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Megabyte

From Biocrawler, the free encyclopedia.

Multiples of bytes
Decimal prefixes			Binary prefixes
Name	Symbol	Multiple	Name	Symbol	Multiple
kilobyte	kB	10³	kibibyte	KiB	2¹⁰
megabyte	MB	10⁶	mebibyte	MiB	2²⁰
gigabyte	GB	10⁹	gibibyte	GiB	2³⁰
terabyte	TB	10¹²	tebibyte	TiB	2⁴⁰
petabyte	PB	10¹⁵	pebibyte	PiB	2⁵⁰
exabyte	EB	10¹⁸	exbibyte	EiB	2⁶⁰
zettabyte	ZB	10²¹
yottabyte	YB	10²⁴

This article is about a unit of data measurement. For the cartoon character, see ReBoot.

A megabyte (derived from the SI prefix mega-) is a unit of information or computer storage equal to one million bytes. It is commonly abbreviated MB in writing (not to be confused with Mb, which is used for megabit) and meg in writing or speech.

Because of irregularities in using the binary prefix in the definition and usage of the kilobyte, the exact number in common practice could be any one of the following:

1 000 000 bytes (1000², 10⁶): This definition is used in most networking contexts and discussions of storage hardware, including hard drives and DVDs. It is consistent with the SI prefix and most other uses of the prefix in computing, like in CPU clock speeds or measures of performance.
1 024 000 bytes (1 024×1 000): This definition is used in a small number of storage contexts, most notably the "1.44 MB" (actually 1 474 560 bytes) "3.5-inch" (actually 90 mm) high-density floppy diskette.
1 048 576 bytes (1024², 2²⁰): This definition is used for nearly all discussions of computer memory (most easily manufactured in power-of-two capacities) and CDs. As of 2005, most software uses this definition to express storage capacity. This quantity may be referred to unambiguously as a mebibyte (see binary prefixes).

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Megabytes in use

As of 2005, the RAM capacity of most personal computers is measured in mebibytes, although the word "megabyte" is (mistakenly) used. For example, 512 "megabytes" of RAM actually designates 512 mebibytes, or a little less than 537 megabytes.

Some rules of thumb: A megabyte stores roughly one book, or a hundred small images, or roughly a minute of compressed music. A digital photograph produced by a typical digital camera might be between 1–4 MB depending on the camera's image resolution and level of compression used.

Until the introduction of hard drives with a capacity of one gigabyte or more, the capacity of hard drives was measured in megabytes.

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