In computing, binary prefixes can be used to quantify large numbers where powers of two are more useful than powers of ten (such as computer memory sizes). Each successive prefix is multiplied by 1024 (2¹⁰) rather than the 1000 (10³) used by the SI prefix system. Binary prefixes are often written and pronounced identically to the SI prefixes, despite the resulting ambiguity. The binary numeral system, or base-2 number system, is a numeral system that represents numeric values using two symbols, usually 0 and 1. ... Look up prefix in Wiktionary, the free dictionary. ... The terms storage (U.K.) or memory (U.S.) refer to the parts of a digital computer that retain physical state (data) for some interval of time, possibly even after electrical power to the computer is turned off. ... An SI prefix (also known as a metric prefix) is a name or associated symbol that precedes a unit of measure (or its symbol) to form a decimal multiple or submultiple. ...

History

Early computers used one of two addressing methods to access the system memory; binary (base-2) or decimal (base-10). The IBM 701 (1952) used binary and could address 2048 36-bit words. The IBM 702 (1953) used decimal and could address 10,000 7-bit words. One of the most successful early computers was the IBM 1401. It was introduced in 1959 and by 1961 one out every four electronic stored-program computers was an IBM 1401. It used decimal addressing and could have 1400, 2000, 4000, 8000, 12000 or 16000 characters of 8-bit core storage.^[1] A reference to a "4k IBM 1401" meant 4000 characters of storage (memory).^[2] The use of K in the binary sense as in a "32K store" can be found as early as 1960.^[3] The IBM 701, known as the Defense Calculator while in development, was announced to the public on April 29, 1952, and was IBM’s first commercial scientific computer. ... The IBM 700/7000 series was a series of incompatible large scale (mainframe) computer systems made by IBM through the 1950s and early 1960s. ... IBM 1401 (Card system) The IBM 1401, the first member of the IBM 1400 series, was a variable wordlength decimal computer that was announced by IBM on October 5, 1959. ... A 16×16 cm area core memory plane of 128×128 bits, i. ...

By the mid 1960s binary addressing was the standard architecture in computer design. The computer system documentation would specify the memory size with an exact number such as 32,768, 65,536 or 131,072 words of storage. There were several methods used to abbreviate these quantities. Gene Amdahl's seminal 1964 article on IBM System/360 used 1K to mean 1024.^[4] This style was used by other computer vendors, the CDC 7600 System Description (1968) made extensive use of K as 1024.^[5] Another style was to truncate the last 3 digits and append K. The exact values 32,768, 65,536 and 131,072 would become 32K, 65K and 131K.^[6] If 32,768 were rounded off it would be 33K. This style was used from about 1965 to 1975. Gene Myron Amdahl (born November 16, 1922) is an American computer architect and hi-tech entrepreneur of Norwegian descent, chiefly known for his work on mainframe computers at International Business Machines (IBM) and later his own companies. ... System 360 Model 65 operators console, with register value lamps and toggle switches (middle of picture) and emergency pull switch (upper right). ... The CDC 7600 was the Seymour Cray-designed successor to the CDC 6600, extending Control Datas dominance of the supercomputer field into the 1970s. ...

The use of the 1024 K was more common than the truncated K. Both were used, sometimes by the same company. The HP 21MX real-time computer (1974) denoted 196,608 as 196K and 1,048,576 as 1 M.^[7] The HP 3000 business computer (1973) could have 64K, 96K, or 128K bytes of memory.^[8] Hewlett-Packards first computer, the 2116A of the HP-2100 series, was developed in the late 1960s. ... The HP 3000 series is a family of minicomputers released by Hewlett-Packard in 1973 after a difficult development project. ...

The terms Kbit, Kbyte, Mbit and Mbyte started to be used as binary units in the early 1970s.^[9] Most memory capacities were expressed in K. The IBM System/370 Model 158 brochure (1972) had the following: "Real storage capacity is available in 512K increments ranging from 512K to 2,048K bytes."^[10] Megabyte was used to describe the 22-bit addressing of DEC PDP-11/70 (1975)^[11] and gigabyte the 30-bit addressing DEC VAX11/780 (1977). The PDP-11 was a 16-bit minicomputer sold by Digital Equipment Corp. ... VAX is a 32-bit computing architecture that supports an orthogonal instruction set (machine language) and virtual addressing (i. ...

By the mid 1970s it was common to see K (or Kbyte) as 1024 and the occasional M (or MByte) as 1,048,576 for words or bytes of memory (RAM). K and M were also used with their decimal meaning for disk storage. The dual use of these prefixes as both decimal and binary was defined in early standards and dictionaries. The ANSI/IEEE Std 1084-1986^[12] is still available for reference and defined kilo and mega. The term "computer storage" means system memory.^[4]

"kilo (K). (1) A prefix indicating 1000. (2) In statements involving size of computer storage, a prefix indicating 2¹⁰, or 1024."

"mega (M). (1) A prefix indicating one million. (2) In statements involving size of computer storage, a prefix indicating 2²⁰, or 1,048,576."

In the 1980s the terms kilobyte, megabyte, and gigabyte became popular along with the abbreviations KB, MB, and GB. The binary units Kbyte and Mbyte were formally defined in ANSI/IEEE Std 1212-1991.^[13] The terms Kbyte, Mbyte, and Gbyte are found in the trade press and in IEEE journals. A kilobyte (derived from the SI prefix kilo-, meaning 1000) is a unit of information or computer storage equal to the decimal 1024 bytes (2 to the 10th power, or 1,024 bytes based in the binary system). ... ReBoot character, see Megabyte (ReBoot). ... A gigabyte (derived from the SI prefix giga-) is a unit of information or computer storage equal to 1000³ bytes or 1024³ bytes (1000³ = one billion). ...

