Internet, the world's largest computer network. The Internet is an electronic conduit through which individuals, organizations, and businesses across the globe view and exchange data in the form of text, graphics, audio, and video. By the beginning of 2003 more than 170 million computers (called hosts, in Internet terminology) were connected to the Internet, according to research by the Internet Software Consortium, in Redwood City, Calif.
The Internet (or, informally, the Net) has neither an owner nor a single individual, organization, or governmental authority controlling its contents or governing access to it. Rather, it comprises many smaller computer networks that have been linked together; costs associated with the system are paid voluntarily by those who use and maintain it. Users typically access the Internet through a computer equipped with the software and hardware necessary to permit data to be sent to and received from other computers. An Internet connection is typically established by linking the computer through a telephone or cable line or by way of wireless technology, to an Internet service provider (ISP), a company whose computers are in turn linked to the Internet's hierarchy of computer networks. Host computers, such as those of an ISP, that provide connection to the Internet or other services are known as servers. Hosts receiving those services are called clients. In many cases a computer both gives and receives services, making it a server as well as a client.
The Internet's origins date back to the early 1960s, when the U.S. government began considering the building of a communications system capable of withstanding large-scale disruptions, even in the event of a nuclear war. It was reasoned that the system should have no central control or authority, so that were any single part of it destroyed, the rest of the system could continue functioning. Moreover, it was agreed that the system should be designed so that even if large portions of it were knocked out of service, the remnants could keep working and that any damaged sections, once repaired, could be quickly returned to service. Ideas formed in response to these requirements focused primarily on packet switching (breaking an electronic data file into smaller units, or packets, and transmitting them separately over the system) and the automatic routing of data.
An experimental packet-switching network went into operation in the fall of 1969, connecting computers at four institutions: the University of California at Los Angeles, the University of California at Santa Barbara, the Stanford Research Institute, and the University of Utah in Salt Lake City. The system was called the ARPANET, named after the United States Department of Defense's Advanced Research Projects Agency, which funded the experiment.
By 1972 the ARPANET comprised 37 host computers spread across the United States. While the network's original purpose was to allow remote use of the few supercomputers then in existence, most of the traffic on the ARPANET soon consisted of electronic mail (e-mail) sent person-to-person or to groups of users belonging to automated mailing lists. The system came to be used therefore not only as a means of scientific collaboration but also as a facility for the discussion of topics of technical and professional concern (for example, computer network design) as well as subjects of more personal interest (such as science fiction). This continued to be the case as the ARPANET expanded through the 1970s, reaching 213 hosts by 1981.
The ARPANET initially used a communication protocol (the set of rules employed by computers when transmitting information back and forth) called the network control program (NCP). This was replaced in 1982 with the more advanced TCP/IP, actually a combination of two protocols: the Internet protocol (IP) and the transmission control protocol (TCP). The IP is used to deliver the data packets that together make up a message file, carrying them from the sender's computer to their destination across a network. Once the packets reach the intended computer, the TCP reassembles them into the complete message file. The introduction of the TCP/IP allowed the ARPANET to accommodate the seamless interconnection of many different computer networks despite variations between them in size, speed, and technology.
The military elements targeted by the original ARPANET design separated from the network in 1983, forming MILNET. In 1986 the U.S. National Science Foundation (NSF) launched its own network based on ARPANET technology. Connected to the ARPANET, the NSFNET was meant to enhance communication within the academic and scientific community.
Although during the 1980s rising personal computer use triggered the rapid growth of the ARPANET, in 1990 the network ceased to exist, having been officially decommissioned and replaced by a much larger one. This new network, the Internet, had evolved from a combination of a series of networks, including the NSFNET. (The Internet took its name from the previously mentioned Internet protocol.)
Every computer on the Internet is assigned a unique number, an IP address, that enables it to receive data using the TCP/IP. When packets making up a computer file are transmitted across the Internet, each packet contains the intended recipient's (as well as the sender's) IP address, allowing the packet to find its destination.
An IP address is made up of a series of numbers that are divided into four groups, or octets, separated from each other by a decimal point (an example being 220.127.116.11). The first (and sometimes the second and third) octet of an IP address represents the network on which the host is located, and the other octets identify the host itself.
