<p>To clarify even further: Calc AB maps mostly to Penn’s Math 103, which isn’t really required for anyone. Calc BC maps to Math 104, which is required for most majors, and is taken by most incoming freshman. If you have a 5 on Calc BC, you place out of Math 104. If you have a 5 on Calc AB, or a 4 on BC, you’ll be well suited for Math 104 (and may want to consider taking the placement test), and if you have anything significantly less than that (3’s, or a 4 or AB, or poor HS grades in Calc) you may want to take Math 103 as a precursor.
This also really depends on your major, as engineers can’t really afford to take 103 (and won’t generally be admitted if they’re not in BC), but Wharton students may want to take 103 so they’re fully ready for 104, and college students should follow their prospective major’s guidelines.
I’d say that most freshman fall into the category of having taken AB and gotten a 4 or 5 or gotten a 5 on BC, so they take 104. Some number got 5’s on BC and skip 104, and very few didn’t take calc, or did poorly on calc and need to take 103.</p>