Welcome to UFOpaedia, Petrus4. I'm magic9mushroom.
You may or may not have noticed that I've reverted the majority of your edits. This is because most of your edits either reflected an incorrect understanding of game mechanics or simply added nothing of value. No offense is intended, and I hope you continue to edit here, but I would advise you to be sure about mechanics before making changes to articles (as opposed to talk pages or your own userspace).
One particular misunderstanding that cropped up several times is that of cover. Put simply, cover doesn't exist in UFO: Enemy Unknown in the way it exists in many more modern games. Being near a solid object or in smoke does not give opponents a penalty to hit chance. A solid object directly in the path of a shot will absorb it (and if the line of a shot you're attempting is blocked, a "No Line of Fire!" warning will come up), but in most cases this works both ways - and when you pop out from behind a solid object into the line of fire of an alien, you'll trigger reaction fire, negating much of the benefit. (Smoke has no effect whatsoever on accuracy; what smoke does is prevent detection.)
Cover in X-Com is useful, but not as something you attack from. Rather, it's something you use to hide an exposed soldier while you pick off the aliens threatening him with other forces.