units

```   Decimal prefixes
The  SI  system  of units uses prefixes that indicate powers of ten.  A
kilometer is 1000 meter, and a megawatt is  1000000  watt.   Below  the
standard prefixes.

Prefix   Name    Value
y        yocto   10^-24 = 0.000000000000000000000001
z        zepto   10^-21 = 0.000000000000000000001
a        atto    10^-18 = 0.000000000000000001
f        femto   10^-15 = 0.000000000000001
p        pico    10^-12 = 0.000000000001
n        nano    10^-9  = 0.000000001
u        micro   10^-6  = 0.000001
m        milli   10^-3  = 0.001
c        centi   10^-2  = 0.01
d        deci    10^-1  = 0.1
da       deka    10^ 1  = 10
h        hecto   10^ 2  = 100
k        kilo    10^ 3  = 1000
M        mega    10^ 6  = 1000000
G        giga    10^ 9  = 1000000000
T        tera    10^12  = 1000000000000
P        peta    10^15  = 1000000000000000
E        exa     10^18  = 1000000000000000000
Z        zetta   10^21  = 1000000000000000000000
Y        yotta   10^24  = 1000000000000000000000000

The  symbol  for  micro  is  the Greek letter mu, often written u in an

<http://physics.nist.gov/cuu/Units/prefixes.html>

Binary prefixes
The binary prefixes resemble the decimal ones, but have  an  additional
'i' (and "Ki" starts with a capital 'K').  The names are formed by tak-
ing the first syllable of the names of the decimal prefix with  roughly
the same size, followed by "bi" for "binary".

Prefix   Name   Value
Ki       kibi   2^10 = 1024
Mi       mebi   2^20 = 1048576
Gi       gibi   2^30 = 1073741824
Ti       tebi   2^40 = 1099511627776
Pi       pebi   2^50 = 1125899906842624
Ei       exbi   2^60 = 1152921504606846976

<http://physics.nist.gov/cuu/Units/binary.html>

Discussion
Before  these  binary prefixes were introduced, it was fairly common to
use k=1000 and K=1024, just like b=bit, B=byte.  Unfortunately,  the  M
is capital already, and cannot be capitalized to indicate binary-ness.
that defines the binary prefixes given above,  enabling  people  to  be
precise and unambiguous.

Thus, today, MB = 1000000B and MiB = 1048576B.

In  the  free  software world programs are slowly being changed to con-
form.  When the Linux kernel boots and says

hda: 120064896 sectors (61473 MB) w/2048KiB Cache

the MB are megabytes and the KiB are kibibytes.

COLOPHON
This page is part of release 4.04 of the Linux  man-pages  project.   A
description  of  the project, information about reporting bugs, and the
latest    version    of    this    page,    can     be     found     at
http://www.kernel.org/doc/man-pages/.

Linux                             2012-08-05                          UNITS(7)```