Well, I'm still in high school I don't know what Uni grades are like, but we have A (excellent) B, C, D, and F (failing)
At most schools 90% is an A, 80% is a B etc but at my school its something like 95% is an A, 85% is a B....I usually still care only about the percentages though. Despite the fact that it's a C (which it shouldn't be IMO) 83% is still a really good grade for an AP Chem class.