X Window System facts for kids

Quick facts for kids
X Window System

twm, the basic X11 window manager
Original author(s)	Project Athena
Developer(s)	X.Org Foundation
Initial release	June 1984; 41 years ago (1984-06)
Stable release	X11R7.7  / 6 June 2012
Preview release	Lua error in Module:Wd at line 1575: attempt to index field 'wikibase' (a nil value).
Operating system	Unix, Unix-like, MVS OpenVMS, DOS
Platform	Cross-platform
Predecessor	W Window System
Type	Windowing system
License	MIT License

The X Window System (also called X11 or just X) is a special program that helps computers show graphics. It's like the foundation for what you see on your screen. It's very common on computers that use Unix-like operating systems, like Linux.

X was first created in 1984 as part of a project at the Massachusetts Institute of Technology (MIT). Since September 1987, it has been at version 11, which is why it's often called "X11." Today, the X.Org Foundation guides the X project. The main version, called X.Org Server, is free for everyone to use and change.

What Does the X Window System Do?

X is a system that helps you see and interact with computer programs using graphics. It works on many different types of computers. It lets you use a mouse, keyboard, or touchscreen to control what's on your screen.

X provides the basic tools for building graphical user interfaces (GUIs). Think of it as the drawing board and basic shapes. It lets programs draw and move windows on your screen. It also handles how you interact with your mouse and keyboard. X doesn't decide what your computer screen should look like. Instead, other programs, like window managers or desktop environments, decide the look and feel. This is why different X-based systems can look very different.

One cool thing about X is that it works well over networks. This means a program running on one computer can show its windows and buttons on another computer's screen. For example, a game running on a powerful computer far away could show up on your laptop screen. The computer showing the graphics is called the "X server." The program running the game is called the "X client."

How Do X Servers and Clients Work?

The idea of "server" and "client" in X can be a bit confusing. Usually, a server provides a service, and a client uses it. With X, your computer's screen and input devices (like your mouse and keyboard) are the "resources." The X server on your computer makes these resources available. The programs you run (the X clients) use these resources to show you things and get your input.

So, the X server is usually running on the computer right in front of you. The X client programs can run anywhere on the network. They talk to your X server to draw graphics and get information from your keyboard and mouse.

How X Software is Built

Simple example: The X server gets input from your keyboard and mouse and shows it on your screen. A web browser and a terminal program run on your computer. Another terminal program runs on a faraway computer but you control it from your machine.

X uses a "client-server" setup. An X server talks to different "client" programs. The server takes requests from programs to draw things on the screen. It also sends back what you do with your mouse, keyboard, or touchscreen.

The X server can be:

• A program showing its windows inside another display system.
• A main program controlling your computer's screen.
• A special piece of hardware.

The way the server and client talk to each other works over a network. This means the client and server can be on the same computer or on different ones. They can even be on computers with different types of hardware or operating systems. You can even use X securely over the internet.

Using X for Remote Access

You can run an X program on a computer far away and see it on your local screen. Here's how it generally works:

• You open a special window on your computer called a "terminal."
• You use a command like `ssh -X` to connect to the remote computer.
• The program on the remote computer then connects to your local X server. This lets you see and control the program from your screen.

This is useful for many things:

• Managing a faraway computer using its graphical interface.
• Working together with many people on the same program.
• Running a big, complex program on a powerful remote computer and seeing the results on your desktop.
• Using graphical software on several computers at once, all controlled from one screen.

How X Looks and Feels

GNOME is a popular graphical user interface.

Xfce is another graphical user interface.

X itself only provides the basic drawing tools. It doesn't tell programs how buttons, menus, or window titles should look. Because of this, the look of X-based systems can be very different. Other software, like window managers and desktop environments, decide the style.

A window manager controls how application windows are placed and how they look. Some window managers make your desktop look like Microsoft Windows or Apple Macintosh (examples are GNOME 2, KDE Plasma, Xfce). Others have very different ways of working.

Many people use X with a desktop environment. This includes a window manager and many other programs that all have a similar look. Popular desktop environments are GNOME, KDE Plasma, and Xfce.

How X is Used Today

The X.Org version is the most common way X is used. Because it's free to use and change, many different versions have appeared. Companies that make Unix systems often take the main X version and change it to work best with their hardware.

For a long time, XFree86 was the most popular version of X on free Unix-like systems. It started as a way to make X work on PCs. By the late 1990s, XFree86 was a major source of new ideas for X. But since 2004, the X.Org Server, which came from XFree86, has become the most widely used.

While X is often linked to Unix, X servers also work on other graphical systems. For example, OpenVMS includes a version of X. Apple used to have X on macOS as X11.app, but now they use XQuartz.

Even Microsoft Windows doesn't come with X built-in, but you can install third-party versions. Examples include Cygwin/X (free) and other paid programs.

What are X Terminals?

An X terminal is a simple computer that only runs an X server. These were popular because they were cheap. Many users could connect to one powerful computer server and run their programs on it. The X terminal would just show the programs' windows. This was very close to the original idea behind X.

X terminals look for available servers on the network. They use a special protocol called XDMCP. A server needs to be running an X display manager to be found.

