Lesson 5 - Exam practice
Test your knowledge
Work through these questions as you would in an exam. The multiple-choice section tests recall; the written questions require justified answers worth multiple marks each. Check the mark scheme only after you have written your answer.
Section 1: Multiple choice
Select one answer per question. Instant feedback will appear when you choose.
Question 1 of 5
Which type of secondary storage uses a laser to read data stored as pits and lands on a spinning disc?
Optical discs (CD, DVD, Blu-ray) store data as microscopic pits and lands on the disc surface.
A laser beam is reflected differently by lands (reflective) and pits (non-reflective), allowing
data to be read. HDDs use magnetic platters; SSDs and flash drives use NAND transistors.
Question 2 of 5
An HDD has a slower average access time than an SSD. What is the main reason for this?
The HDD bottleneck is mechanical: the actuator arm sweeps to the right track (seek time),
then waits for the spinning platter to rotate the correct sector under the head (rotational latency).
This mechanical delay typically adds 5-10 ms per access. An SSD has no moving parts and
accesses data electronically in under 0.1 ms.
Question 3 of 5
A student says "SSDs are always better than HDDs." Which statement best explains why this is incorrect?
Cost per GB for HDDs is roughly 4-5x lower than SSDs at large capacities. A 20 TB HDD
costs a fraction of an equivalent SSD. For bulk cold storage where speed is not a priority,
HDDs remain the better choice. SSDs excel where speed and shock resistance matter most.
SSDs are non-volatile (they do not lose data on power-off).
Question 4 of 5
Why does flash storage (such as USB drives) have a limited lifespan compared to HDDs?
Each write/erase cycle forces electrons through the oxide insulator layer of the floating-gate
transistor. Over time (typically 1,000-100,000 cycles for consumer NAND), the oxide degrades and
the cell can no longer hold charge reliably - it becomes a dead cell. Wear leveling distributes
writes across all cells to extend the overall lifespan of the drive.
Question 5 of 5
A school wants to distribute identical copies of software to 500 students without using a network. Which storage method is most appropriate and why?
Optical discs can be pressed (replicated) in bulk at very low cost per unit. Being read-only
they cannot be accidentally modified, making them ideal for software distribution to large groups.
RAM is volatile and loses data when powered off - it is primary storage, not secondary storage.
USB drives could work but are more expensive per unit at scale and can be modified or lost.
Section 2: Written questions
Write your full answer before revealing the mark scheme. Each bullet point earns one mark. For "justify" questions you must link a property of the technology to the specific requirement in the scenario.
Question A
Explain why a laptop manufacturer might choose an SSD rather than an HDD as the primary storage device. Give two reasons. [4 marks]
[4 marks]
Mark scheme - any 4 from (2 x reason + justification):
SSDs have no moving parts / so they are more resistant to shock damage if the laptop is dropped
SSDs are lighter and smaller / suitable for slim laptop form factors
SSDs consume less power / so the battery lasts longer
SSDs are silent / no noise from spinning platters or moving arm
SSDs have faster read/write speeds / so the operating system boots faster and files load quicker
SSDs have no seek time / because data is accessed electronically rather than mechanically
Note: accept any correct advantage paired with a correct justification. A bare advantage without explanation earns max 1 mark per pair.
Question B
A streaming company stores 20 TB of video content accessed millions of times per day. A medical archive stores patient scans from 25 years ago that are almost never accessed but must be kept permanently. Compare which storage technology is most appropriate for each use case and justify your choices. [6 marks]
[6 marks]
Mark scheme - up to 3 marks per use case:
Streaming company: SSD / NVMe SSD [1]
Because SSDs have high read speeds (500-7000 MB/s) / can serve many simultaneous requests quickly [1]
No seek time means low latency per request / critical for user experience at scale [1]
Medical archive: HDD or optical disc [1]
HDD/optical: much lower cost per GB / important for storing decades of data cost-effectively [1]
Data is rarely accessed so slow seek/access time is acceptable / speed is not the priority [1]
Award up to 3 marks per use case. Require both the technology choice and a relevant justification for full marks.
