouse and/or keyboard. In Computing, a window is a visual area usually rectangular in shape containing some kind of User interface, displaying the output of and allowing input for one X does not mandate the user interface — individual client programs handle this. The user interface (or Human Computer Interface) is the aggregate of means by which people&mdash the users '&mdash interact with the System As such, the visual styling of X-based environments varies greatly; different programs may present radically different interfaces. X is built as an additional application layer on top of the operating system kernel. In Computer science, the kernel is the central component of most computer Operating systems (OS

Unlike previous display protocols, X was specifically designed to be used over network connections rather than on an integral or attached display device. A computer network is a group of interconnected Computers. Networks may be classified according to a wide variety of characteristics X features network transparency: the machine where an application program (the client application) runs can differ from the user's local machine (the display server). Network Transparency in its most general sense refers to the ability of a protocol to transmit data over the network in a manner which is transparent (invisible to those using

X originated at MIT in 1984. The current protocol version, X11, appeared in September 1987. The X.Org Foundation leads the X project, with the current reference implementation, X.org Server, available as free software under the MIT License and similar permissive licences. The XOrg Foundation is the organization holding the stewardship for the development of the X Window System. In Computing, a reference implementation (or less frequently sample implementation or model implementation) is a software example of a Specification The XOrg Server (officially the XOrg Foundation Open Source Public Implementation of X11) is the X server in the official reference implementation of the X Free software or software libre is Software that can be used studied and modified without restriction and which can be copied and redistributed in modified or unmodified The MIT License is a Free software license originating at the Massachusetts Institute of Technology (MIT used by the MIT X Consortium. ^[1]

Design

For more details on this topic, see X Window System protocols and architecture. In Computing, the X Window System (commonly X11 or X) is a network -transparent Windowing system for bitmap displays

For more details on this topic, see X Window System core protocol. The X Window System core protocol is the base protocol of the X Window System, which is a networked Windowing system for Bitmap displays used

X uses a client-server model: an X server communicates with various client programs. The client-server Software architecture model distinguishes client systems from server systems which communicate over a Computer network The server accepts requests for graphical output (windows) and sends back user input (from keyboard, mouse, or touchscreen). The server may function as:

• an application displaying to a window of another display system
• a system program controlling the video output of a PC
• a dedicated piece of hardware. A personal computer ( PC) is any Computer whose original sales price size and capabilities make it useful for individuals and which is intended to be operated

This client-server terminology — the user's terminal as the "server", the remote or local applications as the "clients" — often confuses new X users, because the terms appear reversed. But X takes the perspective of the program, rather than that of the end-user or of the hardware: the local X display provides display services to programs, so it acts as a server; any remote program uses these services, thus it acts as a client.

In this example, the X server takes input from a keyboard and mouse and displays to a screen. A web browser and a terminal emulator run on the user's workstation, and a system updater runs on a remote server but is controlled from the user's machine. A web browser is a software application which enables a user to display and interact with text images videos music games and other information typically located on a A terminal emulator, terminal application, term, or tty for short is a program that emulates a "dumb" video terminal within some other Note that the remote application runs just as it would locally.

The communication protocol between server and client operates network-transparently: the client and server may run on the same machine or on different ones, possibly with different architectures and operating systems, but they run the same in either case. In the field of Telecommunications, a communications protocol is the set of standard rules for data representation signaling authentication and error detection required to A computer network is a group of interconnected Computers. Networks may be classified according to a wide variety of characteristics In Computer engineering, computer architecture is the conceptual design and fundamental operational structure of a Computer system An operating system (commonly abbreviated OS and O/S) is the software component of a Computer system that is responsible for the management and coordination A client and server can even communicate securely over the Internet by tunneling the connection over an encrypted network session. This article describes how security can be achieved through design and engineering The Internet is a global system of interconnected Computer networks The term tunneling protocol is used to describe when one Network protocol called the payload protocol is encapsulated within a different delivery protocol

An X client itself may contain an X server having display of multiple clients. This is known as "X nesting". Open-source clients such as Xnest and Xephyr support such X nesting. Xnest is an X Window System server that shows its output in a window. Xephyr is a KDrive based X server which targets a window on a host X Server as its framebuffer

To start a remote client program displaying to a local server, the user will typically open a terminal window and telnet or ssh to the remote client application or shell and request local display/input service (e. A terminal emulator, terminal application, term, or tty for short is a program that emulates a "dumb" video terminal within some other Telnet ( Tel ecommunication net work is a Network protocol used on the Internet or local area network (LAN connections Secure Shell or SSH is a Network protocol that allows data to be exchanged using a Secure channel between two networked devices g. export DISPLAY=[user's machine]:0 on a remote machine running bash). Bash is a Free software Unix shell written for the GNU Project. The client application or shell then connects to the local server, servicing a display and input session to the local user. Alternatively, the local machine may run a small helper program to connect to a remote machine and start the desired client application there.

Practical examples of remote clients include:

• administering a remote machine graphically
• running a computationally intensive simulation on a remote Unix machine and displaying the results on a local Windows desktop machine
• running graphical software on several machines at once, controlled by a single display, keyboard and mouse.

Principles

In 1984, Bob Scheifler and Jim Gettys set out the early principles of X:

• Do not add new functionality unless an implementor cannot complete a real application without it. Robert William Scheifler (born 1954 is a Computer scientist. He is most notable for leading the development of the X Window System from the project's inception in Jim Gettys is a Computer programmer. Currently he is the Vice President of Software at the One Laptop per Child project working on the software for the
• It is as important to decide what a system is not as to decide what it is. Do not serve all the world's needs; rather, make the system extensible so that additional needs can be met in an upwardly compatible fashion. In Software engineering, extensibility (sometimes confused with Forward compatibility) is a System design principle where the implementation takes into
• The only thing worse than generalizing from one example is generalizing from no examples at all.
• If a problem is not completely understood, it is probably best to provide no solution at all.
• If you can get 90 percent of the desired effect for 10 percent of the work, use the simpler solution. (See also Worse is better. Worse is better, also called the New Jersey style was conceived by Richard P )
• Isolate complexity as much as possible.
• Provide mechanism rather than policy. In particular, place user interface policy in the clients' hands.

