nybble

Half a byte (4 bits) is a nybble. The joke is so awful that it stuck. A nybble can store a single decimal digit; when this is done for many digits, the result is BCD.

One hex digit describes precisely one nybble. Thus, anyone writing hex strings is really writing down nybbles. And any BCD is immediately recognizable in hex -- just read the hex digits (which are all 0,...,9) as decimal.

The most modern machine I know of that uses nybbles is the HP48 (and, presumably, the HP49, not to mention the alphabet soup you can write after either name). The Saturn processor used internally, and the internal RPL, both seem to be heavily oriented towards nybbles. Apparently Saturn is something of a 4 bit CPU!

nybble /nib'l/ (alt. `nibble') n.

[from v. `nibble' by analogy with `bite' => `byte'] Four bits; one hex digit; a half-byte. Though `byte' is now techspeak, this useful relative is still jargon. Compare byte; see also bit. The more mundane spelling "nibble" is also commonly used. Apparently the `nybble' spelling is uncommon in Commonwealth Hackish, as British orthography would suggest the pronunciation /ni:'bl/.

Following `bit', `byte' and `nybble' there have been quite a few analogical attempts to construct unambiguous terms for bit blocks of other sizes. All of these are strictly jargon, not techspeak, and not very common jargon at that (most hackers would recognize them in context but not use them spontaneously). We collect them here for reference together with the ambiguous techspeak terms `word', `half-word', `double word', and `quad' or `quad word'; some (indicated) have substantial information separate entries.

2 bits:

crumb, quad, quarter, tayste, tydbit, morsel

4 bits:

nybble

5 bits:

nickle

10 bits:

deckle

16 bits:

playte, chawmp (on a 32-bit machine), word (on a 16-bit machine), half-word (on a 32-bit machine).

18 bits:

chawmp (on a 36-bit machine), half-word (on a 36-bit machine)

32 bits:

dynner, gawble (on a 32-bit machine), word (on a 32-bit machine), longword (on a 16-bit machine).

36 bits:

word (on a 36-bit machine)

48 bits:

gawble (under circumstances that remain obscure)

64 bits:

double word (on a 32-bit machine) quad (on a 16-bit machine)

128 bits:

quad (on a 32-bit machine)

The fundamental motivation for most of these jargon terms (aside from the normal hackerly enjoyment of punning wordplay) is the extreme ambiguity of the term `word' and its derivatives.

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