Mebibyte

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The mebibyte is a multiple of the unit byte for digital information. [1] The binary prefix mebi means 220; therefore one mebibyte is equal to 1048576bytes, i.e., 1024 kibibytes. The unit symbol for the mebibyte is MiB.

Contents

The unit was established by the International Electrotechnical Commission (IEC) in 1998. [2] It was designed to replace the megabyte when used in the binary sense to mean 220 bytes, which conflicts with the definition of the prefix mega in the International System of Units (SI) as a multiplier of 106. The binary prefixes have been accepted by all major standards organizations and are part of the International System of Quantities. [3] Many Linux distributions use the unit, but it is not widely acknowledged within the industry or media. [4] [5] [6] [7]

Multiples of bytes
Decimal
Value Metric
1B byte
1000kB kilobyte
10002MB megabyte
10003GB gigabyte
10004TB terabyte
10005PB petabyte
10006EB exabyte
10007ZB zettabyte
10008YB yottabyte
Binary
Value IEC JEDEC
1B byte Bbyte
1024KiB kibibyte KBkilobyte
10242MiB mebibyte MBmegabyte
10243GiB gibibyte GBgigabyte
10244TiB tebibyte
10245PiB pebibyte
10246EiB exbibyte
10247ZiB zebibyte
10248YiB yobibyte

Definition

1 MiB = 220 bytes = 1048576bytes = 1024 kibibytes
1024 MiB = 1 gibibyte (GiB)

The prefix mebi is a binary prefix and multiplier derived from the SI prefix mega and the word binary. Its value is 10242, having the same power of 1024 as the power of 1000 of its decimal counterpart, the prefix mega (10002).

Despite its official status, the unit mebibyte is not commonly used even when reporting byte counts calculated in binary multiples, but is often represented as a megabyte. The discrepancy may cause confusion, since operating systems using the binary method report lower numerical values for storage size than advertised by manufacturers, such as disk drive manufacturers, who strictly use decimal units.

History and usage

The binary prefixes, including mebi, were defined by the International Electrotechnical Commission (IEC) in December 1998. All major standards bodies have endorsed the use of them for binary multiples.

Prior to this official definition, the unit megabyte was originally used in computer science to mean one million bytes (for example for 35 MB hard drive would be capable of storing 35 million bytes). Later the same term 'megabyte' was used to mean 1048576 bytes in the context of computer memory, although it continued to mean exactly one million (1000000) bytes in the context of computer storage. [8] The error associated with this ambiguity is relatively small for the megabyte.

In 1995, the International Union of Pure and Applied Chemistry's Interdivisional Committee on Nomenclature and Symbols decided to attempt to resolve this ambiguity by proposing new prefixes for powers of 1024. [9] [10] Accepted by the International Electrotechnical Commission (IEC), the IEC published the standard in January 1999. [11] [12] [13] [14]

Some operating systems still compute file size in mebibytes, but report the number as MB (megabytes). For example, all versions of the Microsoft Windows operating system show a file of 220 bytes as "1.00 MB" or "1,024 KB" in its file properties dialog and show a file of 106 (1000000) bytes as 976 KB.

All versions of Apple's operating systems had the same behavior until 2009 with Mac OS X version 10.6, which instead uses megabytes for all file and disk sizes, so it reports a 106 byte file as 1 MB. [15] [16]

The Ubuntu developer Canonical implemented an updated units policy in 2010 and as of Ubuntu 10.10 all versions use IEC binary prefixes for base-2 quantities and SI prefixes for base-10 quantities. [17]

See also

Related Research Articles

A binary prefix is a unit prefix for multiples of units in data processing, data transmission, and digital information, notably the bit and the byte, to indicate multiplication by a power of 2.

The gigabyte is a multiple of the unit byte for digital information. The prefix giga means 109 in the International System of Units (SI). Therefore, one gigabyte is one billion bytes. The unit symbol for the gigabyte is GB.

Giga ( or ) is a unit prefix in the metric system denoting a factor of a short-scale billion or long-scale milliard (109 or 1000000000). It has the symbol G.

The kilobyte is a multiple of the unit byte for digital information.

The megabyte is a multiple of the unit byte for digital information. Its recommended unit symbol is MB. The unit prefix mega is a multiplier of 1000000 (106) in the International System of Units (SI). Therefore, one megabyte is one million bytes of information. This definition has been incorporated into the International System of Quantities.

A metric prefix is a unit prefix that precedes a basic unit of measure to indicate a multiple or submultiple of the unit. All metric prefixes used today are decadic. Each prefix has a unique symbol that is prepended to any unit symbol. The prefix kilo-, for example, may be added to gram to indicate multiplication by one thousand: one kilogram is equal to one thousand grams. The prefix milli-, likewise, may be added to metre to indicate division by one thousand; one millimetre is equal to one thousandth of a metre.

The gibibyte is a multiple of the unit byte for digital information. The binary prefix gibi means 230, therefore one gibibyte is equal to 1073741824bytes = 1024 mebibytes. The unit symbol for the gibibyte is GiB. It is one of the units with binary prefixes defined by the International Electrotechnical Commission (IEC) in 1998.

