isr.co.ro : glossary Command Line Interface (CLI), Command Line User Interface (CLUI) An interface for programs or operating systems that requires the user to provide instructions by typing in commands and parameters rather than by pointing to icons or menu choices with a mouse. This is the style used by MS-DOS, Unix, and most older Internet services such as File Transfer Protocol (FTP). Those who like CLIs or CLUIs say this command style is fast, allows a wide range of inputs, and permits you to specify multiple parameters for one command. But detractors say it's also hard to learn, hard to remember, and prone to both typographical and conceptual errors.