We are in a transition period right now. Many current divers learned using tables and have some kind of emotional attachment to them. Dive computers, however, are considered by most people to be standard gear so if they explained how computers work and how to go about choosing and using one, then you can dive safely with a computer.
If you want to know about tables, you should probably have asked your instructor to show you. I'm still teaching both but fast-forward 10 years and I doubt I will be. What I see around me is that people learn the tables, then buy a computer and never use the tables again, which means they are taught something they don't use and use something they were not taught.
Moreover, if you don't use tables regularly you can forget important details. When I have divers in for a scuba review who have been using a computer, virtually all of them have forgotten how to use the tables properly. That leads me to believe that teaching computers instead of tables is a far safer way to go unless a student is committed to not diving with a computer at all for the first... say, 100 dives or so.
R..