Nibble: Difference between revisions

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[[File:Octets in CP866 ordered by nibbles.png|192px|thumb|right|An [[Octet (computing)|octet]] [[code page 866]] font table ordered by nibbles.]]
[[File:Octets in CP866 ordered by nibbles.png|192px|thumb|right|An [[Octet (computing)|octet]] [[code page 866]] font table ordered by nibbles.]]


In [[computing]], a '''nibble''',<ref name="Intel_1974_MCS-40"/> or spelled '''nybble''' to match [[byte]], is a [[unit of information]] that is an aggregation of four-[[bit]]s; half of a byte/[[octet (computing)|octet]].<ref name="Intel_1974_MCS-40"/><ref name="Hall_1980"/><ref name="Warren_2013"/> The unit is alternatively called '''nyble''', '''nybl''', '''half-byte'''<ref name="esr"/> or '''tetrade'''.<ref name="Carr_1959"/><ref name="Speiser_1965"/> In [[computer network|networking]] or [[telecommunications]], the unit is often called a '''semi-octet''',<ref name="Puzman_2012"/> '''quadbit''',<ref name="Horak_2007_Websters"/> or '''quartet'''.<ref name="Brewster_1994"/><ref name="Courbis_1989"/>
In [[computing]], a '''nibble''',<ref name="Intel_1974_MCS-40"/> also spelled '''nybble''' to match [[byte]], is a [[unit of information]] that is an aggregation of four-[[bit]]s; half of a byte/[[octet (computing)|octet]].<ref name="Intel_1974_MCS-40"/><ref name="Hall_1980"/><ref name="Warren_2013"/> The unit is alternatively called '''nyble''', '''nybl''', '''half-byte'''<ref name="esr"/> or '''tetrade'''.<ref name="Carr_1959"/><ref name="Speiser_1965"/> In [[computer network|networking]] or [[telecommunications]], the unit is often called a '''semi-octet''',<ref name="Puzman_2012"/> '''quadbit''',<ref name="Horak_2007_Websters"/> or '''quartet'''.<ref name="Brewster_1994"/><ref name="Courbis_1989"/>


As a nibble can represent sixteen ({{math|2<sup>4</sup>}}) possible values, a nibble value is often shown as a [[hexadecimal]] [[digit (math)|digit]] (hex digit).<ref name="Intro_CPP_1997"/> A byte is two nibbles, and therefore, a value can be shown as two hex digits.
As a nibble can represent sixteen ({{math|2<sup>4</sup>}}) possible values, a nibble value is often shown as a [[hexadecimal]] [[digit (math)|digit]] (hex digit).<ref name="Intro_CPP_1997"/> A byte is two nibbles, and therefore, a value can be shown as two hex digits.
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== History ==
== History ==
The term ''nibble'' originates from its representing half a byte, with ''byte'' a [[homophone]] of the [[English (language)|English]] word ''bite''.<ref name="esr"/> In 2014, David B. Benson, a professor emeritus at [[Washington State University]], remembered that he playfully used (and may have possibly coined) the term ''nibble'' as half a byte and unit of storage required to hold a [[binary-coded decimal]] (BCD) digit around 1958, when talking to a programmer from [[Los Alamos Scientific Laboratory]]. The alternative spelling ''nybble'' reflects the spelling of ''byte'', as noted in editorials of ''[[Kilobaud Microcomputing|Kilobaud]]'' and ''[[Byte (magazine)|Byte]]'' in the early 1980s. Another early recorded use of the term ''nybble'' was in 1977 within the consumer-banking technology group at Citibank. It created a pre-[[ISO 8583]] standard for transactional messages between [[cash machine]]s and Citibank's [[data center]]s that used the basic data unit ''nabble''.
The term ''nibble'' originates from its representing half a byte, with ''byte'' a [[homophone]] of the [[English (language)|English]] word ''bite''.<ref name="esr"/>


''Nibble'' is used to describe the amount of memory used to store a digit of a number stored in [[binary-coded decimal|packed decimal format]] (BCD) within an IBM mainframe. This technique is used to make computations faster and debugging easier. An 8-bit byte is split in half and each nibble is used to store one decimal digit. The last (rightmost) nibble of the variable is reserved for the sign. Thus a variable which can store up to nine digits would be "packed" into 5 bytes. Ease of debugging resulted from the numbers' being readable in a [[hex dump]] where two [[hexadecimal|hex]] numbers are used to represent the value of a byte, as {{math|16×16 {{=}} 2<sup>8</sup>}}. For example, a five-byte BCD value of {{code|31}}&nbsp;{{code|41}}&nbsp;{{code|59}}&nbsp;{{code|26}}&nbsp;{{code|5C}} represents a decimal value of +314159265.
Around 1958, David B. Benson might have originated the term. As a professor emeritus at [[Washington State University]] in a 2014 interview, he recalled that he playfully used (and might have possibly coined) the term ''nibble'' as half a byte and unit of storage required to hold a [[binary-coded decimal]] (BCD) digit when talking to a programmer from [[Los Alamos Scientific Laboratory]] at that time.{{fact|date=September 2025}}


