📚 Knowledge Library — Topic 1.4 — Data Representation

Measuring Data Storage

Understand how computers measure file size using bits, bytes and larger storage units, and how to convert between them.

Start LearningWorked Example
1. Invitation

Every file needs space.

A photo, song, video or text file all need storage space.

Computers measure that space using units such as bits, bytes, kibibytes, mebibytes and gibibytes.

💡 Remember: storage size tells us how much data a file or device can hold.
Figure 1.1
Files Need Storage
Text
Image
Sound
Video
↓
Storage Space
2. Big Idea

Bits are the smallest unit.

A bit is one binary digit. It can store either a 0 or a 1.

A byte is a group of 8 bits. A byte is often used to store one character of text.

💡 8 bits = 1 byte.
Figure 2.1
Bit and Byte
1 bit = 0 or 1

1 byte = 8 bits
01000001
A byte can store one ASCII character.
3. Bridge

Think of boxes inside bigger boxes.

Storage units work like boxes. Small units fit inside bigger units.

To move down to a smaller unit, multiply. To move up to a larger unit, divide.

💡 Down the units = multiply by 1024. Up the units = divide by 1024.
Figure 3.1
Storage Ladder
Byte
×1024 ↓
KiB
×1024 ↓
MiB
×1024 ↓
GiB
4. Worked Example

Converting bytes to kibibytes.

When converting to a larger unit, divide by 1024.

Convert 2,048 bytes to KiB

Bytes
2,048
Operation
÷ 1024
Answer
2 KiB
2,048 ÷ 1024 = 2 KiB
Figure 4.1
Going Up Units
bytes
÷ 1024
KiB
Going up the ladder means divide.
5. Worked Example

Converting larger units.

The same rule works for larger storage units.

Convert 2 GiB to MiB

2 × 1024 = 2048 MiB

If you are converting to a smaller unit, multiply by 1024.

Figure 5.1
Going Down Units
GiB
× 1024
MiB
Going down the ladder means multiply.
6. Exam Tip

Show your working.

In storage conversion questions, marks are often awarded for correct working even if the final answer has a small error.

🎯 Exam Tip: Write the operation clearly: multiply by 1024 or divide by 1024.
Figure 6.1
Exam Working
4 KiB
× 1024
= 4096 bytes
Clear working earns marks.
7. Common Mistake

Do not mix up bits and bytes.

A bit is one binary digit. A byte is eight bits.

⚠️ Common Mistake: writing bytes when the question asks for bits, or forgetting that 1 byte = 8 bits.
Figure 7.1
Bit vs Byte
bit
= one 0 or 1

byte
= 8 bits
8. Summary

Measuring data storage in one screen.

A bit is the smallest unit of data. A byte is 8 bits.

Storage units increase by 1024 when using binary-based units such as KiB, MiB, GiB and TiB.

Larger files need more storage capacity. Compression can reduce file size.

💡 Key rule: smaller unit → multiply by 1024. Larger unit → divide by 1024.
Figure 8.1
Storage Units
bit
byte
KiB
MiB
GiB
TiB