Keyboard does not type normal characters all of a sudden- Macbook Air

I've the same or even worst problem as other guy mentioned here:

The numerals line on my keyboard doesn't not type normal characters all of a sudden. I notice especially the alt characters are not the usual ones. Everything was normal,Then this just happened.

When I restart the macbook air it starts on a page with selecting language which I select English. The problem is next alla alfabet are in caplops key is on and the other strange problem all digits (1-9) are not there and you get other characters which are not on key as such. Is it kind of virus which cause it?! I've lost so many hours to get it works but it doesn't. Could you help hot to get it back to as normal?