A limit of X terminals is that they only handle the screen, keyboard, and mouse. All your important files and programs are on the remote server. You can't save or load things from a local USB drive or other device.

Today, dedicated X terminals are not as common. A regular PC or a modern thin client can do the same job for a similar or lower cost.

Other Systems Like X

Some people have tried to create alternatives to X. In the past, there were systems like Sun's NeWS and NeXT's Display PostScript.

Today, some other systems include:

• macOS uses its own system called Quartz. When Apple bought NeXT, they used parts of NeXTSTEP to build Mac OS X. They replaced Display PostScript with Quartz.
• Wayland is being developed by some of the same people who work on X.Org. It's meant to be a future replacement for X. It talks directly to the computer's graphics card. Wayland can even run X programs.
• Mir was another project with similar goals to Wayland. It was made by Canonical Ltd., the company behind Ubuntu Linux. Mir aimed to work on mobile devices and regular computers. It can now act as a Wayland compositor.

Other ways to get a "network transparency" effect (seeing graphics from a remote computer) include:

• Virtual Network Computing (VNC): This system sends compressed images of the screen over the network.
• Remote Desktop Protocol (RDP): Similar to VNC, it started on Microsoft Windows and is now on Unix-like systems.

History of the X Window System

Before X, there were other systems that showed graphics on computer screens. Some famous ones were the Xerox Alto (1973) and the Apple Lisa (1983).

X got its name because it came after a system called W. W was an earlier window system that ran on a different operating system.

How X Started and Grew

The idea for X came about at MIT in 1984. Jim Gettys and Bob Scheifler worked together on it. They needed a good way to show graphics for a project called Project Athena. This project aimed to give all students easy access to computers. They needed a graphics system that would work on many different types of computers.

They created a system that could run programs on the local computer or use resources from computers far away. In 1984, Scheifler made big changes to the old W system, creating X version 1. X was the first windowing system that worked truly independently of the computer's hardware or who made the computer.

X grew quickly. Version 6 came out in January 1985. DEC, a big computer company, saw X as the best option for their new computers. They helped make X better.

In 1985, X gained color support. This led to version 9. A group at Brown University helped make X work on IBM RT PC computers. This led to version 10 in late 1985.

By 1986, other groups wanted to use X. MIT decided to make X10R3 and future versions free to use under what became known as the MIT License. They hoped this would make X more popular and lead to more programs being made for it. X10R3 was the first version to be widely used. Both DEC and Hewlett-Packard released products based on it.

Even though X10 was good, people realized the X system needed a big redesign to work even better with all kinds of hardware. DEC's Western Software Laboratory helped with this. They started working on X11 in May 1986. The final version of X11 was released on September 15, 1987.

The design of X11 was discussed openly online. This made X one of the first very large projects developed by many people working together freely.

The X.Org Foundation Takes Over

In early 2004, people from X.Org and freedesktop.org created the X.Org Foundation. This was a big change. Before, X had been managed by groups of companies. Now, the Foundation was led by software developers. They used an "open development" model, meaning anyone could get involved.

The Foundation oversees X development. Technical decisions are made by agreement among the community members. The Foundation doesn't hire developers itself. It's supported by major companies like Hewlett-Packard.

The Foundation released X11R6.7, also known as the X.Org Server, in April 2004. This version was based on XFree86 but brought back the open development model.

Over the years, X11 has been updated with new features. In the early 2000s, its core parts were improved to fix old problems. These included issues with how fonts worked and how 2D graphics were handled.

X11R6.8 came out in September 2004. It added cool new features like support for see-through windows and other visual effects. It also included tools for screen magnifiers and ways to work with 3D display systems.

On December 21, 2005, X.Org released X11R6.9 and X11R7.0. These versions made big changes to how the code was organized. The Foundation continued to release new versions with many improvements.

What X is Called

The official names for the system are X, X Window System, X Version 11, X Window System, Version 11, or X11.

You might hear people say "X-Windows," but this isn't the official name. It's often used informally, but the people who created X don't use it.

Important X Terms

Some words in the X Window System have special meanings that are different from how you might normally use them:

• Device: This means a graphics card or the graphics part built into a computer's motherboard.
• Monitor: This is the physical screen you look at, like a CRT or a flat screen.
• Screen: This is an area where graphics can be drawn. A graphics device might be able to draw on more than one screen at a time.
• Virtual screen: This can mean two things:
  • A way to move around a larger screen area than your monitor can show at once.
  • An effect created by a window manager that lets you pan around a bigger desktop by moving windows.
• Display: This is a group of screens, often using multiple monitors. You can usually move your mouse pointer across all of them. On Linux computers, you can often switch between different "displays" using special keyboard shortcuts.

The term "display" should not be confused with a "Zaphod display." A Zaphod display is a rare setup where one computer can have multiple users, each with their own screen, mouse, and keyboard, as if they were using separate computers.

X Window System Release History

The X.Org website says that they keep developing and releasing parts of the X Window System software. These parts are released one by one as they are ready. There isn't a plan for a big "X11R7.8" release right now.

Images for kids

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  X11R1 running on a Sun machine

• 

  Common Desktop Environment

See also

In Spanish: Sistema de ventanas X para niños