Numbers. Some of you might be like, "Hey, this is a programming course. I've expected numbers to come up much more and much earlier." I mean that it is especially maybe early on in the life of the computer in our society, we'd really imagined using computers to crunch numbers, right? Lots of numbers. Do a lot of Math repeatedly in a way that's not error-prone like humans are to calculate things, right? Some people say we're errors while obviously that still goes on, but we've reached in sort of a new era of computing with the ability of being able to use computational power to enable creativity or creation of apps, being a great example, but numbers are always at the heart of what computers do. So, we started looking into, at numbers, and we gave you a list of numbers, and we said, "What are things you can do with these?" Well, obviously, for the software sheet, we could add them up, or subtract them, or average them, or all sorts of other sorts of mathematical things, but we can also look at this as a list of an ordered set of things and change the ordering that things were in. So, I sorted this list by hand and let me tell you, it was painful actually. I know it wasn't that bad, but I was really ready to be done and that was only what? I don't know, eight-ish number, something like that. So, this really gets at the essence of people talking about crunching numbers like, "We want the computer to do work for us. It runs really hot. The fan is going, and it's running, and it's doing a lot of difficult work." We think about data, "Oh my gosh. Do we need to store things on supercomputers or this than the other?" How do computers really process numerical things effectively, efficiently, and quickly? So, when we're thinking about unplugged activities that talk about maybe lists, you might have heard the term arrays, or sorting, you kind of imagine two different things you can have unplugged activities around. One of them, like what you did, is about the use that we might have for these lists of numbers like, what do we want to do with them? Do we want to add them or do we want to sort them? Sorting is a huge use case of things that we do a lot. If you want to talk about use, there are some cool unplugged activities out there. This is actually a picture of one from the CS Unplugged group called Parallel Sorting Networks. I've done a number of times with teachers and kids, and they loved it. I have actually an improved lesson plan around this that I'd be happy to share with you. You can go and look at it, but it's not a whole lot of fun just to watch on a video. Moreover, with our unplugged activities, we've been using them to introduce concepts like the nested repeats or methods and how those work in the world. I'll just have to say, so, that's the sort of more about in the case of an array, it's about the representation. How would we represent list? Or you might have heard the term array, brief aside on that in a minute. How do we represent them in a computer and how do we use them? We're not so much used them and they come here a bit, but actually, how we store them and access them? I don't know of any unplugged activities around that, which is why we didn't do one. So, let me go back to list and arrays. If you have no prior programming experience, guess what? You get to hit stop now. Move on along to the next activity. But if you know the term array, and you was like, "Hey, why are we using list in here instead of arrays and what not?" Really, in the K-12 education realm, we are generally calling things lists, and not worrying about the specifics of arrays, and this is sort of representative of where we think programming languages are going, where arrays are different than lists and you have to do much more around the memory management of them if they need to get bigger or smaller or things like that. Whereas lists represent a more abstract way in which we can deal with what are arrays underneath, and not have to worry about just basically memory management. So, we think it's unlikely that we're really going to go into great detail with arrays with students in K-12.