A command-line interface or command language interpreter, also known as command-line user interface, console user interface and character user interface, is a means of interacting with a computer program where the user issues commands to the program in the form of successive lines of text. A program which handles the interface is called a command language interpreter or shell. The CLI was the primary means of interaction with most computer systems on computer terminals in the mid-1960s, and continued to be used throughout the 1970s and 1980s on OpenVMS, Unix systems and personal computer systems including MS-DOS, CP/M and Apple DOS. The interface is usually implemented with a command line shell, which is a program that accepts commands as text input and converts commands into appropriate operating system functions. Command-line interfaces to computer operating systems are less widely used by casual computer users, who favor graphical user interfaces or menu-driven interaction.