Gigabyte was formally defined in IEEE Std 610.10-1994 as either 1,000,000,000 or 2³⁰ bytes.^[14] Kilobyte, Kbyte, and KB are equivalent units and all are defined in current standard, IEEE 100-2000.^[15]

The industry has coped with the dual definitions because system memory (RAM) typically uses the binary meaning while disk storage uses the decimal meaning. (There are exceptions especially with disks.) There are no SI units for computer storage capacity but the decimal meanings of KB, MB, and GB are often referred to as SI prefixes. Cover of brochure The International System of Units. ...

In January 1999, the International Electrotechnical Commission introduced the prefixes kibi-, mebi-, gibi-, etc., and the symbols Ki, Mi, Gi, etc. to specify binary multiples of a quantity and eliminate this ambiguity.^[16] The names for the new standard are derived from the first two letters of the original SI prefixes followed by bi, short for "binary". The new standard also clarifies that, from the point of view of the IEC, the SI prefixes will henceforth only have their base-10 meaning and never have a base-2 meaning. Year 1999 (MCMXCIX) was a common year starting on Friday (link will display full 1999 Gregorian calendar). ... The International Electrotechnical Commission (IEC) is an international standards organization dealing with electrical, electronic and related technologies. ...

The second edition of the standard^[17] defined them only up to exbi-^[18], but in 2005, the third edition added prefixes zebi- and yobi-, thus matching all standard SI prefixes with their binary counterparts.^[19] Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ...

On March 19, 2005 the IEEE standard IEEE 1541-2002 (Prefixes for Binary Multiples) has been elevated to a full-use standard by the IEEE Standards Association after a two-year trial period.^[20] is the 78th day of the year (79th in leap years) in the Gregorian calendar. ... Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... IEEE 1541 is a standard issued by the Institute of Electrical and Electronics Engineers (IEEE) concerning the use of prefixes for binary multiples of units of measurement related to digital electronics and computing. ...

Consumer confusion

This hard disk can hold 160×10⁹ bytes, and is marketed using standard SI prefixes as "160 GB"

Linux's fdisk uses standard SI prefixes to display a 160×10⁹ byte disk as "160.0 GB"

In the early days of computers there was little or no consumer confusion because of the sophisticated nature of the consumers and the practice of the computer manufacturers to specify (as opposed to advertise) their products with decimal digits of sufficient places, e.g., the 1968 IBM stated System 360 "Model 91s can accommodate up to 6,291,496 bytes of main storage."^[21] Hard disk drive manufacturers began using MB, i.e. 10⁶ bytes, to characterize their products as early as 1974^[22]. By 1977, in its first edition, Disk/Trend^[23], a leading hard disk drive industry marketing consultancy segmented the industry according to MB's (decimal sense) of capacity. The presentation of hard disk drive capacity by an operating system using MB in a binary sense appears no earlier than Macintosh Finder after 1984. Prior to that, on the systems that had a hard disk drive, capacity was presented in decimal digits with no prefix of any sort (e.g., MS/PC DOS CHKDSK command). Later, Microsoft Windows 3.11, for example, would report the space available on a 41,959,424 byte hard disk drive as 40 MB. Image File history File links Metadata Size of this preview: 800 × 578 pixelsFull resolution (1748 × 1262 pixel, file size: 282 KB, MIME type: image/jpeg) All of these images are derived from the same physical hard drive: File history Legend: (cur) = this is the current file, (del) = delete this old... Image File history File links Metadata Size of this preview: 800 × 578 pixelsFull resolution (1748 × 1262 pixel, file size: 282 KB, MIME type: image/jpeg) All of these images are derived from the same physical hard drive: File history Legend: (cur) = this is the current file, (del) = delete this old... An SI prefix (also known as a metric prefix) is a name or associated symbol that precedes a unit of measure (or its symbol) to form a decimal multiple or submultiple. ... Image File history File links Size of this preview: 800 × 500 pixelsFull resolution (827 × 517 pixel, file size: 61 KB, MIME type: image/png) All of these images are derived from the same physical hard drive: (I think fdisk is GPL, but I cant find this information anywhere. ... Image File history File links Size of this preview: 800 × 500 pixelsFull resolution (827 × 517 pixel, file size: 61 KB, MIME type: image/png) All of these images are derived from the same physical hard drive: (I think fdisk is GPL, but I cant find this information anywhere. ... This article or section includes a list of works cited or a list of external links, but its sources remain unclear because it lacks in-text citations. ... An SI prefix (also known as a metric prefix) is a name or associated symbol that precedes a unit of measure (or its symbol) to form a decimal multiple or submultiple. ... Generally speaking, advertising is the paid promotion of goods, services, companies and ideas by an identified sponsor. ... The Finder is the default application program used on the Mac OS and Mac OS X operating systems that is responsible for the overall user-management of files, disks, network volumes and the launching of other applications. ... This article does not cite any references or sources. ...

