The Client Side
The Client Side, From the user’s point of view, the web consists of a vast, worldwide collection of documents, usually just called pages for short. Each page may contain links (pointers)to other, related pages,anywhere in the world. Users can follow a link (e.g.,by clicking on it), which then takes them to the page pointed to.this process can be repeated indefinitely, possibly traversing hundreds of linked pages while doing so.pages that point to other pages are said to use hypertext, pages are viewed with a program called a browser, of which mosaic and Netscape are two popular ones. the browser fetches the page requested, interprets the text and formatting commands that it contains, and displays the page, properly formatted, on the screen.
Like many web pages, this one starts with a title, contains some information, and ends with the email address of the page’s maintainer. Strings of text that are links to other pages, called hyperlinks, are highlighted, either by underlining.displaying them in a special color or both.To follow a link.the user places the cursor on the highlighted area (using the mouse or the arrow keys)and selects it(by clicking a mouse button or hitting ENTER).Although nongraphical browsers, such as Lynx,exist,they are not as popular as graphical browsers,so we will concentrate on the latter. Voice-based browsers are also being developed. Users who are curious about the Department of Animal Psychology can learn more about it by clicking on its(underlined)name.The browser then fetches the page to whiceh the name is linked and displays it.Theunderlined items here can also be clicked on to fetch other pages, and so on The new page can be on the same machine as the fifst one,or on a machine halfway around the globe.
Client Side, The user cannot tell.page fetching is done by the browser.without any help form the user.lf the user ener returns to the main page,the links that have already been followed may be shown with a dotted underline(and possibly a different color)to distinguish them from links that havenot been followed.Note that clicking on the campus lnformation line in the main page does nothing.it is not underlined,which means that it is just text and is not linked to another page. most browsers have numerous buttons and features to make it easier to navi gate the Web.many have a button forgoing back to the previous page,a button for going forward to the next page(only operatve afrer the user has gone back form it).and abutton for going suaight to the user’s own home page.mast browsers have a button or menu item to set a bookmark on a gaven page and another one to display tho list of bookmarks.making it possible to revisit any of
WELCOME TO THE UNIVERSITY OF EAST PODUNK www HOME PAGE
- Admission information
- Campus map
- Directions to.campus
- The UTEP student body
- Department of Animal Psychology
- Department of Alternative Studies
- Department of Microbiotic Cooking
- Department of Nontraditional Studies
- Department of Traditional Studies
THE DEPARTMENT OF ANIMAL PSYCHOLOGY
information for prospective majors
- Faculty members
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Our most popular courses
- Dealing with herbivores
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them with single mouse click. Pages can also be saved to disk or printed. Numerous options are generally available for controlling the screen layout and setting various user preferences comparison of the browsers is given in ( Ber-ghel. 1996) In addition to having anti-Vestito underlining and hypertext. Web pages can also contain icons. line drawings maps, and photographs. Each of these can be linked to another page. Clicking on one of these elements cause the browser to fetch the linked page and display it, the same as clicking on text. With music photos and maps, which page is fetched next may depend on what part of the image was clicked on. Not all pages are visible in a conventional way. For example the past coat of audio tracks, video clips or both, When hypertext pages are mixed with other media. the result is called hypermedia Some browsers can display all kinds of hypermedia but others cannot.
Client-Side, Instead they check ha configuration file to see how to handle the received data. Normally, the configuration file uses the name of a program called an external viewer or a helper application, to be run with the incoming pages If no viewers configure, the browser usually as the user to choose one I ho sewer exist the user can tell the browser to save the incoming page to file or to discard it Helper applications for pro touching speech and making it possible for a blind users to access the Web Oder helper applications contain interpreters for special Web languages, making it possible to download and run program from Web pages.
Client-Side, This mechanism makes it possible to extend the functionality of the Web itself. Many Web pages contain large image which takes a long time to load. For example. fetching an uncompressed 640 x 480 (VGA) image with 24 bits per pixel 022 KB) takes about 4 minutes over 288. modem lite Some browsers deal with the low loading of images by first fetching and displaying the text. then getting the images this strategy gives the user something to read while the images are coming in and also allows the user to kill the load if the page is not Sufficiently interesting went waiting an alternative strategy is to provide an option to disable the automatic fetching and display of images Some page writers attempt to placate potentially bored users by displaying images in a special way Fit the image quickly appears in a coarse resolution Then the details are gradually filled in.
For the user seeing the whole image after a few seconds. albeit ar low resolution is often preferable to seeing it built up low from the top scan line by scan line Some Web pages contain forms that request the user to short information Typical applications of these forms are searching a database for a user-supplied Hem ordering a product or participating in a public opinion survey, Other Web pages contain maps that allow users to click on them to room in or get information about some geographical area. Handling fans and active (clickable) maps require more sophisticated processing than just fetching known page. We will Describe later now these features are implemented. Some browsers use the local disk to cache pages that they have fetched. Before a page is fetched. a check is made to see if it is in the 10 is only necessary to check if the page if still up to date.
If so, the purge need not be to see if it is in the local cache. If so it loaded again. As a result. clicking on the BACK button to see the previous page is normally very fast To host a Web browser, a machine must be directly on the Internet. or at least have a SLIP or PPP connection to a router or other machine that is directly on the Internet. This requirement exists because the way a browser fetches a page is to establish a TCP connection to the machine where the page is. and then send a message over the connection asking for the page. If it cannot establish a TCP connection to an arbitrary machine on the Internet, a browser will not work. Sometimes the lengths that people will go to get Web access are amazing At least one company is offering Web-by-Fax service. A client without Internet access calls up the Web-by-Fax server and logs in using the telephone keypad. He then types in a code identifying the Web page desired and it is faxed to the caller’s fax machine.