CE80N Introduction to Networks & The Internet Dr. Chane L. Fullmer UCSC Winter 2002 Happy Valentines Day

February 14, 2002CE80N -- Lecture #122 General 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, 2002CE80N -- Lecture #123 Web 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, 2002CE80N -- Lecture #124 Class Information Web page tutorial available on-line Web page submission: – to Subject: cmpe080n-assgn4 Final Exam –Last class session March 14, 2002

February 14, 2002CE80N -- Lecture #125 Personal Web Pages Jon Otsuki’s web page –

February 14, 2002CE80N -- Lecture #127 Description 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, 2002CE80N -- Lecture #128 Browsing Vs. Information Retrieval 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, 2002CE80N -- Lecture #129 Early Browsing Services Used Menus Gopher popularized a menu-driven approach to information browsing. –Displayed a menu of choices –Designed to fit on the user’s screen

February 14, 2002CE80N -- Lecture #1210 A Menu Item Can Point To Another 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, 2002CE80N -- Lecture #1211 How 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 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, 2002CE80N -- Lecture #1213 An Example Point-And-Click Interface 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, 2002CE80N -- Lecture #1215 Combining Menu Items With Text 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: 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, 2002CE80N -- Lecture #1217 Multimedia 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: Hypermedia 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, 2002CE80N -- Lecture #1219 The 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, 2002CE80N -- Lecture #1220 Browser Software Used To Access 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, 2002CE80N -- Lecture #1221 An 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, 2002CE80N -- Lecture #1222 Control Of The Browser Many browsers divide the display window into two areas. Main area. -- Hypermedia Control area -- Pulldown Menus -- Icons

February 14, 2002CE80N -- Lecture #1223 Recording the Location of Information 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, 2002CE80N -- Lecture #1224 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.

Example display – retrieved page Figure 22.6 An example display that corresponds to the item in Figure 22.5 labeled Types of rocking chairs.

February 14, 2002CE80N -- Lecture #1226 Bookmarks 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, 2002CE80N -- Lecture #1227 How 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 URL Figure 22.7 The meaning assigned to each part of a URL. Not all URLs require all parts.

February 14, 2002CE80N -- Lecture #1229 Use 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  coyote.cse.ucsc.eduwww.cse.ucsc.edu Mapping can be many names to one address

February 14, 2002CE80N -- Lecture #1230 URL Defaults Not all parts are always necessary in the URL type prefix is implied www. server name is implied Index.html page name is implied Example: entering “ucsc.edu” –Implies: “

February 14, 2002CE80N -- Lecture #1231 A Browser Provides Access To Multiple 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, 2002CE80N -- Lecture #1232 Inside the browser Browser software must contain different clients to handle variety of interaction: –HTTP client for WWW pages –FTP client for file transfers – client –News client –Other……..

February 14, 2002CE80N -- Lecture #1233 Inside 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, 2002CE80N -- Lecture #1234 Example Questions for the Final What makes a computer a multimedia system? What are the parts of a URL?

February 14, 2002CE80N -- Lecture #1236 Glossary 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, 2002CE80N -- Lecture #1237 Glossary 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, 2002CE80N -- Lecture #1238 Glossary 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, 2002CE80N -- Lecture #1239 Glossary 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.X