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Dialogue: 0,0:00:00.63,0:00:04.03,Default,,0000,0000,0000,,Welcome to CS 101. I'm Dave Evans. I'll be your guide on this journey.
Dialogue: 0,0:00:04.03,0:00:07.05,Default,,0000,0000,0000,,This course will introduce you to the fundamental ideas in computing
Dialogue: 0,0:00:07.05,0:00:09.56,Default,,0000,0000,0000,,and teach you to read and write your own computer programs.
Dialogue: 0,0:00:09.56,0:00:13.06,Default,,0000,0000,0000,,We're going to do all that in the context of building a Web search engine.
Dialogue: 0,0:00:13.06,0:00:16.36,Default,,0000,0000,0000,,I'm guessing everyone here has at least used a search engine before.
Dialogue: 0,0:00:16.36,0:00:19.56,Default,,0000,0000,0000,,The goal of the first three units in this course is to build a Web crawler.
Dialogue: 0,0:00:19.56,0:00:22.13,Default,,0000,0000,0000,,They will collect data from the Web for our search engine.
Dialogue: 0,0:00:22.13,0:00:24.66,Default,,0000,0000,0000,,And to learn about big ideas in Computing by doing that.
Dialogue: 0,0:00:24.66,0:00:29.68,Default,,0000,0000,0000,,In Unit 1, we'll get started by extracting the first link on a web page.
Dialogue: 0,0:00:29.68,0:00:32.73,Default,,0000,0000,0000,,A Web crawler finds web pages for our search engine
Dialogue: 0,0:00:32.73,0:00:37.80,Default,,0000,0000,0000,,by starting from a "seed" page and following links on that page to find other pages.
Dialogue: 0,0:00:37.80,0:00:43.93,Default,,0000,0000,0000,,Each of those links lead to some new web page, which itself could have links that lead to other pages.
Dialogue: 0,0:00:43.93,0:00:46.51,Default,,0000,0000,0000,,As we follow those links, we'll find more and more web pages
Dialogue: 0,0:00:46.51,0:00:50.23,Default,,0000,0000,0000,,building a collection of data that we'll use for our search engine.
Dialogue: 0,0:00:50.48,0:00:54.71,Default,,0000,0000,0000,,A web page is really just a chunk of text that comes from the Internet into your Web browser.
Dialogue: 0,0:00:54.71,0:00:56.58,Default,,0000,0000,0000,,We'll talk more about how that works in Unit 4.
Dialogue: 0,0:00:56.58,0:00:59.56,Default,,0000,0000,0000,,But for now, the important thing to understand is that
Dialogue: 0,0:00:59.56,0:01:02.50,Default,,0000,0000,0000,,a link is really just a special kind of text in that web page.
Dialogue: 0,0:01:02.50,0:01:07.35,Default,,0000,0000,0000,,When you clic on a link in your browser it will direct you to a new page.
Dialogue: 0,0:01:07.35,0:01:09.50,Default,,0000,0000,0000,,And you can keep following those links (...)
Dialogue: 0,0:01:09.50,0:01:14.21,Default,,0000,0000,0000,,What we'll do in this Unit is write a program to extract that first link from the web page.
Dialogue: 0,0:01:14.21,0:01:18.21,Default,,0000,0000,0000,,In later units, we'll figure out how to extract all the links and build their collection for our search engine