<P> An alphanumeric key labeled with only a single letter (usually the capital form) can generally be struck to type either a lower case or capital letter, the latter requiring the simultaneous holding of the Shift key . The ⇧ Shift key is also used to type the upper of two symbols engraved on a given key, the lower being typed without using the modifier key . </P> <P> The English alphanumeric keyboard has a dedicated key for each of the letters A--Z, along with keys for punctuation and other symbols . In many other languages there are additional letters (often with diacritics) or symbols, which also need to be available on the keyboard . To make room for additional symbols, keyboards often have what is effectively a secondary shift key, labeled AltGr (which typically takes the place of the right - hand Alt key). It can be used to type an extra symbol in addition to the two otherwise available with an alphanumeric key, and using it simultaneously with the Shift key may even give access to a fourth symbol . On the visual layout, these third - level and fourth - level symbols may appear on the right half of the key top, or they may be unmarked . </P> <P> Instead of the Alt and AltGr keys, Apple Keyboards have ⌘ Cmd (command) and ⌥ Option keys . The ⌥ Option key is used much like the AltGr, and the ⌘ Cmd key like the Ctrl on IBM PCs, to access menu options and shortcuts . Macs have a Ctrl key for compatibility with programs that expect a more traditional keyboard layout . It is especially useful when using a terminal, X11 (a Unix environment included with OS X as an install option) or MS Windows . The key can generally be used to produce a secondary mouse click as well . There is also a Fn key on modern Mac keyboards, which is used for switching between use of the F1, F2, etc. keys either as function keys or for other functions like media control, accessing dashboard widgets, controlling the volume, or handling exposé . Fn key can be also found on many IBM PC laptops, where it serves a similar purpose . </P> <P> Many Unix workstations (and also Home Computers like the Amiga) keyboards placed the Ctrl key to the left of the letter A, and the ⇪ Caps Lock key in the bottom left . This layout is often preferred by programmers as it makes the Ctrl key easier to reach . This position of the Ctrl key is also used on the XO laptop, which does not have a ⇪ Caps Lock . The UNIX keyboard layout also differs in the placement of the ESC key, which is to the left of 1 . </P>

Whats the option key on a mac keyboard
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