binary digit

Timeline of binary prefixes

This article presents a terminology timeline of binary prefixes.


*J.W. Tukey coins the word bit as an abbreviation of "binary digit". 1948
* Reference to Tukey's "bit" is made in a paper by information theorist Claude Shannon.


*In the 1950s, "1 kilobit" meant "1000 bits":
**"In the '50s amazingly enough and only total coincidence, I actually was given the job of writing the operational specifications […] they handed me this thing and said, "You're going to define how the hand over process works between direction centers," and- and I had no idea what they were talking about. But we had uh.. one kilobit lines connecting the direction centers and I thought, "Good, God, 1,000 bit a second. Well we’ll surely be able to figure out something to do with that." — Saverah Warenstein 1952
* The first magnetic core memory, from the IBM 405 Alphabetical Accounting Machine, is tested successfully in April 1952. (The image shows 10×12 cores; presumably one of 8)
** Teaming up with a more experienced engineer, [Mike Haynes] built a core memory with just enough capacity to store all the information in an IBM punched card: 960 bits in an 80×12 array. In May 1952 it was successfully tested as a data buffer between a Type 405 alphabetical accounting machine and a Type 517 summary punch. This first functional test of a ferrite core memory was made in the same month that a four-times smaller 16x16-bit ferrite core array was successfully tested at MIT.
* The IBM 701 computer, containing 72 Williams tubes of 1024 bits each, is released in April.
** Principles of Operation does not seem to use "kilobit" anywhere. Specifies that memory tubes (IBM 706) hold 1024 bits each, drum memories (IBM 731) hold 2048 words each.
** The IBM 737 optional magnetic core storage stores 4,096 words. Each plane stored 16×16 = 4,096 bits.1955
*The IBM 704 manual uses decimal arithmetic for powers of two, without prefixes
**"Magnetic core storage units are available with capacities of either 4,096 or 32,768 core storage registers; or two magnetic core storage units, each with a capacity of 4,096 core storage registers, may be used. Thus, magnetic core storage units are available to give the calculator a capacity of 4,096, 8,192, or 32,768 core storage registers."
** "Each drum has a storage capacity of 2048 words."1956
*The IBM 702 Preliminary Manual of Information uses decimal arithmetic for powers of ten, without prefixes.
**"Electrostatic memory is the principal storage medium within the machine. It consists of cathode ray tubes which can store up to 10,000 characters of information in the form of electrostatic charges.... Additional storage, as required, may be provided through the use of magnetic drum storage units, each having a capacity of 60,000 characters."
**"A character may be a letter of the alphabet, a decimal number, or any of eleven different punctuation marks or symbols used in report printing."
**"Each one of the 10,000 positions of memory is numbered from 0000 to 9999 and each stored character must occupy one of these positions." (page 8)
*The word byte is coined by Dr. Werner Buchholz in July 1956, during the early design phase for the IBM Stretch computer.
*IBM 650 RAMAC announcement
**"The 650 RAMAC combines the IBM 650 Magnetic Drum Data Processing Machine with a series of disk memory units which are capable of storing a total of 24-million digits. The 305 RAMAC is an entirely new machine which contains its own input and output devices and processing unit as well as a built-in 5-million-digit disk memory."1957
*The IBM 705 Operating manual uses decimal arithmetic for powers of ten, without prefixes.
**"A total of 40,000 characters can be stored within the main storage unit of the Type 705."
**"Each one of the 40,000 positions in memory is numbered from 0000 to 39,999." (page 17)
**"One or more magnetic drums are available as optional equipment with a capacity of 60,000 characters each."

*Lewis, W.D., Coordinated broadband mobile telephone system
**Earliest instance of "kilobit" in both IEEE explore and Google Scholar: "Central controls the mobile link with a rate of 20 kilobits per second, or less".1959
*The term 32k is introduced to mean one of "approximately 32 x 1000" or "exactly 32 x 1024".
**Real, P. "A generalized analysis of variance program utilizing binary logic.". ACM '59: Preprints of papers presented at the 14th national meeting of the Association for Computing Machinery pg 78-1 - 78-5. The author is with the Westinghouse Electric Corporation.


