bit / byte

Many people wonder where these two computer terms come from. Of the two, bit is older, dating to 1948. It first appears in A Mathematical Theory of Communication by C.E. Shannon in Bell Systems Technical Journal in July and October of that year. (This paper is one of the seminal works of modern information theory. The fact that it is the first known use of bit is simply a footnote to its scientific importance.) In the paper, Shannon credits a J.W. Tukey with the coinage:

The choice of a logarithmic base corresponds to the choice of a unit for measuring information. If the base 2 is used the resulting units may be called binary digits, or more briefly bits, a word suggested by J. W. Tukey.

As Shannon indicates, bit is an abbreviated form of binary digit, chosen probably because it is also a play on the meaning of the then existing word bit signifying a small part.

The term byte is of less certain origin, but probably was coined by someone at IBM (perhaps a Dr. Werner Buchholz) around 1964. The word byte is a play on bit. The original sense of the term was the amount of data required to represent one character—usually, but not always, eight bits. Over time, the predominant sense shifted to mean eight bits exactly.

The first citation in the Oxford English Dictionary is from an article by Messrs. Blaauw and Brooks in a 1964 issue of the IBM Systems Journal:

An 8-bit unit of information is fundamental to most of the formats [of the System/360]. A consecutive group of n such units constitutes a field of length n. Fixed-length fields of length one, two, four, and eight are termed bytes, halfwords, words, and double words respectively.

Some have suggested that it is an abbreviation for BInary digiT Eight and that the Y was substituted for the I so to prevent typographical confusion with bit. Another suggestion is that it is from BinarY TErm. Neither of these claims is well substantiated and are probably false.

Also playful, but less well known, is the term nybble or nibble, meaning half a byte, or four bits.

(Sources: Oxford English Dictionary, 2nd Edition; Safire’s Quoth the Maven; Carver’s A History of English in Its Own Words)

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