Computer Terminals

How does it work?

A terminal is an input and output device that connects you to a mainframe or other type of computer.

Kinds of terminals:

• Dumb terminal - can be used to input and receive data, but it cannot process data independently. It is used to gain access and to send information to a computer. Such a terminal is often used by airline reservation clerks to access a mainframe computer for flight information
• Intelligent terminal - a microcomputer with communications software and a telephone hookup (modem) or other communications link. These connect the terminal to the larger computer or to the internet
• Network terminal - also known as a thin client, is a low-cost alternative to an intelligent terminal. Most network terminals do not have a hard-disk drive and must rely on a host computer or server for application and system software. These devices are becoming increasingly popular in many organizations.[1]

What is it used for?

• A computer terminal is an electronic or electromechanical device that is used for entering data into, and displaying data from, a computer or a computing system.
• The function of a terminal is confined to display and input of data; a device with significant local programmable data processing capability may be called a "smart terminal" or “fat client.” A terminal that depends on the host computer for its processing power is called a “thin client.” A personal computer can run software that “terminal emulation” the function of a terminal, sometimes allowing concurrent use of local programs and access to a distant terminal host system.

Who are the leading providers for terminals?

• ADDS
• Boundless
• DEC
  
• IBM
• Hewlett Packard
• Link
• NCR
• Wyse
  

(Source: http://www.vecmar.com/terminals/computer_terminals.htm)

How is a terminal different from other similar devices?

• Timesharing systems evolved in parallel to terminals, and made up for any inefficiencies of the user's typing ability with the ability to support multiple users on the same machine, each at their own terminal.

• In the early 1990s an industry consortium attempted to define a standard that would allow a single CRT screen to implement multiple windows, each of which was to behave as a distinct terminal. Unfortunately like I20, this suffered from being run as a closed standard: non-members were unable to obtain even minimal information and there was no realistic way a small company or independent developer could join the consortium. Possibly because of this the standard disappeared without trace.

• Computer console : text output device for system administration messages

• Virtual console : permits multiple terminals on one hardware.

• Since the advent and subsequent popularization of the personal computer, few genuine hardware terminals are used to interface with computers today.
  
• Using the computer display and computer keyboard, modern operating systems like Linux and the BSD derivatives feature virtual consoles, which are mostly independent from the hardware used.
  
• When using a graphical user interface (or GUI) like the X Window System, one's display is typically occupied by a collection of windows associated with various applications, rather than a single stream of text associated with a single process.
  
• In this case, one may use a terminal emulator application within the windowing environment. This arrangement permits terminal-like interaction with the computer (for running a command line interpreter, for example) without the need for a physical terminal device.

by JULIENNE RABOCA

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[1] O’Leary, Timothy, and Linda O’Leary. Computing Essentials 2008.