Understand generally what an Internet service provider does. Appreciate the ongoing problems associated with the Internet

Transcription

1 Chapter 7 Internet A Resource for All of Us Appreciate the history of the Internet Learn what is needed to get on the Internet Understand generally what an Internet service provider does Know the rudimentary functions of a browser Understand how to search the Internet Appreciate the non-web parts of the Internet Appreciate the ongoing problems associated with the Internet The Internet as a Phenomenon The Internet is a loosely configured, rapidly growing labyrinth of networks of computers from around the world, from corporations, organizations, and individuals. Although the growth of personal computers over the last few decades has been noteworthy, the rise of connectivity, especially the use of the Internet, has been faster. Over half the sites on the Web are business sites. Chapter 7 page 1

2 Don't Know Much about History The Internet existed for approximately 25 years before the general public even knew about it. It was started by the military as a vehicle for their own purposes; they never imagine that it would become the international giant it is today. First Stirrings at The Department of Defense In the 1950's Cold War, the United States Department of Defense, concerned that a single bomb could wipe out their computing capabilities, decided to rely on several computers, geographically dispersed. A message sent to another computer is divided into packets, each packet labeled with its destination address and winding its way individually through the network. The message is eventually reconstituted at the end of the journey. Thus, if one computer was knocked out the others could still carry on, by using alternative routes. The software that takes care of the packets is Transmission Control Protocol/Internet Protocol (TCP/IP); TCP does the packeting and reassembling of the message and IP handles the addressing, seeing to it that packets are routed across multiple computers. The set of connections was called ARPANet, an acronym that stands for Advanced Research Projects Agency Network. The year was Tim and Marc In 1990, Dr. Tim Berners-Lee, a physicist at a laboratory for particle physics in Geneva, Switzerland, perceived that his work would be easier if he and his far-flung colleagues could easily link to each other s computers. Chapter 7 page 2

3 He saw the set of links from computer to computer to computer as a spider's web; hence the name Web. The CERN site, the name of the particle physics laboratory where Dr. Berners-Lee worked, is considered the birthplace of the World Wide Web. A link on a Web site is easy to see: it is colored text, called hypertext or an icon or image, called a hyperregion. A mouse click on the link appears to transport the user to the site represented by the link, and in common parlance, one speaks of moving or transferring to the new site; actually, data from the new site is transferred to the user s computer. Marc Andreessen was only a student when, in 1993, he lead a team that invented the browser, graphical interface software used to explore the Internet. The first browser was named Mosaic and it made Web page multimedia possible. The Internet Surges Ahead The emergence of the Internet is due to four factors: 1. the universal TCP/IP standard 2. the web-like ability to link from site to site 3. the ease of a graphical interface by using a browser 4. the growth of personal computers and their local area networks that could be connected to the Internet Getting Started We cannot be specific here because many factors computers, servers, browsers, and more vary from place to place. But we can talk about overall strategy and what the various services and software have to offer. The Internet Service Provider and the Browser Chapter 7 page 3

4 An Internet user needs a computer with a modem and its related software, an Internet service provider, and a browser. An Internet service provider (ISP) provides the server computer and the software to connect to the Internet. A browser is the software on the user's computer to access the Internet via the service provider, using a graphical interface. If you wish to access the Internet from your own personal computer, one possibility is to sign up for an online service, such as America Online. The Internet service provider and browser are included in the package, and thus Internet access is available to you as soon as you have signed up for the online service. The main difference between an ISP and an online service is that an ISP is a vehicle to access the Internet, but an online service offers, in addition, member-only content on many topics. You would probably prefer an online service over an ISP if you are new to the online experience, if most of your friends and colleagues use the same online service, people of different skill levels will use your computer to go online, or you want to control what your children see online. The Browser in Action When you invoke your browser software it will dial up the Internet service provider and, once successfully connected, display either the home page initial page of the Web site that created your particular browser, or some other site designated by your ISP. The top part of the screen shows the browser control panel, consisting of lines of menus and buttons. The lower part, by far the largest part of the screen, is the browser display window. At the very bottom of the screen is a status line, which indicates the progress of data being transferred as you move from site to site. Chapter 7 page 4

5 The page can be scrolled moved up and down by using the scroll bar on the right; simply press your mouse button over a scroll bar arrow to see the page move. Browser Functions and Features At the top of the screen is the browser's welcome banner, touting its own name, across the top of the screen. Menus and buttons Using a mouse permits commands to be issued through a set of menus, a series of choices normally laid out across the top of the screen. The menus are called pull-down menus because each initial choice, when clicked with a mouse, reveals lower-level choices that pull down like a window shade from the initial selection at the top of the screen. You can also invoke commands using buttons for functions such as Print to print the current page, Home to return to the browser home page, and Back and Forward, to help retrace sites you have recently traversed. URL The location slot will usually contain a Uniform Resource Locator (URL), the unique address of a Web page or file on the Internet. An URL has a particular format. A Web page URL begins with the protocol http, for HyperText Transfer Protocol, the means of communicating by using links, the clickable text or image that transports a user to the desired site. Next comes the domain name, which is the address of the Internet service provider. The last part of the domain name is called a top-level domain and represents the purpose of the organization or entity, such as case com for "commercial." Links can be pre-stored on your browser's hot list called Bookmarks or Favorites or something similar. Chapter 7 page 5

