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).[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 quantity is designated by the unit mebibyte (MiB). Less common is a convention that used the megabyte to mean 1000×1024 (1024000) bytes.[2]


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 was a convenient term to denote the binary multiple. 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]

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 = 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.

In this convention, one thousand and twenty-four megabytes (1024 MB) is equal to one gigabyte (1 GB), where 1 GB is 10243 bytes.

1 MB = 1024000 bytes (= 1000×1024 B) is the definition used to describe the formatted capacity of the 1.44 MB 3.5-inch 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.
  • approximately 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


  1. ^ "Archived copy". Archived from the original on June 7, 2007. Retrieved June 1, 2007.CS1 maint: Archived copy as title (link)
  2. ^ a b c "Definitions of the SI units: The binary prefixes". National Institute of Standards and Technology.
  3. ^ SanDisk USB Flash Drive "Note: 1 megabyte (MB) = 1 million bytes; 1 gigabyte (GB) = 1 billion bytes."
  4. ^ "How Mac OS X reports drive capacity". Apple Inc. 2009-08-27. Retrieved 2009-10-16.
  5. ^ 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

Binary prefix

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 computer industry has historically used the units kilobyte, megabyte, and gigabyte, and the corresponding symbols KB, MB, and GB, in at least two slightly different measurement systems. In citations of main memory (RAM) capacity, gigabyte customarily means 1073741824 bytes. As this is a power of 1024, and 1024 is a power of two (210), this usage is referred to as a binary measurement.

In most other contexts, the industry uses the multipliers kilo, mega, giga, etc., in a manner consistent with their meaning in the International System of Units (SI), namely as powers of 1000. For example, a 500 gigabyte hard disk holds 500000000000 bytes, and a 1 Gbit/s (gigabit per second) Ethernet connection transfers data at 1000000000 bit/s. In contrast with the binary prefix usage, this use is described as a decimal prefix, as 1000 is a power of 10 (103).

The use of the same unit prefixes with two different meanings has caused confusion. Starting around 1998, the International Electrotechnical Commission (IEC) and several other standards and trade organizations addressed the ambiguity by publishing standards and recommendations for a set of binary prefixes that refer exclusively to powers of 1024. Accordingly, the US National Institute of Standards and Technology (NIST) requires that SI prefixes only be used in the decimal sense: kilobyte and megabyte denote one thousand bytes and one million bytes respectively (consistent with SI), while new terms such as kibibyte, mebibyte and gibibyte, having the symbols KiB, MiB, and GiB, denote 1024 bytes, 1048576 bytes, and 1073741824 bytes, respectively. In 2008, the IEC prefixes were incorporated into the international standard system of units used alongside the International System of Quantities (see ISO/IEC 80000).

Bitcoin Classic

Bitcoin Classic was one of several forks of the Bitcoin reference implementation Bitcoin Core aiming to increase the transaction processing capacity of Bitcoin by increasing the block size limit. Blocks, which contain transaction data, form the basic structure of the immutable blockchain. Bitcoin Classic started out as similar to, though less aggressive than, the Bitcoin XT fork, which never managed to get the support it needed. Bitcoin Classic in its first 8 months promoted a single increase of the maximum block size from one megabyte to two megabytes. In November 2016 this changed and the project moved to a solution that moved the limit out of the software rules into the hands of the miners and nodes.Bitcoin Classic was also an attempt to move the technical governance of this decentralized and independent Bitcoin project from the developers of the original Bitcoin to a voting process involving a larger community of miners, businesses, developers and users. There was no formal activation method for the software, but due to the nature of Bitcoin a supermajority needed to support it.

On November 10, 2017, Bitcoin Classic ceased operation.

