Byte

byte /bi:t/ n.

[techspeak] A unit of memory or data equal to the amount used to represent one character; on modern architectures this is usually 8 bits, but may be 9 on 36-bit machines. Some older architectures used `byte' for quantities of 6 or 7 bits, and the PDP-10 supported `bytes' that were actually bitfields of 1 to 36 bits! These usages are now obsolete, and even 9-bit bytes have become rare in the general trend toward power-of-2 word sizes.

Historical note: The term was coined by Werner Buchholz in 1956 during the early design phase for the IBM Stretch computer; originally it was described as 1 to 6 bits (typical I/O equipment of the period used 6-bit chunks of information). 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. The word was coined by mutating the word `bite' so it would not be accidentally misspelled as bit. See also nybble.

--The Jargon File version 4.3.1, ed. ESR, autonoded by rescdsk.

IEC-Defined Common Multiples of Bytes

kibibyte = (2¹⁰)¹ bytes = 1,024 bytes
mebibyte = (2¹⁰)² bytes = 1,048,576 bytes
gibibyte = (2¹⁰)³ bytes = 1,073,741,824 bytes
tebibyte = (2¹⁰)⁴ bytes = 1,099,511,627,776 bytes
pebibyte = (2¹⁰)⁵ bytes = 1,125,899,906,842,624 bytes
exbibyte = (2¹⁰)⁶ bytes = 1,152,921,504,606,846,976 bytes

kilobyte = 10³ bytes = 1,000 bytes
megabyte = 10⁶ bytes = 1,000,000 bytes
gigabyte = 10⁹ bytes = 1,000,000,000 bytes
terabyte = 10¹² bytes = 1,000,000,000,000 bytes
petabyte = 10¹⁵ bytes = 1,000,000,000,000,000 bytes
exabyte = 10¹⁸ bytes = 1,000,000,000,000,000,000 bytes
zettabyte = 10²¹ bytes = 1,000,000,000,000,000,000,000 bytes
yottabyte = 10²⁴ bytes = 1,000,000,000,000,000,000,000,000 bytes

Traditionally, the term "kilobyte" meant (2¹⁰)¹ or 1024 bytes, megabyte was 1024² bytes, etc. To avoid confusion (!) with the standard SI units, the definitions above were published in January, 1999 by the IEC.