Binary prefixes using SI symbols

The one-letter symbols are identical to SI prefixes, except for "K", which is used interchangeably with "k" (in SI, the upper-case or capital "K" stands for kelvin, and only the lower-case "k" represents 1,000). Kilo (symbol: k) is a prefix in the SI system denoting 103 or 1000. ... mega- (symbol M) is an SI prefix in the SI system of units denoting a factor of 106, i. ... Look up giga- in Wiktionary, the free dictionary. ... tera- (symbol: T) is a prefix in the SI system of units denoting 1012, or 1 000 000 000 000. ... In physics and mathematics, peta- (symbol: P) is a prefix in the SI (system of units) denoting 1015, or 1 000 000 000 000 000. ... In the X Window System, in the X.Org Server, EXA is a graphics acceleration architecture to make the XRender extension more usable, with only minor changes needed to adapt XFree86 video drivers written to use XAA (the XFree86 Acceleration Architecture). ... Zetta (symbol Z) is a SI prefix in the SI (system of units) denoting 1021 or 1 000 000 000 000 000 000 000. ... Yotta (symbol Y) is a SI prefix in the SI (system of units) denoting 1024 or 1 000 000 000 000 000 000 000 000. ... The kelvin (symbol: K) is a unit increment of temperature and is one of the seven SI base units. ...

These prefixes are in common use in contexts such as file and memory sizes. The names and values of the SI prefixes were defined in the 1960 SI standard, with powers-of-1000 values. Standard dictionaries do recognize the binary meanings for these prefixes.^[24][25] Oxford online dictionary define, for example, megabyte as: "Computing a unit of information equal to one million or (strictly) 1,048,576 bytes."^[26] An SI prefix is a prefix which can be applied to any unit of the International System of Units (SI) to give subdivisions and multiples of that unit. ...

BIPM (the International Bureau of Weights and Measures which maintains SI) expressly prohibits the binary prefix usage, and recommends the use of the IEC prefixes as an alternative since computing units are not included in SI.^[27] The Bureau International des Poids et Mesures (International Bureau of Weights and Measures, or BIPM) is a standards organization, one of the three organizations established to maintain the SI system under the terms of the Metre Convention. ... Look up si, Si, SI in Wiktionary, the free dictionary. ...

Some have suggested that "k" be used for 1,000, and "K" for 1,024, but this cannot be extended to the higher order prefixes and has never been widely recognised.

Although the SI prefixes denoting fractions of a bit or byte might theoretically find application in areas such as cryptography, data compression, and data transfer rates, they are not used in practice. The German Lorenz cipher machine, used in World War II for encryption of very high-level general staff messages Cryptography (or cryptology; derived from Greek κρυπτός kryptós hidden, and the verb γράφω gráfo write or λεγειν legein to speak) is the study of message secrecy. ... In computer science and information theory, data compression or source coding is the process of encoding information using fewer bits (or other information-bearing units) than an unencoded representation would use through use of specific encoding schemes. ...

Informally, the prefixes are often used on their own. Thus one might hear about a "256K DRAM" (256 binary kilobytes), "a 160 MB HDD" (160 decimal megabytes) or "a 2M Internet connection" (2 decimal megabits per second). What units are being used, and whether the multipliers are decimal or binary, depends on context and cannot be determined by the units alone.

Windows XP lists the capacity of a 160×109 byte disk drive as "149.05 GB" (binary). Image File history File links Size of this preview: 800 × 449 pixelsFull resolution (1102 × 618 pixel, file size: 34 KB, MIME type: image/png) All of these images are derived from the same physical hard drive: File history Legend: (cur) = this is the current file, (del) = delete this old version... Windows XP is a line of operating systems developed by Microsoft for use on general-purpose computer systems, including home and business desktops, notebook computers, and media centers. ...

Windows XP used to list the capacity of a 160×109 byte disk drive as "152625 MB" (binary). Image File history File links No higher resolution available. ...

Windows XP used to list the size of a 73×109 byte disk drive partition as "68.1 GB" (binary). Image File history File links No higher resolution available. ...

The 536,870,912 byte (512×220) capacity of these RAM modules is stated as "512 MB" (binary). Image File history File links Size of this preview: 800 × 600 pixel Image in higher resolution (2304 × 1728 pixel, file size: 1. ...

IEC standard prefixes

Example: 300 GB ≅ 279.5 GiB.

Approximate ratios between binary and decimal prefixes

As the order of magnitude increases, the percentage difference between the binary and decimal values of a prefix increases, from 2.4% (with the kilo prefix) to over 20% (with the yotta prefix). This makes differentiating between the two increasingly important as larger and larger data storage and transmission technologies are developed.

