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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