IEC standard prefixes
In 1999, the International Electrotechnical 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.
This amendment was included in the next edition of the standard: "IEC 60027-2 (2000-11) Ed. 2.0"
As of 2005 this naming convention has not gained widespread use, but its use is growing. It is strongly supported by many standardization bodies, including IEEE (March 19, 2005) and CIPM.
Name Symbol Value
kibi Ki 210 = 1,024
mebi Mi 220 = 1,048,576
gibi Gi 230 = 1,073,741,824
tebi Ti 240 = 1,099,511,627,776
pebi Pi 250 = 1,125,899,906,842,624
exbi Ei 260 = 1,152,921,504,606,846,976
Example : 300 GB = 279.5 GiB (= 0x117.6592E GiB = 0x45D96.4B8 MiB = 0x1176592E KiB = 0x45D964B800 bytes).
Note that the IEC names are defined only up to exbi-, corresponding to the SI prefix exa-. The two SI prefixes zetta- (1021) and yotta- (1024) have no corresponding IEC binary prefixes, though the obvious continuation would be zebi- (Zi = 270 = 1,180,591,620,717,411,303,424) and yobi- (Yi = 280 = 1,208,925,819,614,629,174,706,176).
http://en.wikipedia.org/wiki/Mebi
But note adopting the above would conflict with Australian directives.
It should be
kib
MiB
GiB
Note lower case K and B in kib but uppercase in mega and beyond..
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http://webdiary.smh.com.au/archives/_comment/001075.html
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"David Candy" <.> wrote in message Modem speed (in BAUD) include control bits so 1 byte takes more than 8 bits to send.
10^0 = 1
2 ^ 0 = 1
10 ^ 3 = k (1 000)
2 ^ 10 = ki (1024) (technically - windows uses k and M for historical reasons as there was no ki when windows was first written)
10 ^ 6 = M (1 000 000)
2 ^ 20 = Mi (1 048 576)
same for G/Gi
1 byte is 8 bits. There are indirect ways of refering to data sizes that do change from processor to processor but bits/bytes isn't one of them.
Here are the official australian rules. They don't specifically cover bytes or bits. From Chapt 11 at
http://www.agimo.gov.au/information/publishing/style_manual
I'd say
kb
MB
for bytes. I'd spell out bits (and in practise I tend to spell bytes in full to be sure) or use baud if appropiate.
Expression of metric units
LOWER CASE
11.11 Names of units and prefixes, when spelt out in full, are expressed in lower-case letters
(except at the beginning of a sentence). The only exception is the capital 'C' in degree Celsius
(°C).
11.12 Unit symbols are expressed in lower-case letters except the symbol for 'litre', the
symbols for units named after people and the symbols for units containing one of the first five
prefixes in table 11.4 (exa, peta, tera, giga and mega). Thus:
litre L millilitre mL pascal Pa newton N
hertz Hz megajoule MJ gigawatt GW ampere A
11.13 The use of the capital 'L' as the symbol for 'litre' is a change from earlier practice, which
was to use the lower-case 'l' or script ' '.
PLURALS
11.14 Unit names take a plural 's' only when associated with numbers greater than unity. For
example:
0.5 metre 1.5 metres 1 kilogram 25 kilograms
11.15 The hertz, the lux and the siemens, however, are not changed in the plural:
10 kilohertz 3 lux 1.5 siemens
11.16 When a measurement is used in an adjectival sense, unit names remain in the singular:
a 50-hectare block of land
a 2-tonne truck
CONSISTENCY
11.17 Unit names and symbols should not be mixed in the same context. If a symbol is used
for one unit, symbols should be used for all units. For example:
km / h not km / hour
PER
11.18 The term 'per' should be used only with words, whereas the solidus denoting 'per'
should be used only with symbols:
kilometres per hour or km / h
not kilometres per h or km / hour
SYMBOLS
11.19 Since symbols are internationally recognised representations of units-not abbreviations
of the unit names-they do not take full stops nor do they change when associated with
numbers greater than unity. For example:
km not km. 2 kg not 2 kgs
11.20 Symbols of units should be set in roman type (that is, upright type as distinct from italic)
irrespective of the type used in the rest of the text. The only exceptions are the symbol for 'ohm',
represented by the upper-case Greek letter omega (W), and the prefix 'micro', represented by
the lower-case Greek letter mu (m).
Is measured 2.8 m overall
But note that symbols of quantities are printed in italics:
In this case, the value of H would be 0.56 m
So due to the velocity of 0.5c, the mass m of the object will increase by
15 per cent.
PREFIXES
11.21 All prefixes except those representing a million or more-that is, exa (E), peta (P), tera
(T), giga (G) and mega (M)-have lower-case symbols.
LESS THAN UNITY
11.22 In the case of measurements less than unity, a nought is placed before the decimal point.
For example:
0.25 metre or 0.25 m not 25 metre or .25 m
USE OF SPACE
11.23 Unit names and symbols should be separated from any associated numerical value by a
thin space:
27 m not 27m 27 metres not 27metres
11.24 Exceptions to this rule are the symbols for degree (°), minute ('), second (") and degree
Celsius (°C). For example:
180° 125' 15" 27°C
CHOICE OF UNITS
11.25 Only one unit name (or symbol) should be included in a statement of measurement:
1.234 m or 1234 mm
not 1 m 234 mm or 1 m 2 dm 3 cm 4 mm
11.26 The unit should be so chosen that the numerical value of the statement of measurement
lies between 0.1 and 1000. For example:
47.32 m not 0.047 32 km
500 kPa or 0.5 Mpa not 500 000 Pa