6 Frames Several browsers support a concept called frames, which allow a given page to be divided into rectangular sections, each of which can operate independent of the other. The advantage is that a site can offer several different functions or areas of focus; a disadvantage of frames is that a small screen, notably a laptop screen, may look cluttered. Competition glitz Fancy features include illuminated buttons, other languages, borderless frames. More will doubtless come. Plug-ins Various vendors offer plug-ins, software that enhances the value of a browser by increasing its functionality or features. Chapter 7 page 6

7 JAVA It is Java that permits the dancing icons, sound clips, flashing messages, banners that scroll across the page and much more. Java is a programming language, developed by Sun Microsystems, that is used to write software that can be used on any machine, hence its appeal to the multifaceted Internet. The programs that provide the moving images and sound clips on a Web page are called applets, a sort of abbreviation for little applications. To benefit from applets, a user must have a Java-capable browser, as the most popular browsers are. Moving from Site to Site Most browsers provide a list of clickable categories, such as sports, weather, news, technology, and even comic strips. Also a button click away are lists of new sites, cool sites, and various comprehensive directories. But suppose you have something more specific in mind. If you know the URL for a desired site, delete the current URL in the location box, then type in the new one carefully and press Enter on the keyboard. Searching the Internet A search engine is software, usually located at its own Web site, that lets a user specify search terms; the search engine then finds sites that fit those terms. Chapter 7 page 7

8 A search engine, over time, builds a database of searchable terms that can be matched to certain web sites. The search engine will then present the list of sites in some format, which varies by search engine. In fact, the nature of the search varies according to the search engine. Each search engine is associated with a constantly updated database of sites and related keywords. Hot Search Engines Note that the use of these search engines is free, although you will, of course, encounter some advertising. Search engines vary widely in size, content, and search methodology and will thus produce different results, even with the same key terms. Narrowing the Search A simple one-word search will yield many sites, most of which are irrelevant to your purposes. The trick is to customize your search criteria. Different search engines offer different methods of narrowing a search. Most search engines offer operators with special functions, based on a mathematical system called Boolean logic. The operators most commonly used are AND, OR, and NOT. The words can be further qualified with parentheses. And means both; or means either or both. Search Engine Limitations Search engines examine only a fraction of the Web. The Web s vastness simply foils even the best search engines. The Web has approximately 400 million pages, with millions of pages being added every year. It is probably impossible to index the entire Web. Chapter 7 page 8

9 The futility of trying to build giant databases will probably lead to a trend toward smaller, specialized search sites. Branching Out Although the World Wide Web is usually the focus of any Internet discussion, there are other parts of the Internet that deserve attention. All of them, in fact, predate the Web. One way to identify such sites is to observe the protocol. Instead of http, to which you may be accustomed for web sites, you may see news or ftp. Newsgroups Usenet is an informal network of computers that allow the posting and reading of messages in newsgroups that focus on specific topics. A more informal name is simply newsgroups. Topics of newsgroup discussions cover almost any subject you could imagine. Today there are more than 10,000 newsgroups. Think of a newsgroup as one large bulletin board, marked off by category. If you happen along, you can read other people's postings. If you wish to respond to a message, or just contribute your own original thought, you leave a message. Lurking refers to just reading newsgroup messages without writing any. There are a few problems associated with newsgroups; in particular, newsgroups are a great source for picking up addresses, which can then be used for directed advertising. Chapter 7 page 9

10 FTP: Downloading Files Whether or not a file is available for downloading depends on two things: (1) whether you are allowed to download files to the hard disk of the computer you are using, and (2) whether the file you want is available for copying. Of course, if you are using your own personal computer, you may copy files to it if you wish. Many computer files are proprietary, and a user who wants them must have an account on that computer and a password. The files available for copying are not proprietary. All kinds of files programs, text, graphics images, even sounds are available to be copied. The free files are public archives, often associated with an educational institution or the government. Computers on the Internet have a standard way to transfer copies of files, a program called FTP, for file transfer protocol. Most downloading is done by a method called anonymous FTP. This means that instead of having to identify yourself with a proper account on the remote computer, you can simply call yourself Anonymous. Also, instead of a password, just use your address. Not Quite Perfect Yet The Internet has been heaped with well-deserved praise, but there are concerns. Behavior Problems There are behavior problems in any aspect of society, from the playground to the boardroom; those who abuse the Internet are, relatively speaking, small in number. Netiquette refers to appropriate behavior in network communications. Chapter 7 page 10

11 Useless, Overburdened, and Misinformed Some people consider some home pages useless. If you are not interested, simply skip such pages. At the other end of the spectrum are sites that, apparently, have so much value that their popularity renders them mostly inaccessible. Any list of "cool" sites, a favorite Web word, is likely to be crowded. There are no guarantees. The Internet is full of misinformation. Lecture Textbook Chapter Covered Keywords Syllabus Covered 10 CHAPTER 7 The Internet: A Resource for All of Us The operating system and operating environment Chapter 7 page 11