Themegabyte is a multiple of the unitbyte for digital information. Its recommended unit symbol isMB. The unit prefixmega is a multiplier of1000000 (106) in theInternational System of Units (SI).[1] Therefore, one megabyte is one million bytes of information. This definition has been incorporated into theInternational System of Quantities.
In the computer and information technology fields, other definitions have been used that arose for historical reasons of convenience. A common usage has been to designate one megabyte as1048576bytes (220 B), a quantity that conveniently expresses the binary architecture of digital computer memory. Standards bodies have deprecated this binary usage of the mega- prefix in favor of a new set ofbinary prefixes,[2] by means of which the quantity 220 B is namedmebibyte (symbol MiB).
Definitions
The unit megabyte is commonly used for 10002 (one million) bytes or 10242 bytes. The interpretation of using base 1024 originated as technical jargon for the bytemultiples that needed to be expressed by the powers of 2 but lacked a convenient name. As 1024 (210) approximates 1000 (103), roughly corresponding to the SI prefixkilo-, it was a convenient term to denote the binary multiple. In 1999, theInternational Electrotechnical Commission (IEC) published standards forbinary prefixes requiring the use ofmegabyte to denote 10002 bytes, andmebibyte to denote 10242 bytes. By the end of 2009, the IEC Standard had been adopted by theIEEE,EU,ISO andNIST. Nevertheless, the term megabyte continues to be widely used with different meanings.
1 MB =1048576 bytes (= 10242 B = 220 B) is the definition used byMicrosoft Windows in reference tocomputer memory, such asrandom-access memory (RAM). This definition is synonymous with the unambiguous binary unitmebibyte. In this convention, one thousand and twenty-four megabytes (1024 MB) is equal to one gigabyte (1 GB), where 1 GB is 10243 bytes (i.e., 1 GiB).
Mixed
1 MB =1024000 bytes (= 1000×1024 B) is the definition used to describe the formatted capacity of the 1.44 MB3.5-inch HDfloppy disk, which actually has a capacity of1474560bytes.[5]
Randomly addressable semiconductor memory doubles in size for each address lane added to an integrated circuit package, which favors counts that are powers of two. The capacity of a disk drive is the product of the sector size, number of sectors per track, number of tracks per side, and the number of disk platters in the drive. Changes in any of these factors would not usually double the size.
Examples of use
1.44 MBfloppy disks can store 1,474,560 bytes of data. The full resolution image of this photograph of a floppy diskette is itself 0.842 megabytes.
Depending on compression methods andfile format,a megabyte of data can roughly be:
