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CE80N CE80N Introduction to Introduction to Networks Networks & & The Internet The Internet Dr. Chane L. Fullmer UCSC Winter 2002 Happy Valentines Day
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CE80NCE80NIntroduction to NetworksIntroduction to Networks
&&The InternetThe Internet
Dr. Chane L. Fullmer
UCSC
Winter 2002
Happy Valentines
Day
February 14, 2002 CE80N -- Lecture #12 2
General InformationGeneral Information
TA Office…– Trailer #15 is no more– TA offices moved to the ISB– However… confusion abounds
• Regents meeting in ISB• For now.. Meet in Jacks Lounge
February 14, 2002 CE80N -- Lecture #12 3
Web Search based EssayWeb Search based Essay
Essay based on Web search results– 1-2 pages on any topic of interest– Must include results from at least four
Web page references– References must be listed in a
bibliography
Due Tuesday, February 26, 2002
February 14, 2002 CE80N -- Lecture #12 4
Class InformationClass InformationWeb page tutorial available on-lineWeb page submission:
– Email to [email protected]• Subject: cmpe080n-assgn4
Final Exam – Last class session
• March 14, 2002
February 14, 2002 CE80N -- Lecture #12 5
Personal Web PagesPersonal Web Pages
Jon Otsuki’s web page– http://www.melodramatic.com/users/jotsuki/
February 14, 2002 CE80N -- Lecture #12 7
Description of FunctionalityDescription of Functionality
A browsing service can perform many tasks.
– Obtain textual information, recorded sounds or graphics
– Display the retrieved information automatically
– Store a copy of retrieved information on disk
– Print a copy of retrieved information on paper
– Follow a reference found in a document
February 14, 2002 CE80N -- Lecture #12 8
Browsing Vs. Information Browsing Vs. Information RetrievalRetrieval
Information retrieval services do not display the contents of documents for users.
A browsing service permits users to view information from remote computers.– Displays the contents– Allows the user to select related documents
February 14, 2002 CE80N -- Lecture #12 9
Early Browsing Services Used Early Browsing Services Used MenusMenus
Gopher popularized a menu-driven approach to information browsing.– Displayed a menu of
choices– Designed to fit on the
user’s screen
February 14, 2002 CE80N -- Lecture #12 10
A Menu Item Can Point To A Menu Item Can Point To Another ComputerAnother Computer
A browser can jump from one computer to another without the user knowing.– Hides boundaries completely– Makes information appear as if a part of
a single integrated system
February 14, 2002 CE80N -- Lecture #12 11
How A Browser WorksHow A Browser Works
Browsing services use client-server interaction .
A user:– Invokes a browser program on the local
computer– Interacts with the browser to control the
selection– Displays information
Browser Client-Server InteractionBrowser Client-Server Interaction
Figure 22.1 A browsing service using client-server interaction. Multiple servers run continuous; the browser is a client that contacts one server at a time.
February 14, 2002 CE80N -- Lecture #12 13
An Example Point-And-Click An Example Point-And-Click InterfaceInterface
A user slides the mouse across the desktop until the cursor shows as an arrow.– Double-clicks on desired item– Fetches the selected item
WIMP environment– Windows, Icons, Menus, Pointer
Figure 22.2 An example of the way gopher presents information on a computer that has a mouse. In the example, the cursor is an arrow that moves as the user moves the mouse.
February 14, 2002 CE80N -- Lecture #12 15
Combining Menu Items With Combining Menu Items With TextText
Recent browsing services :– Embed menu items directly in the text
• hypertext
– Make selection easier since surrounding text adds context
• Complexity is hidden from the user
Example: HypertextExample: Hypertext
Figure 22.3 An illustration of six documents with text obscured except for the title and references to other documents. An arrow has been drawn between a word or phrase and the document it references.
February 14, 2002 CE80N -- Lecture #12 17
MultimediaMultimedia
Modern computer systems can:– Display multiple colors, geometric shapes and
diagrams with animation– Display still or moving pictures– Can emit (or record) audio – Can reproduce the sound of speech or music
Multiple media systems are often called multimedia computers.
Example: HyperExample: Hypermediamedia
Figure 22.4 The conceptual organization of a hypermedia document. When a user selects hear the sounds, the computer plays stored audio. When a user selects view the sights, the computer displays the stored images.
February 14, 2002 CE80N -- Lecture #12 19
The World Wide WebThe World Wide Web
The WWW is a service that links together information stored on many computers.– Allows references in a document on one
computer to refer to information stored on another computer.
