Mebibyte
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A mebibyte (a contraction of mega binary byte) is a unit of information or computer storage, abbreviated MiB.
The mebibyte is closely related to the megabyte (MB), which can be a synonym for mebibyte, or refer to 106 bytes = 1,000,000 bytes, or even refer to 1,000 times 1,024 bytes (e.g. the 1.44 MB floppy disk), depending on context (see binary prefix for background). The three numbers are relatively close together, but mistaking the three has nonetheless led to consumer confusion and even legal disputes. There are times when it is necessary to know the exact size of a file, for example, or exactly how much space remains on a storage device.
The unit was defined by the International Electrotechnical Commission (IEC) in December 1998. Use of mebibyte and related units is endorsed by IEEE and CIPM in contexts where use of a binary prefix makes sense, in order to protect the unambiguous decimal meaning of the "mega" prefix. The binary unit is in wide use by the consumer software industry, but the use of the "mebi-" prefixes is not. This leads to confusion where 220 (1,048,576) bytes is displayed as 1 MB instead of 1 MiB. For example, the operating system Windows XP will show a file of 220 bytes as "1.00 MB" in its file properties dialog. Likewise, a file of 106 (1,000,000) bytes is reported as "976 KB".