Am I the only one who's a final year undergraduate, but isn't sure he/she knows enough about programming and comp sci as they should?

Like I recently went for an interview with a company, and they asked what's the difference between pass by reference and pass by value. Now, this is probably a very basic qs, so I was surprised when I couldn't answer this. So I'm really scared that I don't know enough, also I'm terrible in their group exercises too, I can't see how the others can do it so easily.