Learning objective
Units: Know that quantities of bytes can be described using binary prefixes representing powers of 2 or using decimal prefixes representing powers of 10, eg one kibibyte is written as 1KiB = 210 B and one kilobyte is written as 1 kB = 103 B. Know the names, symbols and corresponding powers of 2 for the binary prefixes: • kibi, Ki - 2 10 • mebi, Mi - 2 20 • gibi, Gi - 2 30 • tebi, Ti - 2 40 Know the names, symbols and corresponding powers of 10 for the decimal prefixes: • kilo, k - 10 3 • mega, M - 10 6 • giga, G - 10 9 • tera, T - 10 12 Historically the terms kilobyte, megabyte, etc have often been used when kibibyte, mebibyte, etc are meant.
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Units of information
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Units
Aqa A Level Computer ScienceFundamentals of data representation
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Quick explanation
Units: Know that quantities of bytes can be described using binary prefixes representing powers of 2 or using decimal prefixes representing powers of 10, eg one kibibyte is written as 1KiB = 210 B and one kilobyte is written as 1 kB = 103 B. Know the names, symbols and corresponding powers of 2 for the binary prefixes: • kibi, Ki - 2 10 • mebi, Mi - 2 20 • gibi, Gi - 2 30 • tebi, Ti - 2 40 Know the names, symbols and corresponding powers of 10 for the decimal prefixes: • kilo, k - 10 3 • mega, M - 10 6 • giga, G - 10 9 • tera, T - 10 12 Historically the terms kilobyte, megabyte, etc have often been used when kibibyte, mebibyte, etc are meant
- This point belongs to Units of information, especially Units.
- You need to be able to units: Know that quantities of bytes can be described using binary prefixes representing powers of 2 or using decimal prefixes representing powers of 10, eg one kibibyte is written as 1KiB = 210 B and one kilobyte is written as 1 kB = 103 B. Know the names, symbols and corresponding powers of 2 for the binary prefixes: • kibi, Ki - 2 10 • mebi, Mi - 2 20 • gibi, Gi - 2 30 • tebi, Ti - 2 40 Know the names, symbols and corresponding powers of 10 for the decimal prefixes: • kilo, k - 10 3 • mega, M - 10 6 • giga, G - 10 9 • tera, T - 10 12 Historically the terms kilobyte, megabyte, etc have often been used when kibibyte, mebibyte, etc are meant.
- Use the linked flashcards and practice questions to check recall, then practise applying the idea in an exam-style answer.
Why it matters
This objective helps connect Units to exam-style questions, flashcards, and revision notes for Units of information.
Quick student answer
Which statement correctly describes 1 KiB?
Direct answer
1 KiB = 1024 B
Key terms
- Binary prefix: A prefix for a unit of information that represents a power of 2, such as kibi (Ki) = 2^10 or mebi (Mi) = 2^20.
- Decimal prefix: A prefix for a unit of information that represents a power of 10, such as kilo (k) = 10^3 or mega (M) = 10^6.
Common trap
Confusing kB with KiB: Remember that kB uses kilo and equals 10^3 B, or 1000 B. KiB uses kibi and equals 2^10 B, or 1024 B. The symbols must be read exactly.
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