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J277 1.2 Data representation consolidation
Part 5 of 5 · J277 1.2.4-1.2.5 · Data representation
The end-of-topic checkpoint for data representation, combining characters, images, sound and compression.
Students will:
- select the right representation idea for an unfamiliar scenario
- calculate text, image and sound file sizes with working shown
- compare lossy and lossless compression in context
- correct flawed statements about resolution, colour depth and sampling
- write a developed answer under exam conditions
Inside: 3 explanation cells, 2 multiple-choice questions, 1 fill-in-the-blanks cell and 8 written answers. 56 marks, about 75 minutes.
Series: J277 1.2.4-1.2.5 · Data representation, part 5 of 5.
Shared by Coding PathwayVerified teacher
- 14 cells
- About 75 minutes
- CC BY-SA 4.0
- Shared 17 Aug 2026
- Updated 9 Sept 2026
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Data representation 5: consolidation
This worksheet combines characters, images, sound and compression. A short reminder is included where needed, but the calculations and scenario questions ask you to select and apply the relevant knowledge independently.
For every calculation, show your working and include a unit. For every recommendation, state the choice and apply the reason to the scenario.
Use the early tasks to identify gaps, then complete the application and final challenge independently.
Which four statements are accurate? Select all that apply.
- AA character set maps characters to unique binary codes
- BMetadata is the code that sets the colour of every individual pixel
- CImage resolution is the number of pixels in an image
- DSound sampling records the wave's frequency as every sample
- ESound bit depth is the number of bits used for each sample
- FLossless compression allows the exact original to be reconstructed
- resolution
- bit depth
- character set
- sample rate
- colour depth
- duration
- metadata
Explain why Unicode may be selected instead of a limited ASCII character set for a worldwide messaging service. Include one possible storage consequence.
Link available character codes to writing systems and symbols, then consider bits per character.
Students type their answer here.
A text file contains 6,000 characters and uses 8 bits per character. Calculate its size in bits, bytes and kilobytes. Use 1 KB = 1,000 bytes.
Use bits per character × number of characters, then convert units.
Students type their answer here.
An uncompressed image is 400 pixels wide, 250 pixels high and has a colour depth of 8 bits. Calculate its size in bits, bytes and kilobytes. Use 1 KB = 1,000 bytes.
Multiply width × height × colour depth, then convert.
Students type their answer here.
An uncompressed sound file has a sample rate of 10,000 Hz, a duration of 20 seconds and a bit depth of 16 bits. Calculate its size in bits, bytes and kilobytes. Use 1 KB = 1,000 bytes.
Use sample rate × duration × bit depth, then convert.
Students type their answer here.
Compare how resolution and colour depth affect an image, and how sample rate and bit depth affect a sound recording.
For each term, state what changes, one possible quality effect and the file-size effect.
Students type their answer here.
A website contains a text-based timetable, preview photographs and a downloadable master image for professional printing. Which combination is most appropriate?
- ALossy for the timetable, lossless for previews, lossy for the master
- BLossless for the timetable, lossy for previews, lossless for the master
- CLossy for every file because it always improves quality
- DLossless for every file because it always creates the smallest size
Integrated scenario
A school is creating an online exhibition. Each entry contains:
- a student's name and description
- a high-resolution photograph
- a spoken audio explanation
The public website must load quickly, while the school also keeps exact master copies for future exhibitions.
Explain how the text, photograph and audio are represented. Then recommend compression approaches for the public website and the master copies.
Use character sets and binary codes for text, pixels for images, amplitude samples for sound, and apply lossy or lossless choices to each purpose.
Students type their answer here.
Correct all four claims: “Colour depth adds pixels. Metadata stores every pixel colour. Sampling measures the wave's frequency. Lossless files cannot be made smaller.”
Write one precise correction for each claim.
Students type their answer here.
Challenge: the school wants to reduce the download size of an exhibition entry. Evaluate four possible changes: reducing image resolution, reducing image colour depth, reducing audio sample rate and applying lossy compression. Recommend a balanced approach.
For each change, explain what data is reduced, the likely quality effect and the file-size effect. Apply your final recommendation to a public exhibition.
Students type their answer here.
Final data representation check
You should now be able to:
- explain character sets, unique codes, ASCII, Unicode and logical ordering
- calculate a text-file size
- explain pixels, resolution, colour depth and metadata
- calculate an image-file size
- explain amplitude sampling, sample rate, bit depth and duration
- calculate a sound-file size
- compare lossy and lossless compression
- recommend compression in context
- use precise language about quality, file size, storage and transmission
Return to any term that you still confuse with another. Accurate distinctions are central to this topic.