A kilobyte (derived from the SI prefix kilo-, meaning 1000) is a unit of information or computer storage equal to the decimal 1024 bytes (2 to the 10th power, or 1,024 bytes based in the binary system). ... A kibibyte (a contraction of kilo binary byte) is a unit of information or computer storage, commonly abbreviated KiB (never kiB). 1 kibibyte = 210 bytes = 1,024 bytes The kibibyte is closely related to the kilobyte, which can be used either as a synonym for kibibyte or to refer to... ReBoot character, see Megabyte (ReBoot). ... A mebibyte (a contraction of mega binary byte) is a unit of information or computer storage, abbreviated MiB. 1 MiB = 220 bytes = 1,048,576 bytes = 1,024 kibibytes 1 MiB = 1024 (= 210) kibibytes (KiB), and 1024 MiB equal one gibibyte (GiB). ... A gigabyte (derived from the SI prefix giga-) is a unit of information or computer storage equal to 1000³ bytes or 1024³ bytes (1000³ = one billion). ... A gibibyte is a unit of information or computer storage. ... This article is about a measurement term for data storage capacity. ... A tebibyte is a unit of information or computer storage, commonly abbreviated TiB. 1 tebibyte = 240 bytes = 1,099,511,627,776 bytes The tebibyte is closely related to the terabyte, which can either be a synonym for tebibyte, or refer to 1012 bytes = 1,000,000,000,000 bytes... A petabyte (derived from the SI prefix peta- ) is a unit of information or computer storage equal to one quadrillion bytes. ... A pebibyte is a unit of information or computer storage. ... An exabyte (derived from the SI prefix exa-) is a unit of information or computer storage equal to approximately one quintillion bytes. ... An exbibyte (a contraction of exa binary byte) is a unit of information or computer storage, abbreviated EiB. 1 exbibyte = 260 bytes = 1,152,921,504,606,846,976 bytes = 1,024 pebibytes The exbibyte is closely related to the exabyte, which can either be a synonym for exbibyte, or... A zettabyte (derived from the SI prefix zetta-) is a unit of information or computer storage equal to one sextillion (one long scale trilliard) bytes. ... A zettabyte (derived from the SI prefix zetta-) is a unit of information or computer storage equal to one sextillion (one long scale trilliard) bytes. ... A yottabyte (derived from the SI prefix yotta-) is a unit of information or computer storage equal to one septillion (one long scale quadrillion or 1024) bytes. ... This article or section does not cite any references or sources. ...

Adoption

As of 2007, the IEC binary naming convention is not widespread. Most publications, computer manufacturers and software companies are still using the traditional binary units defined in IEEE 100, The Authoritative Dictionary of IEEE Standards Terms, Seventh Edition, 2000. ^[15] 2007 is a common year starting on Monday of the Gregorian calendar. ... The International Electrotechnical Commission (IEC) is an international standards organization dealing with electrical, electronic and related technologies. ...

It is strongly supported by many standardization bodies and technical organizations, such as IEEE, CIPM, NIST, and SAE.^{[28][27][29][30]} The new binary prefixes have also been adopted by the European Committee for Electrotechnical Standardization (CENELEC) as the harmonization document HD 60027-2:2003-03.^[31] This document will be adopted as a European standard.^[32] The Institute of Electrical and Electronics Engineers or IEEE (pronounced as eye-triple-ee) is an international non-profit, professional organization incorporated in the State of New York, United States. ... The Comité international des poids et mesures or The International Committee for Weights and Measures (CIPM) consists of eighteen persons from Member States of the Metre Convention. ... As a non-regulatory agency of the United States Department of Commerce’s Technology Administration, the National Institute of Standards (NIST) develops and promotes measurement, standards, and technology to enhance productivity, facilitate trade, and improve the quality of life. ... SAE may refer to: Soviet Antarctic Expeditions Scientific Audio Electronics Society of Automotive Engineers SAE Institute (formerly the School of Audio Engineering) Sigma Alpha Epsilon fraternity Stichting Academisch Erfgoed Standard American Equivalent (in relation to tool sizing see Standard and Imperial; different from Metric tool sizing but pertaining to same... CENELEC (French: Comité Européen de Normalisation Electrotechnique) is the European Committee for Electrotechnical Standardization. ... CEN, the European Committee for Standardization, is a private non-profit organization whose mission is to foster the European economy in global trading, the welfare of European citizens and the environment by providing an efficient infrastructure to interested parties for the development, maintenance and distribution of coherent sets of standards...

The prefixes are beginning to be used in technical articles and software where it is important to avoid ambiguity. Examples of software that use IEC standard prefixes (along with standard SI prefixes) include the Linux kernel,^[33] GNU Core Utilities,^[34] Launchpad, GParted,^[35] ifconfig,^[36] Deluge (BitTorrent client), ^[37] and BitTornado. Other programs like fdisk and apt-get use SI prefixes with their decimal meaning. The Linux kernel is a Unix-like operating system kernel. ... The GNU Core Utilities or coreutils is a package of GNU software containing many of the basic tools such as cat, ls, and rm needed for Unix-like operating systems. ... Launchpad is a web application and web site supporting software development, particularly that of free software. ... GParted stands for GNOME Partition Editor. ... Sample output from ifconfig on Linux The Unix command ifconfig is a tool used to configure a network interface for TCP/IP. It was originally released as part of the BSD TCP/IP suite - so in effect, its part of the original internet toolkit. ... Deluge is a BitTorrent client, created using Python and GTK+ (through PyGTK). ... BitTornado in Ubuntu Linux BitTornado is a BitTorrent client. ... This article or section includes a list of works cited or a list of external links, but its sources remain unclear because it lacks in-text citations. ... Advanced Packaging Tool, or APT, is a package management system used by the Debian project. ...

It can be argued that the main purpose of the binary prefixes is to clarify that, according to national and international standards, the traditional SI prefixes always refer to powers of ten, even in the context of information technology. Therefore, rather than measuring the success of the binary prefixes based on how commonly they appear in technical and marketing literature, it may be more appropriate to judge them by their success in restoring the original power-of-ten meaning of the standard SI prefixes in information technology. Binary prefixes are only convenient for a small number of information-technology quantities, most notably the size of address spaces (e.g., of RAM chips). They provide no practical advantage for quantities where powers-of-two times a small integer are not preferred numbers, such as file sizes, download speeds, line rates, symbol rates, clock frequencies, tape or disk capacities. There, decimal prefixes are far more convenient for mental arithmetic. In industrial design, product developers must choose numerous lengths, distances, diameters, volumes, and other characteristic quantities. ...

