20 November 2006

Command Line Interface

Screen capture of DOS DIR /?

A command line interface (CLI) is a type of user interface in which the user types in commands at a prompt. Prior to 1984, virtually all computers used a CLI.

The illustration above is of a DOS "window" available in all installations of Windows. I entered a command dir, accompanied by the /? switch; dir lists the contents of the directory (in this case, my root drive C:\), while the switch modifies the command so that it supplies detailed instructions on how to use the command, rather than actually execute it.

Below is an illustration (stolen, I'm sorry to admit) of a session of WordStar for DOS. WordStar was actually very popular until it was superseded by WordPerfect for DOS. Both enjoyed great loyalty among users, but unfortunately, were unable to compete with MS Word for the MS Windows environment. WordStar assisted users by constantly displaying the command "cheat sheet" at the top of the screen; by the time WordPerfect came along, arrow keys, function keys, and command keys were commonplace; but it too included an always-visible cheat sheet.

Screen capture of WordStar for DOS

Unix shells are well-known examples of CLI's. In contrast to the MS Windows computing milieu, Unix users tend to use shells alongside their system's particular GUI.

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