メガバイト
- 関
- Mbyte
WordNet
- a unit of information equal to 1000 kilobytes or 10^6 (1,000,000) bytes (同)M, MB
- a unit of information equal to 1024 kibibytes or 2^20 (1,048,576) bytes (同)mebibyte, M, MB, MiB
Wikipedia preview
出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/09/19 03:20:15」(JST)
[Wiki ja表示]
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この項目では、大きさを表す単位について説明しています。ゲーム『バイオハザード アウトブレイク FILE2』に登場する同名クリーチャーについては「バイオハザード アウトブレイク FILE2」をご覧ください。 |
| バイトの単位一覧 |
| SI接頭辞 |
2進接頭辞 |
| 単位（記号） |
慣用値 |
SI基準 |
単位（記号） |
値 |
SIとの差（概数） |
| キロバイト (kB) |
210 |
103 |
キビバイト (KiB) |
210 |
2.400000% |
| メガバイト (MB) |
220 |
106 |
メビバイト (MiB) |
220 |
4.857600% |
| ギガバイト (GB) |
230 |
109 |
ギビバイト (GiB) |
230 |
7.374182% |
| テラバイト (TB) |
240 |
1012 |
テビバイト (TiB) |
240 |
9.951163% |
| ペタバイト (PB) |
250 |
1015 |
ペビバイト (PiB) |
250 |
12.589991% |
| エクサバイト (EB) |
260 |
1018 |
エクスビバイト (EiB) |
260 |
15.292150% |
| ゼタバイト (ZB) |
270 |
1021 |
ゼビバイト (ZiB) |
270 |
18.059162% |
| ヨタバイト (YB) |
280 |
1024 |
ヨビバイト (YiB) |
280 |
20.892582% |
メガバイト (megabyte) は、データの量やコンピュータの記憶装置の大きさを表す単位である。MBと略記される（Mbはメガビットの意味で用いられることが多い）。
メガは本来はSI接頭辞の一つで基本となる単位の106倍を意味するので、メガバイトは本来は106バイト（1000000バイト、すなわち1000キロバイト）となる。しかし、実際には異なる意味で用いられることが多い。
バイト・ビットに対しては、SI接頭辞を10の累乗倍ではなく 210 = 1024 の累乗倍の意味として用いる慣習がある。それによれば、キロ (k) は 210 = 1024 倍、メガは 220 = 10242 = 1048576 倍となる。よって 1MB = 1048576B となる。このような混乱があるため、1048576Bは2進接頭辞を用い、1メビバイト (mebibyte, mega binary byte) と呼び、MBではなくMiBと書く方式が近年少しずつ普及しはじめている。なお、1MB = 1048576B と 1MB = 1000000B の間には、キロバイトを 1KB = 1024B と 1kB = 1000B で区別するような記号の区別はない。
実際の使い分け
半導体メモリやソフトウェアのメーカーは 1MB = 1024KB とし、ソフトウェアはユーザー向けにも1MB = 1024KB で表示する。一方、ハードディスクやCD-ROMなどのメーカーは 1MB = 1000000B とする。そのため、同じディスクでもメーカー公称とOSによる表示とでは容量が異なる。
まれに1000と1024が混ざった 1024000B を意味して 1MB とされていることがある。2HDフロッピーディスクの、18セクタフォーマットの容量は1.44MBとされるが、これは 1474560B であり、1.44 × 1024000 である。2EDの2.88MB等も同様である。
ビットレートの単位Mbps（メガビット毎秒）は、常に1000000bpsである。
関連項目
[Wiki en表示]
This article is about the unit of data. For the ReBoot character, see Megabyte (ReBoot).
|
Multiples of bytes |
| Decimal |
| Value |
Metric |
| 1000 |
kB |
kilobyte |
| 10002 |
MB |
megabyte |
| 10003 |
GB |
gigabyte |
| 10004 |
TB |
terabyte |
| 10005 |
PB |
petabyte |
| 10006 |
EB |
exabyte |
| 10007 |
ZB |
zettabyte |
| 10008 |
YB |
yottabyte |
|
| Binary |
| Value |
IEC |
JEDEC |
| 1024 |
KiB |
kibibyte |
KB |
kilobyte |
| 10242 |
MiB |
mebibyte |
MB |
megabyte |
| 10243 |
GiB |
gibibyte |
GB |
gigabyte |
| 10244 |
TiB |
tebibyte |
– |
| 10245 |
PiB |
pebibyte |
– |
| 10246 |
EiB |
exbibyte |
– |
| 10247 |
ZiB |
zebibyte |
– |
| 10248 |
YiB |
yobibyte |
– |
|
| Orders of magnitude of data |
The megabyte is a multiple of the unit byte for digital information. Its recommended unit symbol is MB, but sometimes MByte is used. The unit prefix mega is a multiplier of 1000000 (106) in the International System of Units (SI).[1] Therefore, one megabyte is one million bytes of information. This definition has been incorporated into the International System of Quantities.
