binary prefix
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symbol placed before units of digital information to indicate multiplication by a power of two
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Article
A binary prefix is a unit prefix that indicates a multiple of a unit of measurement by an integer power of two. The most commonly used binary prefixes are kibi (symbol Ki, meaning 2 = 1024), mebi (Mi, 2 = 1048576), and gibi (Gi, 2 = 1073741824). They are most often used in information technology as multipliers of bit and byte, when expressing the capacity of storage devices or the size of computer files.
The binary prefixes "kibi", "mebi", etc. were defined in 1999 by the International Electrotechnical Commission (IEC), in the IEC 60027-2 standard (Amendment 2). They were meant to replace the metric (SI) decimal power prefixes, such as "kilo" (k, 10 = 1000), "mega" (M, 10 = 1000000) and "giga" (G, 10 = 1000000000), that were commonly used in the computer industry to indicate the nearest powers of two. For example, a memory module whose capacity was specified by the manufacturer as "2 megabytes" or "2 MB" would hold 2 × 2 = 2097152 bytes, instead of 2 × 10 = 2000000.