The web, DNS, cookies and cloud services
Trace a URL from browser to web server, then explain cookies and public, private and hybrid cloud storage.
Section Component 1 · Computer Systems and Logic
Mapped to the Cambridge IGCSE Computer Science 0265 syllabus for exams in 2029. These original explanations and self-checks are independent study support, not Cambridge papers, official marks or grades. Practical programming is taught with worked code and trace tasks; an executable Python workspace and timed digital-exam simulation are not yet available.
Before you begin
- Use the 2029 syllabus for this course. Cambridge specifies Python 3.10 or higher for programming and digital exams for both components. The syllabus currently identifies this route for 2029 only; confirm later-year availability with Cambridge and your school.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Before the web, dns, cookies and cloud services, which statement is the safest starting point?
What you will learn
- Describe URLs, HTTP/HTTPS and the browser–DNS–server process
- Explain session and persistent cookies
- Evaluate local and cloud storage choices
A browser finds and displays a web resource
A URL identifies a web resource and includes a scheme such as HTTP or HTTPS, a domain name and often a path. DNS translates the human-readable domain to an IP address. The browser uses that address to request a resource from a web server, commonly using HTTP; HTML describes the page structure that the browser renders.
HTTPS is a secure version of HTTP that uses encryption to protect communication in transit. The browser requests a page, the server returns resources, and the browser interprets HTML and related content to display the page. Cookies are small text files stored by a browser to retain pieces of data for a site.
Cloud choices trade access against control
A session cookie is usually removed when the browsing session ends; a persistent cookie remains until its expiry or deletion. Sites can use cookies to remember choices or maintain a session, so users should understand privacy settings.
Cloud services provide computing or storage over a network. Public cloud resources are shared across customers, private cloud is reserved for one organisation, and hybrid combines the two. Cloud storage can enable access across devices and simplify collaboration, but depends on connectivity and provider security; local storage gives direct control but may be harder to share or back up.
Pause and explain
Which habit best checks your understanding of the web, dns, cookies and cloud services?
Worked example
A learner enters https://learn.example/course into a browser. Put DNS and the web server into the correct sequence.
Show the worked solution
- The browser separates the domain learn.example from the path /course.
- DNS resolves the domain to an IP address.
- The browser requests the resource from the server at that address, then renders returned HTML.
Answer Browser asks DNS for the address, then requests the page from the web server.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Describe the purpose of the scheme, domain and path in https://study.example/units/4.
Give me a hint
Separate how communication is made, which host is contacted and which resource is requested.
Compare my reasoning
- https specifies the secure protocol for communication.
- study.example is the domain name that DNS can resolve.
- /units/4 identifies a resource path on that server.
Scheme: HTTPS; domain: study.example; path: /units/4.
Look for these in your work
- Three URL parts named
- Purpose of scheme
- Host/resource distinction
Compare a session cookie with a persistent cookie, and give one appropriate use for each.
Give me a hint
Focus on how long each lasts, then connect it to a site task.
Compare my reasoning
- A session cookie lasts for the browsing session, such as keeping a user signed in while navigating.
- A persistent cookie remains until its expiry or deletion, such as remembering a preference.
- Both store small pieces of browser data and should be managed with privacy in mind.
Session: temporary session state; persistent: saved preference or similar state until expiry/deletion.
Look for these in your work
- Lifetime contrasted
- Use cases matched
- Privacy considered
A school stores public course videos in a cloud service but keeps confidential student records on its own private systems. Explain the possible model and one trade-off.
Give me a hint
Identify whether services are combined and compare accessibility with control.
Compare my reasoning
- Using cloud resources for some data and private systems for other data is a hybrid approach.
- Cloud videos can be accessed from different locations and may scale easily.
- Confidential records need access controls; the school must still manage security, backups and network dependence.
Hybrid use can fit different needs, balancing access and scale against control, security and connectivity.
Look for these in your work
- Model identified
- Benefit linked
- Risk/control discussed
Common mistakes
- Saying DNS sends the page contents.
- Claiming HTTPS proves a website is trustworthy.
- Assuming every cloud service is public cloud.
What can you explain now?
What does DNS translate for a browser?
Compare with the explanation
A domain name to an IP address
The browser needs an address to locate the web server.
After trying it yourself, choose your next review. This is your self-assessment.
Your review choice appears on Today. Sign in to sync it across devices.
Make it stick
Trace how a browser uses DNS and HTTP(S), and compare cookie lifetimes and cloud models.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.