Since the late 1980s the number of hosts accessing the Internet has grown so rapidly that by 1995 a new generation of IP was designed, primarily owing to the prediction that the total number of addresses that the current IP allows would be exhausted by the year 2000. The newer IP, officially IP version 6, can provide up to 2128 addresses, a virtually infinite supply.
However, in the late 1990s, through a combination of more conservative IP address allocation and the introduction of technology permitting the reuse of addresses, the demand for additional addresses slowed. Consequently, it was predicted that conversion to IP version 6 would probably not be needed until 2010 or later.
Rather than require users to type in an IP address in order to direct e-mail to a specific host or to locate a Web page (discussed below), the Internet employs the domain naming system (DNS), which transforms IP addresses into more easily remembered words and letters. Internet hosts are assigned within the DNS to one of several basic "domains," including government (abbreviated gov), military (mil), educational (edu), commercial (com), nonprofit organization (org), network operator (net), business (biz), information service (info), cooperative (coop), museum (museum), aeronautical organization (aero), professional service (pro), and individual person (name). In addition, there are several hundred geographic domains that exist, such as Canada (ca), Japan (jp), and Antarctica (aq).
A name within a domain is appended to the front of the address, as, for example, in whitehouse.gov (for the U.S. White House), ucla.edu (for the University of California at Los Angeles), and ibm.com (for the International Business Machines Corporation). Subdomains also are commonly used, to indicate a more specific address. For example, eecs.berkeley.edu is the host for both the electrical engineering and computer sciences divisions at the University of California at Berkeley. Once a user sends an e-mail message, the Internet utilizes a domain name server to translate the DNS address back into an IP address for the network computers to read.
Tasks performed on the Internet, including the transmission of person-to-person e-mail and the transfer of files between computers, parallel those that are carried out on smaller computer networks. It is the vast size of the Internet that adds to the complexity of accomplishing these particular tasks.
E-mail. By the early 21st century, billions of e-mail messages were being routed over the Internet each day. E-mail transmissions utilize the simple mail transfer protocol (SMTP). The addresses to which they are sent take the form userid@host, in which host indicates the name (assigned via the DNS) of the computer or group of computers that is receiving the message and userid identifies a specific individual or group accessing that computer.
File Transfer. Another significant use of the Internet is the electronic transfer of documents and other filed data between computers. This is accomplished using the file transfer protocol (FTP). The protocol can also be used to distribute both free and commercial software over the Internet.
USENET Discussion groups have thrived over USENET (short for users' network), also known as Netnews, a worldwide electronic system employed by the general public to post messages on topics of special or general interest. The messages, referred to as articles, appear in USENET discussion forums known as newsgroups, which are typically dedicated to specific topics. Although USENET articles are sent over the Internet, non-Internet computer networks transmit them as well. Therefore, while USENET makes use of the Internet, it is not, strictly speaking, an actual part of the Internet.
Each of the thousands of existing newsgroups has a hierarchically constructed name. For example, the newsgroup comp.arch, which is one of a large number of newsgroups about computers (comp), was created specifically for the discussion of computer architecture (arch). Similarly, the comp.lang.c++ newsgroup was devised for often arcane discussions on the C++ programming language, while the misc.computers group was developed for miscellaneous (misc), and relatively simple, computer-related questions and discussions. Other examples of newsgroup abbreviations include soc, for newsgroups oriented toward social issues (such as soc.culture.japan), and rec, used by recreation-related groups (such as rec.sport.hockey).
USENET operates by way of specialized protocols that transmit a news feed (that is, a batch of articles) to a server. A program called a news reader lets a client see the list of newsgroups available on the server and gives the client access to specific articles. It also enables articles to be sent from the client to a newsgroup.
Starting in the early 2000s, new technologies and softwares allowed the World Wide Web (see below) to become an outlet for discourse that had previously taken place on USENET. Chat rooms, weblogs (or "blogs"), wikis, and other Web applications allowed users to quickly share information. The new technologies also provided users with the ability to better personalize content to their needs.
