Harry the Hacker!
An original editorial by Javier Ruiz de Ojeda
I would be extremely selfish to consider myself the only Harry Potter fan who knows about computer programming, but since reading OotP, I've developed quite a theory. I must tell you that I'm now halfway through GoF (since I'm re-reading them all after Book 5), and it gets repeated ever so frequently.
I believe Joanne K. Rowling has no knowledge about programming whatsoever, but I wouldn't be the slightest bit amazed if I learned that she did. However, my claim is that every single word in the Harry Potter world that relates to magic could perfectly be swapped by an equivalent in the computer world. I don't expect you to believe me right away, I only encourage those of you slightly interested in this (wonderful) world to read on and draw their own conclusions.
To begin with, you could consider Hogwarts the ultimate school computer-room. As a matter of a fact, underage students aren't allowed to perform magic outside there, because you can't show a guy how to crack into the CIA via computer and let him do it alone. There must be some sort of guidance until the student is at least old enough to know when he is meant to use magic. Else, he will (unless he is as good as Voldemort, claimed to be the best hacker for a century) be immediately punished, or judged or whatever by either the Ministry of Magic or his own government's Computer Crimes Unit.
Moreover, I like to think every single magical spell Harry learns could be related to a program. For example, transfiguration lessons teach you how to disguise a powerful virus in the innocent appearance of a picture (.jpeg). Potions is the art of creating programs with aims as diverse as shrinking (compressing) objects, change your appearance (what's known as an anonimizer) like a Polyjuice potion, or anything you can think of. No use trying to explain what defense against the dark arts would teach you, the most advanced anti-viruses and firewalls to protect you while in the magical world (Internet). Schools like Durmstrang are known to give more importance to their actual performance, also known as virus-creating. This could either have evil effects, like Voldemort or any other cracker around, or just amusing ones (I like to think the Weasley twins are the most annoying hackers around).
No need to remind you what owls we use today. What's more important, we don't even have to know where the person we are writing is at that moment, so long as our owl (server) knows how to locate them.
And that's it for the moment, not at all because I can't think of anything else, but because the examples of it are just infinite throughout the 5 books so far. Perhaps now you can start to spot them yourself.