The mebibyte (a contraction of megabinary byte, pronounced MEH-bee-byte) is a standards-based binary multiple (prefix mebi-, symbol Mi-) of the byte, a unit of digital information storage. Mebibyte is abbreviated MiB.^[1][2]

1 MiB = 2²⁰ bytes = 1,024 kibibytes = 1,048,576 bytes

The unit prefix mebi was defined by the International Electrotechnical Commission (IEC) in December 1998. Use of mebibyte and related units is endorsed by the Institute of Electrical and Electronics Engineers (IEEE) and the International Committee for Weights and Measures (CIPM) in contexts where use of a binary prefix makes sense, in order to protect the unambiguous definition of the unit prefix mega. Megabyte is sometimes used in place of mebibyte, or to refer to 10⁶ bytes = 1,000,000 bytes, or even 1,000 times 1,024 bytes, depending on context.

The historical binary interpretation of mega is still in wide use by the consumer software industry and use of the mebi prefix is still not common. This leads to consumer confusion when 2²⁰ (1,048,576) bytes is referenced as 1 MB (megabyte) instead of 1 MiB. For example, the operating system Windows XP shows a file of 2²⁰ bytes as "1.00 MB" in its file properties dialog, while showing a file of 10⁶ (1,000,000) bytes as "976 KB". Apple's Mac OS X 10.6, on the other hand, would report a 10⁶ byte file correctly as "1 MB".^[3]

In another example, the 1.44 MB floppy disk's storage capacity is calculated using 1,024,000 bytes per "MB" (i.e. 1.44×1024×1000), rather than 1.47 MB (1.47×1000×1000) or 1.40 MiB (1.40×1024×1024). The three size designations are similar in value.

In The Art of Computer Programming, Donald Knuth proposed that this unit be called a large megabyte (abbreviated MMB), though this usage has never been common.

[edit] See also

• SI prefix
• IEEE 1541
• Orders of magnitude (data)

[edit] References