Units of Data Storage (Cambridge International IGCSE Computer Science)

Spec point — 1.3.1 · 1 Understand how data storage is measured

Units of Data Storage

What are units of data storage?

• A unit of data is a term given to describe different amounts of binary digits stored on a digital device
• These are the units you need to know for IGCSE:

Megabyte vs Mebibyte

• 1 kibibyte (1KiB) = 1024 bytes (1024 B) - binary prefixes (to the power of 2)
• 1 kilobyte (1KB) = 1000 bytes (1000 B) - decimal prefixes (to the power of 10)

Converting between units

• It is often a requirement of the exam to be able to convert between different units of data, for example bytes to mebibytes (larger) or kibibytes to bytes (smaller)
• This process involves division, moving up in size of unit and multiplication, moving down in size of unit
• When dealing with all units bigger than a byte we use multiples of **1024 **(2¹⁰)
• For example, 2000 kibibytes in mebibytes would be 2000 / 1024 = 1.95 MiB and 2 tebibytes in gibibytes would be 2 * 1024 = 2048 GiB
• When dealing with** bits and bytes** the same process is used with the value **8 **as there are 8 bits in a byte
• For example, 24 bits in bytes would be 24 / 8 =** 3 B** and 10 bytes in bits would be 10 * 8 = 80 b
• The same multiply or divide by 1024 rule applies when converting beyond TiB to PiB and EiB

Worked Example Convert 1 PiB to GiB

[2]

Answer

• 1 PiB = 1024 TiB
• 1 TiB = 1024 GiB

So:

• 1 PiB = 1024 × 1024 GiB [1 mark]
• 1 PiB = 1,048,576 GiB [1 mark]