The first principle was modified during the design of X11 to: "Do not add new functionality unless you know of some real application that will require it. "

X has largely kept to these principles since. The reference implementation is developed with a view to extension and improvement of the implementation, whilst remaining almost entirely compatible with the original 1987 protocol.

User interfaces

X deliberately contains no specification as to application user interface, such as buttons, menus, window title bars and so on. The user interface (or Human Computer Interface) is the aggregate of means by which people&mdash the users '&mdash interact with the System In Computing, a button (sometimes known as a command button or Push button) is a widget that provides In Computing and Telecommunications a menu is a list of commands presented to an operator by a Computer or Communications system. In Computing, the title bar (or titlebar) consists of that part of a window where the title of the window appears Instead, user software – such as window managers, GUI widget toolkits and desktop environments, or application-specific graphical user interfaces – provide/define all such details. A window manager is Computer software that controls the placement and appearance of windows within a Windowing system in a Graphical user interface A widget toolkit, widget library, or GUI toolkit is a set of widgets for use in designing applications with Graphical user interfaces (GUIs In graphical computing a desktop environment ( DE) commonly refers to a style of Graphical user interface (GUI that is based on the Desktop metaphor which As such, it isn't possible to point to a "typical" X interface as at most times several interfaces have been popular among users.

A window manager controls the placement and appearance of application windows. An X window manager is a Window manager which runs on top of the X Window System, a Windowing system mainly used on Unix-like systems This may have an interface akin to that of Microsoft Windows or of the Macintosh (examples include Metacity in GNOME, KWin in KDE or Xfwm in Xfce) or have radically different controls (such as a tiling window manager). Microsoft Windows is a series of Software Operating systems and Graphical user interfaces produced by Microsoft. Macintosh, commonly nicknamed Mac is a Brand name which covers several lines of Personal computers designed developed and marketed by Apple Inc Metacity ( rhyming with "capacity" with the stress on the second syllable is a Compositing window manager used by default in the GNOME Desktop A gnome is a Mythical creature characterized by its extremely small size and subterranean lifestyle KWIN is a commercial Radio station located in Lodi California, broadcasting to the Stockton California area on 97 KDE ( K Desktop Environment) (ˌkeɪdiːˈiː is a Free software project which aims to be a powerful system for an easy-to-use Desktop environment. Xfce ( ɛf siː iː is a Free software Desktop environment for Unix and other Unix-like platforms such as Linux, Solaris Xfce ( ɛf siː iː is a Free software Desktop environment for Unix and other Unix-like platforms such as Linux, Solaris In computing a tiling window manager is a Window manager with an organization of the screen into mutually non-overlapping frames as opposed to the more popular approach The window manager may be bare-bones (e. g. twm, the basic window manager supplied with X, or evilwm, an extremely light window manager) or offer functionality verging on that of a full desktop environment (e. In Computing, twm ( Timeless Windows Manager) is the standard window manager for the X Window System, version X11R4 onwards evilwm is a minimalist Window manager for the X Window System. g. Enlightenment). Enlightenment, also known simply as E, is a Free software / Open source Window manager for the X Window System which can be used alone

Many users use X with a full desktop environment, which includes a window manager, various applications and a consistent interface. In graphical computing a desktop environment ( DE) commonly refers to a style of Graphical user interface (GUI that is based on the Desktop metaphor which GNOME, KDE and Xfce are the most popular desktop environments. A gnome is a Mythical creature characterized by its extremely small size and subterranean lifestyle KDE ( K Desktop Environment) (ˌkeɪdiːˈiː is a Free software project which aims to be a powerful system for an easy-to-use Desktop environment. Xfce ( ɛf siː iː is a Free software Desktop environment for Unix and other Unix-like platforms such as Linux, Solaris The Unix standard environment is the Common Desktop Environment (CDE). The Single UNIX Specification ( SUS) is the collective name of a family of standards for Computer Operating systems to qualify for the name " Unix The Common Desktop Environment ( CDE) a Graphical Desktop environment for Unix, leverages the Motif Widget toolkit The freedesktop.org initiative addresses interoperability between desktops and the components needed for a competitive X desktop.

As X is responsible for keyboard and mouse interaction with graphical desktops, certain keyboard shortcuts have become associated with X. A keyboard shortcut (or accelerator key, shortcut key, hot key, key binding, keybinding, key combo, etc Control-Alt-Backspace typically terminates the currently running X session, while Control-Alt in conjunction with a function key switches to the associated virtual console. A function key is a key on a Computer or terminal keyboard which can be programmed so as to cause an operating system command interpreter or application In Computing, some Operating systems such as UnixWare, Linux and BSD, feature a virtual console ( VC, sometimes Note, however, that this is an implementation detail left to an individual X server and is by no means universal; for example, X server implementations for Windows and Macintosh typically do not provide these shortcuts.

Implementations

The X. Org reference implementation serves as the canonical implementation of X. In Computing, a reference implementation (or less frequently sample implementation or model implementation) is a software example of a Specification Canonical is an Adjective derived from canon. Canon comes from the Greek word kanon, "rule" (perhaps originally from Due to liberal licensing, a number of variations, both free and proprietary, have appeared. A software license (or software licence in commonwealth usage is a Legal instrument governing the usage or redistribution of copyright protected software Free software or software libre is Software that can be used studied and modified without restriction and which can be copied and redistributed in modified or unmodified Proprietary software is Computer software on which the producer has set restrictions on use private modification copying, or republishing. Commercial UNIX vendors have tended to take the reference implementation and adapt it for their hardware, usually customising it heavily and adding proprietary extensions.

