2008-05-21 (from http://www.iec.ch/zone/si/si_bytes.htm)

Binary multiples

The new prefixes and symbols for binary multiples standardized in 
IEC 60027-2 are not part of the SI metric system of units. But as the 
table below shows, they are related to the SI prefixes and symbols for 
positive powers of ten in a simple way so that they are easy to remember 
and use.

Factor  Name    Symbol  Origin                          SI derivation

2^10    kibi    Ki      kilobinary      (2^10)^1        kilo    (10^3)^1
2^20    mebi    Mi      megabinary      (2^10)^2        mega    (10^3)^2
2^30    gibi    Gi      gigabinary      (2^10)^3        giga    (10^3)^3
2^40    tebi    Ti      terabinary      (2^10)^4        tera    (10^3)^4
2^50    pebi    Pi      petabinary      (2^10)^5        peta    (10^3)^5
2^60    exbi    Ei      exabinary       (2^10)^6        exa     (10^3)^6
2^70    zebi    Zi      zettabinary     (2^10)^7        zetta   (10^3)^7
2^80    yobi    Yi      yottabinary     (2^10)^8        yotta   (10^3)^8

Remark [PB]: B is the abbreviation for the Non-SI unit Bel