How the Web Works

The Web is the World-Wide-Web of web pages that are interconnected through hyper-text. Hyper-text once referred to text that could contain links to other web pages but now hyper-text can include movies, animations, sounds, and interactive forms. Web pages are written in Hyper-Text Mark up Language (HTML) and transferred between computers using Hyper-Text Transfer Protocol (http).

The Internet

The Internet is the Interconnected Network of computers that started with a few computers in the United States of America and now includes millions of computers around the world. The Internet is the single most important development in human communication since the printing press.

Every computer on the Internet has an assigned Internet Protocol address or IP Address. This address uniquely identifies each computer just as each house in a neighborhood has a unique physical address. These addresses take the form of 4, single-byte numbers (from 0 to 255) separated by periods. Examples include "158.58.47.18" and "127.0.0.1".

Clients and Servers

All computers on the Internet are either a client or a server (and sometimes both).

• Client: requests and receives data
• Server: receives requests and serves data

To put a web page on the web, you need a server. These are dedicated computers that are typically stored in environmentally controlled rooms and managed by an Information Technology (IT) department. While HSU maintains servers for web sites, HSU no longer provides a means for students to create web sites so we will be using an external hosting company.

Requesting a Page

Everything you see in a browser was transferred from a server computer to a client computer.

1. Client sends an request with a Uniform Resource Locator (URL) to a server
2. Server finds the file based on the URL and returns it
3. Requests can be for HTML files or mpegs, jpegs, gifs, etc.

When you enter "www.google.com" into your browser, your client computer sends this URL to the server and the server then returns an HTML page (or an error).

Dissecting a URL

URLs can be divided up into pieces. In the example below, the http specifies the hyper-text transfer protocol. There are other protocols on the Internet but this is the most commonly used as it transfers HTML pages. After the "http://" is the domain name or IP address. Domain names can be registered on special servers on the web that turn them into IP addresses. The IP address then specifies the server to send the request to, in this case, one at Google.

• http://www.google.com
  • http: = hypertext transfer protocol
  • www.google.com = server address

Following the domain name, you can have the path to a file stored on the server. These files can be HTML pages, images, or scripts. If there is a question mark (?) after the file path, then there are additional parameters that will be passed to the script. If you take a look at the URLs generated by many web sites, you'll see them using this format.

• https://gsp.humboldt.edu/websites/HSUBotanicalMap/CM2DMap.html?Editing=true
  • /websites/HSUBotanicalMap/CM2DMap.html
    • This is a file path to the file that will be loaded by the browser. Notice that this looks like any other file path you've used except it does not start with a drive letter. Instead, it is in a special folder (wwwroot) on the server.
  • ?Editing=true
    • This is a parameter that is sent to the web server and then on to the file that is loaded. Files are not just HTML, they can be "script" that excecute code on the server. In this case, we're passing the value "true" into a variable "Editing" which will add additional editing features to the web page.
  • Note: Parameters can be hidden so you won't always see them in the URL

Definitions

Refer back to the definitions below periodically as they are important in developing web sites and will appear on quizzes!

Internet - The "Interconnected Network" of computers. The "Internet" refers to the client and server computers that are physically (or wirelessly) connected throughout the globe. The "Web" runs on top of the Internet.

World Wide Web or "The Web" - The Web is the set of HTML documents that are linked together and are viewed through a browser. This creates a "web" of documents.

Hypertext - Text that is "linked" to other text. This includes links in web pages that link to other pages or to an area within the same page (in HTML, links point to "anchor" tags).

Hypertext Transfer Protocol or HTTP - The protocol that is used to transfer HTML documents, and images, for the Web.

Uniform Resource Locator or URL - The string of text that uniquely identifies a "resource", typically a file, in the Web. Also known as a "link" or "hypertext reference" or "href". URLs appear in the text box at the top of your browser, "http://www.google.com" is one example.

Note that the Internet supports a wide variety of protocols for mail, file transfer, and hypertext. The Internet is even used by your ATM when you get cash from your bank account. When you open a browser, you may see "http" or "https" as part of the URL. Some browsers are now hiding this but it is still there and indicates that you are using the HTTP protocol to communicate between your computer and the server.

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