Computer terminal

Historical

A computer terminal is an electronic or electromechanical hardware device. It is used for entering data into, and displaying data from, a computer or a computing system. Early terminals were Teletypes (TTYs), later ones use a Visual Display Units (VDU). Typically a terminal communicates with the computer via a serial line, often using the RS232 protocol.

Later, so called intelligent terminals were introduced, such as the VT100 and VT102, which are still widely emulated in software. Notable non-VT100 computer terminal types include the IBM 3270 and Wyse.

Most terminals were connected to Mainframe computers and often had a green or amber screen. A very small number of terminals with a few colors were created prior to the widespread introduction of the CRT.

While IBM PCs had single color green screens, these would not have been considered terminals. They could, however, emulate a terminal, if connected to a mainframe computer.

Contemporary

Since the advent and subsequent growth in popularity of the personal computer, one will not find many real terminals that are used to interface with computers today. Using the monitor and keyboard, current operating systems like Linux and the BSD derivates feature virtual terminals, which are mostly indepent from the hardware used.

When using a graphical user interface like the X Window System, this occupies the virtual terminal that would be used for input. In this case, one commonly uses a terminal emulator, an application that emulates being a terminal, to allow the user to access the computer like he is used to.