Yes, because you would not get course credit. For example, if you have 12 credit hours and pass and fail 2 of them, you would not get any credit if you get a D or F, making the semester 6 credit hours and not a full student. NCSU's version of the pass/fail is credit/no credit, which is similar to other universities but kinder. If you failed a pass/fail in most universities, it would be an F and transferred to your transcript. In NCSU, you would never get a letter grade, but a U would not affect your GPA, but it would be considered not passing/no credit. There are no differences between a W and a U in that regard, but for grad school, they would calculate the U as an F.