The Theory of Evolution, as it applies to Keyboards:
First there were Letter keys and Digit keys. Then there quickly developed the Shift key. These were called Typewriter.
We'll skip telegraphs and teletypes.
When paper was no longer the medium, it was necessary to develop the Insert, Delete, arrow, etc. keys
When Computers came along, soon there grew the Alt- key, because the Letter (and Digit) keys didn't have enough to do. Then came Program Function keys (later renamed as Function keys (F1 ... F12 [... F24 on some keyboards])).
Keyboards were now approaching their maximum utility size, so the Ctrl- key grew. It is possible to use all three of these simultaneously, it is up to the OS to interpret or pass to an application the key(s) pressed. But, generally, BIOS has reserved to itself the Ctrl-Alt-Del combination, although that can be redefined sometimes.
With small computers and limited keyboard geography available (notebooks, laptops), the numeric key pad has been mapped to a section of the letter keys, and other key usages also have been doubled-up. Enter the Fn key (not to be confused with the F1-F12 keys), which is used for additional functional controls. These are hardware manufacturer / BIOS - dependent, not OS defined. On some computers the Fn key engraving is in blue, and the Fn-functions of the keyboard keys also are in blue, above/below/on-the-keyfront of the 'regular' definition in white.
Recalling that the Fn key is for hardware configuration controls, some Fn functions are: Screen intensity, external monitor control, speaker volume. Thus, refer to the User manual, or possibly to the manufacturer's Help files on the computer, for the usage on your specific system.
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