Nibble

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This article explains the meaning of the computing term. See Nibble (magazine) for the old home computer magazine. See also Nibbles (computer game).

A nibble (or less commonly, nybble) is the computing term for the aggregation of four bits, or half an octet (an octet being an 8-bit byte). As a nibble contains four bits, there are sixteen (2⁴) possible values, so a nibble corresponds to a single hexadecimal digit (thus, it is often referred to as a "hex digit" or "hexit"). A full byte is represented by two hexadecimal digits; therefore, it is common to display a byte of information as two nibbles. The nibble is often called a "semioctet" or a "quartet" in a networking or telecommunication context.

The term "nibble" originates from the fact that the term "byte" is a pun on the English word "bite". A nibble is a small bite, which in this context is humourously construed as "half a bite". The alternative "nybble" spelling parallels the spelling of "byte".

Historically, there have been cases where the term "nybble" was used for a set of bits fewer than 8, but not necessarily 4. In the Apple II microcomputer line, much of the disk drive control was implemented in software. Writing data to a disk was done by converting 256-byte pages into sets of 5-bit or, later, 6-bit nybbles; loading data from the disk required the reverse. Note that the term byte also had this ambiguity; at one time, byte meant a set of bits but not necessarily 8. Today, the terms "byte" and "nibble" ("nybble") generally refer to 8- and 4-bit collections, respectively, and are not often used for other sizes.

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