* Frequency Diversity Communications System is filed on May 13, 1960:
**"In actual construction, the delay line, which provides a total delay from one end to the other of one baud (10 microseconds for a 100 kilobit per second information rate), may be fabricated from lumped parameter elements, i.e., inductors and capacitors, in a well-known manner."
**"At a 100 kilobit per second information rate, both mark and space signals will generally be transmitted in any 0.0001 sec, interval, and therefore this requirement is easily met with conventional resistors and capacitors."
*Gruenberger, Fred "Letters to the Editor". Communications of the ACM 3 (10):
**The 8K core stores were getting fairly common in this country in 1954. The 32K store started mass production in 1956; it is the standard now for large machines and at least 200 machines of the size (or its equivalent in the character addressable machines) are in existence today (and at least 100 were in existence in mid-1959).1955-1961
*A search of the Computer History Museum's Stretch collection of 931 text documents dated from September 1955 through September 1961 shows no usage of k or K to describe main storage size.1961
*Gray, L; R Graham (1961). Radio Transmitters
. New York: McGraw-Hill.
**Quoted in OED as first instance of "kilobit", though "it is more usual" suggests it is already in common use (see timeline entry for 1957)
February 17
*Described device contains 512 words, 24 bits each (=12,288 bits)
*"It is no longer reasonable to spend as much time to transmit an 80 bit address as 12 kilobits of message information-a 1500 to 1 ratio.... We have theoretically and experimentally proved that speech can be compressed from the straightforward requirement for 48 kilobit PCM channel capability to 2400 bits by the application of the Dudley syllabic vocoder.

*The IBM 7090 Data Processing System, Additional Core Storage - RPQ E02120 uses the prefix K in its decimal sense (65K means "approximately 65000")
**"The Additional Core Storage feature for the IBM 7090 Data Processing System provides a second IBM 7302 Core Storage, increasing the capacity of main storage by 32,768 words. The block of storage represented by both 7302 units is referred to as "main storage unit."
**"Additional core storage provides two methods of using main storage: (1) The 65K mode—the computer program is enabled to address both of the main storage units, and (2) the 32K mode—the computer program is able to address only one storage unit, so that main storage capacity available to that program is effectively 32,768 words."
*The IBM 1410 Data Processing System uses decimal arithmetic for powers of ten, without prefixes
**"Core storage units are available in 10,000-, 20,000- or 40,000-character position capacities."
**"The matrix switch makes it possible to address any one of the 100 X-drive lines (in a 10K core array)."
**"The 40K core array requires 40,000 valid five-position addresses from 0,000 to 39,999."
**"This operation check detects errors in programming that cause invalid addresses. Examples: 40,000-and-above on a 40K core array; 20,000-and-above on a 20K core array. On a 10K core array, invalid addresses are detected by the address-bus validity check."1962
*A reference to a "4k IBM 1401" meant 4,000 characters of storage (memory).1963
* Ludwig uses kilobit in the decimal sense
*DEC Serial Drum Type 24
**"Drums are equipped to store either 64, 128, or 256 data blocks, providing a memory capability of 16384, 32768, or 65536 computer words" (no abbreviations)

*Honeywell 200 Summary Description
**"The main memory is a magnetic core ... The memory unit supplied as part of the basic central processor has a capacity of 2,048 characters, each of which is stored in a separate, addressable, memory location. This capacity may be expanded in modular increments by adding one 2,048-character module and additional 4,096-character modules."
**"Random access disc file and control (disc capacities of up to 100 million characters are available.)"
**"Up to eight drum storage units can be connected to the Model 270 Random Access Drum Control. Each drum provides storage for 2,621,441 characters, allowing a total capacity of approximately 21 million characters."1964
*Gene Amdahl's seminal April 1964 article on IBM System/360 used 1K to mean 1024.
*Leng, Gordon Bell, et al, use K in the binary sense:
"The computer has two blocks of 4K, 18-bit words of memory, (1K=1024 words), attached to its central processor