The Internet's content runs the gamut from current and classic scientific, social, and cultural material to family entertainment, commercial advertising, and even graphic pornography. However, once an individual has accessed the Internet through his or her computer, it would be a daunting task to find unaided the specific host among millions that has the content the user desires and then to locate that data in the host computer's file system. Various programs have been devised to ease the problem. For example, the Archie program, created in 1989, provided a searchable index of FTP-transmittable files.
Accessing Internet content was further simplified with the creation in the early 1990s of the World Wide Web, at CERN (the European Organization for Nuclear Research; formerly, Conseil Européene pour la Recherche Nucléaire), the joint European atomic research facility in Geneva. The World Wide Web, or, simply, the Web, is a collection of electronic documents, or Web pages. A Web page, in turn, is a single file comprising text, multimedia material (such as images, video, and audio), or both that is created and accessed using the hypertext markup language (HTML), the hypertext transfer protocol (HTTP), and the uniform resource locator (URL).
HTML and HTTP. An individual constructing a Web page controls the material's appearance and organization using HTML tags, a set of codes that divides the document into separate elements, such as headings and paragraphs, and that controls where these elements are placed within the page. The tags also allow multimedia material to be inserted and positioned in the page and permit the insertion of hypertext links.
A hypertext link is literally a connection between documents. Following a link is usually a simple "point-and-click" operation, in which a computer mouse is used to place an onscreen cursor over the linked element in the page (such as a piece of text or an image); a click on the mouse button activates the link, sending the user to the targeted document. The HTTP enables a client computer (usually one running a browser, described below) to send a request to a server to retrieve a Web page.
Browsers. Web pages are displayed and their links accessed using a browser, a computer program that utilizes the HTTP to communicate with Web servers (servers that store and transmit Web pages). The Netscape and Internet Explorer browsers (from Netscape Communications Corporation and Microsoft Corporation, respectively) have been particularly popular.
URL. Each Web page is assigned a URL so that the page can be retrieved from among the hundreds of millions of publicly accessible pages on the World Wide Web. The URL is a text string that contains the name (as created through the domain naming system) of the server being accessed and the location of information stored in that server. A typical URL would therefore have the form www.scholastic.com/earlylearner, with www.scholastic.com being the domain name and earlylearner being a Web page. (However, just typing in a domain name without a file name attached will typically bring up a default Web page from the server rather than leave the computer screen blank.) Hypertext links on the Web typically connect users to additional URLs, which means that by following a link, the user can easily be routed to a Web page stored on a server located anywhere in the world.
XML. Extensible markup language (XML) is a newer and more versatile system than HTML for Web document creation. Actually a scaled-down version of a more complex tool, standard generalized markup language (SGML), XML permits customized tags to be placed in a Web page. In this way XML can be used to create more intricately structured Web pages than can HTML. Moreover, XML is better adapted than HTML for creating links. Although by 2003 XML had not supplanted HTML, the newer tool's popularity was increasing.
Commercial use of the Internet has become widespread, as has Web-based advertising. The late 1990s saw a surge in the creation of new, publicly traded companies selling goods and services through the Web. Public confidence in the viability of Web-based businesses (referred to colloquially as dot.coms) swelled so greatly that the stock value of many of these companies quickly reached dizzying heights, even among businesses with little chance of becoming profitable. By the beginning of the 21st century, however, Internet stock prices had fallen dramatically as it became apparent that numerous dot.coms were not succeeding financially. Although the commercial potential of the Internet continues to be tapped, entrepreneurs and investors have come to better understand both the potential and the limitations associated with Internet-based commerce.
The social ramifications of Internet use are not necessarily clear-cut. For example, in the mid- to late 1990s the American psychologist Robert Kraut and his colleagues found evidence that individuals who extensively use the Internet experience increased loneliness and depression. Moreover, heavy Internet use appeared to shrink, rather than expand, the individuals' social circle and reduce their interactions with family members. However, in later research Kraut discovered that these problems seemed largely to have dissipated in persons from the original study and that for individuals with a normally extroverted personality, Internet use could over time lead to increased community involvement and improved self-esteem. Nonetheless, Kraut found that, for reasons not clearly understood, spending a great deal of time on the Internet also appeared to intensify emotional stress in persons studied.
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