Часть полного текста документа:What is the Internet USING the Internet, David, a teacher in the United States, acquired course materials. A Canadian father accessed it to stay in contact with his daughter in Russia. Loma, a housewife, used it to examine scientific research on the early beginnings of the universe. A farmer turned to it to find information about new planting methods that make use of satellites. Corporations are drawn to it because of its power to advertise their products and services to millions of potential customers. People around the globe read the latest national and international news by means of its vast reporting and information services. What is this computer phenomenon called the Internet, or the Net? Do you personally have need of it? Before you decide to get "on" the Internet, you may want to know something about it. In spite of all the hype, there are reasons to exercise caution, especially if there are children in the home. What Is It? Imagine a room filled with many spiders, each spinning its own web. The webs are so interconnected that the spiders can travel freely within this maze. You now have a simplified view of the Internet-a global collection of many different types of computers and computer networks that are linked together. Just as a telephone enables you to talk to someone on the other side of the earth who also has a phone, the Internet enables a person to sit at his computer and exchange information with other computers and computer users anyplace in the world. Some refer to the Internet as the information superhighway. Just as a road allows travel through different areas of a country, so the Internet allows information to flow through many different interconnected computer networks. As messages travel, each network that is reached contains information that assists in connecting to the adjacent network. The final destination may be in a different city or country. Each network can "speak" with its neighbor network by means of a common set of rules created by the Internet designers. Worldwide, how many networks are connected? Some estimates say over 30,-000. According to recent surveys, these networks connect over 10,000,000 computers and some 30,000,000 users throughout the world. It is estimated that the number of connected computers is doubling each year. What can people locate on the Internet? It offers a rapidly growing collection of information, with topics ranging from medicine to science and technology. It features exhaustive material on the arts as well as research material for students and coverage of recreation, entertainment, sports, shopping, and employment opportunities. The Internet provides access to almanacs, dictionaries, encyclopedias, and maps. There are, however, some disturbing aspects to consider. Can everything on the Internet be regarded as wholesome? What services and resources does the Internet offer? What precautions are in order? The following articles will discuss these questions. Services and Resources of the Internet A COMMON resource provided by the Internet is a worldwide system for sending and receiving electronic mail, known as E-mail. In fact, E-mail represents a large portion of all Internet traffic and is for many the only Internet resource they use. How does it work? To answer that question, let's review the ordinary mail system first. Imagine that you live in Canada and wish to send a letter to your daughter living in Moscow. After properly addressing the envelope, you mail it, starting the letter's journey. At a postal facility, the letter is routed to the next location, perhaps a regional or national distribution center, and then to a local post office near your daughter. A similar process occurs with E-mail. After your letter is composed on your computer, you must specify an E-mail address that identifies your daughter. Once you send this electronic letter, it travels from your computer, often through a device called a modem, which connects your computer to the Internet via the telephone network. Off it goes, bound for various computers that act like local and national postal routing facilities. They have enough information to get the letter to a destination computer, where your daughter can retrieve it. Unlike the regular mail, E-mail often reaches its destination, even on other continents, in minutes or less unless some part of the network is heavily congested or temporarily out of order. When your daughter inspects her electronic mailbox, she will discover your E-mail. The speed of E-mail and the ease with which it can be sent even to multiple recipients all over the world make it a popular form of communication. Newsgroups Another popular service is called Usenet. Usenet offers access to newsgroups for group discussions on specific topics. Some newsgroups focus on buying or selling various consumer items. There are thousands of newsgroups, and once a user has gained access to Usenet, there is no cost to subscribe to them. Let's imagine that someone has joined a newsgroup involved in stamp collecting. As new messages about this hobby are sent by others subscribing to this group, the messages become available to this newcomer. This person reviews not only what someone has sent to the newsgroup but also what others have written in response. If, for example, someone requests information about a particular stamp series, shortly afterward there may be many responses from around the world, offering information that would be immediately available to all who subscribe to this newsgroup. A variation of this idea is the Bulletin Board System (BBS). BBSs are similar to Usenet, except that all files are located on a single computer, usually maintained by one person or group. The content of news-groups reflects the varied interests, viewpoints, and moral values of those who use them, so discretion is needed. File Sharing and Topic Searching One of the original Internet goals was global information sharing. ............ |