GNOME's partition editor uses IEC prefixes to display partition sizes. The total capacity of the 160×109 byte disk is displayed as "149.05 GiB" Image File history File links No higher resolution available. ... This article needs additional references or sources for verification. ... A gibibyte is a unit of information or computer storage. ...

GNOME's system monitor uses IEC prefixes to show memory size and networking data rate. Image File history File links Size of this preview: 463 × 600 pixelsFull resolution (541 × 701 pixel, file size: 53 KB, MIME type: image/png) Note: if the screenshot shows any work that is not a direct result of the program code itself, such as a text or graphics that are...

BitTornado uses standard SI prefixes for data rates and IEC prefixes for file sizes Image File history File links No higher resolution available. ... BitTornado in Ubuntu Linux BitTornado is a BitTorrent client. ...

Deluge (BitTorrent client) uses IEC prefixes for data rates as well as file sizes Image File history File links Size of this preview: 788 × 600 pixelsFull resolution (1280 × 974 pixel, file size: 63 KB, MIME type: image/png)t is a screenshot of Deluge (0. ... Deluge is a BitTorrent client, created using Python and GTK+ (through PyGTK). ...

Usage notes

The phrase "decimal unit" will be used to denote "SI designation understood in its standard, decimal, power-of-1000 sense" and "binary unit" will mean "SI designation understood in its binary, power-of-1024 sense." B will be used as the symbol for byte as per computer-industry standard (IEEE 1541 and IEC 60027; B is also the symbol for bel, a common non-SI unit used for ratio measurement). IEEE 1541 is a standard issued by the Institute of Electrical and Electronics Engineers (IEEE) concerning the use of prefixes for binary multiples of units of measurement related to digital electronics and computing. ... IEC 60027 (formerly IEC 27) is the International Electrotechnical Commissions standard on Letter symbols to be used in electrical technology. ... The decibel (dB) is a logarithmic unit of measurement that expresses the magnitude of a physical quantity (usually power) relative to a specified or implied reference level. ...

Certain units are always understood as decimal even in computing contexts. For example, hertz (Hz), which is used to measure clock rates of electronic components, and bit/s, used to measure bit rate. So a 1 GHz processor performs 1,000,000,000 clock ticks per second, a 128 kbit/s MP3 stream consumes 128,000 bits (16 kB, 15.625 KiB) per second, and a 1 Mbit/s Internet connection can transfer 1,000,000 bits (125 kB, approx 122 KiB) per second, assuming an 8-bit byte, and no overhead.^[38] MHZ redirects here. ... It has been suggested that this article or section be merged into Clock signal. ... In telecommunications and computing, bit rate (sometimes written bitrate) is the frequency at which bits are passing a given (physical or metaphorical) point. It is quantified using the bit per second (bit/s) unit. ... MPEG-1 Audio Layer 3, more commonly referred to as MP3, is an audio encoding format. ...

Pronunciation

It is suggested that in English, the first syllable of the name of the binary-multiple prefix should be pronounced in the same way as the first syllable of the name of the corresponding SI prefix, and that the second syllable should be pronounced as "bee." ^[29]

Computer memory

Main article: JEDEC memory standards

Measurements of most types of electronic memory such as RAM and ROM and Flash (large scale disk-like flash is sometimes an exception) are given in binary units, as they are made in power-of-two sizes. This is the most natural configuration for memory, as all combinations of their address lines map to a valid address, allowing easy aggregation into a larger contiguous block of memory. It has been suggested that this article or section be merged with JEDEC. (Discuss) The JEDEC Solid State Technology Association is the semiconductor engineering standardization body of the Electronic Industries Alliance (EIA). ... The terms storage (U.K.) or memory (U.S.) refer to the parts of a digital computer that retain physical state (data) for some interval of time, possibly even after electrical power to the computer is turned off. ... Random access memory (usually known by its acronym, RAM) is a type of data storage used in computers. ... Read-only memory (usually known by its acronym, ROM) is a class of storage media used in computers and other electronic devices. ... A USB flash drive. ...

JEDEC Solid State Technology Association, the semiconductor engineering standardization body of the Electronic Industries Alliance (EIA) in Standard 100B.01[6]^[39] defines in the binary sense K, M and G as prefixes to units of semiconductor memory, noting that these definitions are “only included to reflect common usage” and noting that ‘IEEE/ASTM SI 10-1997 state “This practice frequently leads to confusion and is deprecated.” ’. All standards published by JEDEC are still using the common usage, including end-user packaging recommendations for memory chips.

Many computer programming tasks naturally reference memory in terms of powers of two. For example, a 16-bit pointer can reference at most 65,536 items (bytes, words, or other objects), or an operating system might map memory in terms of 4,096-byte pages, in which case exactly 8,192 pages could be allocated within 33,554,432 bytes of hardware memory. It is convenient to informally express these numbers, respectively, as 64K items, or as 8K pages of 4 Kbytes (KiB) each within 32 MBytes (MiB) of memory. A programmer can easily mentally calculate that "8K × 4K is 32 meg" and get it exactly right, within this powers-of-two context. This convenience is likely one source of originally adapting "kilo" and "mega" from SI as shorthand for 1,024 and 1,048,576, as specialized jargon within a segment of the industry. In mathematics, a power of two is any of the nonnegative integer powers of the number two; in other words, two times itself a certain number of times. ... In computer science, a pointer is a programming language data type whose value refers directly to (or “points to”) another value stored elsewhere in the computer memory using its address. ...