*IBM Data Processing Division press release distributed on April 7, 1964.
**"System/360 core storage memory capacity ranges from 8,000 characters of information to more than 8,000,000."
*IBM 7090/7094 Support Package for IBM System/360 - November
**"An IBM 1401 Data Processing System with the following minimum configuration is also required: 1. 4K positions of core storage" - ADDRESS SELECTION CONTROL APPARATUS - Filed April 6, 1964
**'To facilitate understanding of the invention, the main storage area has been illustrated as being of 8K capacity; however, it is to be understood that the main storage area may be of larger capacity (e.g., 16K, 32K or 64K) by storing address selection control data in bit positions "2," "1" and "0" of M register 197, respectively.'1965
*Wilkes, M.V. "Slave Memories and Dynamic Storage Allocation". Electronic Computers, IEEE Transactions on EC-14 (2): pg. 270-271. "One method of designing a slave memory for instructions is as follows. Suppose that the main memory has 64K words (where K=1024) and, therefore, 16 address bits, and that the slave memory has 32 words and, therefore, 5 address bits."
*IBM 1620 CPU Model 1 System Reference Library, dated 7/19/65, states:
**"A core storage module, which is 20,000 addressable positions of magnetic core storage, is located in the 1620. Two additional modules are available ... Each core storage module (20,000 positions) is made up of 12 core planes as shown in Figure 3. Each core plane contains all cores for a specific bit value."1966
**'Note that "K" as used herein indicates "thousands." Each storage location in the present embodiment includes 64 data bits and 8 related parity bits, as described herein.'
**"Thus, if only storage unit 1A were provided, it would contain addresses 0 through 32K; storage IB would include addresses between 32K and 64K, storage 2A would contain addresses between 64K and 96K, ..."1969
*IBM 1401 Simulator for IBM OS/360
**"1401 features supported are advanced programming, sense switches, tapes, multiply, divide, 16K core, and all standard instructions except Select Stacker."
**"1401 core is simulated by 16,000 bytes of S/360 core obtained dynamically."
**"Enough core must be available to allow at least 70K for a problem program area. If tape simulation is not required, this core requirement may be reduced to 50K with the removal of the tape Buffer area."
* HIGH DENSITY PERMANENT DATA STORAGE AND RETRIEVAL SYSTEM is filed on March 17, 1969 earliest Google Patent search containing "kilobyte")
**"The data word processor 606 handles the inflow and out-flow of byte-oriented input/output data and interleaved signals at a rate of, for example, 500 kilobytes per second. Instruction processing rates of four to eight per microsecond are required for such a data flow."
* Memory Control System is filed on Oct 29, 1969
**"FIG. 2a shows a practical example of an operand address which consists of, for example 24 bits. It is assumed herein that each block includes 32 bytes, each sector includes 1 kilobyte, the buffer memory 116 includes 4 kilobytes, and read data is represented by one double word or 64 bits, as one word in this case consists of 32 bits."
*IBM System/360 Component Descriptions (IBM 2314 Direct Access Storage Facility)
**"Each module can store 29.17 million bytes or 58.35 million packed decimal digits ... total on-line storage capacity is 233.4 million bytes"
*DEC PDP-11 Handbook
**"PDP-11 addressing modes include . . . and direct addressing to 32K words" (Page 2) This appears to be the only use of K in this manual, though; elsewhere sizes are spelled out in full. Contrast the 1973 PDP-11/40 Manual, which defines K as 1024. (Below)


