Since the 1990s Alt has been printed on the Option key ( ⌥ Opt) on most Mac keyboards. The Alt key should not be confused with the Altmode key (sometimes also labelled Alt) on some Teletype and ASCII terminals, which is a synonym for the ASCII escape character. Macintosh keyboards equate the Alt key with the ⌥ Option key, which has its own symbol, similar to that of the ISO standard.
This symbol is encoded in Unicode as U+2387 alternative key symbol (⎇). The standardized keyboard symbol for the Alt key, ⎇ (which may be used when the usual Latin lettering “Alt” is not preferred for labeling the key) is given in ISO/IEC 9995-7 as symbol 25, and in ISO 7000 “Graphical symbols for use on equipment” as symbol ISO-7000-2105. Both placements are in accordance with ISO/IEC 9995-2. The key is located on either side of the space bar, but in non-US PC keyboard layouts, rather than a second Alt key, there is an ' Alt Gr' key to the right of the space bar. The international standard ISO/IEC 9995-2 calls it Alternate key. For example, simply pressing A will type the letter 'a', but holding down the Alt key while pressing A will cause the computer to perform an Alt+ A function, which varies from program to program. Thus, the Alt key is a modifier key, used in a similar fashion to the Shift key. The Alt key Alt (pronounced / ˈ ɔː l t/ or / ˈ ʌ l t/) on a computer keyboard is used to change (alternate) the function of other pressed keys.