– The Web is the most popular service on the Internet
February 14, 2002 CE80N -- Lecture #12 20
Browser Software Used To Browser Software Used To Access The WebAccess The Web
The first Web browser was developed at the National Center for Supercomputer Applications. (NCSA)– Called Mosaic– Controlled user’s display– Permitted user to navigate through
hypermedia
Today we are left mostly with Netscape and Internet Explorer
February 14, 2002 CE80N -- Lecture #12 21
An Example Hypermedia DisplayAn Example Hypermedia Display
Figure 22.5 A hypothetical example of how WWW information can be displayed by a Web browser. Any highlighted item, whether text or a graphic image, can be selected.
February 14, 2002 CE80N -- Lecture #12 22
Control Of The BrowserControl Of The Browser
Many browsers divide the display window into two areas.
Main area.
-- Hypermedia
Control area
-- Pulldown Menus
-- Icons
February 14, 2002 CE80N -- Lecture #12 23
Recording the Location of Recording the Location of InformationInformation
The WWW assigns each page of information a unique identifier.– Known as a URL
• Uniform Resource Locator
– Uses precise syntax to retrieve information
February 14, 2002 CE80N -- Lecture #12 24
Hypermedia DisplayHypermedia Display
Figure 22.5 A hypothetical example of how WWW information can be displayed by a Web browser. Any highlighted item, whether text or a graphic image, can be selected.
Example display – retrieved pageExample display – retrieved page
Figure 22.6 An example display that corresponds to the item in Figure 22.5 labeled Types of rocking chairs.
http://www.hrocker.com/types
February 14, 2002 CE80N -- Lecture #12 26
BookmarksBookmarks
Bookmarks allow users to keep a list of their favorite URLs.– AKA Hotlist– Are permanent
• Saved in a file– Can be edited
– Are convenient• Don’t have to remember long URLs
February 14, 2002 CE80N -- Lecture #12 27
How The World Wide Web WorksHow The World Wide Web Works
The WWW uses client-server interaction.– Uses HTTP (HyperText Transfer Protocol)
The client:– Uses the Internet to contact a remote server
The server:– Returns a copy of the requested page with
additional information The URL determines the location of the server.
– Computer name is part of the URL
Example URLExample URL
Figure 22.7 The meaning assigned to each part of a URL. Not all URLs require all parts.
February 14, 2002 CE80N -- Lecture #12 29
Use Of The Name WWW In URLsUse Of The Name WWW In URLs
The domain name in a URL does not need to begin with WWW.– Provides a uniform name– Makes the name easy to remember– Usually aliases another computers
name• www.cse.ucsc.edu coyote.cse.ucsc.edu• Mapping can be many names to one
address
February 14, 2002 CE80N -- Lecture #12 30
URL DefaultsURL DefaultsNot all parts are always necessary in
the URLhttp:// type prefix is impliedwww. server name is impliedIndex.html page name is impliedExample: entering “ucsc.edu”
– Implies: “http://www.ucsc.edu/index.html”
February 14, 2002 CE80N -- Lecture #12 31
A Browser Provides Access To A Browser Provides Access To Multiple ServicesMultiple Services
The WWW provides access to multiple services.– Accesses information from the gopher
service– Transfers files– Employs the same
technique as a business card• Initial string specifies where the number can
be used
February 14, 2002 CE80N -- Lecture #12 32
Inside the browserInside the browser
Browser software must contain different clients to handle variety of interaction:– HTTP client for WWW pages– FTP client for file transfers– Email client– News client– Other……..
February 14, 2002 CE80N -- Lecture #12 33
Inside A Browser ProgramInside A Browser Program
Figure 22.8 Conceptual organization of a browser. A user interacts with a single, uniform interface that uses information in the URL to choose one of the built-in client programs to access information on the Internet.
February 14, 2002 CE80N -- Lecture #12 34
Example Questions for the FinalExample Questions for the Final
What makes a computer a multimedia system?
What are the parts of a URL?
February 14, 2002 CE80N -- Lecture #12 36
GlossaryGlossary
Bookmark – A facility in a browser used to record
the location of a particular page, making it possible to return to the page later.
Browsing – The act of looking through information
by repeatedly scanning and selecting.
February 14, 2002 CE80N -- Lecture #12 37
GlossaryGlossary
Gopher – The name of an early Internet browsing
service in which all information is organized into a hierarchy of menus.
Information browsing service – A service that permits a user to browse
information by repeatedly scanning and selecting.
February 14, 2002 CE80N -- Lecture #12 38
GlossaryGlossary
Menu – A list of items from which a user can select.
Point-and-click Interface – A style of interacting with a computer that uses a
mouse instead of a keyboard.
February 14, 2002 CE80N -- Lecture #12 39
GlossaryGlossary
Textual Interface – A style of interacting with a computer that
uses a keyboard.
WIMP– Windows, Icons, Menus and Pointer. A
graphical-user-interface environment such as M$ Windows, X or the Macintosh interface.
