SI System v/s IEC System - General Knowledge Today

SI System v/s IEC System

In computing, binary prefixes can be used to quantify large numbers where powers of two are more useful than powers of ten. Each successive prefix is multiplied by 1024(210) rather than the 1000 (103) used by the SI prefix system. Despite the ambiguity, binary prefixes are often written and pronounced identically to the SI prefixes, rather than using the IEC system.

In 1999, the international electro technical commission (IEC) published amendment 2 to "IEC 60027-2; letter symbols to be used in electrical technology-part 2; telecommunications and electronics". This standard, which was approved in 1998, introduced the prefixes kibi-, mebi-, gibi-, tebi-, pebi-, exbi-, to be used in specifying binary multiples of a quantity. The names come from the first two letters of the original SI prefixes followed by bi which is short for "binary". It also clarifies that, from the point of view of the IEC, the SI prefixes only have their base-10 meaning and never have a base-2 meaning. So, here is how IEC proposes them to be used:

Multiples of Bits

SI decimal prefixes

Binary
usage

IEC binary prefixes

Name
(Symbol)

Value

Name
(Symbol)

Value

kilobit (kbit)

103

210

kibibit (Kibit)

210

megabit (Mbit)

106

220

mebibit (Mibit)

220

gigabit (Gbit)

109

230

gibibit (Gibit)

230

terabit (Tbit)

1012

240

tebibit (Tibit)

240

petabit (Pbit)

1015

250

pebibit (Pibit)

250

exabit (Ebit)

1018

260

exbibit (Eibit)

260

zettabit (Zbit)

1021

270

zebibit (Zibit)

270

yottabit (Ybit)

1024

280

yobibit (Yibit)

280

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Last Updated: November 22, 2013