Bitcoin Unlimited

Bitcoin Unlimited (BU) is a full node implementation for the bitcoin and Bitcoin Cash networks. Compared to the Bitcoin Core client hard-coding the block size limit to one megabyte, from which it is forked, Bitcoin Unlimited allows users to signal which block size limit they prefer, find the limit having a majority consensus and automatically track the largest proof-of-work, regardless of block size. However, if a block greater than one megabyte in size is accepted by Bitcoin Unlimited and rejected by nodes with a block size limit, a fork of the network will occur, resulting in two separate blockchains with Bitcoin Unlimited nodes following the chain with the largest proof-of-work.The release of Bitcoin Unlimited follows the release of Bitcoin XT and Bitcoin Classic, alternative proposals which aimed to increase bitcoin's transaction capacity of around 2.5-3 transactions per second by increasing the hard-coded block size limit. Bitcoin Unlimited developers maintain an edition of their software that works on the Bitcoin Cash network, known as "BU Cash".

Data-rate units

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).

File size

File size is a measure of how much data a computer file contains or, alternately, how much storage it consumes. Typically, file size is expressed in units of measurement based on the byte. By convention, file size units use either a metric prefix (as in megabyte and gigabyte) or a binary prefix (as in mebibyte and gibibyte).When a file is written to a file system, which is the case in most modern devices, it may consume slightly more disk space than the file requires. This is because the file system rounds the size up to include any unused space left over in the last disk sector used by the file. (A sector is the smallest amount of space addressable by the file system. The size of a disk sectors is several hundred or several thousands bytes.) The wasted space is called slack space or internal fragmentation. Although smaller sector sizes allow for denser use of disk space, they decrease the operational efficiency of the file system.

The maximum file size a file system supports depends not only on the capacity of the file system, but also on the number of bits reserved for the storage of file size information. The maximum file size in the FAT32 file system, for example, is 4,294,967,295 bytes, which is one byte less than four gibibytes.

Kilobyte (KB) (JEDEC), is sometimes referred to unambiguously as kibibyte (KiB)(IEC). Sometimes kB, with lower cased SI-prefix k- for kilo (1000), is used, then always equaling 1000 bytes.

A file system may display all sizes with the metric system with only kB on small files indicating it, while some file systems/operating systems would display sizes in, the traditionally used on computers, binary system for all sizes, e.g. KB, even if hard disk manufacturers may prefer to use the metric system (for e.g. GB = 1,000,000,000 bytes and TB = 1000 GB), to show higher capacity numbers for their products.

File transfers (e.g. "downloads") may use rates of units of bytes (e.g. MB/s) in binary rather than metric system, while networking hardware, such as WiFi, always uses the metric system (Mbits/s, Gbits/s etc.). of units of bits (and it needs to send more than the files themselves, so some overhead needs to be factored in), making superficially similar terms very incompatible.


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 1000000000bytes. The unit symbol for the gigabyte is GB.

This definition is used in all contexts of science, engineering, business, and many areas of computing, including hard drive, solid state drive, and tape capacities, as well as data transmission speeds. However, the term is also used in some fields of computer science and information technology to denote 1073741824 (10243 or 230) bytes, particularly for sizes of RAM. The use of gigabyte may thus be ambiguous. Hard disk capacities as described and marketed by drive manufacturers using the standard metric definition of the gigabyte, but when a 500-GB drive's capacity is displayed by, for example, Microsoft Windows, it is reported as 465 GB, using a binary interpretation.

To address this ambiguity, the International System of Quantities standardizes the binary prefixes which denote a series of integer powers of 1024. With these prefixes, a memory module that is labeled as having the size 1GB has one gibibyte (1GiB) of storage capacity.

Intel 80188

The Intel 80188 microprocessor was a variant of the Intel 80186. The 80188 had an 8-bit external data bus instead of the 16-bit bus of the 80186; this made it less expensive to connect to peripherals. The 16-bit registers and the one megabyte address range were unchanged, however. It had a throughput of 1 million instructions per second.


The kibibyte is a multiple of the unit byte for quantities of 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 unit was established by the International Electrotechnical Commission (IEC) in 1998, has been accepted for use by all major standards organizations, and is part of the International System of Quantities. The kibibyte was designed to replace the kilobyte in those computer science contexts in which the term kilobyte is used to mean 1024 bytes. The interpretation of kilobyte to denote 1024 bytes, conflicting with the SI definition of the prefix kilo (1000), used to be common.


