How Do Spells Work?

How do spells work? I’ve been wondering about this since reading the sixth Harry Potter book, when the Half-Blood Prince made up some spells, or curses, that when said for the first time with the right amount of meaning, caused something to happen. So how does that work?

I can understand potions. You mix together certain ingredients, and the combination yields certain results. I myself have created “potions” in chemistry lab and in the kitchen. It is logical. And the concept of creating new potions makes sense too – put together a combination of ingredients that have never been put together exactly like that before, and you’ve created a new potion. Trial and error will determine what effect (if any) that new potion will have.

But spells? Please somebody explain it to me. You say a certain phrase (which, perhaps, you’ve just made up) with the right frame of mind and something happens? Why? And evidently if you write down the word and someone else says it, it still has the same effect. But how? To me, this implies that the power is already in the word. For example, if I were a witch, and decided that if I wiggled my nose (or pointed my wand) while saying the word ‘Jujubeeify,’ and my intent was that whoever I was looking at when I did that would be turned into a giant Jujubee, then this would happen. And in the event that it did happen, then anyone else could then do the same thing. But how did the word get to be associated with the action of turning someone into a giant Jujubee?

Let me explain my confusion. As a computer scientist, my understanding of how programming works leads me to interpret things in a certain way. I write a program, compile it (converting it to a runnable program), and then anyone with the program (in its executable form) can run it. So, for example, I could write a simple program that allowed me to type the word “Jujubeeify” and a picture of a jujubee would appear. Then, if I sent this program to someone else, they could run the program, type “Jujubeeify”, and see a picture of a jujubee. The code itself, which is sent around, is what makes the picture of the jujubee appear with the proper input (in this case typing the word; in magic, wiggling the nose or pointing the wand).

So, given that process, how is the magical meaning of the new curse or spell distributed? The book seemed to imply that anyone who says the word would see the same result. But what if they don’t want that result? What if someone else creates a curse using the same word that has a different result? What happens then? Is that even possible? Or, as I said before, is the spell already out there, and it’s just a matter of discovering the pre-determined meaning? In which case, witches and wizards would at most be able to discover curses as opposed to create them. Or, is there some great magical server where all magic resides, and once somebody creates a curse, it is automatically uploaded and accessible by every magical being, though not everyone knows how to find it?