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>> Alright, welcome to CS50. This is the start of week eight, as you see on the big board here. We have our own little big board, which is currently ranking those that have tackled Psets 6 already, realize that this is purely optional, it's really just meant to add a fun twist to what's otherwise an interesting assignment. And you'll notice that I was number one on this board for like the first five minutes of having put it up and then I was quickly crushed by several of the teaching fellows, most of them former students themselves and we already have an appearance of several students and over the course of the week, I'm sure, I'm sure we'll see others. Realize that right now, the lower bound, if you're a little nervous or socially awkward about having your name and you're results put up there. So right now the lowest number, perhaps intentionally infinity amount of memory and amount of CPU cycles, so there's a nice healthy lower bound already and the upper bound right now is by our own Drew Rob, who I think was the top of the big board last year as well. So, he is perhaps among those of you, more comfortable this year, the guy to beat, but again this is purely for fun. So the past many weeks, we've focused on this fairly low level language C and hopefully you've gotten a sense, for better or for worse, how you can easily manipulate a machine on down to the specific bytes in memory. Now, that's often for the worst, since you've induced plenty of seg faults by now, but finally this week do we take things to a so called higher level language. This language is called PHP and next week a little bit of java script. And these are higher level in the sense that they hide a lot of those low level details that at the one hand are empowering but the other hand are also very dangerous and very time consuming. Problem sets 6 has you implementing the fastest dictionary that you can and part of that involves implementing a hash table or a tri. These fairly intricate and very powerful data structures that thankfully you get for free in a lot of languages. That is to say in PHP if you need a hash table, you pretty much write dollar sign hash table Done, you can start using it. You don't need to reinvent that wheel yourself and this is true of many languages, Java, PHP, Pearl, Java Script and a whole bunch of others, so the point of this week and next is to now take a big step upward in terms of your familiarity with languages and problem solving so that you now have more tools to choose from. So as much as we've emphasized C in this course, it's absolutely the wrong language to use for a lot of problems. For instance, all of these little demos I've done with the twitter site, the events site and the news site absolutely should you not use C to implement those kinds of web sites because it will just take you way too long and you'll have to implement so many annoying low level details that it will one, completely take the fun out of the entire experience and that itself is valuable, to actually enjoy what you do and two, you're just going to literally be reinventing wheels that other people have packaged up nicely in newer, more modern languages. So you'll find that this week onward and after CS50, hopefully you'll have a sense now of how these machines work and how you can really, really manipulate them, especially this week with Pset 6 to your will and to maximize performance, but it's not going to be the only tool in your tool kit and among them henceforth will be PHP, java script, an actual data base and some more.