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

The International System of Units (SI) defines the prefix kilo as 1000 (103); per this definition, one kilobyte is 1000 bytes. The internationally recommended unit symbol for the kilobyte is kB.In some areas of information technology, particularly in reference to digital memory capacity, kilobyte instead denotes 1024 (210) bytes. This arises from the powers-of-two sizing common to memory circuit design. In this context, the symbols K and KB are often used.

List of ReBoot characters

This is a list of characters from the animated television series ReBoot.

Most ReBoot characters are named after technical computer terms or pieces of computer hardware.


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

The unit was established by the International Electrotechnical Commission (IEC) in 1998. 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. Many Linux distributions use the unit, but it is not widely acknowledged within the industry or media.


The megabit is a multiple of the unit 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

1 megabit = 106bits = 1000000bits = 1000 kilobits.The megabit has the unit symbol Mb or Mbit.

The megabit is closely related to the mebibit, a unit multiple derived from the binary prefix mebi (symbol Mi) of the same order of magnitude, which is equal to 220bits = 1048576bits, or approximately 5% larger than the megabit. Despite the definitions of these new prefixes for binary-based quantities of storage by international standards organizations, memory semiconductor chips are still marketed using the metric prefix names to designate binary multiples.

Using the common byte size of eight bits and the standardized metric definition of megabit and kilobyte, 1 megabit is equal to 125 kilobytes (kB) or approximately 122 kibibytes (KiB).

The megabit is widely used when referring to data transfer rates of computer networks or telecommunications systems. Network transfer rates and download speeds often use the megabit as the amount transferred per time unit, e.g., a 100 Mbit/s (megabit per second) Fast-Ethernet connection, or a 10 Mbit/s Internet access service, whereas the sizes of data units (files) transferred over these networks are often measured in megabytes. To achieve a transfer rate of one megabyte per second one needs a network connection with a transfer rate of eight megabits per second.

Nokia 6620

The 6620 is a smartphone created by Nokia, announced in 2005, running on Series 60 2nd Edition and the Symbian operating system. It was the first EDGE-capable phone for the Americas' market.It is a version of Nokia's 6600 smartphone for the North American market, with all the features of the 6600 such as the VGA camera, MultiMediaCard slot, Bluetooth and color screen, but with a change to the North American GSM frequencies, newer version of Nokia Series 60 v2 with Feature Pack 1 (the original 6600 had common Series 60 v2 without Feature Packs), the doubling of internal RAM, the addition of Nokia's new Pop-Port connector, the inclusion of stereo sound, and a new EDGE capability, effectively giving it double the download speeds of contemporary General Packet Radio Service (GPRS)-equipped phones.

This phone usually came packaged with a charger, battery, 32-megabyte MMC card and USB cable.

One More Megabyte

One More Megabyte is the ninth studio album by the English punk rock band Toy Dolls. After the release of Orcastrated (1995), the band's bassist John "K'Cee" Casey left the band and was replaced with Gary "Gary Fun" Dunn. The new line up of the band recorded One More Megabyte at Fairview Studios, Hull, in January 1997, with the band's lead singer and guitarist Michael "Olgar" Algar producing the album. The album also contains backing vocals from members of other punk rock bands, including members of the Vibrators, The Lurkers, The Wildhearts, Sugar Snatch, and the Inmates.

The album continues the band's humorous approach to punk rock and Oi! music. A key concept to the album were the increasing popularity of computers, with the album cover, album title and several tracks referring to them. The title track itself refers to a young man obsessed with playing computer games who requires "one more megabyte." Other topics on the album include the quarrels of lovers, the subject of at least four songs, "snotty" Shakespearean actors and "lonely introverts." The album also contains several cover versions, including The Proclaimers' "I'm Gonna Be (500 Miles)". The songs on the album begin and end with brief comedy sketches, or "skits" that relate to the songs, which in the words of one critic "put a wonderful novelty "spin" to the album."

