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BCS Glossary of Computing and ICT 13th edition by BCS Academy Glossary Working Party

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E2 UNITS

Prefixes for metric multiples

In scientific notation prefixes are used to absorb some of the powers that might otherwise occur. Thus instead of 1,000,000 metres we say 1 Mm.

Each prefix is 1000 times the last so that they represent powers of 1000.

Thus a kilometre is 1000 metres and a mega-metre is 1000 km.

Binary multiples also have prefixes and these are spaced with factors of 210 or 1024.

The use of the metric prefixes above (kilo, mega etc.) in computing has often caused confusion. It was convenient to use these metric prefixes as binary prefixes as well, leaving the reader to work out what was meant from the context. For example, as a metric prefix, kilo is defined as 1000 (derived from 103 ), whereas the binary prefix kilo is ...

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