Alt key

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Alt
Names Alt, Alternate, Option
Mac symbol
ISO/IEC symbol
X11 Alt_L, Alt_R
USB Keyboard LeftAlt (7:0xE2), Keyboard RightAlt (7:0xE6)

The Alt or Alternate key is a modifier key found on many platform's keyboards. On Macintosh, the same key is called "Option". Most keyboards have one on the left and one on the right.

Role

The key often modifies the behaviour of the cursor, navigation and editing keys. Several conventions exist, and can be different from program to program on the same platform.

On Macintosh and on most vintage platforms (such as Atari ST, Amiga and NeXT) the key is used to access third (and fourth) symbols on alphanumeric keys.

On PC keyboards, however, the Alt key is used only for navigation and program control. PC layouts with more symbols than standard ANSI layout have instead reassigned the right Alt as an Alt Gr key — which is exclusively a typographical modifier. In the days of MS-DOS, there existed a convention for navigating menus with the keyboard, where a menu item had one letter underlined, reached by holding Alt and pressing that letter.

ASCII input

On PC and Atari ST, any character can be input by holding Alt and typing its ASCII code on the numeric keypad.

See also