The album was released by Receiver Records in the UK in April 1997. It was also their first domestic release in the United States, where it was released by Rotten Records. The album was a critical success, with Steve Huey of Allmusic saying the album contained "more good-humored, melodic Ramones/Pistols/etc. punk," whilst David Lee Beowülf of Ink 19 saying that he " absolutely, totally [recommends] the Toy Dolls, not just because it’s great punk rock, but because they represent the novelty of punk rock. They have wild choruses, blazing guitar riffs, lightning-fast cover tunes (e.g., “I’m Gonna Be 500 Miles”), and make your heart open up!" The band promoted the album with a year-long world tour entitled the "Mega World Tour 1997".


ReBoot is a Canadian computer-animated action-adventure television series that originally aired from 1994 to 2001. It was produced by Vancouver-based production company Mainframe Entertainment, Alliance Communications and BLT Productions. The animated series was created by Gavin Blair, Ian Pearson, Phil Mitchell, and John Grace, with the visuals designed by Brendan McCarthy after an initial attempt by Ian Gibson. The series follows the adventures of a Guardian named Bob and his companions Enzo and Dot Matrix as they work to keep the computer system of Mainframe safe from the viruses known as Megabyte and Hexadecimal. It was the world's first completely computer-animated TV series.A reimagined, live-action/CG-animated series, ReBoot: The Guardian Code, was announced in 2015, and the first ten episodes debuted on Netflix worldwide (excluding Canada) on March 30, 2018. YTV aired all twenty episodes from June 4 to July 5, 2018.

SS-50 bus

The SS-50 bus was an early computer bus designed as a part of the SWTPC 6800 Computer System that used the Motorola 6800 CPU. The SS-50 motherboard would have around seven 50-pin connectors for CPU and memory boards plus eight 30-pin connectors for I/O boards. The I/O section was sometimes called the SS-30 bus.

Southwest Technical Products Corporation introduced this bus in November 1975 and soon other companies were selling add-in boards. Some of the early boards were floppy disk systems from Midwest Scientific Instruments, Smoke Signal Broadcasting, and PerCom Data; an EPROM programmer from the Micro Works; video display boards from Gimix; memory boards from Seals. By 1978 there were a dozen SS-50 board suppliers and several compatible SS-50 computers.

In 1979 SWTPC modified the SS-50 bus to support the new Motorola MC6809 processor. These changes were compatible with most existing boards and this upgrade gave the SS-50 Bus a long life. SS-50 based computers were made until the late 1980s.

The SS-50C bus, the S/09 version of the SS-50 bus, extended the address by four address lines to 20 address lines to allow up to a megabyte of memory in a system.Boards for the SS-50 bus were typically 9 inches wide and 5.5 inches high. The board had Molex 0.156 inch connectors while the motherboard had the pins. This arrangement made for low cost printed circuit boards that did not need gold plated edge connectors. The tin plated Molex connectors were only rated for a few insertions and were sometimes a problem in hobbyist systems where the boards were being swapped often. Later systems would often come with gold plated Molex connectors.

The SS-30 I/O Bus had the address decoding on the motherboard. Each slot was allocated 4 address (the later MC6809 version upped this to 16 address.) This made for very simple I/O boards, the Motorola peripheral chips connected directly to this bus.


The tebibyte 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 TiB.

The prefix tebi (symbol Ti) represents multiplication by 10244, therefore:

1 tebibyte = 240 bytes = 1099511627776bytes = 1024 gibibytes1024 TiB = 1 pebibyte (PiB)The tebibyte is closely related to the terabyte (TB), which is defined as 1012 bytes = 1000000000000bytes. It follows that one tebibyte (1 TiB) is approximately equal to 1.1 TB.

In some contexts, the terabyte has been used as a synonym for tebibyte. (see Consumer confusion).


The terabyte is a multiple of the unit byte for digital information. The prefix tera represents the fourth power of 1000, and means 1012 in the International System of Units (SI), and therefore one terabyte is one trillion (short scale) bytes. The unit symbol for the terabyte is TB.

Base unit
Platform-dependent units
Platform-independent units
Traditional bit units
Traditional byte units
IEC bit units
IEC byte units

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