Programming Methodology-Lecture03 Instructor (Mehran Sahami):Couple quick announcements before we dive into things. There's one handout, which, hopefully, you should have gotten. It will contain the Karel example we did in class last time, the steeple chase, as well as some more examples that we're gonna go over this time. But I encourage you to actually pay attention to what we do in class rather than sort of looking at it on the handout, because one thing that's always true about programs is once you see the solution to a program, it's easy to lull yourself into thinking oh, I could have done that, it seems so easy. But when you're actually sitting there staring at sort of a blank page on your monitor, it's a lot harder to generate the program. And we'll actually generate a couple of programs together in class today, so I'd encourage you to sort of take part in that that we do in class, and then you'll have the actual listing for the code to take home with you so you don't need to worry about scribbling everything down quickly. A couple quick announcements, the class website, one more time – every time I look on Access there's more and more people enrolled in this class, which begins to frighten me after a while but that means there's people who haven't gotten any of the previous handouts. So if you need to know where to get all the previous handouts if you just joined the class, CS106A.Stanford.edu is the website for the class, you can get all the handouts there, and there's a whole bunch of stuff you should read right away. Section sign-ups. How many people have already signed up for a section? Oh, yeah, that's a good time. If you haven't at this point, you should have looked around at all those hands that went up and just realized that sections are just filling up to the left and right of you, literally. Section sign-ups are open, and if you go to CS106A.Stanford.edu/section, you can sign up for a section. The section sign-ups close on Sunday at 5:00 p.m. You need to sign up for a section in addition to enrolling on Access to actually be enrolled in the course – important thing. Another thing just real quickly is just for your convenience, I mentioned last time sort of the conditions of the [inaudible] about the world. For your convenience, we actually posted them up off a link on the announcements on the CS106A website, so if you're programming somewhere and you forgot your little Karel book and you're like what are all those things that Karel can check in the world, like is front is clear, or is facing north or whatever, you can just go to a link off the website and you'll find them all listed there. One other thing I would encourage you to do is we haven't been picking up the audio on questions that are asked, so one of the things I'd encourage you all to do right now is you'll notice there should be microphones on the fronts or on the backs of the seat in front of you.Pick up the microphone right now, just pull it out of the slot and just keep it in your lap. Don't worry, it won't damage anything on you personally. It's just kind of fun. You can keep you there, it'll keep you warm, and that way if you ask a question it'll remind you to use the microphone, all right? So with that said, I wanna take a quick poll, because last time you got your first assignment and the download instructions and everything. How many people have already downloaded Eclipse? Oh, rock on, good time. How many people have gotten the first assignment filed that you needed to get? And how many people have started on the first assignment? Wow, I love that. Oh, that just warms the cockles of my heart. How many people are done with the first assignment? Oh, yeah, just [inaudible] and you're like oh, yeah, I got Karel to run around, and it's just a good time. So you’ve still got a week to do it, but that's a good thing to keep in mind. So a little bit of additional background on Karel before we dive into the real meat of things, okay? One thing you may have noticed is all the Karel code that you’ve either started writing, if you're already working on assignment number one or all the code that we write in class is all in file that ends with dot Java. If you haven't noticed that before, you'll – now you know, it ends with dot Java. Because in fact, Karel is all implemented in Java. So one of the things you might be wondering is hey, I know a little Java; can I use some Java in conjunction with Karel? And the answer is no. For the purpose of the Karel assignments, you should just use the constructs that you’ve been shown in class and in the Karel reader, just keep it to those constructs. That still gives you plenty of stuff to do with Karel, it's a good time, but keep it to that, and actually starting on Monday we're gonna, like, sort of leave Karel behind and say bye-bye, Karel, and I'll be, like, bye-bye, I love you, call me. But we'll get into Java, so if you know Java now, just use the Karel stuff in the Karel assignments that we actually do. All right, so with that said, any questions to start off with before we dive into something new? Um-hm? Student:How do you stop the program? Like, I had a problem, it goes up into the corner and just kind of like it says an error message. Instructor (Mehran Sahami):And it kept looping there forever? Student:Yeah, and I tried making, like, an empty program called Stop, but that didn’t really work. Instructor (Mehran Sahami):No, just go up to the little icon – or the little thing in the top of the window that allows you to close the window and just close the window. Karel will be okay, he knows how to deal with that.As a matter of fact, that's – I am so glad you asked that question. It's just a wonderful thing, because it actually leads into the first topic that I want to talk about, which is common errors. And so there are some common errors that may come up, and these are good things to kind of know about. And one of them is the thing you just ran into. But before we actually talk about that at sort of the level of Karel, I wanna ask you a question: [inaudible] another one of these strange questions. How many people have actually ever read the instructions on a bottle of shampoo? A few folks – oh, wow. Man, that's more than – I was, like, you’ve really gotta get out more often, right? But I'm surprised that many. And what do those instructions say? Rinse, right, that's where you rinse your hair, and then you lather, and