A locked Function (Fn) key may sound like a minor problem, but can be a bit troublesome for you if you are not aware of the solution. This FAQ will introduce you to the solution to this issue.
Unlock a Function (Fn) Key
If your keyboard is producing numbers instead of letters, hold down the Function key (Fn) on your keyboard in order to be able to write normally.
If this doesn’t work, try pressing Fn + Numlk or, depending on the model, Fn + Shift + Numlk. On an IBM Thinkpad, press Shift + Scroll Lock Num.