<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> <P> Some early keyboards experimented with using large numbers of modifier keys . The most extreme example of such a keyboard, the so - called "Space - cadet keyboard" found on MIT LISP machines, had no fewer than seven modifier keys: four control keys, Ctrl, Meta, Hyper, and Super, along with three shift keys, Shift, Top, and Front . This allowed the user to type over 8000 possible characters by playing suitable "chords" with many modifier keys pressed simultaneously . </P> <P> A dead key is a special kind of a modifier key that, instead of being held while another key is struck, is pressed and released before the other key . The dead key does not generate a character by itself, but it modifies the character generated by the key struck immediately after, typically making it possible to type a letter with a specific diacritic . For example, on some keyboard layouts, the grave accent key ` is a dead key; in this case, striking ` and then A results in à (a with grave accent), whereas ` followed by E results in è (e with grave accent). A grave accent in isolated form can be typed by striking ` and then Space bar . </P>

With one exception black keys are grouped on the keyboard in which way