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Data Storage Units Explained – Bit, Byte, KB, MB, GB & TB (O Level Computer Science 2210 / IGCSE 0478)

What Are Data Storage Units?

Computers store all information using binary digits (0 and 1).

To measure the size of digital data, computers use data storage units.

These units help us understand:

  • File sizes

  • Memory capacity

  • Storage space

Examples include:

  • Bits

  • Bytes

  • Kilobytes

  • Megabytes

  • Gigabytes

Bit

A bit (binary digit) is the smallest unit of data in a computer.

It can only store:

0 or 1

Example:

1 bit = 0 or 1

Bits are used as the basic building blocks of digital data.

Byte

A byte is a group of 8 bits.

Example:

1 byte = 8 bits

A single byte is usually enough to store one character such as:

  • A

  • B

  • 7

Kilobyte (KB)

A kilobyte represents 1024 bytes.

Example:

1 KB = 1024 bytes

Small text files are often measured in kilobytes.

Megabyte (MB)

A megabyte equals 1024 kilobytes.

Example:

1 MB = 1024 KB

Typical uses:

  • Images

  • Small software files

Gigabyte (GB)

A gigabyte equals 1024 megabytes.

Example:

1 GB = 1024 MB

Common examples:

  • Movies

  • Large programs

  • Smartphone storage

Terabyte (TB)

A terabyte equals 1024 gigabytes.

Example:

1 TB = 1024 GB

Used for:

  • Large databases

  • Cloud storage

  • Backup systems

Data Storage Unit Table

UnitSizeBit1 binary digitByte8 bitsKilobyte (KB)1024 bytesMegabyte (MB)1024 KBGigabyte (GB)1024 MBTerabyte (TB)1024 GB

Computers use 1024 instead of 1000 because data is stored using binary systems.

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Why Data Storage Units Are Important

Understanding storage units helps students learn:

  • How large files are stored

  • How memory and storage devices work

  • How to calculate file sizes

This knowledge is essential in computer science exams.

Exam Tip (2210 / 0478)

Students are often asked to:

  • Convert between bytes, KB, MB and GB

  • Calculate file sizes

Always remember:

1 KB = 1024 bytes

Not 1000.

Practice Question

How many bytes are in 1 MB?

Step 1:

1 MB = 1024 KB

Step 2:

1 KB = 1024 bytes

Answer:

1 MB = 1,048,576 bytes

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  • Cambridge O Level Computer Science (2210)

  • Cambridge IGCSE Computer Science (0478)

with IVY Online.

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