Cygwin/X running rootless on Microsoft Windows XP. Cygwin/X is an implementation of the X Window System that runs under Microsoft Windows. Windows XP is a family of 32-bit and 64-bit Operating systems produced by Microsoft for use on Personal computers including home and The screen shows X applications (xeyes, xclock, xterm) sharing the screen with native Windows applications (Date and Time, Calculator). xeyes is a graphical Computer program showing two Googly eyes which follow the Cursor movements on the screen as if they were watching it In Computing, xterm is the standard Terminal emulator for the X Window System.

Up to 2004, XFree86 provided the most common X variant on free Unix-like systems. XFree86 is an implementation of the X Window System. It was originally written for Unix-like Operating systems on IBM PC compatibles and is now A Unix-like (sometimes shortened to *nix) Operating system is one that behaves in a manner similar to a Unix system while not necessarily conforming XFree86 started as a port of X for 386-compatible PCs and, by the end of the 1990s, had become the greatest source of technical innovation in X and the de facto standard of X development. See also Software portability In Computer science, porting is the process of adapting software so that an executable program can be created ^[2] Since 2004, however, the X.Org reference implementation, a fork of XFree86, has become predominant. The XOrg Server (officially the XOrg Foundation Open Source Public Implementation of X11) is the X server in the official reference implementation of the X In Software engineering, a project fork happens when developers take a copy of Source code from one software package and start independent development

While computer aficionados most often associate X with Unix, X servers also exist natively within other graphical environments. Hewlett-Packard's OpenVMS operating system includes a version of X with CDE, known as DECwindows, as its standard desktop environment. Open Virtual Memory System ( OpenVMS) initially known just as Virtual Memory System ( VMS) is the name of a High-end Computer server The Common Desktop Environment ( CDE) a Graphical Desktop environment for Unix, leverages the Motif Widget toolkit The Common Desktop Environment ( CDE) a Graphical Desktop environment for Unix, leverages the Motif Widget toolkit Apple's Mac OS X v10.3 (Panther) and up includes X11.app, based on XFree86 4. Apple Inc, ( formerly Apple Computer Inc, is an American Multinational corporation with a focus on designing and manufacturing Consumer electronics Mac OS X version 103 “Panther” was the fourth major release of Mac OS X, Apple’s desktop and server Operating system. X11app is Apple Computer 's implementation of the X Window System for Mac OS X. 3 and X11R6. 6, with better Mac OS X integration. Mac OS X (mæk oʊ ɛs tɛn is a line of computer Operating systems developed marketed and sold by Apple Inc, the latest of which is pre-loaded on all currently Third-party servers under Mac OS 7, 8 and 9 included MacX. MacX is an X11 server implementation that ran on System 7, Mac OS 8, and Mac OS 9.

Microsoft Windows does not come with support for X, but many third-party implementations exist, both free software such as Cygwin/X, Xming and WeirdX; and proprietary products such as MKS X/Server, Exceed and X-Win32. Microsoft Windows is a series of Software Operating systems and Graphical user interfaces produced by Microsoft. Free software or software libre is Software that can be used studied and modified without restriction and which can be copied and redistributed in modified or unmodified Cygwin/X is an implementation of the X Window System that runs under Microsoft Windows. In computing Xming is a port of the X Window System to the Microsoft Windows operating system WeirdX is an X Window System server written in pure Java and licensed under GNU GPL by JCraft. MKS X/Server is for a commercial X server product for accessing UNIX / Linux systems from a PC developed by MKS Inc Hummingbird Ltd (previously NASDAQ: HUMC TSX: HUM is a subsidiary of Open Text and is a provider of enterprise software solutions In Computing, X-Win32 is a proprietary X Window System server for Microsoft Windows, produced by StarNet Communications. They normally serve to control remote X clients.

When another windowing system (such as those of Microsoft Windows or Mac OS) hosts X, the X system generally runs "rootless", meaning the host windowing environment looks after the root window (the background and associated menus) and manages the geometry of the hosted X windows — although some servers (Xmanager, and Exceed, for example) can also create the root window for the remote clients to display to as a separate window in the host system.

X terminals

A Network Computing Devices NCD-88k X terminal

Main article: X terminal

An X terminal is a thin client that runs an X server. Network Computing Devices (NCD was a company founded in 1987 to produce a new class of products now known as a " Thin client " See also HP X-Terminals A thin client (sometimes also called a lean or slim client) is a client computer or client software in Client-server architecture networks This architecture became popular for building inexpensive terminal parks for many users to simultaneously use the same large server (making programs being run on the server clients of the X terminal). This use very much aligns with the original intention of the MIT project.

X terminals explore the network (the local broadcast domain) using the X Display Manager Control Protocol to generate a list of available hosts that they can run clients from. A broadcast domain is a logical division of a Computer network, in which all nodes can reach each other by broadcast at the Data link layer In the X Window System, an X display manager runs as a program that allows the starting of a session on an X server from the same or another Computer The initial host needs to run an X display manager. In the X Window System, an X display manager runs as a program that allows the starting of a session on an X server from the same or another Computer

Dedicated (hardware) X terminals have become less common; a PC or modern thin client with an X server typically provides the same functionality at the same, or lower, cost. A personal computer ( PC) is any Computer whose original sales price size and capabilities make it useful for individuals and which is intended to be operated A thin client (sometimes also called a lean or slim client) is a client computer or client software in Client-server architecture networks

Limitations and criticisms of X

The UNIX-HATERS Handbook (1994) devoted an entire chapter to the problems of X. The UNIX-HATERS Handbook is a semi-humorous edited compilation of messages to the UNIX-HATERS Mailing list. ^[3] Why X Is Not Our Ideal Window System (1990) by Gajewska, Manasse and McCormack detailed problems in the protocol with recommendations for improvement.

