byte

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byte

byte

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byte

/bi:t/ (B) A component in the machine data hierarchy usually larger than a bit and smaller than a word; now most often eight bits and the smallest addressable unit of storage. A byte typically holds one character.

A byte may be 9 bits on 36-bit computers. Some older architectures used "byte" for quantities of 6 or 7 bits, and the PDP-10 and IBM 7030 supported "bytes" that were actually bit-fields of 1 to 36 (or 64) bits! These usages are now obsolete, and even 9-bit bytes have become rare in the general trend toward power-of-2 word sizes.

The term was coined by Werner Buchholz in 1956 during the early design phase for the IBM Stretch computer. It was a mutation of the word "bite" intended to avoid confusion with "bit". In 1962 he described it as "a group of bits used to encode a character, or the number of bits transmitted in parallel to and from input-output units". The move to an 8-bit byte happened in late 1956, and this size was later adopted and promulgated as a standard by the System/360 operating system (announced April 1964).

James S. Jones adds:

I am sure I read in a mid-1970's brochure by IBM that outlined the history of computers that BYTE was an acronym that stood for "Bit asYnchronous Transmission E__?__" which related to width of the bus between the Stretch CPU and its CRT-memory (prior to Core).

Terry Carr says:

In the early days IBM taught that a series of bits transferred together (like so many yoked oxen) formed a Binary Yoked Transfer Element (BYTE).

[True origin? First 8-bit byte architecture?]

See also nibble, octet.

[Jargon File]

(2003-09-21)