The World Wide Web Text A

1. The World Wide Web is a service on the Internet. 2. It consists of sets of linked documents known as webpageswhich can be viewed using a program called a browser. 3. The links on a webpage contain the Web address of the webpage that will be displayed if the user clicks on the link.

4. The Web address of a webpage is also known as a URL e.g. http://www.hw.ac.uk./lib WWW/irn/irn. html. 5. This example indicates the following:

-http:// is known as the protocol prefix and indicates that the hypertext transfer protocol should be used to transfer the webpage across the Internet.

- www indicates that this is a World Wide Web document i.e. a webpage.

- hw.ac.uk is the domain name and indicates the network domain in which the page is stored.

- ac is the domain name extension and indicates the type of domain e.g. ac or edit is an educational domain, co or com is a company.

- uk is the country code indicating that this webpage is stored on a computer in the United Kingdom.

- HbWWW/irn gives the path of the directory where the webpage is stored on the server.

- irn.html is the name of the webpage file. 6. The extension used in webpage filenames is either htm or html to indicate that the file is written using HTML.

7. When a user clicks on a hyperlink on a webpage, the browser program contacts a server computer known as a DNS server to look up the IP address of remote Web server computer given in the URL of the linked webpage. 8. The DNS has a stored table of names and addresses of nodes on the Internet. 9. The request for the linked webpage is then sent to a computer or electronic device known as a router that uses the Internet address obtained form the DNS server to route the request.

10. The message requesting the webpage is divided up into small sections called packets and each separate data packet is passed from router to router until they reach the remote Web server where they are put back together again. 11. The remote Web server sends the requested webpage back to the browser computer that made the request in a similar way using the IP address of the browser computer to determine the best available route for each packet. 12. When the packets arrive at the browser computer, they are combined and the requested webpage is displayed in the browser.

13. Special websites (e.g. AltaVista) provide a facility known as a search engine that can be used to search for other websites. 14. A search engine uses special programs to collect information about websites on the World Wide Web and stores the information in a database. 15. The user can then search the database to obtain a list of links to relevant websites. 16. To search using a search engine, the user types keywords into a search box). 17. The search engine then displays a list of website links that are relevant to the given keywords. 18. Keywords can be used to form search phrases by putting quotation marks around the keywords and they can be combined in different ways using special logical operators such as the words OR, AND or NEAR which can be grouped by enclosing them in brackets. 19. Sometimes, symbols such as + or - can be used to represent the operators. 20. Special symbols known as wildcards can also be used with keywords. 21. These symbols represent certain characters or combinations of characters. 22. For example, an asterisk (*) is often used to represent any combination of characters. 23. A search for ‘col*’ would look for any word beginning with ‘col’.

24. Search engines can also be used for field searches. 25. This allows the user to search webpage fields such as the title field of a webpage or its Web address. 26. The Web address is sometimes referred to as its URL (uniform resource locator).

27. The user can store the links to useful websites using a bookmark facility in the browser program used to view the webpages. 28. The webpage that is set to be displayed when the browser program is first started is referred to as the user’s homepage. 29. The user can return to the homepage by clicking a button known as the Home button in the toolbar at the top of the browser program.

30. Because a video signal contains so much data, it is difficult to download it from an Internet server in real-time. 31. The connection would need to have a huge bandwidth. 32. One way of doing this with a normal Internet connection involves using a section of memory as a storage buffer. 33. This allows part of the video signal to be downloaded and stored so that the user can begin to view the video before it is completely downloaded. 34. Feeding the video signal from the storage buffer to the display makes space in the storage buffer for more of the video to be downloaded. 35. Therefore, as the user is watching the first part of the video, the next part is being downloaded into the storage buffer. 36. The video can therefore be shown to the user at a steady rate. 37. This method of downloading video signals using a storage buffer to obtain a steady display is known as streaming.

Notes

: = colon /ˈkolǝn / n – двокрапка

/ =slash /slæ∫/ n – коса лінія

. =dot /dot/ n – крапка

“ ” = quotation marks /kwɜυˈtei∫n ˈma:ks/ n – лапки