In computing, xterm is the standard terminal emulator for the X Window System. A user can have many different invocations of xterm running at once on the same display, each of which provides independent input/output for the process running in it. xterm originated prior to the XWindow System. It was originally written as a stand-alone terminal emulator for the VAXStation 100 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, around 1996 the main line of development then shifted to XFree86, 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: Added in patch 24.
VT320: Added in patch 24.
VT420: DECSTR was added in patch 34.
VT520: Although not officially emulated, parts of VT520 features were implemented. Controls DECSMBV and DECSWBV for setting the margin- and warning-bell volume was added in patch 254.
Customization
As with most X applications, xterm can be customized via global X resources files, per-user resource files, 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 resourceclass 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.
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.