It may appear to be a plain old C major scale at first, but it’s not. So here’s how it works:
The object of this exercise is to not move your fingers until you absolutely have to, while playing the C major scale in the open position. If you do it right, you should end up with a C6add4 chord on the way up, and a Cmaj9 chord on the way down.
Too technical? I’m sorry.