*"The following are excerpts from an IBM Data Processing Division press technical fact sheet distributed on June 30, 1970.
**Users of the Model 165 will have a choice of five main core storage sizes, ranging from 512,000 to over 3-million bytes. Seven main memory sizes are available for the Model 155, ranging from 256,000 to over 2-million bytes.
*First 1,024-bit DRAM chip, the Intel 1103.
*Weiler, Paul W.; Richard S. Kopp, Richard G. Dorman "A Real-Time Operating System for Manned Spaceflight". Computers , IEEE Transactions on 19 (5): 388-398. ISSN=0018-9340. "Each of the five system/360 model 75 computers (Fig. 2) has one megabyte of primary core storage plus four megabytes of large core storage (LCS, IBM 2361)."1971
*IBM System/360 Operating System: Storage Estimates
**"System/360 Configuration: Model 40 with 64K bytes of storage and storage protection"
**Contains a lot of examples of "30K", "136K", "next highest multiple of 2K", "The maximum buffer size is 64K bytes" and the like, as well as calculations, which could be used to determine their precise meaning. The letter "K" is also apparently used as a variable in this document?1972
*Lin and Mattson introduce the term Mbyte.
*Habib, Stanley "Notes from industry". ACM SIGMICRO Newsletter 4 (3): pg 29. .
**OCEANPORT, N.J., SEPT. 25, 1973 -- A 16-bit minicomputer priced at under $2,000.00 in quantities and a 32-bit minicomputer priced at under $6,000.00 in quantities were introduced today by Interdata, Inc. The 16-bit mini, the Model 7/16, includes an 8KB memory unit in its basic configuration, and will be available for delivery in the first quarter of 1974. The single unit price of the 7/16 is $3,200.00. The 32-bit mini, the Model 7/32, includes a 32KB memory unit and will be available for delivery in the second quarter of 1974. The single unit price of the 7/32 is $9,950.00.
*DEC PDP-11/40 Manual
**"Direct addressing of 32K 16-bit words or 64K 8-bit bytes (K = 1024)" (Page 1-1) Contrast the 1969 PDP-11 Handbook, which avoids this usage almost everywhere. (Above)1974
*The seminal 1974 Winchester HDD article which makes extensive use of Mbytes with M being used in the conventional, 106 sense. Arguably all of todays HDD's derive from this technology.
*The October 1974 CDC Product Line Card unambiguous uses MB to characterize HDD capacity in millions of bytes.1975
*Byte Magazine Dec 1975 article on IBM 5100 includes the following:
**"User memory starts at 16K bytes in the minimum configuration and can be expanded to 64K bytes (65,536)."
*Gordon Bell uses the term megabytes:
*DEC RK05/RK05J/RK05F disk drive maintenance manual
**"Bit Capacities (unformatted)" "25 million" | "50 million" (57,600 bits/ track * 406 | 812 tracks = 23,385,600 | 46,771,200 bits
*The Memorex 1976 annual report has 10 instances of the use of megabyte to describe storage devices and media.
*Caleus Model 206-306 Maintenance Manual uses 3MB to characterize a drive having 3,060,000 bytes capacity.
*The first 5 1/4 inch floppy disk drive, the Shugart SA 400, is introduced in August 1976. The drive had 35 tracks and was single sided. The data sheet gives the unformatted capacity as 3125 bytes per track for a total of 109.4 Kbytes (3125 x 35 = 109,375). When formatted with 256 byte sectors and 10 sectors per track the capacity is 89.6 Kbytes (256 x 10 x 35 = 89,600).1977
*HP 7905A Disc Drive Operator's Manual
**"nearly 15 million bytes" with no other abbreviations

*1977 Disk/Trend Report - Rigid Disk Drives, published June 1977
**This first edition of the annual report on the hard disk drive industry makes extensive use of MB as 106 bytes. The industry, in 1977, is segmented into nine segments ranging from "Disk Cartridge Drives, up to 12 MB" to "Fixed Disk Drives, over 200 MB." While the categories changed during the next 22 years of publication, Disk/Trend, the principal marketing study of the hard disk drive industry always and consistently categorized the industry in segments using prefixes M and later G in the decimal sense.