User interface features

X deliberately contains no specification as to user interface or most inter-application communication. This has resulted in several vastly different interfaces, and in applications that have not always worked well together. The ICCCM, a specification for client interoperability, has a reputation as difficult to implement correctly. In Computing, the Inter-Client Communication Conventions Manual (ICCCM is a standard for interoperability between X Window System clients of the same Further standards efforts such as Motif and CDE did not remedy matters. In computing Motif refers to both a Graphical user interface (GUI specification and the Widget toolkit for building applications that follow that specification The Common Desktop Environment ( CDE) a Graphical Desktop environment for Unix, leverages the Motif Widget toolkit This has frustrated users and programmers for a long time. ^[4] Graphics programmers now generally address consistency of application look and feel and communication by coding to a specific desktop environment or to a specific widget toolkit, which also avoids having to deal directly with the ICCCM. Look and feel is a term used in descriptions of products and fields such as Marketing, Branding and Trademarking to signify the experience a person has using

The X protocol provides no facilities for handling audio, leaving it to the operating system or audio systems like OSS or ALSA to provide support for audio hardware and sound playback. The Open Sound System (OSS is a standard interface for making and capturing sound in Unix operating systems Advanced Linux Sound Architecture (known by the Acronym ALSA) is a Linux kernel component intended to replace the original Open Sound System Most programmers simply use local, OS-specific sound APIs. The first generation of client-server sound systems included rplay and Network Audio System. The Network Audio System ( NAS) is an open-source, network-transparent, Client-server audio transport system More recent efforts have produced EsounD (GNOME), aRts (KDE), and PulseAudio to name a few. In Computing, the Enlightened Sound Daemon ( ESD or EsounD) is the Sound server for Enlightenment and GNOME. aRts, which stands for a nalog R eal t ime s ynthesizer is an audio framework that is no longer under development PulseAudio (formerly PolypAudio) is a Cross-platform, networked Sound server project In 2001, the X.org foundation announced the development of the Media Application Server (MAS) to remedy this problem. The XOrg Server (officially the XOrg Foundation Open Source Public Implementation of X11) is the X server in the official reference implementation of the X However, none of these are generally used as a solution to the problem.

Network

Example of tunnelling an X11 application over SSH.

An X client cannot generally be detached from one server and reattached to another, as with Virtual Network Computing (VNC), though certain specific applications and toolkits are able to provide this facility. In computing Virtual Network Computing ( VNC) is a graphical Desktop sharing system which uses the RFB protocol to remotely control another Computer ^[5] Workarounds (VNC :0 viewers) also exist to make the current X-server screen available via VNC.

Network traffic between an X server and remote X clients is not encrypted by default. An attacker with a packet sniffer can intercept it, making it possible to view anything displayed to or sent from the user's screen. The most common way to encrypt X traffic is to tunnel it over SSH. Secure Shell or SSH is a Network protocol that allows data to be exchanged using a Secure channel between two networked devices

Client-server separation

X's design requires the clients and server to operate separately, and device independence and the separation of client and server incur overhead compared to an operating system where the graphics are integrated into the OS, such as early versions of Microsoft Windows or Mac OS. Microsoft Windows is a series of Software Operating systems and Graphical user interfaces produced by Microsoft. Mac OS is the trademarked name for a series of Graphical user interface -based Operating systems developed by Apple Inc X advocates recommended 4 to 8 MB of RAM for reasonable performance; until the mid-1990s, this seemed bloated compared to Windows or Mac OS. A megabyte is a unit of Information or Computer storage equal to either 106 (1000000 Bytes or 220 (1048576 bytes depending on

Current versions of Windows and Mac OS X Quartz have internal subsystem separation similar to the client/server divide in X and comparable performance and higher resource usage to X with GNOME or KDE. Mac OS X (mæk oʊ ɛs tɛn is a line of computer Operating systems developed marketed and sold by Apple Inc, the latest of which is pre-loaded on all currently Quartz specifically refers to a pair of Mac OS X technologies each part of the Core Graphics framework Quartz 2D and Quartz Compositor. A gnome is a Mythical creature characterized by its extremely small size and subterranean lifestyle KDE ( K Desktop Environment) (ˌkeɪdiːˈiː is a Free software project which aims to be a powerful system for an easy-to-use Desktop environment. Most of the overhead comes from network round-trip delay time between client and server (latency rather than from the protocol itself): the best solutions to performance issues involve paying attention to application design. In Telecommunications the term round-trip delay time or round-trip time (RTT has the following meanings The elapsed Time for transit Latency is a time delay between the moment something is initiated and the moment one of its effects begins or becomes detectable ^[6] A common criticism of X is that its network features result in excessive complexity and decreased performance if only used locally. That used to be the case, but modern X implementations are able to use unix domain sockets and shared memory (the MIT-SHM extension) to work around the network overhead. A Unix domain socket (UDS or IPC socket (inter-process communication socket is a virtual socket similar to an Internet socket that is used in POSIX In Computing, shared memory is a memory that may be simultaneously accessed by multiple programs with an intent to provide communication among them or avoid redundant copies The MIT Shared Memory Extension or MIT-SHM is a X Window System extension for exchange of image data between client and server using Shared memory. The programmer must still explicitly activate and use those extensions in order to improve performance and must also provide fallback paths in order to stay compatible with older implementations.

