I'm baffled by your comment. The article is defining the notation that is used when one performs an analysis of an algorithm, but is not talking about any specific algorithm. The notation is equally applicable in all the cases you mention.
For the avoidance of doubt - I'm not the author, I'm just trying to understand your comment.
This page looks like my notes (cheat) I used in finals. You need to know what you are doing to make that information useful.