In computing, an X terminal is a display/input terminal for X Window System

X Window System

The X window system is a computer software system and network protocol that provides a basis for graphical user interfaces and rich input device capability for networked computers...

 client applications. X terminals enjoyed a period of popularity in the early 1990s when they offered a lower total cost of ownership

Total cost of ownership

Total cost of ownership is a financial estimate whose purpose is to help consumers and enterprise managers determine direct and indirect costs of a product or system...

 alternative to a full Unix

Unix

Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...

 workstation

Workstation

A workstation is a high-end microcomputer designed for technical or scientific applications. Intended primarily to be used by one person at a time, they are commonly connected to a local area network and run multi-user operating systems...

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An X terminal runs an X server. (In X, the usage of "client" and "server" is from the viewpoint of the programs: the X server supplies a screen, keyboard, mouse and touchscreen to client applications.) This connects to an X display manager (introduced in X11R3) running on a central machine, using XDMCP (X Display Manager Control Protocol, introduced in X11R4).

Thin client

Thin client

A thin client is a computer or a computer program which depends heavily on some other computer to fulfill its traditional computational roles. This stands in contrast to the traditional fat client, a computer designed to take on these roles by itself...

s have somewhat supplanted X terminals in that they are 'fattened' with added flash memory

Flash memory

Flash memory is a non-volatile computer storage chip that can be electrically erased and reprogrammed. It was developed from EEPROM and must be erased in fairly large blocks before these can be rewritten with new data...

 which contains software that duplicates much of the various Microsoft operating systems, thus acquiring the ability to "speak" a range of remote desktop

Remote desktop software

In computing, the term remote desktop refers to a software or an OS feature allowing applications, either command line programs or graphical applications, to be run remotely on a server, while being displayed locally. Remote desktop applications have varying features...

 protocols. Due to the existence of free software

Free software

Free software, software libre or libre software is software that can be used, studied, and modified without restriction, and which can be copied and redistributed in modified or unmodified form either without restriction, or with restrictions that only ensure that further recipients can also do...

 implementations of multiple protocols, X terminals which do not have this extra flash memory have been commercially obsoleted by more general-purpose thin clients and by low cost PCs running an X server.

Vendors

In the early 1990s, several vendors introduced X terminals including Network Computing Devices

Network Computing Devices

Network Computing Devices was a company founded in 1987 to produce a new class of products now known as a "thin client". It was founded in Mountain View, CA, and when it closed it was headquartered in Portland, Oregon....

 (NCD), Gipsi, Hewlett Packard

HP X-Terminals

HP X-Terminals are a line of X terminals from Hewlett Packard introduced in the early- to mid-1990s, including the 700/X and 700/RX, Envizex and Entria, and the Envizex II and Entria II. They were often sold alongside PA-RISC-based HP 9000 Unix systems...

 (HP), Digital Equipment Corporation

Digital Equipment Corporation

Digital Equipment Corporation was a major American company in the computer industry and a leading vendor of computer systems, software and peripherals from the 1960s to the 1990s...

 (DEC, later absorbed by HP), IBM

IBM

International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...

, Samsung

Samsung

The Samsung Group is a South Korean multinational conglomerate corporation headquartered in Samsung Town, Seoul, South Korea...

 and Tektronix

Tektronix

Tektronix, Inc. is an American company best known for its test and measurement equipment such as oscilloscopes, logic analyzers, and video and mobile test protocol equipment. In November 2007, Tektronix became a subsidiary of Danaher Corporation....

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