Command Line Interface

Command line interface (CLI) - a kind of textual interface between a person and a computer, in which computer instructions are given mainly by typing text strings (commands) from the keyboard, on UNIX-systems it is possible to use a mouse. Also known as the console user interface.

The command-line interface, often mentioned as command-line user interface, is contrasted with the menu-based control systems of the program, as well as to various implementations of the graphic user interface (GUI).

The output format of the information in the command-line interface is not regulated; usually, this is a simple text output, but it can also be graphic, audio, etc.

Advantages

• Small memory consumption compared to the menu system.
• In modern software, there is a large number of commands, many of which are extremely rare. Therefore, even in some programs with a graphical interface, the command line is used: the command set (provided that the user knows this command) is much faster than, for example, navigating through the menu.
• A natural extension of the command line interface is the batch interface. In essence its a sequence of commands written to a file of ordinary text format, after which the file can be executed in the program, which will lead to the same (in most cases) effect, as if these commands were entered one by one on the command line. Examples - .bat-files in DOS and Windows, shell-scripts in Unix-systems.

If the program is fully or almost completely managed by commands from the command line interface, and supports a batch interface, a skilful combination of the command line interface with a graphical interface provides the user with very powerful capabilities.

Disadvantages

• The command-line interface is not user-friendly for those, who have begun familiarizing themselves with the computer with a graphical mode, due to the almost unavailable discoverability.
• The need to study the syntax of commands and memorize abbreviations is complicated, because each command can have its own designations.
• Without auto-completion, entering long and special characters from the keyboard can be difficult.
• No analog input. For example, adjusting the volume with the sounded slider allows you to set the appropriate volume faster than a command like aumix -v 90.

Usage

Historically, the main areas of application of the command line interface were on computer terminals  in 1960-1980s, for MS-DOS, Unix operational systems and later on on Apple DOS. Now it’s used for development of chats, computer games and program testing.