Competitors to X

For graphics, Unix-like systems use X almost universally. A Unix-like (sometimes shortened to *nix) Operating system is one that behaves in a manner similar to a Unix system while not necessarily conforming However, some people have attempted writing alternatives to and replacements for X. Historical alternatives include Sun's NeWS, which failed in the market, and NeXT's Display PostScript, which was discarded in favor of Apple's entirely new Quartz in Mac OS X. Sun Microsystems Inc ( is a multinational vendor of Computers computer components Computer software, and Information technology services News is any new information or information on Current events which is presented by print, broadcast, Internet, or Word of mouth NeXT Computer Inc (later NeXT Software Inc) was an American Computer company headquartered in Redwood City, California that Display PostScript (or DPS) is an on-screen display system As the name implies DPS uses the PostScript (PS imaging model and language to generate on-screen graphics Apple Inc, ( formerly Apple Computer Inc, is an American Multinational corporation with a focus on designing and manufacturing Consumer electronics Quartz specifically refers to a pair of Mac OS X technologies each part of the Core Graphics framework Quartz 2D and Quartz Compositor. Mac OS X (mæk oʊ ɛs tɛn is a line of computer Operating systems developed marketed and sold by Apple Inc, the latest of which is pre-loaded on all currently

Mike Paquette, one of the authors of Quartz, explained why Apple did not move from Display PostScript to X, and chose instead to develop its own window server, by saying that once Apple added support for all the features it wanted to include in to X11, it would not bear much resemblance to X11 nor be compatible with other servers anyway. ^[7]

Other attempts to address criticisms of X by replacing it completely include Berlin/Fresco and the Y Window System. In Computing, Fresco (formerly known as Berlin) is a Windowing system. The Y Window System (also known as Y-Windows is a Windowing system, consisting of a window server and a client library for writing applications These alternatives have seen negligible take-up, however, and commentators widely doubt the viability of any replacement that does not preserve backward compatibility with X.

Other competitors attempt to avoid the overhead of X by working directly with the hardware. Such projects include DirectFB and the very small FBUI. DirectFB stands for Direct Frame Buffer It is a software library for the GNU / Linux operating system that provides "hardware graphics acceleration FrameBuffer UI (FBUI is an in-kernel Windowing system for Linux (kernel version 2 The Direct Rendering Infrastructure (DRI), which aims to provide a reliable kernel-level interface to the framebuffer, may make these efforts redundant. In Computing, the Direct Rendering Infrastructure ( DRI) is an interface and a Free software implementation used in the X Window System A framebuffer is a video output device that drives a video display from a memory buffer containing a complete frame of data However, in Linux embedded systems requiring real-time capabilities (e. g. using RTAI), the use of hardware acceleration via DRI is discouraged; X may be unsuitable for such applications. RTAI stands for '''R'''eal-'''T'''ime A pplication I nterface

Other ways to achieve network transparency for graphical services include:

• the SVG Terminal, a protocol to update Scalable Vector Graphics (SVG) content in a browser in near-real-time
• Virtual Network Computing (VNC), a very low-level system which sends compressed bitmaps across the network; the Unix implementation includes an X server
• Citrix XenApp, an X-like product for Microsoft Windows
• Tarantella, which provides a Java client for use in web browsers
• RAWT, IBM's Java-only Remote AWT, which implements a Java "server" and simple hooks for any remote Java client

History

Predecessors

Several bitmap display systems preceded X. In computing Virtual Network Computing ( VNC) is a graphical Desktop sharing system which uses the RFB protocol to remotely control another Computer Citrix XenApp (formerly Citrix MetaFrame Server and Citrix Presentation Server) is a Remote access / Application publishing product that allows Tarantella was a line of products developed by a branch of the company Santa Cruz Operation (SCO since 1993 From Xerox came the Alto (1973) and the Star (1981). Xerox Corporation ( (name ˈziːrɒks is a global document management company which manufactures and sells a range of color and black-and-white printers, multifunction The Xerox Alto was an early Personal computer developed at Xerox PARC in 1973. The Star Workstation, officially known as the Xerox 8010 Information System, was introduced From Apple came the Lisa (1983) and the Macintosh (1984). Apple Inc, ( formerly Apple Computer Inc, is an American Multinational corporation with a focus on designing and manufacturing Consumer electronics For the MOS 6502 assembler for Apple II computers see Lisa assembler. Macintosh, commonly nicknamed Mac is a Brand name which covers several lines of Personal computers designed developed and marketed by Apple Inc The Unix world had the Andrew Project (1982) and Rob Pike's Blit terminal (1982). Unix (officially trademarked as UNIX, sometimes also written as Unix with Small caps) is a computer The Andrew Project was a distributed computing environment begun in 1983 driven by the Information Technology Center, a joint Carnegie Mellon University and Robert C Pike (born 1956 is a Software engineer and Author. He is best known for his work at Bell Labs, where he was a member of the Unix In Computing, the Blit is a programmable Bitmap graphics terminal designed by Rob Pike and Bart Locanthi of Bell Labs

X derives its name as a successor to a pre-1983 window system called W (the letter X directly following W in the Latin alphabet). The W Window System is a graphical windowing system and precursor in name and concept to the modern X Window System. W Window System ran under the V operating system. The V operating system (sometimes written V-System, not to be confused with System V) is a microkernel Operating system that was developed by W used a network protocol supporting terminal and graphics windows, the server maintaining display lists.

