I've been in maths courses where this has occurred, and the lecturer's response is usually to give a brief overview as a refresher, then point them in the right

I've been in maths courses where this has occurred, and the lecturer's response is usually to give a brief overview as a refresher, then point them in the right direction to learn those prerequisite skills if they don't have them. I think the same can be applied to programming, but if you don't ask at all, you may never learn where to start.