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The Internet Book Chapter 23 Display Hardware Varies • A variety of computers around the world are used to display web pages. 3 A Browser Translates And Displays A Web Document • A Web page is created to be used with any display hardware. • The computer language provides general display guidelines without giving details. 4 A Consequence of the Web Approach • The same web page may appear differently. – Using different browsers – Using different computer hardware 5 HTML • Each web page is written in Hypertext Markup Language. –Has its own grammar rules –Uses punctuation symbols in unusual ways –Does not show spaces on displayed page 6 Instructions On A Web Page Control The Output • Tags are instructions that tell a browser how to display the page. –Uses brackets < >to indicate a tag –Uses tags in pairs (usually) 7 A Web Page is Divided Into Two Main Sections • The two main sections of a web page are: – Heading • <HEAD> • </HEAD> – Body • <BODY> • </BODY> 8 Indentation Can Make HTML Readable • Indentation makes it easier for people to read. – Place tags on separate lines – Indent items • This is important when updating. – Not done by the original creator as a rule 9 HTML Text • HTML uses tags to organize text into paragraphs. –Tells the browser to end one paragraph and begin the next •<P> –Tells the browser to end the line and start a new line •<br> 10 A Web Page Can Link To Another Page • Items that correspond to a link are anchored. – Use tags: • <A> • </A> – Use HREF to specify a link to a page: • <A HREF=“http://www.site.com”> Link </A> 11 HTML Allows Numbered And Unnumbered Lists • HTML can be used to create a numbered (Ordered) list. – Uses tags: • <OL> • </OL> • For an unnumbered (Unordered) list. – Use tags: • <UL> • </UL> 12 Images On A Web Page Are Digital • Images must be converted into numbers stored in a file. • Two methods of digitizing a picture are: –To use a digital camera –To use a scanner 13 Figure 23.8 Figure 23.8 Illustrations of (a) a digital scanner, and (b) a digital camera. Either produces a file stored on the computer’s disk. Digital Image Formats • There are two popular forms of representing digital images. –Including: •Graphics Image Format (GIF) •Joint Picture Encoding Group (JPEG) 15 HTML Allows A Web Page To Include An Image • Once an image has been stored on a hard disk, a web page can reference the file. –Uses the tag: •<IMG SRC=“xxx.gif”> 16 Text Can Appear Adjacent To An Image • An image on a web page can appear by itself or adjacent to text. • HTML treats an image like an oversized “word” 17 Figure 23.9 Figure 23.9 (a) Part of a Web page that includes an image along with text, and (b) the result when a browser displays the web page. A browser treats an image like a giant word. Text Can Be Aligned • HTML provides a way to control the details of how an image is aligned with surrounding text. –Using the ALIGN tag •ALIGN=TOP •ALIGN=CENTER 19 Figure 23.10 Figure 23.10 (a) Part of a Web page that combines images with text, and (b) an illustration of how a browser interprets the alignment requests. Images Can Link To Another Web Page • HTML uses the same pair of tags for text links as for image links. – Use: • <A HREF=“http://www.sample.com/ index.html”> <IMG SRC=“yyy.jpeg”> </A> 21 Some Browsers Can Stretch Or Shrink Images • The IMG tag may include image height and width. • Not all browsers can resize images. • It is best to store images in the desired size. 22 The Background Can Be Controlled • HTML allows one to specify the background of a Web page. –Choose the color –Specify the image 23 Other Features Of HTML • When a browser displays a table, it – Aligns information into • Rows • Columns • Multiple links may be associated with a single image. 24 Importance Of HTML • Before HTML, displayed combinations of text and graphics required complex computer programs. 25 GUI Tools Help With Web Page Creation • Web authoring tools make it possible to compose a web page without learning HTML. • Files are saved as HTML. 26 Conclusion • What is the significance of HTML? 27 28 Glossary • Homepage • – A page of information accessible through the World Wide Web that is the main page for an individual or a company. Hot List – The original term used for a list of bookmarks. Now essentially obsolete. 29 Glossary • Hypermedia • – An information storage system in which each page of information can contain embedded references to imags, sounds, and other pages of information. GUI – (Graphical User Interface) An interface tht presents the user with pictures and icons rather than words. 30 Glossary • Hypertext • – A system for storing pages of textual information that each contain embedded references to other pages of information. Mosaic – The first browser program for the World Wide Web. 31 Glossary • Multimedia • – A term describing any facility that can display text, graphics, images, and sounds. Uniform Resource Locator – (URL) A short character string used by browsers to identify a particular page of information on the World Wide Web. 32 Glossary • World Wide Web – (WWW) An Internet service that organizes information using hypermedia. 33
