Web Pages (Cambridge (CIE) O Level Computer Science)
Revision Note
Author
Robert HamptonExpertise
Computer Science Content Creator
Loading a Web Page
How is a web page loaded?
Web pages are held on web servers (1), known as 'hosting'
To access a web page on a web server, a web browser is used
In the browser, a user enters a web page URL (2)
The browser sends the domain name to a DNS (3)
The browser connects to the web server and requests to access the page
HTML (4) is transferred and rendered by the browser, displaying the web page
Web Servers (1)
What is a web server?
A web server is a remote computer that stores the files needed to display a web page on the Internet
Web servers are generally available 24/7 and security is managed by the owner of the hardware
Web servers provide access to multiple users at the same time
Uniform Resource
Locator (URL) (2)
What is a URL?
A Uniform Resource Locator (URL) is a unique identifier for a web page, known as the website address
A user enters a URL into a web browser to view a web page
An example of a URL is:
https://www.savemyexams.com/igcse/computer-science/cie/23/revision-notes/
A URL can typically be split into three parts:
Protocol
Domain name
Web page/file name
Using the example about the URL would be split as follows:
Protocol | https | Communication method to transfer data between client and server |
|---|---|---|
Domain name | www.savemyexams.com | Name of the server where the resource is located |
Web page/file name | /igcse/computer-science/cie/23/revision-notes/ | Location of the file or resources on the server |
Domain Name System (DNS) (3)
What is a DNS?
The Domain Name System (DNS) can be thought of as the Internet's equivalent to a phone book
It is essentially a directory of domain names and is used to translate human-readable domain names to the numeric IP addresses that computers use
When you type a URL into your browser, the DNS translates the domain name into its associated IP address so your computer can connect to the server hosting the website
Without DNS, we would have to remember the IP address of every site we want to visit
HTML (4)
What is HTML?
Hypertext Markup Language (HTML), is the foundational language used to structure content on the web
HTML consists of a series of elements, often referred to as "tags," which can be used to structure and format a webpage
The
<html>tag is the root element of an HTML page. The tag includes all other HTML elements used on the pageMost tags are opened and closed e.g.
<html>and</html>whereas some tags are only opened e.g.<img>and<link>The content layer of a web page is made up of HTML elements such as headings (
<h1>, <h2>, etc.), paragraphs (<p>), links (<a>), images (<img>), and more
Worked Example
A company sells products over the Internet.
Explain how the information stored on the company’s website is requested by the customer, sent to the customer’s computer and displayed on the screen.
[7]
Answer
Seven from:
Requested
a web browser is used
user enters the URL / web address (into the address bar) // clicks a link containing the web address // clicks an element of the webpage
the URL / web address specifies the protocol
protocols used are Hyper Text Transfer Protocol (HTTP) / Hyper Text Transfer Protocol Secure (HTTPS)
Sent
the URL / web address contains the domain name
the domain name is used to look up the IP address of the company
the domain name server (DNS) stores an index of domain names and IP addresses
web browser sends a request to the web server / IP address
Received
Data for the website is stored on the company’s web server
webserver sends the data for the website back to the web browser
web server uses the customer’s IP address to return the data
the data is transferred into Hyper Text Mark-up Language (HTML)
HTML is interpreted/rendered by the web browser (to display the website)
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