An early-1990s style Unix desktop running the X Window System graphical user interface shows many client applications common to the MIT X Consortium's distribution, including the twm window manager, an X Terminal, Xbiff, xload and a graphical manual page browser. In Computing, twm ( Timeless Windows Manager) is the standard window manager for the X Window System, version X11R4 onwards In Computing, xterm is the standard Terminal emulator for the X Window System. xbiff is a small utility for the X Window System that shows a mailbox with its flag raised whenever the user has new E-mail. Almost all substantial UNIX and Unix-like Operating systems have extensive documentation known as man pages (short for "manual pages"

Origin and early development

The original idea of X emerged at MIT in 1984 as a collaboration between Jim Gettys (of Project Athena) and Bob Scheifler (of the MIT Laboratory for Computer Science). Jim Gettys is a Computer programmer. Currently he is the Vice President of Software at the One Laptop per Child project working on the software for the Project Athena was a joint project of MIT, Digital Equipment Corporation, and IBM. Robert William Scheifler (born 1954 is a Computer scientist. He is most notable for leading the development of the X Window System from the project's inception in Project MAC (the MIT Project on Mathematics and Computation later the MIT Laboratory for Computer Science ( LCS) was a research laboratory at MIT Scheifler needed a usable display environment for debugging the Argus system. Project Athena (a joint project between Digital Equipment Corporation (DEC), MIT and IBM to provide easy access to computing resources for all students) needed a platform-independent graphics system to link together its heterogeneous multiple-vendor systems; the window system then under development in Carnegie Mellon University's Andrew Project did not make licenses available, and no alternatives existed. Digital Equipment Corporation was a pioneering American company in the Computer industry International Business Machines Corporation abbreviated IBM and nicknamed "Big Blue", is a multinational Computer Technology Carnegie Mellon University (also known as CMU) is a private Research University in Pittsburgh, Pennsylvania, United The Andrew Project was a distributed computing environment begun in 1983 driven by the Information Technology Center, a joint Carnegie Mellon University and

The project solved this by creating a protocol that could both run local applications and call on remote resources. In mid-1983 an initial port of W to Unix ran at one-fifth of its speed under V; in May 1984, Scheifler replaced the synchronous protocol of W with an asynchronous protocol and the display lists with immediate mode graphics to make X version 1. In computing, a protocol is a convention or standard that controls or enables the connection Communication, and Data transfer between two computing Asynchrony, in the general meaning is the state of not being synchronized. X became the first windowing system environment to offer true hardware-independence and vendor-independence.

Scheifler, Gettys and Ron Newman set to work and X progressed rapidly. Ron Newman is a Computer programmer. He is most famous for his work in the early development of the X Window System, from the first version in 1984 to X11R2 in 1988 They released Version 6 in January 1985. DEC, then preparing to release its first Ultrix workstation, judged X the only windowing system likely to become available in time. Ultrix (officially all-caps ULTRIX) was the brand name of Digital Equipment Corporation 's (DEC native Unix systems DEC engineers ported X6 to DEC's QVSS display on MicroVAX. Name "VAX" was originally an Acronym for V irtual A ddress e' X' tension, both because the VAX was seen as a 32-bit

In the second quarter of 1985 X acquired color support to function in the DEC VAXstation-II/GPX, forming what became version 9. In Computing, on the X Window System, X11 color names are represented in a simple text file which maps certain strings to RGB Color values Name "VAX" was originally an Acronym for V irtual A ddress e' X' tension, both because the VAX was seen as a 32-bit Although MIT had licensed X6 to some outside groups for a fee, it decided at this time to license X9 and future versions under what became known as the MIT License. The MIT License is a Free software license originating at the Massachusetts Institute of Technology (MIT used by the MIT X Consortium. X9 appeared in September 1985.

A group at Brown University ported version 9 to the IBM RT/PC, but problems with reading unaligned data on the RT forced an incompatible protocol change, leading to version 10 in late 1985. Brown University is a highly esteemed private University located in Providence, Rhode Island and is a member of the Ivy League. International Business Machines Corporation abbreviated IBM and nicknamed "Big Blue", is a multinational Computer Technology The IBM RT (or IBM 6150 series was a Computer workstation sold by IBM and based around IBM's ROMP By 1986, outside organizations had started asking for X. The release of X10R2 took place in January 1986; that of X10R3 in February 1986. X10R3 became the first version to achieve wide deployment, with both DEC and Hewlett-Packard releasing products based on it. Other groups ported X10 to Apollo and to Sun workstations and even to the IBM PC/AT. Sun Microsystems Inc ( is a multinational vendor of Computers computer components Computer software, and Information technology services The IBM Personal Computer/AT, more commonly known as the IBM AT and also sometimes called the PC AT or PC/AT, was IBM 's second-generation Demonstrations of the first commercial application for X (a mechanical computer-aided engineering system from Cognition Inc. that ran on VAXes and displayed on PCs running an X server) took place at the Autofact trade show at that time. The last version of X10, X10R4, appeared in December 1986.

Attempts were made to enable X servers as real-time collaboration devices, much as Virtual Network Computing (VNC) would later allow a desktop to be shared. In computing Virtual Network Computing ( VNC) is a graphical Desktop sharing system which uses the RFB protocol to remotely control another Computer One such early effort was Philip J. Gust's SharedX tool. SharedX was a tool developed at HP in the mid 1980s to allow X servers to "shared" a window thus allowing users at multiple workstations to interact with the same X window

Although X10 offered interesting and powerful functionality, it had become obvious that the X protocol could use a more hardware-neutral redesign before it became too widely deployed; but MIT alone would not have the resources available for such a complete redesign. As it happened, DEC's Western Software Laboratory found itself between projects. Smokey Wallace of DEC WSL and Jim Gettys proposed that DEC WSL build X11 and make it freely available under the same terms as X9 and X10. This process started in May 1986, with the protocol finalised in August. Alpha-testing of the software started in February 1987, beta-testing in May; the release of X11 finally occurred on September 15, 1987. Events 668 - Eastern Roman Emperor Constans II is assassinated in his bath at Syracuse Italy. Year 1987 ( MCMLXXXVII) was a Common year starting on Thursday (link displays 1987 Gregorian calendar)

The X11 protocol design, led by Scheifler, got extensively discussed on open mailing lists on the nascent Internet that were bridged to USENET newsgroups. The Internet is a global system of interconnected Computer networks X therefore represents one of the first very large-scale free software projects. Free software or software libre is Software that can be used studied and modified without restriction and which can be copied and redistributed in modified or unmodified

The MIT X Consortium and the X Consortium, Inc.

