What is the main purpose of a web browser?

to render HTML and display web pages. It turns HTML into the page you see.

What does a domain name server (DNS) do?

finds the IP address that matches a domain name. It works like a phone book for the internet.

Where does the HTML of a web page come from?

the web server. The web server sends it to the browser.

What is the difference between HTTP and HTTPS?

HTTPS encrypts the data that is sent. The S stands for secure.

Which of these is a function of a web browser?

storing bookmarks. Others are recording history, allowing tabs and storing cookies.

What happens if the first DNS does not know the IP address for a domain name?

It passes the request on to another DNS. The request is passed on until a DNS that knows the address is found.

Browsers, DNS and how a web page reaches you · Cambridge IGCSE Computer Science (9

In plain words

You type an address and a page appears a second later. In that second, your browser has asked one computer where the page lives, asked another for the page itself, and turned what came back into the picture on your screen.

6 things to know

A web browser's main purpose is to render HTML and display web pages. HTML is the language web pages are written in.
A browser also stores bookmarks and favourites, records the user's history, allows several tabs, stores cookies, and provides navigation tools and an address bar.
When a URL is entered, the browser sends it to a domain name server (DNS). The DNS looks up the domain name and returns the IP address of the web server.
If that DNS does not have the address, it passes the request on to another DNS.
The browser sends a request to the web server at that IP address. The web server sends back the HTML for the page, and the browser renders it and displays it.
HTTP (hypertext transfer protocol) is the set of rules for sending web pages. HTTPS is the secure version: the data is encrypted as it travels.

Worked example

A user types a URL into a browser. Describe how the web page is found and displayed.

The browser sends the URL to a domain name server.
The DNS finds the IP address that matches the domain name and sends it back to the browser.
The browser sends a request to the web server at that IP address.
The web server sends the HTML of the page to the browser, which renders it and displays the page.

Tips and tricks

The DNS does not store or send web pages. It only turns a domain name into an IP address.
"Render HTML" is the phrase for what a browser does. "Opens the internet" earns nothing.

6 questions, about 2 minutes.

It lands in your notebook with its questions as flashcards.

Browsers, DNS and how a web page reaches you: 6 questions and answers

These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.

What is the main purpose of a web browser?
- to store files
- to render HTML and display web pages (the answer)
- to send email
- to assign IP addresses
It turns HTML into the page you see.
What does a domain name server (DNS) do?
- stores every web page
- finds the IP address that matches a domain name (the answer)
- encrypts web pages
- blocks viruses
It works like a phone book for the internet.
Where does the HTML of a web page come from?
- the DNS
- the browser's bookmarks
- the web server (the answer)
- the router
The web server sends it to the browser.
What is the difference between HTTP and HTTPS?
- HTTPS is faster.
- HTTPS encrypts the data that is sent. (the answer)
- HTTP is newer.
- HTTP is only for images.
The S stands for secure.
Which of these is a function of a web browser?
- assigning MAC addresses
- storing bookmarks (the answer)
- compiling programs
- hosting websites
Others are recording history, allowing tabs and storing cookies.
What happens if the first DNS does not know the IP address for a domain name?Stretch
- The page cannot be found.
- It passes the request on to another DNS. (the answer)
- It makes up an address.
- It asks the user.
The request is passed on until a DNS that knows the address is found.

6 questions

Tap an answer and you’ll see straight away whether it’s right, and why.

Worksheet

2 questions, 6 marks. Write your answers on paper, then check them.

Browsers, DNS and how a web page reaches you

Cambridge IGCSE Computer Science (9–1) 0984 · 6 marks · papermunch.org

Name ______________________________ Date ______________

Describe the role of the domain name server (DNS) and the web server when a user requests a web page.[4]
Show answerHide answer
The DNS looks up the domain name from the URL and returns the IP address of the web server. The web server, at that IP address, receives the browser's request and sends back the HTML of the web page.
I got this one
Describe the difference between HTTP and HTTPS.[2]
Show answerHide answer
Both are protocols for transferring web pages. HTTPS is secure: the data is encrypted while it is transmitted.
I got this one

Answers: Browsers, DNS and how a web page reaches you

1. The DNS looks up the domain name from the URL and returns the IP address of the web server. The web server, at that IP address, receives the browser's request and sends back the HTML of the web page.
2. Both are protocols for transferring web pages. HTTPS is secure: the data is encrypted while it is transmitted.