HOME

TheInfoList



OR:

The megabyte is a multiple of the unit
byte The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable uni ...
for digital information. Its recommended unit symbol is MB. The unit prefix ''mega'' is a multiplier of (106) in the
International System of Units The International System of Units, known by the international abbreviation SI in all languages and sometimes pleonastically as the SI system, is the modern form of the metric system and the world's most widely used system of measurement. ...
(SI). Therefore, one megabyte is one million bytes of information. This definition has been incorporated into the International 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 as (220 B), a quantity that conveniently expresses the binary architecture of digital computer memory. The standards bodies have deprecated this usage of the megabyte in favor of a new set of binary prefixes, in which this quantity is designated by the unit mebibyte (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 byte multiples 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 prefix
kilo- Kilo is a decimal unit prefix in the metric system denoting multiplication by one thousand (103). It is used in the International System of Units, where it has the symbol k, in lowercase. The prefix ''kilo'' is derived from the Greek wor ...
, it was a convenient term to denote the binary multiple. In 1998, the
International Electrotechnical Commission The International Electrotechnical Commission (IEC; in French: ''Commission électrotechnique internationale'') is an international standards organization that prepares and publishes international standards for all electrical, electronic and ...
(IEC) proposed standards for
binary prefix A binary prefix is a unit prefix for multiples of units. It is most often used in data processing, data transmission, and digital information, principally in association with the bit and the byte, to indicate multiplication by a power  ...
es requiring the use of ''megabyte'' to denote 10002 bytes, and '' mebibyte'' to denote 10242 bytes. By the end of 2009, the IEC Standard had been adopted by the
IEEE The Institute of Electrical and Electronics Engineers (IEEE) is a 501(c)(3) professional association for electronic engineering and electrical engineering (and associated disciplines) with its corporate office in New York City and its operati ...
, EU, ISO and NIST. Nevertheless, the term megabyte continues to be widely used with different meanings. ; Base 10 : 1 MB = bytes (= 10002 B = 106 B) is the definition following the rules of the
International System of Units The International System of Units, known by the international abbreviation SI in all languages and sometimes pleonastically as the SI system, is the modern form of the metric system and the world's most widely used system of measurement. ...
(SI), and the
International Electrotechnical Commission The International Electrotechnical Commission (IEC; in French: ''Commission électrotechnique internationale'') is an international standards organization that prepares and publishes international standards for all electrical, electronic and ...
(IEC). This definition is used in
computer network A computer network is a set of computers sharing resources located on or provided by network nodes. The computers use common communication protocols over digital interconnections to communicate with each other. These interconnections are ...
ing contexts and most storage media, particularly
hard drive A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device that stores and retrieves digital data using magnetic storage with one or more rigid rapidly rotating platters coated with mag ...
s, flash-based storage, and DVDs, and is also consistent with the other uses of the SI prefix in computing, such as CPU clock speeds or measures of performance. The
Mac OS X macOS (; previously OS X and originally Mac OS X) is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac computers. Within the market of desktop and lap ...
10.6 file manager is a notable example of this usage in software. Since Snow Leopard, file sizes are reported in decimal units. In this convention, one thousand megabytes (1000 MB) is equal to one gigabyte (1 GB), where 1 GB is one billion bytes. ;Base 2 : 1 MB = bytes (= 10242 B = 220 B) is the definition used by
Microsoft Windows Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for ...
in reference to
computer memory In computing, memory is a device or system that is used to store information for immediate use in a computer or related computer hardware and digital electronic devices. The term ''memory'' is often synonymous with the term '' primary storag ...
, such as
random-access memory Random-access memory (RAM; ) is a form of computer memory that can be read and changed in any order, typically used to store working data and machine code. A random-access memory device allows data items to be read or written in almost the ...
(RAM). This definition is synonymous with the unambiguous binary unit mebibyte. 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 = bytes (= 1000×1024 B) is the definition used to describe the formatted capacity of the 1.44 MB HD floppy disk, which actually has a capacity of .Tracing the History of the Computer - History of the Floppy Disk
/ref> 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

Depending on compression methods and file format, a megabyte of data can roughly be: * a 1
megapixel In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a raster image, or the smallest point in an all points addressable display device. In most digital display devices, pixels are the ...
bitmap image (e.g. ~ 1152 × 864) with 256 colors (8 bits/pixel color depth) stored without any compression. * a 4megapixel
JPEG JPEG ( ) is a commonly used method of lossy compression for digital images, particularly for those images produced by digital photography. The degree of compression can be adjusted, allowing a selectable tradeoff between storage size and imag ...
image (e.g. ~ 2560 × 1600) with normal compression. * 6seconds of 44.1 kHz/16 bit uncompressed CD audio. * 1minute of 128 kbit/s MP3 lossy compressed audio. * a typical English book volume in plain text format (500 pages × 2000 characters per page). The human genome consists of DNA representing 800MB of data. The parts that differentiate one person from another can be compressed to 4MB.


See also

* Timeline of binary prefixes *


References


External links


Historical Notes About The Cost Of Hard Drive Storage Space


(established definition in Networking and Storage industries; fro




IEC prefixes and symbols for binary multiplesAdded Archived
t
How Many MB in a GB
{{Computer Storage Volumes Units of information