In 1987, with the success of X11 becoming apparent, MIT wished to relinquish the stewardship of X, but at a June 1987 meeting with nine vendors, the vendors told MIT that they believed in the need for a neutral party to keep X from fragmenting in the marketplace. In January 1988, the MIT X Consortium formed as a non-profit vendor group, with Scheifler as director, to direct the future development of X in a neutral atmosphere inclusive of commercial and educational interests. Jim Fulton joined in January 1988 and Keith Packard in March 1988 as senior developers, with Jim focusing on Xlib, fonts, window managers, and utilities; and Keith re-implementing the server. Keith Packard is a Software developer, best known for his work on the X Window System. A programmer is someone who writes Computer software. The term computer programmer can refer to a specialist in one area of computer programming or to a generalist Xlib is an X Window System protocol client library in the C programming language. Donna Converse and Chris D. Peterson joined later that year, focusing on toolkits and widget sets, working closely with Ralph Swick of MIT Project Athena. The MIT X Consortium produced several significant revisions to X11, the first (Release 2 - X11R2) in February 1988.

DECwindows CDE on OpenVMS 7. Open Virtual Memory System ( OpenVMS) initially known just as Virtual Memory System ( VMS) is the name of a High-end Computer server 3-1

In 1993, the X Consortium, Inc. (a non-profit corporation) formed as the successor to the MIT X Consortium. It released X11R6 on May 16, 1994. Events 1204 - Baldwin IX Count of Flanders is crowned as the first Emperor of the Latin Empire. Year 1994 ( MCMXCIV) was a Common year starting on Saturday (link will display full 1994 Gregorian calendar) In 1995 it took over stewardship of the Motif toolkit and of the Common Desktop Environment for Unix systems. In computing Motif refers to both a Graphical user interface (GUI specification and the Widget toolkit for building applications that follow that specification The Common Desktop Environment ( CDE) a Graphical Desktop environment for Unix, leverages the Motif Widget toolkit The X Consortium dissolved at the end of 1996, producing a final revision, X11R6. 3, and a legacy of increasing commercial influence in the development. ^[8][9]

The Open Group

In mid-1997 the X Consortium passed stewardship of X to The Open Group, a vendor group formed in early 1996 by the merger of the Open Software Foundation and X/Open. The Open Group is an industry Consortium to set vendor- and technology-neutral open standards for Computing infrastructure The Open Software Foundation ( OSF) was an organization founded in 1988 to create an Open standard for an implementation of the Unix operating X/Open Company Ltd was a Consortium founded by several European UNIX systems manufacturers in 1984 to identify and promote Open standards in the field

The Open Group released X11R6. 4 in early 1998. Controversially, X11R6. 4 departed from the traditional liberal licensing terms, as the Open Group sought to assure funding for X's development. ^[10] The new terms would have prevented its adoption by many projects (such as XFree86) and even by some commercial vendors. XFree86 is an implementation of the X Window System. It was originally written for Unix-like Operating systems on IBM PC compatibles and is now After XFree86 seemed poised to fork, the Open Group relicensed X11R6. In Software engineering, a project fork happens when developers take a copy of Source code from one software package and start independent development 4 under the traditional license in September 1998. ^[11] The Open Group's last release came as X11R6. 4 patch 3.

X. Org and XFree86

XFree86 originated in 1992 from the X386 server for IBM PC compatibles included with X11R5 in 1991, written by Thomas Roell and Mark W. XFree86 is an implementation of the X Window System. It was originally written for Unix-like Operating systems on IBM PC compatibles and is now X386 was the first implementation of the X Window System for IBM PC compatible computers IBM PC compatible computers are those generally similar to the original IBM PC, XT, and AT. Snitily and donated to the MIT X Consortium by Snitily Graphics Consulting Services (SGCS). XFree86 evolved over time from just one port of X to the leading and most popular implementation and the de facto steward of X's development. ^[12]

In May 1999, the Open Group formed X.Org. X. Org supervised the release of versions X11R6. 5. 1 onward. X development at this time had become moribund^[13]; most technical innovation since the X Consortium had dissolved had taken place in the XFree86 project. ^[14] In 1999, the XFree86 team joined X. Org as an honorary (non-paying) member^[15], encouraged by various hardware companies^[16] interested in using XFree86 with Linux and in its status as the most popular version of X.

By 2003, while the popularity of Linux (and hence the installed base of X) surged, X. Org remained inactive^[17], and active development took place largely within XFree86. However, considerable dissent developed within XFree86. The XFree86 project suffered from a perception of a far too cathedral-like development model; developers could not get CVS commit access^[18][19] and vendors had to maintain extensive patch sets. The Cathedral and the Bazaar (abbreviated CatB) is an essay by Eric S In the field of Software development, the Concurrent Versions System ( CVS) also known as the Concurrent Versioning System, provides a Version ^[20] In March 2003 the XFree86 organization expelled Keith Packard, who had joined XFree86 after the end of the original MIT X Consortium, with considerable ill-feeling. ^[21][22][23]

X. Org and XFree86 began discussing a reorganisation suited to properly nurturing the development of X. ^[24][25][26] Jim Gettys had been pushing strongly for an open development model since at least 2000. ^[27] Gettys, Packard and several others began discussing in detail the requirements for the effective governance of X with open development.

