Chapter 24. What is a Computer?

In order to understand software, the first thing we need to understand is what a computer really is.

Now, you'd think that would be a fairly simple question. After all, I'm using one to type this up, I ought to know what it is, right? I mean obviously, it's a…computer! I mean, it's got a keyboard, and a monitor, and there's that box down there…

But what is it that makes all that stuff a computer? Why do we look at it and go, "Oh yeah, that's a computer," as opposed to, say, "Oh, that's just a TV," or "That's where I keep the leprechauns at night."?

Some people try to define the word "computer" just by saying "it's got such and such parts and they all work this way," but that's like saying "airplanes have two wings and jet engines." It's true, but I could build an airplane that didn't have two wings or jet engines. The...