computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes, and development of both hardware and software. Computing has scientific, ...

, xterm is the standard

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 ...

for the

X Window System The X Window System (X11, or simply X) is a windowing system for bitmap displays, common on Unix-like operating systems. X provides the basic framework for a GUI environment: drawing and moving windows on the display device and interacting wi ...

. It allows users to run programs which require a

command-line interface A command-line interpreter or command-line processor uses a command-line interface (CLI) to receive commands from a user in the form of lines of text. This provides a means of setting parameters for the environment, invoking executables and pro ...

. If no particular program is specified, xterm runs the user's shell. An X display can show one or more user's xterm windows output at the same time. Each xterm window is a separate process, but all share the same

keyboard Keyboard may refer to: Text input * Keyboard, part of a typewriter * Computer keyboard ** Keyboard layout, the software control of computer keyboards and their mapping ** Keyboard technology, computer keyboard hardware and firmware Music * Mu ...

, taking turns as each xterm process acquires ''focus''. Normally focus switches between X applications as the user moves the pointer (e.g., a mouse cursor) about the screen, but xterm provides options to ''grab focus'' (the ''Secure Keyboard'' feature) as well as accept input events sent without using the keyboard (the ''Allow SendEvents'' feature). Those options have limitations, as discussed in the xterm manual. xterm originated prior to the X Window System. It was originally written as a stand-alone terminal emulator for the

VAXStation 100 The VAXstation is a discontinued family of workstation computers developed and manufactured by Digital Equipment Corporation using processors implementing the VAX instruction set architecture. VAXstation systems were typically shipped with ei ...

(VS100) by Mark Vandevoorde, a student of Jim Gettys, in the summer of 1984, when work on X started. It rapidly became clear that it would be more useful as part of X than as a standalone program, so it was retargeted to X. As Gettys tells the story, "part of why xterm's internals are so horrifying is that it was originally intended that a single process be able to drive multiple VS100 displays." After many years as part of the X

reference implementation In the software development process, a reference implementation (or, less frequently, sample implementation or model implementation) is a program that implements all requirements from a corresponding specification. The reference implementation o ...

, around 1996 the main line of development then shifted to

XFree86 XFree86 is an implementation of the X Window System. It was originally written for Unix-like operating systems on IBM PC compatibles and was available for many other operating systems and platforms. It is free and open source software under the X ...

(which itself forked from X11R6.3), and it is now maintained by Thomas Dickey. Many xterm variants are also available. Most terminal emulators for X started as variations on xterm.

Features

Terminal emulation

Early versions emulated the VT102 and Tektronix 4014. Later versions added control sequences for DEC and other terminals such as: *

VT220 The VT220 is a computer terminal introduced by Digital Equipment Corporation (DEC) in November 1983. The VT240 added monochrome ReGIS vector graphics support to the base model, while the VT241 did the same in color. The 200 series replaced the ...

: Added in patch 24. Later, in 1998, xterm added support for

features, such as extending its support of

ISO-2022 ISO/IEC 2022 ''Information technology—Character code structure and extension techniques'', is an ISO/IEC standard (equivalent to the ECMA standard ECMA-35, the ANSI standard ANSI X3.41 and the Japanese Industrial Standard JIS X 0202) in the f ...

''shift functions'' to provide the National Replacement Character Set feature. *

VT320 The VT320 is an ANSI standard computer terminal introduced by Digital Equipment Corporation (DEC) in 1987. The VT320 is the text-only version, while the VT330 adds monochrome ReGIS, Sixel and Tektronix 4010 graphics, and the VT340 adds colo ...

: Added in patch 24. * VT420: DECSTR (soft terminal reset) was added in patch 34. In 2012, xterm's default emulation was changed to VT420 to allow

tmux tmux is an open-source terminal multiplexer for Unix-like operating systems. It allows multiple terminal sessions to be accessed simultaneously in a single window. It is useful for running more than one command-line program at the same time. ...

to assume the corresponding left/right margin support. *

VT520 The VT520 is an ANSI standard computer terminal introduced by Digital Equipment Corporation (DEC) in 1993 and 1994. The VT520 is a multi-session monochrome text-only terminal with a built-in 14" monitor. The VT510 was a single-session version, ...

: Although not officially emulated, parts of VT520 features were implemented. Controls DECSMBV and DECSWBV for setting the margin- and warning-bell volume were added in patch 254.

Customization

As with most X applications, xterm can be customized via global

X resources In the X Window System, the X resources are parameters of computer programs such as the name of the font used in the buttons, the background color of menus, etc. They are used in conjunction with or as an alternative to command line parameters an ...

files (e.g. /usr/lib/X11/app-defaults/XTerm), per-user resource files (e.g. ~/XTerm, ~/.Xresources), or command-line arguments. Most of the command-line options correspond to resource settings, as noted in the manual page. While the name of the program is ''xterm'', the X resource class is ''XTerm''. The uxterm script overrides this, using the ''UXTerm'' resource class. xterm normally does not have a menu bar. To access xterm's three menus, users hold the control key and press the left, middle, or right mouse button. Support for a "toolbar" can be compiled-in, which invokes the same menus.

Protocols

Supported terminal control functions include: * ANSI X3.64 * Sixel * Digital Equipment Corporation VT family: ** VT52 ** VT102 **

** VT420 * Tektronix family: ** Tektronix 4014 In addition to protocols used in commercially available terminal machines, xterm added a few protocols that have been adopted by other terminal emulators, such as: * Mouse tracking: Support for buttons 4 and 5 was added in patch 120. * 16-colour terminal protocol: Added in patch 39. * 256 colors terminal protocol: Added in patch 111. * 88-colour terminal protocol: Added in patch 115. * Custom colour palette: Ability to specifying the RGB values for palette entries was added in patch 111.

Fonts

Initially Xterm supported only

Portable Compiled Format Portable Compiled Format (PCF) is a bitmap font format used by X Window System in its core font system, and has been used for decades. PCF fonts are usually installed, by default, on most Unix-based operating systems, and are used in terminals such ...

(PCF) bitmap font until 2000 when

Xft Xft, the X FreeType interface library, is a free computer program library written by Keith Packard. It uses the MIT/X license that The Open Group applied after the post X11R6.4 license restoration. It is designed to allow the FreeType font ...

library was introduced to support modern stroke-based fonts like

TrueType TrueType is an outline font standard developed by Apple in the late 1980s as a competitor to Adobe's Type 1 fonts used in PostScript. It has become the most common format for fonts on the classic Mac OS, macOS, and Microsoft Windows operating ...

References

External links

* {{XWinSys Free software programmed in C Free terminal emulators Software using the MIT license X Window programs