Finally, in an echo of the X11R6. 4 licensing dispute, XFree86 released version 4. 4 in February 2004 under a more restricted license which many projects relying on X found unacceptable. ^[28] The added clause to the license was based upon the original BSD license's advertising clause, which was viewed by the Free Software Foundation and Debian as incompatible with the GNU General Public License. BSD licenses represent a family of Permissive free software licences. The Free Software Foundation ( FSF) is a Non-profit corporation founded by Richard Stallman on 4 October 1985 to support the Free software movement Debian ( pronounced) is a computer Operating system composed entirely of Free and open source software. ^[29] Other groups saw further restrictions as being against the spirit of the original X (OpenBSD threatening a fork, for example). OpenBSD is a Unix-like computer Operating system descended from Berkeley Software Distribution (BSD a Unix derivative developed at the In Software engineering, a project fork happens when developers take a copy of Source code from one software package and start independent development The license issue, combined with the difficulties in getting changes in, left many feeling the time was ripe for a fork. ^[30]

The X. Org Foundation

In early 2004 various people from X. Org and freedesktop. org formed the X.Org Foundation, and the Open Group gave it control of the x. The XOrg Foundation is the organization holding the stewardship for the development of the X Window System. org domain name. In Computer networking, a domain name is a name given to a collection of network devices that belong to a domain which is an administrative space managed according This marked a radical change in the governance of X. Whereas the stewards of X since 1988 (including the previous X. Org) had been vendor organizations, the Foundation was led by software developers and used community development based on the bazaar model, which relies on outside involvement. The Cathedral and the Bazaar (abbreviated CatB) is an essay by Eric S Membership was opened to individuals, with corporate membership being in the form of sponsorship. Several major corporations such as Hewlett-Packard and Sun Microsystems currently support the X. Sun Microsystems Inc ( is a multinational vendor of Computers computer components Computer software, and Information technology services Org Foundation.

The Foundation takes an oversight role over X development: technical decisions are made on their merits by achieving rough consensus among community members. Technical decisions are not made by the board of directors; in this sense, it is strongly modelled on the technically non-interventionist GNOME Foundation. The GNOME Foundation is a non-profit organization based in Cambridge Massachusetts, United States coordinating the efforts in the GNOME project The Foundation does not employ any developers.

The Foundation released X11R6. 7, the X.Org Server, in April 2004, based on XFree86 4. The XOrg Server (officially the XOrg Foundation Open Source Public Implementation of X11) is the X server in the official reference implementation of the X 4RC2 with X11R6. 6 changes merged. Gettys and Packard had taken the last version of XFree86 under the old license and, by making a point of an open development model and retaining GPL compatibility, brought many of the old XFree86 developers on board. ^[31]

X11R6. 8 came out in September 2004. It added significant new features, including preliminary support for translucent windows and other sophisticated visual effects, screen magnifiers and thumbnailers, and facilities to integrate with 3D immersive display systems such as Sun's Project Looking Glass and the Croquet project. Project Looking Glass is a Free software project under the GPL to create an innovative 3D Desktop environment for Linux, Solaris The Croquet Project is an International effort to promote the continued development of Croquet a free software platform and a External applications called compositing window managers provide policy for the visual appearance. A Compositing window manager is a component of a computer's Graphical user interface that draws windows and/or their borders

On December 21, 2005^[32] , X. Events 69 - The end of the Year of the four emperors: Following Galba, Otho and Vitellius, Vespasian Year 2005 ( MMV) was a Common year starting on Saturday (link displays full calendar of the Gregorian calendar. Org released X11R6. 9, the monolithic source tree for legacy users, and X11R7. In Computer science, source code (commonly just source or code) is any sequence of statements or declarations written in some Human-readable 0, the same source code separated into independent modules, each maintainable in separate projects. ^[33] The Foundation released X11R7. 1 on May 22, 2006, about four months after 7. Events 334 BC - The Greek army of Alexander the Great defeats Darius III of Persia in the Battle of the Granicus. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. 0, with considerable feature improvements. ^[34]

Future directions

With the X. Org Foundation and freedesktop. org, the main line of X development has started to progress rapidly once more. The developers intend to release present and future versions as usable finished products, not merely as bases for vendors to build a product upon.

For sufficiently capable combinations of hardware and operating systems, X. Org plans to access the video hardware only via OpenGL and the Direct Rendering Infrastructure (DRI). OpenGL ( Open G raphics L ibrary is a standard specification defining a cross-language Cross-platform API for writing applications that produce In Computing, the Direct Rendering Infrastructure ( DRI) is an interface and a Free software implementation used in the X Window System The DRI first appeared in XFree86 version 4. 0 and became standard in X11R6. 7 and later. ^[35] Many operating systems have started to add kernel support for hardware manipulation. This work proceeds incrementally.

Nomenclature

People in the computer trade commonly shorten the phrase "X Window System" to "X11" or simply to "X". The term "X Windows" (in the manner of "Microsoft Windows") is not officially endorsed, though it has been in common use since early in the history of X and has been used deliberately for literary effect, for example in the UNIX-HATERS Handbook. The UNIX-HATERS Handbook is a semi-humorous edited compilation of messages to the UNIX-HATERS Mailing list. ^[36]

Release history

See also: XFree86#Release history

Forthcoming releases

See also

• History of the graphical user interface
• X11 color names
• Xgl
• General Graphics Interface
• VirtualGL
• rio (program)
• List of Unix programs
• DESQview/X
• Cairo (graphics)
• Y Window System
• XFree86

Notes

Date of retrieval, or, where available, of original posting, listed after the link

References

External links

• X.Org Foundation Official website
• The X Window System: A Brief Introduction
• Window managers for X
• The State of Linux Graphics (Jon Smirl, 30 August 2005)
• Writing a Graphics Device Driver and DDX for the DIGITAL UNIX X Server
• Kenton Lee: Technical X Window System and Motif WWW Sites
• RFC 1198 - FYI on the X Window System