A command line interface (CLI) is a computer instrument that allows users to control computers through a text command — or command line — instead of a mouse click. While there are many ways to control a computer, the command line interface is typically considered the opposite of the graphical user interface (GUI). The CLI requires less system memory and there is no need to load graphics, so this is usually quicker than a GUI system. Professionals most commonly use CLI, because it can be easier to execute functions and open files if one knows all the commands.
When someone uses a command line interface computer, he has to enter text commands to interact with the computer. Unlike GUI systems, in which commands are typically entered through mouse clicks, a command must be typed with a CLI. For example, to make a file in GUI, the user may click an application to open it and then click the “Save” button. The same operation through a CLI may look like this: “pico text_file.txt” to make a text document. There typically is a learning curve associated with CLI but, once the user learns the commands, it may be easier to use.
Many people think of GUI and command line interface systems as opposites. GUI systems are reliant on graphics and mouse clicks, and they typically use many different images for folders, files, applications, backgrounds and nearly everything else. CLI systems have no or very few graphics, mouse clicks are seldom and they are commonly blank screens with text. Both GUI and CLI systems commonly use keyboard shortcuts to execute commands.
While there is a learning curve and the command line interface does not have the same aesthetically pleasing appearance as GUI systems, CLI has a functional benefit. To load and use all those graphics, GUI systems must use a lot of memory just to maintain appearances. CLI systems do not use these graphics, so all that memory goes toward speeding up functions and increasing responsiveness.
Most casual computer users do not use the command line interface, but many professionals and computer enthusiasts run CLI systems. Aside from better speed and responsiveness, a skilled user can typically go through functions with much better efficiency. For example, the user may be able to perform three or four commands in the time it would take GUI systems to run a single function. If the user does not know the commands, then this benefit may decrease.