Units of Data Storage (Cambridge (CIE) O Level Computer Science): Revision Note

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