*VAX11/780 Architecture Handbook 1977-78. Copyright 1977 Digital Equipment Corporation.
**Page 2-1 "physical address space of 1 gigabyte (30 bits of address)" The initial hardware was limited to 2 M bytes of memory utilizing the 4K MOS RAM chips. The VAX11/780 handbooks use M byte and Mbyte in the same paragraph.1978
*DEC RM02/03 Adapter Technical Description Manual
**"The RM02 or RM03 Disk Drive (Figure 1-1) is an 80M byte (unformatted; 67M byte formatted) … storage device … in the 16-bit format, the maximum storage capacity is 33,710,080 data words per disk pack" (33,710,080 * 16/8 = 67,420,160 8-bit bytes)1979
*Fujitsu M228X Manual
**"Storage capacity (unformatted)" "67.4 MB", "84.2 MB", etc.
**"20,480 Bytes" per track, 4 tracks per cylinder, 808+15 cylinders = 67,420,160 bytes

*Sperry Univac Series V77 Microcomputer Systems Brochure, Circa 1978, Printed July 1979
**Page 5: Table list memory options as 64KB, 128KB, and 256KB. Memory Expansion is up to 2048KB
**Page 9: "Memory for the V77-800 is available in 128K byte and 256K byte increments up to a maximum of 2 megabytes "
**Page 21: Moving Head Disks - units up to 232 million byte disk pack systems. Diskette - storage of 0.5 MB per drive.

*The following statistics were taken from the Dec 1979 editions of Byte Magazine and Datamation. The first number is the number of articles or advertisements that used any variant of megabyte for HDDs or Main memory while the second number is the total number of times it was used in the advertisement or article.
Variant Used In Decimal Sense Used In Binary Sense
million 1 / 1
megabyte 9 / 12 1 / 1
MByte or M Byte 3 /10
MB 5 / 18
Mb 2 / 2 1 / 3
M 1 / 1
Total 20 / 43 2 / 4


*Shugart Associates Product Brochure, published Jun 1980 specifies the capacity of its two HDDs using megabytes and MB in a decimal sense, e.g. SA1000 formated capacity is stated as "8.4 MB" and is actually 256×32×1024 = 8,388,608 bytes.
*Shugart Associates SA410/460 Data Sheet published Oct 1980 contains capacity specifications as follows:
Formatted Capacity SA410
Single/Double Density
Single/Double Density
Per Disk 204.8/409.6 KBytes 409.6/819.2 KBytes
Per Surface 204.8/409.6 KBytes 204.8/409.6 KBytes
Per Track 2.56/5.12 KBytes 2.56/5.12 KBytes
Sectors/Track 10 10
*Shugart Associates was one of the companies that invented the 5¼" FD using K in a decimal sense.
*Note that the same data sheet uses MByte in a decimal sense.1981
*8086 Object Module Formats
**"The 8086 MAS is 1 megabyte (1,048,576)"

*Quantum Q2000 8" Media Fixed Disk Drive Service Manual
**"four models ... the Q2010 having an unformatted 10.66 Mb capacity on one disk platter and two heads, the ... 21.33 Mb ... 32.00 Mb ... 42.66 Mb"
**(1024 tracks × "10.40Kb" per track = 10649 "Kb", which they write as "10.66Mb", so 1 "Mb" = 1000 "Kb")
**(256 Bytes per sector, 32 Sectors/tk = 8192 bytes, which they write as "8.20Kb" per track)
**"Storage capacity of 10, 20, 30, or 40 megabytes"
**"4.34M bits/second transfer rate"

*Apple Disk III data sheet
**"Formated Data Capacity: 140K bytes"
**Apple uses K is a binary sense since the actual formated capacity is 35 tracks * 16 Sectors * 256 bytes = 140 KiB = 143.360 kB1982
*Brochure for the IBM Personal Computer (PC)
**"User memory: 16KB to more than 512KB", "single-sided 160KB or double-sided 320KB diskette drives"

Technical Reference: Personal Computer Hardware Reference Library. Revised Edition, IBM Corp.. 6025008.
"The drives are soft sectored, single or double sided, with 40 tracks per side. They are Modified Frequency Modulation (MFM) coded in 512 byte sectors, giving a formatted capacity of 163,840 bytes per drive for single sided and 327,680 bytes per drive for double sided."

