← IGCSE Computer Science Paper 1

Magnetic storage: reading and writing with electromagnets

A read/write head uses an electromagnet to magnetise tiny areas of the spinning platter to store 1s and 0s, and reads the data back by detecting the magnetic pattern.

Part of: IGCSE Computer Science 0478 — 3.3 Data Storage — Module 10

Understanding Magnetic storage: reading and writing with electromagnets in IGCSE Computer Science Paper 1

What it does: Writing means magnetising a small area of the platter with the electromagnet in the read/write head. Reading is done by detecting the magnetic pattern, which is then interpreted as 1s and 0s. Different magnetised areas represent the binary values 1 and 0. The drive stores data, not file names, in these patterns. The platter spins and the head moves across the tracks to reach the right spot. The head does not spin. Pits and lasers belong to optical discs; magnetic drives rely on magnetised areas written by an electromagnet.

Common mistakes: Magnetised areas only stand for binary data, so an area is set to 1 or 0. 9 is not a valid bit. It should be MAGNETISE area AS 1. The platter must keep spinning so the areas pass under the read/write head. It should be SPIN platter.

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This module's key terms are also in a printable crossword (Modules 304–313) and word search (Modules 304–324).

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Learning

Duo

How does a magnetic drive store data on its platter?

It burns pits into the platter with a laserIt magnetises tiny areas of the platter

Matches

A magnetic drive stores data by burning pits into the platter with a laser

↓

This describes optical storage. A magnetic drive uses an electromagnet in the read/write head to magnetise tiny areas of the platter.

Applying

Meanings

Term

magnetise

Meaning

A read/write head uses an electromagnet to magnetise tiny areas of the spinning platter to store 1s and 0s, and reads the data back by detecting the magnetic pattern.

Practice

SPIN platter

Testing

Gaps

WRITE: head uses an

Check Answer

Spots

2MOVE head TO track 4

3MAGNETISE area AS 9

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Quick Questions

1. How does a magnetic drive store data on its platter?

A. It magnetises tiny areas of the platter ✓

B. It burns pits into the platter with a laser

A read/write head uses an electromagnet to magnetise tiny areas of the platter. Burning pits with a laser is how optical discs work.

2. Which part of a magnetic drive writes and reads the data?

A. The read/write head ✓

B. The transistor gate

The read/write head uses an electromagnet to write and detects the magnetic pattern to read. Transistor gates are used in solid-state storage.

3. In a magnetic drive, what do the magnetised areas of the platter stand for?

A. The names of the files

B. The 1s and 0s of binary data ✓

Different magnetised areas represent the binary values 1 and 0. The drive stores data, not file names, in these patterns.

4. How does the drive read data back from the platter?

A. It detects the magnetic pattern on the platter ✓

B. It measures how much light bounces off the platter

Reading works by detecting the pattern of magnetised areas. Measuring reflected light is how optical drives read.

5. What happens to the platter and the head while data is read or written?

A. The platter stays still while the head spins

B. The platter spins while the head moves across the tracks ✓

The platter spins and the head moves across the tracks to reach the right spot. The head does not spin.

Match the Pairs

read/write head → The part that moves across the platter and uses an electromagnet to write data, or detects the magnetic pattern to read it

magnetised area → A tiny area of the platter whose magnetic state stands for a binary 1 or 0

To write data, the head uses an electromagnet to change the magnetic state of a tiny area of the platter → head.magnetise(area)

To read data, the head detects the magnetic pattern of the areas as the platter spins beneath it → pattern = head.detect(area)

A magnetic drive stores data by burning pits into the platter with a laser → This describes optical storage. A magnetic drive uses an electromagnet in the read/write head to magnetise tiny areas of the platter.

The head stays still and only the platter moves, so one head position reaches all the data → The platter spins while the head also moves across the tracks, so the head can reach different tracks of the platter.

Key Term

magnetise

A read/write head uses an electromagnet to magnetise tiny areas of the spinning platter to store 1s and 0s, and reads the data back by detecting the magnetic pattern.

Fill in the Blanks

1. WRITE: head uses an electromagnet

Hint: Type the component in the head that creates a magnetic field to change the platter.

2. READ: head detects the magnetic pattern

Hint: Type the verb for what the head does to the magnetised areas when reading data back.

3. platter spins while the head moves

Hint: Type the action the platter performs so the head can reach any part of it.

4. Binary data: magnetic patterns for 1 and 0

Hint: Type the other binary digit stored by the magnetic patterns.

5. head moves across tracks on the platter

Hint: Type the name for the circular paths on the platter that the head moves between.

Spot the Error

Question 1

A SPIN platter

B MOVE head TO track 4

C MAGNETISE area AS 9

Line C — Magnetised areas only stand for binary data, so an area is set to 1 or 0. 9 is not a valid bit. It should be MAGNETISE area AS 1.

Question 2

A STOP platter

B MOVE head TO track 2

C MAGNETISE area AS 0

Line A — The platter must keep spinning so the areas pass under the read/write head. It should be SPIN platter.

Question 3

A SPIN platter

B MOVE platter TO track 3

C DETECT pattern IN area

D OUTPUT bit

Line B — The platter spins and the head moves across the tracks. The platter does not move to a track. It should be MOVE head TO track 3.

Question 4

A USE laser IN head

B SPIN platter

C MAGNETISE area AS 1

Line A — A magnetic drive head uses an electromagnet to magnetise areas. A laser is used in optical storage. It should be USE electromagnet IN head.

Question 5

A SPIN platter

B MOVE head TO track 1

C count ← 0

D WHILE count > 8 DO

E MAGNETISE area AS bit

F count ← count + 1

Line D — count starts at 0, so count > 8 is false at once and no areas are magnetised. To write 8 bits the condition should be count < 8.

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