How did older games do collision detection with walls, floors and ceilings?

Question

I have been reading about collision detection in games on stackoverflow and other sites. A lot of them talk about BSPs, bounding elipses, integration etc. However, on the

Answer 1

There is article here that is an in-depth look at programming a Nintendo Entertainment System (NES) "platform game".

• Programming M.C. Kids

I may not have been googling right because I haven't stumbled upon this article before.