<P> Some applications support only a CLI, presenting a CLI prompt to the user and acting upon command lines as they are entered . Other programs support both a CLI and a GUI . In some cases, a GUI is simply a wrapper around a separate CLI executable file . In other cases, a program may provide a CLI as an optional alternative to its GUI . CLIs and GUIs often support different functionality . For example, all features of MATLAB, a numerical analysis computer program, are available via the CLI, whereas the MATLAB GUI exposes only a subset of features . </P> <P> The early Sierra games, like the first three King's Quest games (1984--1986), used commands from an internal command line to move the character around in the graphic window . </P> <P> The command - line interface evolved from a form of dialog once conducted by humans over teleprinter (TTY) machines, in which human operators remotely exchanged information, usually one line of text at a time . Early computer systems often used teleprinter machines as the means of interaction with a human operator . The computer became one end of the human - to - human teleprinter model . So instead of a human communicating with another human over a teleprinter, a human communicated with a computer . </P> <P> The mechanical teleprinter was replaced by a "glass tty", a keyboard and screen emulating the teleprinter . "Smart" terminals permitted additional functions, such as cursor movement over the entire screen, or local editing of data on the terminal for transmission to the computer . As the microcomputer revolution replaced the traditional--minicomputer + terminals--time sharing architecture, hardware terminals were replaced by terminal emulators--PC software that interpreted terminal signals sent through the PC's serial ports . These were typically used to interface an organization's new PC's with their existing mini - or mainframe computers, or to connect PC to PC . Some of these PCs were running Bulletin Board System software . </P>

Three sources of input and output at the windows command line