Almost all computer user tasks (and many high-level programming tasks) have no natural affinity or need for explicit powers of two. The consumer confusion between powers of 1000 and powers of 1024 may derive largely from some operating systems and applications that were originally written by and for programmers, and which thus reported quantities such as file sizes in familiar (to programmers) powers of 1024 while using SI (powers of 1000) abbreviations. Without such reporting, most users might not have been substantially exposed to powers of 1024, as the net memory available to users after various overheads is rarely a power of two. This legacy behavior of operating systems reporting sizes in powers of 1024 has continued to this day (in 2007) even in many GUI oriented operating systems intended mainly for non-programmers.

Hard disk drives

HDD manufacturers state capacity in decimal units. This usage has a long tradition, even predating the SI system of decimal prefixes adopted in 1960, as follows: Typical hard drives of the mid-1990s. ... An SI prefix is a prefix which can be applied to any unit of the International System of Units (SI) to give subdivisions and multiples of that unit. ...

• The first disk drive the IBM 350 (1950s) had 5,000,000 6 bit characters organized in 100 character sectors (i.e., blocks). This predates the SI system.
• In the 1960s virtually all disk drives used IBM's variable block length format (called, Count Key Data or "CKD^[40]"). Any block size could be specified up to the maximum track length. Blocks ("records" in IBM's terminology) of 88, 96, 880 and 960 were often used because they related to the fixed block size of punch cards. The drive capacity was usually stated in full track record blocking, for example, the 100 Megabyte 3336 disk pack only achieved that capacity with a full track block size of 13,030 bytes.
• CKD continued into the 1990s and perhaps into this day. In the 1970s and 1980s most drives were specified with unformatted tracks (the unformatted capacity) with the particular block size and formatted capacity a function of the controller design. For example, the ST412 of IBM PC/XT fame had an unformatted capacity of 12.75 MB (not MiB) and with the Xebec controller and 512 byte blocks it formatted to and was advertised as a 10.0 MB (not MiB) HDD. Other controllers supported other block sizes resulting in other formatted capacities.
• The advent of intelligent interfaces (SCSI and IDE) in the early 1990s took the block size decision into the drive and virtually all chose 512 bytes, for no reason other than that was what IBM had chosen when they picked the Xebec controller for the PC/XT. Capacity continued to be specified by the HDD manufacturers with SI prefix definitions.

Regardless of the HDD manufacturers' continuous practice of specifying with conventional SI prefixes, some systems' GUIs took the HDD capacity, reported by the operating system as a binary number without prefixes, and reported the HDD capacity in a mixed decimal number/binary prefix^{[citation needed]} leading to some confusion. As of January 2007, most, if not all, HDD manufacturers continue to use decimal prefixes to identify capacity.^[41] RAMAC is an IBM trademark for mass storage products. ... This article or section does not cite any references or sources. ... This article does not cite any references or sources. ... The Bulgarian political party Citizens for European Development of Bulgaria, which had only been founded on 2006-12-03 by Sofia mayor Boyko Borisov, instantly comes second in a public poll on party support, trailing only the Bulgarian Socialist Party. ...

Flash drives

USB Flash Drive and Flash-based memory cards like CompactFlash and Secure Digital are typically classified in "powers of two" multiples of decimal megabytes; for example, a "256 MB" card would hold 256 million bytes.[2] Although the devices usually have at least the expected byte capacity, each manufacturer allocates different portions of the device's ultimate capacity for such things as wear levelling. A USB flash drive, shown with a 24 mm U.S. quarter coin for scale. ... A 64 MB CompactFlash Type I card A 32 MB High Speed CompactFlash Type I card CompactFlash (CF) was originally developed as a type of data storage device used in portable electronic devices. ... 16Mb SD Card Secure Digital, or SD, is a flash memory data storage device based on Toshibas earlier Multi Media Cards (MMC). ... Wear levelling (also written -levelling) is a technique for prolonging the service life of some kinds of eraseable computer storage media, e. ...

Floppy drives

Floppy disk drive and media manufacturers use decimal units for unformatted recording capacity while most computer operating systems use binary units to measure the formatted capacity. The original IBM Personal Computer (1981) used a Tandon TM100 5¼ inch floppy disk drive. The single sided drive was rated at 250 kilobytes (unformatted) and the double sided version was rated at 500 kilobytes. ^[42] IBM PC (IBM 5150) with keyboard and green screen monochrome monitor (IBM 5151), running MS-DOS 5. ... Image File history File links Metadata Size of this preview: 750 × 600 pixelsFull resolution (2000 × 1600 pixel, file size: 398 KB, MIME type: image/jpeg) IBM PC 5 1/4 inch Diskette Drive shown with DOS 1. ...

A 5¼ inch diskette recorded at double density (MFM) will hold 6,250 bytes per track and has 40 tracks per side, yielding 250,000 bytes per side. To make it practical to record smaller blocks of data, the tracks are formatted into sectors with gaps between them. The gaps allow individual sectors to be recorded without overwriting adjacent sectors. Each sector also has additional header bytes to identify the sector. Modified Frequency Modulation, commonly MFM, is a line coding scheme used to encode information on most floppy disk formats, which include the floppy disk formats used in most CP/M machines as well as PCs running DOS. MFM is a modification to the original FM (frequency modulation) scheme for encoding...

