Tab key

Tab ↹ Tab key (abbreviation of tabulator key or tabular key) on a keyboard is used to advance the cursor to the next tab stop.

The word tab derives from the word tabulate, which means "to arrange data in a tabular, or table, form." When a person wanted to type a table (of numbers or text) on a typewriter, there was a lot of time-consuming and repetitive use of the space bar and backspace key. To simplify this, a horizontal bar was placed in the mechanism with a moveable lever stop for every position across the page, called a tab stop. Initially these were set by hand, but later tab set and tab clear keys were added. When the tab key was depressed, the carriage advanced to the next tab stop. These were set to correspond to the particular column locations of the table, hence tab, being worked on.

The tab mechanism also came into its own as a rapid and consistent way of uniformly indenting the first line of each paragraph, often a first tab stop at 5 or 6 characters was used for this, far larger than the indentation used when typesetting.

In word processing and text editing the Tab key will often move the insertion point to the next tab stop in a table, or may insert the ASCII tab character or many space characters.

When filling out a computerized form, pressing Tab will move the cursor to the next field (and Shift-Tab will move the cursor to the previous field), eliminating the need to use a mouse to click in an adjacent field.

In many graphical applications, especially on Windows, the Tab key will move the focus to every control or widget such as buttons so that the user interface can be used without a mouse at all (this was part of the IBM Common User Access design). On OS X, this is an option called "Full Keyboard Access".

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