As a CMU alumn, I have to add that part of the reason that the CS department has the 3 levels is that most majors at the school require a programming course. I

As a CMU alumn, I have to add that part of the reason that the CS department has the 3 levels is that most majors at the school require a programming course. I'd guess that your intro course had more non-CS majors in it than the other 2 freshmen courses which tend to have a higher proportion of CS majors.