However, in the computer and information technology fields, several other definitions are used that arose for historical reasons of convenience. A common usage has been to designate one megabyte as 1048576bytes (220 B), a measurement that conveniently expresses the binary multiples inherent in digital computer memory architectures. However, most standards bodies have deprecated this usage in favor of a set of binary prefixes,[2] in which this measurement is designated by the unit mebibyte (MiB). Less common is a measurement that used the megabyte to mean 1000×1024 (1024000) bytes.[2]
Contents
- 1 Definitions
- 2 Examples of use
- 3 See also
- 4 References
- 5 External links
Definitions
The megabyte is commonly used to measure either 10002 bytes or 10242 bytes. The interpretation of using base 1024 originated as a compromise 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-, it began to be used for binary multiples as well. In 1998 the International Electrotechnical Commission (IEC) proposed standards for binary prefixes requiring the use of megabyte to strictly denote 10002 bytes and mebibyte to denote 10242 bytes. By the end of 2009, the IEC Standard had been adopted by the IEEE, EU, ISO and NIST. Nevertheless, the term megabyte continues to be widely used with different meanings:
- Base 10
- 1 MB = 1000000 bytes (= 10002 B = 106 B) is the definition recommended by the International System of Units (SI) and the International Electrotechnical Commission IEC.[2] This definition is used in networking contexts and most storage media, particularly hard drives, flash-based storage,[3] 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 10.6 file manager is a notable example of this usage in software. Since Snow Leopard, file sizes are reported in decimal units.[4]
- Base 2
Main article: mebibyte
- 1 MB = 1048576 bytes (= 10242 B = 220 B) is the definition used by Microsoft Windows in reference to computer memory, such as RAM. This definition is synonymous with the unambiguous binary prefix mebibyte.
- Mixed
- 1 MB = 1024000 bytes (= 1000×1024) B is the definition used to describe the formatted capacity of the 1.44 MB 3.5inch HD floppy disk, which actually has a capacity of 1474560bytes.
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. Sector sizes were set as powers of two (most common 512 bytes or 4096 bytes) for convenience in processing. It was a natural extension to give the capacity of a disk drive in multiples of the sector size, giving a mix of decimal and binary multiples when expressing total disk capacity.
Examples of use
1.44 MB floppy disks can store 1,474,560 bytes of data. MB in this context means 1,000×1,024 bytes.
Depending on compression methods and file format, a megabyte of data can roughly be:
- a 1 megapixel bitmap image with 256 colors (8 bits/pixel color depth) stored without any compression.
- a 4 megapixel JPEG image with normal compression.
- about 1 minute of 128 kbit/s MP3 compressed music.
- 6 seconds of uncompressed CD audio.
- a typical English book volume in plain text format (500 pages × 2000 characters per page).
The human genome consists of DNA representing 800 MB of data. The parts that differentiate one person from another can be compressed to 4 MB.[5]
See also
- Timeline of binary prefixes
- Gigabyte § Consumer confusion
References
- ^ http://www.bipm.org/en/si/si_brochure/chapter3/prefixes.html
- ^ a b c "Definitions of the SI units: The binary prefixes". National Institute of Standards and Technology.
- ^ SanDisk USB Flash Drive "Note: 1 megabyte (MB) = 1 million bytes; 1 gigabyte (GB) = 1 billion bytes."
- ^ "How Mac OS X reports drive capacity". Apple Inc. 2009-08-27. Retrieved 2009-10-16.
- ^ Christley, S. .; Lu, Y. .; Li, C. .; Xie, X. . (2008). "Human genomes as email attachments". Bioinformatics 25 (2): 274–275. doi:10.1093/bioinformatics/btn582. PMID 18996942.
External links
- Historical Notes About The Cost Of Hard Drive Storage Space
- the megabyte (established definition in Networking and Storage industries; from whatis.com)
- International Electrotechnical Commission definitions
- IEC prefixes and symbols for binary multiples
|
Units of information
|
|
| Base unit |
|
|
| Platform-dependent units |
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| Platform-independent units |
- Quartet
- Octet
- Hextet
(Triad
- Tetrad
- Octad)
|
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| Traditional bit units |
- Kilobit
- Megabit
- Gigabit
- Terabit
- Petabit
- Exabit
- Zettabit
- Yottabit
|
|
| Traditional byte units |
- Kilobyte
- Megabyte
- Gigabyte
- Terabyte
- Petabyte
- Exabyte
- Zettabyte
- Yottabyte
|
|
| IEC bit units |
- Kibibit
- Mebibit
- Gibibit
- Tebibit
- Pebibit
- Exbibit
- Zebibit
- Yobibit
|
|
| IEC byte units |
- Kibibyte
- Mebibyte
- Gibibyte
- Tebibyte
- Pebibyte
- Exbibyte
- Zebibyte
- Yobibyte
|
|
English Journal
- Retinal video recordings at different compression levels: a novel video-based imaging technology for diabetic retinopathy screening.
