terminal

A terminal, in computing, is a device or program that provides a text-based interface for issuing commands and viewing output from a computer system. Historically, terminals were hardware devices such as teletypewriters and video terminals connected to mainframes and minicomputers. In modern computing, the term also refers to terminal emulator software that runs on general-purpose computers or mobile devices and provides access to a shell or other command-line applications.

Hardware terminals were largely replaced by interactive consoles, but the term endures in software. Early terminals used fixed-width displays and simple input/output protocols; later models supported graphical interfaces. The VT100 family, whose escape sequences influenced most contemporary terminal emulators, is a common reference point.

A terminal emulator is software that mimics a traditional terminal inside a graphical environment. It runs a shell such as Bash, Zsh, or PowerShell and communicates with the operating system through standard input and output streams. Emulators render text, interpret escape sequences for cursor movement, color, and formatting, and often support features such as tabs, scrollback, and Unicode.

Communication can occur locally or over a network. Terminals may connect to hosts via serial lines, Telnet, SSH, or other protocols. In Unix-like systems, the terminal type is indicated by the TERM variable and described by terminfo or termcap databases, which define capabilities such as color support and cursor positioning.

In computing, the concept also extends to virtual consoles and multiplexers, which provide multiple command-line sessions within a single device or window. See also shell, command-line interface, terminal emulator, SSH, and Telnet.