← IGCSE Computer Science Paper 1

Why domain names are used instead of IP addresses

An easy-to-remember name, like example.com, that stands in for a numeric IP address. It must be converted into the IP address before the computer can find the web server.

Part of: IGCSE Computer Science 0478 — 5.1 The Internet and the World Wide Web — Module 27, ACARA Digital Technologies Years 9–10 — Networked Systems and Access Control — Module 28, WA Computer Science ATAR Year 11 — Network Communications — Module 59

Understanding Why domain names are used instead of IP addresses in IGCSE Computer Science Paper 1

What it does: The name version is short and memorable, while the number version is hard to recall and easy to mistype. The name still points to the site after the move; only the stored IP address behind the name is updated, so users keep typing the same name. People find words easier to remember than long strings of numbers. Computers still use the numeric IP address to find the server. Computers locate servers using IP addresses. The domain name must first be converted into the IP address.

Common mistakes: The DNS table is keyed by domain name, and ip does not exist yet. The lookup must use the name: ip = dns[name]. Each domain name matches one IP address, so the name is the key you look up. It should be print(table["shop.com"]), which returns the IP.

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Learning
Duo
Why do websites use domain names like example.com as well as IP addresses?
Computers find names faster than numbersNames are easier for people to remember than numbers
Matches
A computer uses www.example.com directly to find the web server
↓
Computers cannot use a domain name directly. The name must first be converted into a numeric IP address, which is used to find the server.
Applying
Meanings
Term
domain name
Meaning
An easy-to-remember name, like example.com, that stands in for a numeric IP address. It must be converted into the IP address before the computer can find the web server.
Practice
name ← "www.example.com"
Testing
Gaps
www.example.com is a
Check Answer
Spots
3name = "example.com"
4ip = dns[ip]

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Quick Questions

1. Why do websites use domain names like example.com as well as IP addresses?
A. Computers find names faster than numbers
B. Names are easier for people to remember than numbers ✓
People find words easier to remember than long strings of numbers. Computers still use the numeric IP address to find the server.
2. Which does a computer need in order to locate a web server on the internet?
A. The numeric IP address ✓
B. The domain name alone
Computers locate servers using IP addresses. The domain name must first be converted into the IP address.
3. Which of these is the easier address for a person to remember?
A. www.bbc.co.uk ✓
B. 151.101.0.81
A domain name uses words that are simple to remember, while an IP address is a string of numbers that is hard to remember.
4. What must happen to a domain name before the browser can contact the web server?
A. It must be converted into a URL
B. It must be converted into an IP address ✓
A DNS server converts the domain name into the matching IP address. The browser then uses that address to reach the web server.
5. How many IP addresses does one domain name match to?
A. One domain name matches one IP address ✓
B. One domain name matches every IP address on the internet
Each domain name is linked to one IP address, so the name points to a single web server address.

Match the Pairs

www.example.com → A domain name: easy for people to remember and type instead of a number
93.184.216.34 → An IP address: the numeric address computers actually use to find a web server
People find names easier to remember than numbers, so a website is typed as a name rather than as numbers → https://www.bbc.co.uk instead of https://151.101.0.81
The IP address of a server can change, but the domain name stays the same so users are not affected → www.shop.com: 203.0.113.5 changes to 203.0.113.9
A computer uses www.example.com directly to find the web server → Computers cannot use a domain name directly. The name must first be converted into a numeric IP address, which is used to find the server.
If a website changes its IP address, everyone must learn a new domain name → The domain name stays the same when the IP address changes. Only the address linked to the name is updated, so users notice nothing.

Key Term

domain name
An easy-to-remember name, like example.com, that stands in for a numeric IP address. It must be converted into the IP address before the computer can find the web server.

Fill in the Blanks

1. www.example.com is a domain name
Hint: Type the term for an easy-to-remember name that people type instead of numbers
2. 93.184.216.34 is an IP address
Hint: Type the term for the numeric address that computers use to find a server
3. 1 domain name = 1 IP address
Hint: Type the number of IP addresses that one domain name matches
4. Name stays the same, IP address can change
Hint: Type the word that describes what happens to the domain name when the IP address changes
5. A DNS server converts names into IP addresses
Hint: Type the three-letter abbreviation for the system that converts a name into an address

Spot the Error

Question 1
A dns = {}
B dns["example.com"] = "93.184.216.34"
C name = "example.com"
D ip = dns[ip]
Line D — The DNS table is keyed by domain name, and ip does not exist yet. The lookup must use the name: ip = dns[name].
Question 2
A table = {}
B table["shop.com"] = "10.0.0.5"
C print(table["10.0.0.5"])
Line C — Each domain name matches one IP address, so the name is the key you look up. It should be print(table["shop.com"]), which returns the IP.
Question 3
A site = example.com
B ip = lookup(site)
C print("Connecting to", ip)
Line A — The domain name is text, so it must be in quotes: site = "example.com".
Question 4
A name = "shop.com"
B dns["10.0.0.5"] = name
C dns[name] = "10.0.0.9"
D print(name)
Line B — The name is the key and the IP address is the value. It should be dns[name] = "10.0.0.5". The IP can later be changed while the name stays the same.
Question 5
A name = "bank.com"
B ip = dns(name)
C print("IP is", ip)
Line B — dns is a table (dictionary), so you look up a name with square brackets: ip = dns[name]. Round brackets would try to call it like a function.

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