<P> This 78 - key UK layout is taken from the Apple iBook . Characters in blue are accessed through the Fn key, but functions on the top row can be accessed without Fn key in Mac OS X . </P> <P> Fn is a modifier key, and works like other modifiers keys, such as Ctrl, Shift, Alt and AltGr . For a standard modifier key, the microcontroller inside the keyboard sends a scancode for the modifier itself, which is then interpreted by the operating system and combined with other simultaneous key - presses . The Fn key is a form of meta - modifier key, in that it causes the operating system to see altered scancodes when other keys on the keyboard are pressed . This allows the keyboard to directly emulate a full - sized keyboard, so the operating system can use standard keymaps designed for a full - sized keyboard . However, because the operating system has no notion of the Fn key, the key cannot normally be remapped in software, unlike all other standard keyboard keys . </P> <P> While it is most common for the Fn key processing to happen directly in the keyboard micro-controller, offering no knowledge to the main computer of whether the Fn key was pressed, some manufacturers, like Lenovo, perform this mapping in BIOS running on the main CPU, allowing remapping the Fn key by modifying the BIOS interrupt handler; and Apple, in which the Fn key is mappable and serves other uses too, as triggering the Dictation function by pressing the Fn key twice . </P> <P> In addition to being mapped to standard keyboard keys like Scroll Lock and Num Lock, the Fn key combinations may also be mapped to control system interfaces to change the LCD brightness, VGA output, or speaker volume on most laptop computers . </P>

What is the use of fn key in mac