This timeline of binary prefixes lists events in the history of the evolution, development, and use of units of measure that are germane to the definition of the binary prefixes by the International Electrotechnical Commission (IEC) in 1998, used primarily with units of information such as the bit and the byte.
Historically, computers have used many systems of internal data representation, methods of operating on data elements, and data addressing. Early decimal computers included the ENIAC, UNIVAC 1, IBM 702, IBM 705, IBM 650, IBM 1400 series, and IBM 1620. Early binary addressed computers included Zuse Z3, Colossus, Whirlwind, AN/FSQ-7, IBM 701, IBM 704, IBM 709, IBM 7030, IBM 7090, IBM 7040, IBM System/360, and the DEC PDP-1, PDP-4, PDP-5, and PDP-6.
Decimal systems typically had memory configured in whole decimal multiples, e.g., blocks of 100 and later . The unit abbreviation '' or '' if it was used, represented multiplication by . Binary memory had sizes of powers of two or small multiples thereof. In this context, '' or '' was sometimes used to denote multiples of units or just the approximate size, e.g., either '64K' or '65K' for (216).
1790s 1793 The French Commission temporaire de Poids & Mesures rêpublicaines, Décrets de la Convention Nationale, proposes the binary prefixes double and demi, denoting a factor of 2 (21) and (2−1), respectively, in 1793.
1795 The prefixes double and demi are part of the original metric system adopted by France (with kilo for 1000) in 1795. These were not retained when the decadic SI prefixes were internationally adopted by the 11th CGPM conference in 1960.
1870s The British Science Association established metric prefix "" in 1873. (Committee members: Professor Joseph David Everett (reporter), Sir W Thomson, Professor GC Foster, Professor JC Maxwell, Mr GJ Stoney, Professor Flemming Jenkin, Dr. CW Siemens, Mr FJ Bramwell)
1930s Metric prefixes "" (established 1795) and "" (established 1873) are widely used as decimal multipliers 1,000 and 1,000,000 for units of frequency and impedance in the electronics industry. The Committee of the Verband Deutscher Elektrotechniker publishes suggested names and symbols for the metric prefixes with decimal meaning, i.e., ( = 109) and ( = 1012).
1940s 1943–1944 J. W. Tukey coins the word "bit" as a contraction of "binary digit".
1947 "The Whirlwind I Computer is planned with a storage capacity of numbers of 16 binary digits each."
1948 Tukey's "bit" is referenced in the work of information theorist Claude Shannon.
1950s In the 1950s, "1 bit" meant bits: "In the '50s, amazingly enough—and only total coincidence—I actually was given the job of writing the operational specifications [...] for what was called cross telling. They handed me this thing and said, 'You're going to define how the hand-over process works between direction centers', [...] and I had no idea what they were talking about. But we had [...] one-kilobit lines connecting the direction centers and I thought, 'Good God! bits a second. Well, we'll surely be able to figure out something to do with that. — Saverah Warenstein, former programmer at Lincoln Laboratory, IBM
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 16 × 16-bit ferrite core array was successfully tested at MIT." The IBM 701, a binary-addressed computer containing 72 Williams tubes of bits each, is released in April. Principles of Operation Type 701 does not use prefixes with lengths of words or size of storage. For example, it specifies that memory tubes hold words each. The IBM 737 optional magnetic core storage stores 36-bit words. Each plane stored 64 × 64 = bits.
1955 The IBM 704 (a binary machine) manual uses decimal arithmetic for powers of two, without prefixes "Magnetic core storage units are available with capacities of either or core storage registers; or two magnetic core storage units, each with a capacity of core storage registers, may be used. Thus, magnetic core storage units are available to give the calculator a capacity of , , or core storage registers." "Each drum has a storage capacity of words."
1956 The IBM 702 (a decimally addressed machine) 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 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 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 positions of memory is numbered from to and each stored character must occupy one of these positions." (page 8) The word byte, meaning eight bits, is coined by Dr. Werner Buchholz in June 1956, during the early design phase for the IBM Stretch computer. IBM 650 RAMAC (a decimal addressed machine) 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 (a decimal addressed machine) Operating manual uses decimal arithmetic for powers of ten, without prefixes. "A total of characters can be stored within the main storage unit of the Type 705." "Each one of the positions in memory is numbered from 0000 to ." (page 17) "One or more magnetic drums are available as optional equipment with a capacity of 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".
1958 "64 million (226) bytes" is used in a memo by Dr. Werner Buchholz
1959 The term 32k is used in print to refer to a memory size of 32768 (215). The author is with the Westinghouse Electric Corporation.
1960s 1960 The 11th Conférence Générale des Poids et Mesures (CGPM) announces the Système International d'Unités (SI) and adds the decimal metric prefixes giga, and tera, defined as 109 and 1012 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."
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).The symbol K used in 8K and 32K could have meant 1000 or 1024.
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
Quoted in OED as first instance of "bit", though "it is more usual" suggests it is already in common use (see timeline entry for 1957) Described device contains 512 words, 24 bits each (= bits) "It is no longer reasonable to spend as much time to transmit an 80-bit address as 12 bits 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 bit PCM channel capability to 2400 bits by the application of the Dudley syllabic vocoder." The IBM 7090 Data Processing System (a binary machine), Additional Core Storage (65 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 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 65 mode – the computer program is enabled to address both of the main storage units, and (2) the 32 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, which used modified decimal addressing, uses decimal arithmetic for powers of ten, without prefixes "Core storage units are available in -, - or -character position capacities." "The matrix switch makes it possible to address any one of the 100 X-drive lines (in a 10 core array)." "The 40 core array requires valid five-position addresses from to ." "This operation check detects errors in programming that cause invalid addresses. Examples: -and-above on a 40 core array; -and-above on a 20 core array. On a 10 core array, invalid addresses are detected by the address-bus validity check."
1962 A reference to a "4 IBM 1401" meant characters of storage (memory).
1963 Ludwig uses bit 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 characters, each of which is stored in a separate, addressable, memory location. This capacity may be expanded in modular increments by adding one -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 characters, allowing a total capacity of approximately 21 million characters."
1964 Gene Amdahl's seminal April 1964 article on IBM System/360 used 1 to mean 1024. (NB. Figure 1 gives storage (memory) capacity ranges of the various models in "Capacity 8-bit bytes, 1 = 1024") Leng, Gordon Bell, et al., use in the binary sense: "The computer has two blocks of 4, 18-bit words of memory, (1 = 1024 words), attached to its central processor"
Data Processing Division press release distributed on April 7, 1964. "System/360 core storage memory capacity ranges from characters of information to more than ." 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