Units of Information

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Number bases


Converting number bases


Units of information


Binary arithmetic


Character encoding


Representing images


Representing sound


Data compression

Syllabus content

Content   Additional Information

Know that:

  • • a bit is the fundamental unit of information
  • • A bit is either a 0 or a 1.

A bit is either a 0 or a 1.

  • • b represents bit
  • • B represents byte

Know that quantities of bytes can be described using prefixes. Know the names, symbols and corresponding values for the decimal prefixes:

  • • kilo, 1 kB is 1,000 bytes
  • • mega, 1 MB is 1,000 kilobytes
  • • giga, 1 GB is 1,000 Megabytes
  • • tera, 1 TB is 1,000 Gigabytes.

Students might benefit from knowing that historically the terms kilobyte, megabyte, etc have often been used to represent powers of 2.

The SI units of kilo, mega and so forth refer to values based on powers of 10. When referring to powers of 2 the terms kibi, mebi and so forth would normally be used but students do not need to know these.



Data Storage
One extended-ASCII character in a text file (eg 'A') 1 byte
The word 'Monday' in a document 6 bytes
A plain-text email 2 KB
64 pixel x 64 pixel GIF 12 KB
Hi-res 2000 x 2000 pixel RAW photo 11.4 MB
Three minute MP3 audio file 3 MB
One minute uncompressed WAV audio file 15 MB
One hour film compressed as MPEG4 4 GB


3.1 Fundamentals of algorithms

3.2 Programming

3.3 Fundamentals of data representation

3.4 Computer systems

3.5 Fundamentals of computer networks

3.6 Fundamentals of cyber security

3.7 Ethical, legal and environmental impacts of digital technology on wider society, including issues of privacy

3.8 Aspects of software development

Glossary and other links

Glossary of computing terms.

AQA 8520: The 2016 syllabus