How the web actually gets to you
Typing an address starts a short conversation between machines. Knowing the steps makes debugging anything online much less mysterious.
Part of your national curriculum
- Computer systems and networks: Understand the hardware and software components that make up computer systems, and how they communicate with one another and with other systems
- Computer systems and networks: Understand how computer networks, including the internet, can provide multiple services such as the World Wide Web
Lesson overview
What you'll learn in this lesson
Describe how web pages are requested and delivered
Key learning points
- • Request and response
- • Client and server
This lesson at a glance
- 25 minutes
- 10 parts to scroll through
- 3 quick checks
- Marked quiz at the end
- Gentle pace: short sittings with pauses
Words to know
Scroll down — the lesson carries on below
Watch & discover
Part 1 of 10
Watch first
How the web actually gets to you
An English teaching video on this topic from CPD College. Watch it, then scroll down for the lesson.
In a nutshell
Describe how web pages are requested and delivered
Explore the idea
Part 2 of 10
Learn
Request and response
The browser looks up the domain through DNS, opens a connection to the server, sends an HTTP request, and receives HTML, CSS, images and scripts back.
Explore the idea
Part 3 of 10
Learn
Client and server
The server decides what to send; the browser decides how to display it. HTTPS encrypts the exchange so others on the network cannot read it.
Quick check
Part 4 of 10
Quick check
DNS turns a domain name into…
Quick check
Part 5 of 10
Quick check
HTTPS mainly provides…
Quick check
Part 6 of 10
Quick check
The browser is the…
Challenge round
Part 7 of 10
Game · Sort it
Which of these are true?
Drag each card into the right column. Tap a card first if dragging is fiddly.
True
Not true
Challenge round
Part 8 of 10
Game · Fill the gaps
Finish the sentences
Choose the word that belongs in each gap.
The browser looks up the domain through DNS, opens a connection to the server, sends an HTTP ____, and receives HTML, CSS, images and scripts back.
Mastery quiz
Part 9 of 10
Marked quiz
End of lesson quiz: How the web actually gets to you
3 questions, marked with the reasoning shown. No timer.
1. DNS turns a domain name into…
2. HTTPS mainly provides…
3. The browser is the…
Lesson round-up
Part 10 of 10
Lesson round-up
Ready when you are
Quiz score
Not sat
Games
Not played
Points this lesson
0
Best run
0 in a row
Luna: 0 out of 3 on the practice checks. Only if you feel up to it — one more?
Ask LunaDo the work
Your written work for this lesson
This is the part you'd do in your book at school. Pick the pieces below, write here or on paper, and photograph anything you draw or work out.
How a supermarket checkout knows the price
When a barcode is scanned, the checkout does not store the price itself. It sends the barcode number to a database and reads back a record: product name, price, whether it needs an age check. The record is the single place the price lives, so changing one row changes every till in the shop at once.
Problems come from bad data, not bad scanners. If two products share a barcode, or a price update reaches the shop overnight but the till holds an old copy in its cache, customers are charged the wrong amount. Shops check this with test transactions: scan a known item, expect a known price, record what actually happened.
Good systems also log every scan. If a customer complains, the log shows exactly which record was used and when.
Written for Good Learning Co.
Reading questions
- Write in your own words what the checkout sends and what it receives back.
- Explain one way bad data could cause a wrong price, and how logging helps find it.
- Design a test table with four tests for a new checkout, with expected and actual results.
Reading and notes
ReadingRead the lesson text again and note the key terms and how each one is used, in your own words — as you would for revision.
Half a page of notes
Extended writing
WritingExplain a real system that uses this idea — how it works, where it can go wrong, and how you would make it safer or better.
250–350 words
Algorithm on paper
DiagramWrite your steps out as pseudocode or a flowchart before you type anything, then photograph it.
1 flowchart or 10 lines
Code write-up
WritingCopy your code in, then explain underneath what each part does and what you had to fix.
Code + 5 sentences
Test table
Working outMake a test table: what you tried, what you expected, what actually happened.
4–6 tests
Saved as you type.
Part 1 of 10 · Watch & discover
How this is going
- Not looked at yet
Understand the hardware and software components that make up computer systems, and how they communicate with one another and with other systems
- Not looked at yet
Understand how computer networks, including the internet, can provide multiple services such as the World Wide Web