What’s the 100 door problem?

It’s a just for fun problem in “beginning” math and computer courses. The idea is simple:

There are 100 closed doors in a row.

You walk past the doors 100 times (100 passes)

The first time, visit every door. If the door is closed, open it. If it is open, close it. In programming, you’d probably call this toggling the door so let’s call it that.