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 1000. The unit abbreviation 'K' or 'k' if it was used, represented multiplication by 1000. Binary memory had sizes of powers of two or small multiples thereof. In this context, 'K' or 'k' was sometimes used to denote multiples of 1024 units or just the approximate size, e.g., either '64K' or '65K' for 65536 (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 1⁄2 (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 "mega-" in 1873.
1930s Metric prefixes "kilo-" (established 1795) and "mega-" (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., giga (G = 109) and tera (T = 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 2048 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 kilobit" meant 1000 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! 1000 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 1024 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 2048 words each. The IBM 737 optional magnetic core storage stores 4096 36-bit words. Each plane stored 64 × 64 = 4096 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 4096 or 32768 core storage registers; or two magnetic core storage units, each with a capacity of 4096 core storage registers, may be used. Thus, magnetic core storage units are available to give the calculator a capacity of 4096, 8192, or 32768 core storage registers." "Each drum has a storage capacity of 2048 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 10000 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 60000 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 10000 positions of memory is numbered from 0000 to 9999 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."
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