*Seagate ST 506/412 OEM Manual
**"Total formatted capacity ... is 5/10 megabytes (32 sectors per track, 256 bytes per sector, 612/1224 tracks)"1983
*IBM S/360 S/370 Principles Of Operation GA22-7000 includes as statement:
**"In this publication, the letters K, M and G denote the multipliers 210, 220 and 230 respectively. Although the letters are borrowed from the decimal system and stand for kilo 103, mega 106 and giga 109 they do not have decimal meaning but instead present the power of 2 closest to the corresponding power of 10."
*IBM 341 4-inch Diskette Drive
**unformatted capacity "358,087 bytes"
**"Total unformatted capacity (in kilobytes): 358.0"
*Maxtor XT-1000 brochure
**"Capacity, unformatted" 9.57 MB per surface = 10,416 bytes per track * 918 tracks per surface = 9,561,888 byte (decimal MB)
*Shugart Associates SA300/350 Data Sheet published circa Nov 1983 (one of the first MIC standard 3.5" FDDs) contains capacity specifications as follows:
Formatted Capacity Single Sided
Single/Double Density
Double Sided
Single/Double Density
Per Disk 204.8/409.6 kbytes 409.6/819.2 kbytes
Per Surface 204.8/409.6 kbytes 204.8/409.6 kbytes
Per Track 2.56/5.12 kbytes 2.56/5.12 kbytes
Sectors/Track 10 10
Shugart Associates, one of the leading FD companies used k in a decimal sense.1984
The Macintosh Operating System is an early, if not the earliest, operating system consistently using SI prefixes in a binary sense.
In the original 1984 Apple Macintosh ad, page 8, Apple characterized its 3½ floppy disk as "400K," that is, 800×512 byte sectors or 409,600 bytes = 400 KiB. Screenshots of Macintosh Finder shows the same usage of K in the Ki sense. Similarly, the February 1984 Byte Magazine review describes the FD as "400K bytes".1986
Apple IIgs introduced September 1986
ProDos16 uses MB in a binary sense.
Similar usage in "ProDOS Technical Reference Manual" (c) 1985, p. 5 & p. 163
Digital Large System Mass Storage Handbook (c) dated Sep 1986
"GByte: An abbreviation for one billion (one thousand million) bytes." p. 442
"M: An abbreviation for one million. Typically combined with a unit of measure, such as bytes (MBytes), or Hertz (MHz)." p4441987
*Seagate Universal Installation Handbook
**ST125 listed as 21 "Megabytes" formatted capacity, later document seems to confirm that this is decimal
*Disk/Trend Report - Rigid Disk Drives, October 1987
**First use of GB in a decimal sense in this HDD marketing survey; Figure 1 states "FIXED DISK DRIVES more than 1 GB" market size as $10,786.6 million.
*Webster's Ninth New Collegiate Dictionary (1987) has binary definitions for kilobyte and megabyte.
**kilobyte n [from the fact that 1024 (210) is the power of 2 closest to 1000] (1970): 1024 bytes
**megabyte n (1970): 1,048,576 bytes1988
*Imprimis Wren VII 5¼ Inch Rigid Disk Drive Data Sheet, printed 11/88
**"Capacity of 1.2 gigabyte (GB)"1989
*IBM Enterprise Systems Architecture/370, Reference Summary (GX20-0406-0), p50 (the last page), has a two table, one to recap the decimal value of power of 2 and 16 to 260, and one that read:
Symbol Value
K(kilo) 1,024 = 210
M(mega) 1,048,576 = 220
G(giga) 1,073,741,824 = 230
*Electronic News, Sep 25, "Market 1.5GB Drives"
**"Imprimis and Maxtor are the only two drive makers to offer the new generation of drives in the 1.5GB capacity range…"
**"IBM, Hewlett-Packard, Fujitsu, Toshiba, Hitachi and Micropolis are expected to enter the market for 1.5GB capacity…"