With IBM PC-DOS 1.0 and 1.1, each track has 8 sectors of 512 bytes and this provides 163,840 bytes per side (8 × 512 × 40). The IBM user documentation referred to this as "160KB" for single sided diskette and "320KB" for double sided diskette.^[43] Starting with PC-DOS 2.0 (1983), each track had 9 sectors of 512 bytes. The formatted capacity was increased to 184,320 bytes per side or 368,640 bytes per diskette. The IBM documentation referred to these as "180KB" and "360KB" diskettes. The same drives and media can have different capacities depending on format.^[44] IBM PC-DOS was one of three major operating systems that dominated the personal computer market from about 1985 to 1995. ...

On all diskettes the capacity available to the user will be smaller that the total number of sectors because some are reserved by the operating system for boot records or directory tables.

The IBM Personal Computer/AT (1984) had a new 5¼ inch disk drive that had 80 tracks per side, rotated at 360 rpm (versus 300 rpm) and had a new diskette media. The formatted capacity was 1,228,800 bytes or 1200 KiB. (80 tracks × 15 sectors × 512 bytes × 2 sides) The IBM Personal Computer/AT (IBM 5170), more commonly known as the IBM AT and also sometimes called the PC AT or PC/AT, was IBMs second-generation PC, designed around the Intel 80286 microprocessor running at 6 MHz and released in 1984. ...

The IBM PC Convertible (1986) used the 3½ inch diskettes. These were similar in recording technology to the original 5¼ inch drives except they had 80 tracks per side. The formatted capacity was 737,280 bytes or 720 KiB. Apple used the same disk with a different recording technology, GRC, that gave a formatted capacity of 819,200 bytes or 800 KiB. Apple referred to this as an "800K" disk.^[45] IBM PC Convertible The IBM PC Convertible, released April 3, 1986, was IBMs first laptop computer and was also the first IBM computer to utilize the now-standard 3. ... Group Code Recording (GCR) is a floppy disk data encoding format used by the Apple II and Commodore Business Machines in the 5¼ disk drives for their 8-bit computers (the best-known drives being the Disk II for the Apple II family and the Commodore 1541, used with the...

The last widely adopted diskette was the 3½ inch high density. This has twice the capacity as the 720 KiB diskettes, 1,474,560 bytes or 1440 KiB. The drive was marketed as 1.44 MB when a more accurate value would have been 1.4 MiB (1.40625 MiB). Some users have noticed the missing 0.04 MiB and both Apple and Microsoft have support bulletins referring to them as 1.4 MB.^{[46] [45]} The 1200 KiB 5½ inch diskette was marketed as 1.2 MB (1.171875 MiB) without any controversy.

CD and DVD

CD capacities are always given in binary units. A "700 MB" (or "80 minute") CD has a nominal capacity of about 700 MiB (approx 730MB).^[47] But DVD capacities are given in decimal units. A "4.7 GB" DVD has a nominal capacity of about 4.38 GiB.^[48] A Compact Disc or CD is an optical disc used to store digital data, originally developed for storing digital audio. ... The three-letter acronym MIB may refer to any of several concepts: Management information base, a computing information repository used (for example) by SNMP In marbles, any marble, but esp. ... Size comparison: A 12 cm Sony DVD+RW and a 19 cm Dixon Ticonderoga pencil. ... The term gib may refer to: a castrated male cat or ferret an abbreviation for gibibyte (GiB) or gibibit (Gib) an abbreviation for Gibraltar an abbreviation for Gib Board, itself an abbreviation of Gibraltar Board, all Winston Wallboards[1] tradenames for drywall (plasterboard). ...

Buses

Bus bandwidth is given in decimal units. This is not because hard drive capacities use the decimal versions, nor because bit rates do, but because clock speeds do. For example, "PC3200" memory runs on a double pumped 200 MHz bus, transferring 8 bytes per cycle, and hence has a bandwidth of 200,000,000×2×8 = 3,200,000,000 byte/s. In computer architecture, a bus is a subsystem that transfers data or power between computer components inside a computer or between computers and typically is controlled by device driver software. ... DDR SDRAM or double-data-rate synchronous dynamic random access memory is a type of memory integrated circuit used in computers. ... In computing, a computer bus operating with double data rate transfers data on both the rising and falling edges of the clock signal, effectively nearly doubling the data transmission rate without having to deal with the additional problems of timing skew that increasing the number of data lines would introduce. ...

Legal disputes

There have been two significant class action lawsuits against digital storage manufactures. One case involved flash memory and the other involved hard disk drives. Both were settled with the manufactures agreeing to clarify the storage capacity of their products on the consumer packaging.

