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For the computer industry magazine, see Byte (magazine). A byte is commonly used as a unit of storage measurement in computers, regardless of the type of data being stored. It is also one of the basic integral data types in many programming languages.
Meanings The word "byte" has numerous closely related meanings: History The term byte was coined by Werner Buchholz in 1957 during the early design phase for the IBM Stretch computer. Originally it was defined in instructions by a 4-bit byte-size field, allowing from one to sixteen bits (the production design reduced this to a 3-bit byte-size field, allowing from one to eight bits in a byte); typical I/O equipment of the period used six-bit units. A fixed eight-bit byte size was later adopted and promulgated as a standard by the System/360. The term "byte" comes from "bite," as in the smallest amount of data a computer could "bite" at once. The spelling change not only reduced the chance of a "bite" being mistaken for a "bit," but also was consistent with the penchant of early computer scientists to make up words and change spellings. However, back in the 1960s, the luminaries at IBM Education Department in the UK were teaching that a bit was a Binary digIT and a byte was a BinarY TuplE (from n-tuple, i.e. quintuple, sextuple, septuple, octuple ...). A byte was also often referred to as "an 8-bit byte", reinforcing the notion that it was a tuple of n bits, and that other sizes were possible. Other sources have also said that the word byte comes from the following: BinarY TablE char integral data type can hold at least 8 bits (clause 5.2.4.2.1), a byte in C is at least capable of holding 256 different values (signed or unsigned char doesn't matter). Java's primitive byte data type is always defined as consisting of 8 bits and being a signed data type, holding values from -128 to 127.Early microprocessors, such as Intel's 8008 (the direct predecessor of the 8080, and then 8086) could perform a small number of operations on four bits, such as the DAA (decimal adjust) instruction, and the "half carry" flag, that were used to implement decimal arithmetic routines. These four-bit quantities were called "nibbles," in homage to the then-common 8-bit "bytes." Alternate words The eight-bit byte is often called an octet in formal contexts such as industry standards, as well as in networking and telecommunication, in order to avoid any confusion about the number of bits involved. However, 8-bit bytes are now firmly embedded in such common standards as Ethernet and HTML. Octet is also the word used for the eight-bit quantity in many non-English languages, where the pun on bite does not translate. Half of an eight-bit byte (four bits) is sometimes called a nibble (sometimes spelled nybble) or a hex digit. The nibble is often called a semioctet in a networking or telecommunication context and also by some standards organizations. Abbreviation/Symbol IEEE 1541 and Metric-Interchange-Format specify "B" as the symbol for byte (e.g. MB means megabyte), whilst IEC 60027 seems silent on the subject. Furthermore, B means bel (see decibel), another (logarithmic) unit used in the same field. IEEE 1541 specifies "b" as the symbol for bit; however the IEC 60027 and Metric-Interchange-Format specify "bit" (e.g. Mbit for megabit) for the symbol, achieving maximum disambiguation from byte. "b" vs. "B" confusion seems to be common enough to have inspired the creation of a dedicated website b is not B. French-speaking countries sometimes use an uppercase "o" for "octet". This is not allowed in SI because of the risk of confusion with the zero and the convention that capitals are reserved for unit names derived from proper names, e.g., A=ampere, J=joule; s=second, m=metre. Therefore, lowercase 'o' is good, and already in use with multiples ko, Mo Octet (computing). Names for different units The prefixes used for byte measurements are usually the same as the SI prefixes used for other measurements, but have slightly different values. The former are based on powers of 1,024 (210), a convenient binary number, while the SI prefixes are based on powers of 1,000 (103), a convenient decimal number. The table below illustrates these differences. See binary prefix for further discussion. Fractional information is usually measured in bits, nats, or bans. See also | ||||||||
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