*GEOS ad
**"512K of memory"
*DEC RA90/RA92 Disk Drive Service Manual
**"Storage capacity, formatted" "1.216 gigabytes"1991
*Micropolis 1528 Rigid Disk Drive Product Description
**"1.53 GBytes" ... "Up to 1.53 gigabytes (unformatted) per drive" "MBytes/Unit: 1531.1" (2100×48,608×15 = 1,531,152,000)1993
*Microsoft Windows 3.11 File Manager uses MB in a binary sense.1994
*Micropolis 4410 Disk Drive Information
**"1,052 MB Formatted Capacity"
**"Unformatted Per Drive 1,205 MB" (133.85 MB per surface, 9 read-write heads)1996
*FOLDOC defines the exabyte (1 EB) as 1024 petabytes (1024 PB), with petabyte used in the binary sense of 10245 B.1997
*FOLDOC defines the zettabyte (1 ZB) as 1024 exabytes (1024 EB) and the yottabyte (1 YB) as 1024 zettabytes (1024 ZB).1998
*IEC introduces unambigous prefixes for binary multiples (KiB, MiB, GiB etc.), reserving kB, MB, GB and so on for their decimal sense.


*IBM, z/Architecture, Reference Summary
**Page 59, list the power of 2 and 16, and their decimal value. There is a column name 'Symbol', which list K(kilo), M(mega), G(giga), T(tera), P(peta) and E(exa) for the power of 2 of, respectively, 10, 20, 30, 40, 50, 60

*Peuhkuri adopts IEC prefixes in his paper at the 2001 Internet Measurement Conference: "... allows maximum size of 224 that requires 1 GiB of RAM ... or acknowledgement numer [sic] is within 32 KiB range. ... on a PC with Celeron processor with 512 MiB of memory ... 2004
*2004 revision of IEEE Standard Letter Symbols for Units of Measurement (SI Units, Customary Inch-Pound Units, and Certain Other Units), IEEE Std 260.1, incorporates IEC definitions for KiB, MiB etc, reserving the symbols kB, MB etc for their decimal counterparts.2005
*IEC prefixes are adopted by the IEEE after a two-year trial period.
**On March 19, 2005 the IEEE standard IEEE 1541-2002 (Prefixes for Binary Multiples) was elevated to a full-use standard by the IEEE Standards Association after a two-year trial period.2007
*Windows Vista uses the KB = 1024 bytes, MB = 1048576 bytes convention for file and drive sizes, and for data rates
*xxK or xxM convention in common use anywhere?
*GParted uses IEC prefixes for partition sizes
*Advanced Packaging Tool and Synaptic Package Manager use standard SI prefixes for file sizes
*BitTornado uses IEC prefixes for file sizes and standard SI prefixes for data rates
* IBM uses "exabyte" to mean 10246 bytes. "Each address space, called a 64-bit address space, is 16 exabytes (EB) in size; an exabyte is slightly more than one billion gigabytes. The new address space has logically 264 addresses. It is 8 billion times the size of the former 2-gigabyte address space, or 18,446,744,073,709,600,000 bytes."2008
* NIST guidelines require use of IEC prefixes KiB, MiB ... (and not kB, MB) for binary byte multiples
**p29, “The names and symbols for the prefixes corresponding to 2 10 , 2 20 , 2 30 , 2 40 , 2 50 , and 2 60 are, respectively: kibi, Ki; mebi, Mi; gibi, Gi; tebi, Ti; pebi, Pi; and exbi, Ei. Thus, for example, one kibibyte would be written: 1 KiB = 2 10 B = 1024 B, where B denotes a byte. Although these prefixes are not part of the SI, they should be used in the field of information technology to avoid the incorrect usage of the SI prefixes.”


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