I want to learn how to code, please help.?

After just watching: http://www.youtube.com/watch?v=nKIu9yen5nc&list=PL...

I have become inspired to learn how to code. I will heading off to university in september to study Physics and I will no doubt be taught programming there, but I want to start now, I want to learn the basics and most importantly: I want to learn more about computers.

At the moment I don't know what I can use code for, I don't know what language to learn and if I was to immediately dive into learning Python for example, I would come out not having a clue what to do next.

My computer is a mac, so I basically want to start off simple. I don't want to go learn a computer program that I can't use on my laptop (if that is even possible). I don't want someone to leave a comment saying: " Coding can be used to make websites and apps, so go learn this code here: XXXX ". I don't particularly want to come out of this knowing how to make a website, I want to know the ins and outs of my laptop to begin with, I want to know what I can use the terminal for etc.

If I go learn python, what do I do next? Like I said, I don't really want to start making websites, I just want to understand computer programming, coding etc and see where that leads me.

Help? aha