- Ting DS1, Tay-Kearney ML, Constable I, Vignarajan J, Kanagasingam Y.
- Eye (London, England).Eye (Lond).2013 Jul;27(7):848-53. doi: 10.1038/eye.2013.53. Epub 2013 May 10.
- BACKGROUND: To evaluate the optimal compression level of retinal color digital video recordings, a novel video-based imaging technology, in screening for diabetic retinopathy (DR).DESIGN: Evaluation of a diagnostic technique.METHODS: A total of 36 retinal videos, captured using EyeScan (Ophthalmic I
- PMID 23661156
- The cost of being wireless: a usage analysis of the 'PubMed for Handhelds' portal at the point-of-care.
- Ducut E1, Liu F, Fontelo P.
- AMIA ... Annual Symposium proceedings / AMIA Symposium. AMIA Symposium.AMIA Annu Symp Proc.2008 Nov 6:936.
- We analyzed the server logs of the 'PubMed for Handhelds' portal for a 30-day period, defined user characteristics and used a smartphone to do 'typical' MEDLINE searches. We then determined the amount of data exchanged between server and mobile device. Wireless Web access can be a useful tool to the
- PMID 18998780
- Evaluation of a documentation system for airway management training.
- Cone SW1, Rafiq A, Merrell RC.
- Simulation in healthcare : journal of the Society for Simulation in Healthcare.Simul Healthc.2008 Summer;3(2):111-5. doi: 10.1097/SIH.0b013e31815c96f7.
- INTRODUCTION: Resuscitation science is a dynamic part of healthcare training, with an expanding role for simulation. Historically, performance measurement and documentation relied upon the presence of an instructor, an expensive and potentially inaccurate assessment tradition that tied performance t
- PMID 19088650
- High performance computing environment for multidimensional image analysis.
- Rao AR1, Cecchi GA, Magnasco M.
- BMC cell biology.BMC Cell Biol.2007 Jul 10;8 Suppl 1:S9.
- BACKGROUND: The processing of images acquired through microscopy is a challenging task due to the large size of datasets (several gigabytes) and the fast turnaround time required. If the throughput of the image processing stage is significantly increased, it can have a major impact in microscopy app
- PMID 17634099
Japanese Journal
- Ultra-Fast Spectrometric Cathodoluminescence Scanning Microscopy for Materials Analysis
- ,
- MATERIALS TRANSACTIONS 51(2), 231-236, 2010
- … The shortest signal sampling time is 8 s for a frame of 512×512 pixels and all the imaging and spectroscopic signals are stored in two 8-megabyte files. …
- NAID 130004454407
- 山内 長承,城下 輝治,佐野 哲央 [他],高橋 修
- 情報処理学会論文誌 39(6), 2009-2019, 1998-06-15
- コンピュータネットワークを介して同一の情報を多数の受信者に効率良く配布する機構として, 高信頼同報バルク転送機構RMTP (Reliable Multicast Transport Protocol)を設計し, 評価する.本論文では, 適用例から要求条件を整理した結果, 数千から数万端末への数10MBのバルクデータの一斉同報配布, TCPと同程度の転送信頼性, 送信サーバによる到着確認, 情報秘匿 …
- NAID 110002722214
- Simplification of Optical Disk Cluster Drive
- TANAKA Kunimaro,NEGISHI Yoshinori,YOSHIMOTO Kyosuke,TAKAHASHI Yasunori
- IEICE transactions on electronics E80-C(9), 1149-1153, 1997-09-25
- … Cluster drives, which use optical disk drives, are a good buffer memory for this purpose because the cost per megabyte is low. …
- NAID 110003211325
- A 500Megabyte/s Data-Rate 4.5M DRAM (Special Section on the 1992 VLSI Circuits Symposium)
- Kushiyama Natsuki,Ohshima Shigeo,Stark Don,Noji Hiroyuki,Sakurai Kiyofumi,Takase Satoru,Furuyama Tohru,Barth RichardM.,Chan Andy,Dillon John,Gasbarro JamesA.,Griffin MatthewM.,Horowitz Mark,Lee ThomasH.,LeeVictor
- IEICE transactions on electronics E76-C(5), 830-838, 1993-05-25
- … A 4.5M DRAM that interfaces to the bus directly and provides a 500-megabyte / s data rate has been developed. …
- NAID 110003220178
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メガバイト
- 関
- megabyte