On February 20, 2004, Willem Vroegh filed a lawsuit against Lexar Media, Dane–Elec Memory, Fuji Photo Film USA, Eastman Kodak Company, Kingston Technology Company, Inc., Memorex Products, Inc.; PNY Technologies Inc., SanDisk Corporation, Verbatim Corporation, and Viking InterWorks alleging that their descriptions of the capacity of their flash memory cards were false and misleading. is the 51st day of the year in the Gregorian calendar. ... Year 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... // Willem Vroegh v. ... Fujifilm Holdings Corporation, or Fujifilm, is a Japanese company known for its photographic film and cameras. ... Eastman Kodak Company (NYSE: EK) is an American multinational public company. ... Established in 1961 in Silicon Valley, Memorex is today a consumer electronics brand of Imation specializing in recordable media (CD & DVD Drives), travel drives, flash storage, computer accessories and other electronics. ... PNY Technologies, Inc. ... SanDisk Corporation (NASDAQ: SNDK), formerly SunDisk, is an American multinational corporation which designs and markets flash memory card products. ... The Verbatim Corporation is a US company. ... A USB flash drive. ...

Vroegh claimed that a 256 MB Flash Memory Device had only 244 MB of accessible memory. "Plaintiffs allege that Defendants marketed the memory capacity of their products by assuming that one megabyte equals one million bytes and one gigabyte equals one billion bytes." The plaintiffs wanted to use the binary values 2²⁰ for megabyte and 2³⁰ for gigabyte. The plaintiffs acknowledged that the IEC and IEEE standards define a MB as one million bytes but stated that the industry has largely ignored the IEC standards.[3]

The manufactures agreed to clarify the flash memory card capacity on the packaging and web sites. [4] The consumers could apply for "a discount of ten percent off a future online purchase from Defendants' Online Stores Flash Memory Device."[5] The law firms Gutride Safier, LLP and Milberg Weiss received $2.4 million.

On July 7, 2005, an action entitled Orin Safier v. Western Digital Corporation, et al., was filed in the Superior Court for the City and County of San Francisco, Case No. CGC-05-442812. The case was subsequently moved to the Northern District of California, Case No. 05-03353 BZ. [6] is the 188th day of the year (189th in leap years) in the Gregorian calendar. ... Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... Western Digital Corporation (NYSE: WDC) (often abbreviated to WD) is a manufacturer of a large proportion of the worlds hard disks, and has a long history in the electronics industry as an IC maker and a storage products company. ...

Although Western Digital maintained that their usage of units is consistent with "the indisputably correct industry standard for measuring and describing storage capacity", and that they "cannot be expected to reform the software industry", they agreed to settle[7] in March 2006 with June 14, 2006 as the Final Approval hearing date. June 14 is the 165th day of the year (166th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday (link displays full 2006 calendar) of the Gregorian calendar. ...

Western Digital offered to compensate customers with a free download of backup and recovery software valued at US$30. They also paid $500,000 in fees and expenses to San Francisco lawyers Adam Gutride and Seth Safier, who filed the suit.[8]

Western Digital had this footnote in their settlement. "Apparently, Plaintiff believes that he could sue an egg company for fraud for labeling a carton of 12 eggs a “dozen,” because some bakers would view a “dozen” as including 13 items."[9]

The flash memory and hard disk manufactures now have disclaimers on their packaging and web sites clarifying the formatted capacity of the flash memory[10] or defining MB as 1 million bytes and 1 GB as 1 billion bytes.[11]

Also the Class Action Fairness Act of 2005 requires greater scrutiny on coupon settlements. One of the plaintiff law firms in the Vroegh case, Milberg Weiss & Bershad, was indicted for fraud in unrelated class action cases.[12] The U.S. Class Action Fairness Act of 2005, 28 U.S.C. Sections 1332(d), 1453, and 1711-1715, grants federal courts original jurisdiction over certain mass actions and class actions (forms of civil action) in which the amount in controversy exceeds $5 million, and any of the members...

See also

• Integral data type
• Bit
• Nibble
• Byte
• Octet
• IEC 60027-2
• IEEE 1541
• SI prefix

In computer science, the term integer is used to refer to any data type which can represent some subset of the mathematical integers. ... This article is about the unit of information. ... A nibble (or less commonly but more accurately, nybble) is the computing term for a four-bit aggregation, or half an octet (an octet being an 8-bit byte). ... In computer science a byte (pronounced bite) is a unit of measurement of information storage, most often consisting of eight bits. ... In computer technology and networking, an octet is a group of 8 bits. ... In information technology there is sometimes confusion about measurement of bits and bytes. ... IEEE 1541 is a standard issued by the Institute of Electrical and Electronics Engineers (IEEE) concerning the use of prefixes for binary multiples of units of measurement related to digital electronics and computing. ... An SI prefix (also known as a metric prefix) is a name or associated symbol that precedes a unit of measure (or its symbol) to form a decimal multiple or submultiple. ...

Specific units of IEC 60027-2 A.2

These units have individual articles:

In telecommunications and computing, bit rate (sometimes written bitrate) is the frequency at which bits are passing a given (physical or metaphorical) point. It is quantified using the bit per second (bit/s) unit. ... An SI prefix (also known as a metric prefix) is a name or associated symbol that precedes a unit of measure (or its symbol) to form a decimal multiple or submultiple. ... Look up si, Si, SI in Wiktionary, the free dictionary. ... A kilobit per second (kbit/s or kbps or kBaud) is a unit of data transfer rate equal to 1,000 bits per second. ... Look up one thousand in Wiktionary, the free dictionary. ... A megabit per second (Mbps or Mbit/s or Mb/s) is a unit of data transmission equal to 1,024 kilobits per second or 1048576 bits per second. ... (Redirected from 1 E6) One million (1000000), one thousand thousand, is the natural number following 999999 and preceding 1000001. ... A gigabit per second (Gbps or Gbit/s) is a unit