command line interface
A command line interface (or CLI) is a type of user interface wherein the user types characters on the keyboard, generally in the form of a command followed by parameters. Characters are displayed as the user types them; when done typing, the user presses "Enter" (or "Return" on older keyboards) to signal that the user is ready for the computer to take action based on what has been typed. The computer's response is also in the form of text.
CLI Text is traditionally shown in a fixed-pitch font. This was originally because it was easier to implement in hardware, but was kept later (when CLI became more commonly used via a window in a GUI, rather than dedicated hardware such as a teleprinter or video terminal, and could easily be switched to variable-pitch) to allow a limited degree of formatting by the insertion of spaces or other characters.
Most command line interfaces have some sort of standard indicator or prompt to let the user know that computation has finished and the computer is ready for more user input. Probably the best-known prompt is the DOS "C prompt", which defaulted to "C:\>" in later versions of DOS when the user is using the primary fixed disk.
The use of a command line interface is also referred to as using "text mode", although "text mode" can also include full-screen text-only interaction.