← IGCSE Computer Science Paper 1

Comparing magnetic, optical and solid-state storage

Three types of secondary storage that store data in different ways (magnets, laser pits, flash cells), so they differ in capacity, speed, durability, portability and cost.

Part of: IGCSE Computer Science 0478 — 3.3 Data Storage — Module 18

Understanding Comparing magnetic, optical and solid-state storage in IGCSE Computer Science Paper 1

What it does: Optical discs are read by a laser that follows a single track of pits and lands. They are portable and cheap but have low capacity and slow access. A hard disk drive has spinning platters and a moving read/write head, so a knock can damage it. Solid-state storage has no moving parts. HDDs give a large capacity for a low price per gigabyte. SSDs of the same size usually cost more. An SSD is light, silent, fast and has no moving parts, so it is more durable and portable for a laptop. Even a Blu-ray disc holds far less than a modern HDD, which can store terabytes.

Common mistakes: A hard disk drive has moving parts (spinning platters and a read/write head), so the value should be True. That is why it is fragile. A CD stores data as pits and lands read by a laser, so it is optical storage. It should be cd = "optical".

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This module's key terms are also in a printable crossword (Modules 314–324) and word search (Modules 304–324).

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Learning
Duo
Which type of storage has moving parts that can be damaged if the device is dropped?
Magnetic storage (HDD)Solid-state storage (SSD)
Matches
SSD: spinning platters make it fragile
↓
Spinning platters belong to a magnetic HDD, not an SSD. An SSD has no moving parts, which makes it durable.
Applying
Meanings
Term
magnetic, optical and solid-state storage
Meaning
Three types of secondary storage that store data in different ways (magnets, laser pits, flash cells), so they differ in capacity, speed, durability, portability and cost.
Practice
Magnetic: moving parts, high capacity, cheap per GB
Testing
Gaps
hddHasMovingParts ←
Check Answer
Spots
1hdd_moving_parts = False
2ssd_moving_parts = False

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Quick Questions

1. Which type of storage has moving parts that can be damaged if the device is dropped?
A. Magnetic storage (HDD) ✓
B. Solid-state storage (SSD)
A hard disk drive has spinning platters and a moving read/write head, so a knock can damage it. Solid-state storage has no moving parts.
2. Which type of storage usually gives the fastest access to data?
A. Optical storage
B. Solid-state storage ✓
Solid-state storage reads data electronically with no waiting for a disc to spin or a head to move, so it is much faster than optical discs.
3. Which type of storage is usually the cheapest per gigabyte for very large amounts of data?
A. Magnetic storage (HDD) ✓
B. Solid-state storage (SSD)
HDDs give a large capacity for a low price per gigabyte. SSDs of the same size usually cost more.
4. Which is a good reason to use a DVD or Blu-ray disc to give a film to a friend?
A. Optical discs are cheap and light to post ✓
B. Optical discs are the fastest storage available
Optical discs are low cost and portable, but they have low capacity and slow access compared with other types.
5. How does optical storage store data?
A. Tiny magnetised areas read by a laser
B. Pits and lands read by a laser ✓
Optical discs have pits and lands burned into the surface and a laser reads them. Magnetic storage uses magnetised areas instead.

Match the Pairs

Magnetic storage (HDD) → Large capacity and low cost per gigabyte, but it has moving parts, so it is slower and more fragile
Solid-state storage (SSD) → No moving parts, so it is fast, durable and portable, but it costs more per gigabyte
Optical discs are cheap and easy to carry around, but hold little data and are slow to access compared with the other types → CD / DVD / Blu-ray
A school laptop that is carried in a bag and often knocked needs storage with no moving parts that is also quick to access → SSD (solid-state)
SSD: spinning platters make it fragile → Spinning platters belong to a magnetic HDD, not an SSD. An SSD has no moving parts, which makes it durable.
Optical discs: biggest capacity and fastest access → Optical discs have the lowest capacity of the three types and slow access. SSDs are the fastest, and HDDs have the highest capacity for the price.

Key Term

magnetic, optical and solid-state storage
Three types of secondary storage that store data in different ways (magnets, laser pits, flash cells), so they differ in capacity, speed, durability, portability and cost.

Fill in the Blanks

1. hddHasMovingParts ← TRUE
Hint: Type the Boolean value showing that a hard disk drive has moving parts, which makes it fragile.
2. ssdHasMovingParts ← FALSE
Hint: Type the Boolean value showing that solid-state storage has no moving parts, so it is more durable.
3. IF device = "CD" THEN usesLaser ← TRUE
Hint: Type the operator that checks whether the device is equal to a value.
4. IF costPerGB < 0.05 THEN device ← "HDD"
Hint: Type the comparison operator meaning the cost per gigabyte is lower than the number shown.
5. IF device = "SD card" THEN portable ← TRUE
Hint: Type the keyword that starts the action to run when the IF condition is true.

Spot the Error

Question 1
A hdd_moving_parts = False
B ssd_moving_parts = False
C if hdd_moving_parts:
D print("HDD is fragile")
Line A — A hard disk drive has moving parts (spinning platters and a read/write head), so the value should be True. That is why it is fragile.
Question 2
A hdd = "magnetic"
B ssd = "solid-state"
C cd = "magnetic"
D print(hdd, ssd, cd)
Line C — A CD stores data as pits and lands read by a laser, so it is optical storage. It should be cd = "optical".
Question 3
A storage = "SSD"
B if storage == "SSD":
C print("Has moving parts")
Line C — An SSD uses flash memory with no moving parts. The line should print "No moving parts".
Question 4
A hdd_cost = 0.03
B ssd_cost = 0.08
C if hdd_cost < ssd_cost:
D print("SSD is cheaper")
Line D — The HDD has the lower cost per gigabyte, so the message should say HDD is cheaper, matching the condition.
Question 5
A hdd_gb = 4000
B ssd_gb = 1000
C bluray_gb = 50
D if hdd_gb < bluray_gb:
E print("HDD holds more")
Line D — An HDD has a much bigger capacity than a Blu-ray disc. The condition should use > so that the message "HDD holds more" is true.

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