8b. URLs: Pointers to the Internet

URL? Earl? Yurl? hurl? gyrl?
It's getting time to link to that Big Wide Web using the web's addressing scheme.

Objectives

After this lesson you will be able to:

Identify the function of Uniform Resource Locators (URLs).
Recognize the structure of a URL.
Examine the URLs in the hypertext links of any web page.

Lesson

Note: For this lesson, you will not need your HTML text file. This is another low-effort lesson!

What is a URL?

The Uniform Resource Locator (URL) is what the WWW uses to find the location of files and documents from computers on the Internet. On your web browser screen, the URL for this document is typically displayed in the upper part of the Web browser window. The URL includes:

an identifier for the type of Internet server;
an Internet address; and
a file path to the particular item of interest.

The URL is what you will need to build a link from the web page that you are creating to connect to some other piece of information available on the Internet. For more information, see Curling Up To URLs (v0.2)

How are URLs Structured?

The structure of a URL is:

    type://in.ter.net.address/directory/sub-directory/.../filename

The "type" indicates the type of Internet server being accessed:

http: a web server, "HTTP" stands for HyperText Transfer Protocol
gopher: an Internet Gopher site or menu driven directories of files and information
ftp: an anonymous File Transfer Protocol (FTP) site, archives of files.br>
telnet: initiates a Telnet session to log on remotely to another computer When selected, your web browser will launch a Telnet external program and connect to the specified site.
WAIS: Wide Area Indexed Server -- a site to search a collection of subject oriented documents by keywords
file: A file on your local computer system (hard drive, floppy, local file server)

The type is always followed by "://" and the Internet address of a remote computer. This is in the structure of:

     host.domain.domain.domain

For example:

     machine.department.college.edu
     123.45.6.78
     office.company.com
     agency.branch.gov
     machine.organization.country

If the URL is to the main level of this host (its "home page"), then the URL is terminated with a slash "/". If you are linking to a sub-directory or a file, you must also add the exact path to that item using the slash character to indicate the entire file path.

Note: For most web servers spelling does count! So does capitalization! File names on UNIX computers are case sensitive, meaning that a file named
SpiffyText.html
is a different file than
spiffytext.html

Experimenting With URLs

Note that URLs can link to any site, directory, subdirectory, text file, image, digital movie, or sound file on any Internet site that is set up for public access. The best way to see different URLs is just to move your mouse over any hypertext link in any web page -- if you look at the bottom of your web browser, it should display the URL that you would connect to if you clicked on that link. You could go to a big site such as Yahoo and "peek" at URLs (did you see the URL for Yahoo when you moved your mouse over the link in the this sentence?)

Here is an easy way to copy a URL for a link in any page. You first must access the "secret" pop-up menu from any hypertext link in a web page -- click and hold the mouse for Macintosh; click the right mouse button for Windows and Unix. From this menu, select Copy This Link Location (or similar menu item). After releasing the mouse button, jump to any text document and select Paste from the Edit menu. Voilà! You've just nabbed a URL from a link in the web page (this way, you can copy a URL without even visiting the page it links to!)

Review Topics

What purpose do URLs serve for the World Wide Web?
Where are URLs found on a WWW screen?
What is the basic structure of an URL?
How can you see the URLs that a hypertext link will jump to?

Independent Practice

Find some sites on the Internet that intrigue you. For each one, record its name and its URL displayed near the top of your browser window. See if you can copy and paste the URLs into a text document. You will use this list later to add links from your own web pages to these sites that you found.

Coming Next....

You will use URLs in anchor tags to create links to files on the Internet for your Volcano Web page.

GO TO.... | Lesson Index | previous: " Links to Local Files" | next: "Links to the Internet" |

Writing HTML: Lesson 8b: URLs: Pointers to the Internet
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