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Usenet is a worldwide distributed discussion system. It was developed from the general-purpose UUCP dial-up network architecture. Tom Truscott and Jim Ellis conceived the idea in 1979, and it was established in 1980.〔''From Usenet to CoWebs: interacting with social information spaces'', Christopher Lueg, Danyel Fisher, Springer (2003), ISBN 1-85233-532-7, ISBN 978-1-85233-532-8〕 Users read and post messages (called ''articles'' or ''posts'', and collectively termed ''news'') to one or more categories, known as newsgroups. Usenet resembles a bulletin board system (BBS) in many respects and is the precursor to Internet forums that are widely used today. Usenet can be superficially regarded as a hybrid between email and web forums. Discussions are threaded, as with web forums and BBSes, though posts are stored on the server sequentially. One notable difference between a BBS or web forum and Usenet is the absence of a central server and dedicated administrator. Usenet is distributed among a large, constantly changing conglomeration of servers that store and forward messages to one another in so-called news feeds. Individual users may read messages from and post messages to a local server operated by a commercial usenet provider, their Internet service provider, university, employer, or their own server. ==Introduction== Usenet was conceived in 1979, and publicly established in 1980, at the University of North Carolina at Chapel Hill and Duke University,〔 over a decade before the World Wide Web was developed and the general public received access to the Internet, making it one of the oldest computer network communications systems still in widespread use. It was originally built on the "poor man's ARPANET", employing UUCP as its transport protocol to offer mail and file transfers, as well as announcements through the newly developed news software such as A News. The name Usenet emphasized its creators' hope that the USENIX organization would take an active role in its operation.〔("Invitation to a General Access UNIX Network )", James Ellis and Tom Truscott, in First Official Announcement of USENET, NewsDemon (K&L Technologies, Inc), 1979〕 The articles that users post to Usenet are organized into topical categories called newsgroups, which are themselves logically organized into hierarchies of subjects. For instance, ''(sci.math )'' and ''(sci.physics )'' are within the ''sci. *'' hierarchy, for science. Or, ''(talk.origins )'' and ''(talk.atheism )'' are in the ''talk. *'' hierarchy. When a user subscribes to a newsgroup, the news client software keeps track of which articles that user has read.〔Lehnert, Wendy G.; Kopec, Richard (2007). ''Web 101.'' Addison Wesley. p. 291. ISBN 9780321424679〕 In most newsgroups, the majority of the articles are responses to some other article. The set of articles that can be traced to one single non-reply article is called a thread. Most modern newsreaders display the articles arranged into threads and subthreads. When a user posts an article, it is initially only available on that user's news server. Each news server talks to one or more other servers (its "newsfeeds") and exchanges articles with them. In this fashion, the article is copied from server to server and should eventually reach every server in the network. The later peer-to-peer networks operate on a similar principle, but for Usenet it is normally the sender, rather than the receiver, who initiates transfers. Some have noted that this seems an inefficient protocol in the era of abundant high-speed network access. Usenet was designed under conditions when networks were much slower and not always available. Many sites on the original Usenet network would connect only once or twice a day to batch-transfer messages in and out.〔. Carnegie Mellon School of Computer Science.〕 This is largely because the POTS network was typically used for transfers, and phone charges were lower at night. Usenet has significant cultural importance in the networked world, having given rise to, or popularized, many widely recognized concepts and terms such as "FAQ", "flame", and "spam". The format and transmission of Usenet articles is similar to that of Internet e-mail messages. The difference between the two is that Usenet articles can be read by any user whose news server carries the group to which the message was posted, as opposed to email messages, which have one or more specific recipients.〔Kozierok, Charles M. (2005). ''The TCP/IP guide: a comprehensive, illustrated Internet protocols reference.'' No Starch Press. p. 1401. ISBN 978-159327-047-6〕 Today, Usenet has diminished in importance with respect to Internet forums, blogs and mailing lists. Usenet differs from such media in several ways: Usenet requires no personal registration with the group concerned; information need not be stored on a remote server; archives are always available; and reading the messages requires not a mail or web client, but a news client. The groups in ''alt.binaries'' are still widely used for data transfer. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「usenet」の詳細全文を読む スポンサード リンク
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