The exbibyte (symbol EiB) is 260 bytes of digital information. It is one of a set of units with binary prefixes defined by the International Electrotechnical Commission (IEC).

The kibibyte is a multiple of the unit byte for digital information. The binary prefix kibi means 210, or 1024; therefore, 1 kibibyte is 1024 bytes. The unit symbol for the kibibyte is KiB.

The megabit is a multiple of the unit

  1. [[]] bit for digital information. The prefix mega (symbol M) is defined in the International System of Units (SI) as a multiplier of 106 (1 million), and therefore

The pebibyte is a multiple of the unit byte for digital information. It is a member of the set of units with binary prefixes defined by the International Electrotechnical Commission (IEC). Its unit symbol is PiB.

IEC 60027 is a technical international standard for letter symbols published by the International Electrotechnical Commission, comprising the following parts:

The kibibit is a multiple of the bit, a unit of digital information storage, using the standard binary prefix kibi, which has the symbol Ki, meaning 210. The unit symbol of the kibibit is Kibit.

The mebibit is a multiple of the bit, a unit of information, prefixed by the standards-based multiplier "mebi" (symbol Mi), a binary prefix meaning 220. The unit symbol of the mebibit is Mibit.

A unit prefix is a specifier or mnemonic that is prepended to units of measurement to indicate multiples or fractions of the units. Units of various sizes are commonly formed by the use of such prefixes. The prefixes of the metric system, such as kilo and milli, represent multiplication by powers of ten. In information technology it is common to use binary prefixes, which are based on powers of two. Historically, many prefixes have been used or proposed by various sources, but only a narrow set has been recognised by standards organisations.

IEEE 1541-2002 is a standard issued in 2002 by the Institute of Electrical and Electronics Engineers (IEEE) concerning the use of prefixes for binary multiples of units of measurement related to digital electronics and computing.

ISO 80000 or IEC 80000 is an international standard developed and promulgated jointly by the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC).

The JEDEC memory standards are the specifications for semiconductor memory circuits and similar storage devices promulgated by the Joint Electron Device Engineering Council (JEDEC) Solid State Technology Association, a semiconductor trade and engineering standardization organization.

In telecommunications, data-transfer rate is the average number of bits (bitrate), characters or symbols (baudrate), or data blocks per unit time passing through a communication link in a data-transmission system. Common data rate units are multiples of bits per second (bit/s) and bytes per second (B/s). For example, the data rates of modern residential high-speed Internet connections are commonly expressed in megabits per second (Mbit/s).

This timeline of binary prefixes lists events in the history of the evolution, development, and use of units of measure for information, the bit and the byte, which are germane to the definition of the binary prefixes by the International Electrotechnical Commission (IEC) in 1998.

References

  1. International Electrotechnical Commission (January 2010). "IEC 60050 - International Electrotechnical Vocabulary - Details for IEV number 112-01-27" . Retrieved 2011-06-19.
  2. International Electrotechnical Commission (January 1999), IEC 60027-2 Amendment 2: Letter symbols to be used in electrical technology - Part 2: Telecommunications and electronics.
  3. "IEC 80000-13:2008". International Organization for Standardization . Retrieved 21 July 2013.
  4. Upgrading and Repairing PCs, Scott Mueller, Pg. 596, ISBN   0-7897-2974-1
  5. The silicon web: physics for the Internet age, Michael G. Raymer, Pg. 40, ISBN   978-1-4398-0311-0
  6. Knuth: Recent News. Cs-staff.stanford.edu. Retrieved on 2011-01-07.
  7. Atwood, Jeff. (2007-09-10) Gigabyte: Decimal vs. Binary. Coding Horror. Retrieved on 2011-01-07.
  8. NIST "Prefixes for binary multiples" https://physics.nist.gov/cuu/Units/binary.html
  9. IUCr 1995 Report - IUPAC Interdivisional Committee on Nomenclature and Symbols (IDCNS) http://ww1.iucr.org/iucr-top/cexec/rep95/idcns.htm
  10. "Binary Prefix" University of Aukland Department of Computer Science https://wiki.cs.auckland.ac.nz/stageonewiki/index.php/Binary_prefix
  11. NIST "Prefixes for binary multiples" https://physics.nist.gov/cuu/Units/binary.html
  12. Amendment 2 to IEC International Standard IEC 60027-2: Letter symbols to be used in electrical technology - Part 2: Telecommunications and electronics.
  13. HDD Turns 50 Years Today - The Chronicles
  14. Backman, R. B. (2004). The Description, Evolution, and Applications of Binary Prefixes.
  15. "How Mac OS X reports drive capacity". Apple Inc. 2009-08-27. Retrieved 2009-10-16.
  16. David Pogue (2011), Mac OS X Lion: The Missing Manual Missing Manual, Oreilly Series, O'Reilly Media, pp. 473–474, ISBN   978-1-4493-9749-4
  17. "Ubuntu UnitsPolicy". Ubuntu. 2010. Retrieved 2013-09-26.