Question C
Describe how data is written to and read from an optical disc. Use the terms "pit", "land", and "laser" in your answer. [4 marks]
[4 marks]
Mark scheme - any 4 from:
Writing: a high-power laser burns microscopic indentations called pits into the disc surface / dye layer
Unburned areas remain flat and are called lands
Pits and lands represent binary data - pits = 0, lands = 1 (or vice versa - accept either)
Reading: a low-power laser is shone onto the disc surface
Lands reflect the laser back to a sensor / pits scatter or absorb the light differently
The sensor detects the difference in reflection to reconstruct the binary data
Exam technique
For "justify your choice" questions, always: (1) state the storage type, (2) give a specific property of that type, (3) link it explicitly to the scenario. Example: "An SSD is most suitable because it has no moving parts, making it shock-resistant - important for a portable device used in the field." One-word answers score no marks.
Section 3: Research activities
Open-ended tasks for independent or paired study. Use a reliable source such as a UK retailer, manufacturer spec sheet, or Wikipedia for technical claims.
Research task 1 - NVMe vs SATA SSD
NVMe and SATA are two different interfaces for connecting SSDs to a computer. Research the difference and answer:
- What does NVMe stand for, and which bus does it use to connect to the CPU?
- What are typical sequential read speeds for a SATA SSD versus an NVMe SSD?
- Why is NVMe faster than SATA even though both use NAND flash cells internally?
- At what price point does an NVMe SSD become worthwhile over a SATA SSD for a home user?
Research task 2 - Hyperscale tape archives
Google, Amazon and Meta store enormous quantities of data on magnetic tape. Research this and answer:
- What is "cold storage" and why do hyperscalers use tape rather than HDD for it?
- Approximately how many exabytes of data does Google store on tape?
- What is the LTO standard and what is the capacity of the latest generation (LTO-9)?
- Why does offline tape storage have an advantage over online HDDs against ransomware attacks?
Research task 3 - Real-world storage pricing
Visit a major UK retailer (Scan, Amazon UK, or Currys) and compare current storage prices:
- Find the cost per GB for: a 4 TB HDD, a 2 TB SATA SSD, a 1 TB NVMe SSD, and a 256 GB USB 3.2 flash drive.
- Which technology has seen the most dramatic cost-per-GB improvement in the last 5 years?
- At what capacity does HDD become cheaper per GB than SSD?
- Create a simple table summarising your findings for the four storage types.
Section 4: End of unit worksheets
Three printable worksheets covering all five lessons of the Computer Systems unit - FDE cycle, CPU components, performance, memory, and secondary storage. Questions cover all five lessons.
End of Unit Worksheet 1 - Mixed unit review
Matching, True/False and fill-in-table questions across all five topics. Each question is labelled with its topic.
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End of Unit Worksheet 2 - Mixed application
Calculation, justification, and evaluation questions drawing on all five topics. Includes a cross-unit evaluate question.
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End of Unit Worksheet 3 - Higher exam paper
31-mark paper covering all five topics at Higher level. Full instruction trace, extended discussion, and cross-topic evaluation.
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Section 5: Ready-made class tests
Three printable class tests covering all five lessons - complete the table, true/false, describe, explain, and extended writing. Answer spaces sized to exam paper standard. Print-and-go format.
Class Test 1 - CPU Architecture & FDE Cycle
Covers Lessons 1 and 2: registers, FDE cycle stages, stored program concept, CU and ALU. Eight questions with a variety of question types.
Open test
Class Test 2 - Performance, Memory & Storage
Covers Lessons 3, 4 and 5: clock speed, cache, multi-core, RAM vs ROM, virtual memory, HDD vs SSD. Eight questions including scenario-based apply questions.
Open test
Full Unit Assessment - All 5 lessons
40-mark timed assessment covering all five lessons. Three sections: short answer, scenario-based apply questions, and a 6-mark extended writing question.
Open assessment