Command-line completion

The user then presses Return or ↵ Enter to run the command or open the file.

Commonly accessed commands, especially ones with long names, require fewer keystrokes to reach.

An alternate form of completion rotates through all matching results when the input is ambiguous.

Completable elements may include commands, arguments, file names and other entities, depending on the specific interpreter and its configuration.

Tab completion showed up early in computing history; one of the first examples appeared in the Berkeley Timesharing System for the SDS 940, where if a typed string were ambiguous, the interpreter would do nothing, but if the string was not ambiguous, it would automatically complete it without any command from the user.

This feature was imitated by Tenex's developers who made an important change: Tenex used "escape recognition", in which the interpreter would not attempt to autocomplete unless the escape key was struck (thus the name) by the user.