Windows scancodes for F11 and F12 are different. Why?

Question

Why are they separate from the rest of the scan codes? Is there some reason for it?

F9 is 67
F10 is 68
Numlock is 69
F11 is 87
F12 is 88

Answer 1

Yes, there is. Keyboards with function keys used to only go up to F10. The addition of F11 and F12 as standard happened some time in the late 80s or early 90s, from memory. Changing the enumeration for existing scan codes 69 and 70 would have broken compatibility with old keyboards. Remember that prior to USB (or PS/2, for that matter), keyboards had a chunky 5-pin DIN connector, and you couldn't really tell what was on the other end of it.