Historically, there are cases where ''nybble'' was used for a group of bits greater than 4. On the [[Apple II]], much of the disk drive control and [[group-coded recording]] was implemented in software. Writing data to a disk was done by converting 256-byte pages into sets of [[5-and-3 encoding|5-bit]] (later, [[6-and-2 encoding|6-bit]]) nibbles and loading disk data required the reverse.<ref name="Lechner_1982_Beneath_Apple_DOS"/><ref name="Lechner_1985_Beneath_Apple_ProDOS"/><ref name="CP_1989_CopyII"/> Moreover, 1982 documentation for the [[Integrated Woz Machine]] refers consistently to an "8 bit nibble".<ref name="Apple_1982_IWM"/> The term ''byte'' once had the same ambiguity and meant a set of bits but not necessarily 8, hence the distinction of ''bytes'' and ''[[octet (computing)|octet]]s'' or of ''nibbles'' and ''quartets'' (or ''quadbits''). Today, the terms ''byte'' and ''nibble'' almost always refer to 8-bit and 4-bit collections, respectively and are very rarely used to express any other sizes.
In 1977, an early use of the spelling ''nybble'' for the term was recorded within the consumer-banking technology group at Citibank. It created a pre-[[ISO 8583]] standard for transactional messages between [[cash machine]]s and Citibank's [[data center]]s that used the basic data unit ''nabble''.{{fact|date=September 2025}}
 
In the early 1980s, the alternative spelling ''nybble'' reflected the spelling of ''byte'', as noted in editorials of ''[[Kilobaud Microcomputing|Kilobaud]]'' and ''[[Byte (magazine)|Byte]]''.{{fact|date=September 2025}}
 
==Usage==
''Nibble'' is used to describe the amount of memory used to store a digit of a number stored in [[binary-coded decimal|packed decimal format]] (BCD) within an IBM mainframe. This technique is used to make computations faster and debugging easier. An 8-bit byte is split in half and each nibble is used to store one decimal digit. The last (rightmost) nibble of the variable is reserved for the sign. Thus a variable which can store up to nine digits would be "packed" into 5 bytes. Ease of debugging resulted from the numbers' being readable in a [[hex dump]] where two [[hexadecimal|hex]] numbers are used to represent the value of a byte, as {{math|16×16 {{=}} 2<sup>8</sup>}}. For example, a five-byte BCD value of {{code|31}}&nbsp;{{code|41}}&nbsp;{{code|59}}&nbsp;{{code|26}}&nbsp;{{code|5C}} represents a decimal value of +314159265.{{fact|date=September 2025}}
 
Historically, ''nybble'' was used in many cases for a group of bits greater than 4. On the [[Apple II]], much of the disk drive control and [[group-coded recording]] was implemented in software. Writing data to a disk was done by converting 256-byte pages into sets of [[5-and-3 encoding|5-bit]] (later, [[6-and-2 encoding|6-bit]]) nibbles and loading disk data required the reverse.<ref name="Lechner_1982_Beneath_Apple_DOS"/><ref name="Lechner_1985_Beneath_Apple_ProDOS"/><ref name="CP_1989_CopyII"/> Moreover, 1982 documentation for the [[Integrated Woz Machine]] refers consistently to an "8 bit nibble".<ref name="Apple_1982_IWM"/> The term ''byte'' once had the same ambiguity and meant a set of bits but not necessarily 8, hence the distinction of ''bytes'' and ''[[octet (computing)|octet]]s'' or of ''nibbles'' and ''quartets'' (or ''quadbits''). Today, the terms ''byte'' and ''nibble'' almost always refer to 8-bit and 4-bit collections, respectively, and are very rarely used to express any other sizes.{{fact|date=September 2025}}


== Value representation ==
== Value representation ==

Latest revision as of 14:45, 19 November 2025

Template:Short description Script error: No such module "about". Template:More citations needed Template:Use dmy dates Template:Use American English

File:Octets in CP866 ordered by nibbles.png
An octet code page 866 font table ordered by nibbles.

In computing, a nibble,[1] also spelled nybble to match byte, is a unit of information that is an aggregation of four-bits; half of a byte/octet.[1][2][3] The unit is alternatively called nyble, nybl, half-byte[4] or tetrade.[5][6] In networking or telecommunications, the unit is often called a semi-octet,[7] quadbit,[8] or quartet.[9][10]

As a nibble can represent sixteen (Template:Math) possible values, a nibble value is often shown as a hexadecimal digit (hex digit).[11] A byte is two nibbles, and therefore, a value can be shown as two hex digits.

Four-bit computers use nibble-sized data for storage and operations; as the word unit. Such computers were used in early microprocessors, pocket calculators and pocket computers. They continue to be used in some microcontrollers. In this context, 4-bit groups were sometimes also called characters[12] rather than nibbles.[1]

History

The term nibble originates from its representing half a byte, with byte a homophone of the English word bite.[4]

Around 1958, David B. Benson might have originated the term. As a professor emeritus at Washington State University in a 2014 interview, he recalled that he playfully used (and might have possibly coined) the term nibble as half a byte and unit of storage required to hold a binary-coded decimal (BCD) digit when talking to a programmer from Los Alamos Scientific Laboratory at that time.Template:Fact

In 1977, an early use of the spelling nybble for the term was recorded within the consumer-banking technology group at Citibank. It created a pre-ISO 8583 standard for transactional messages between cash machines and Citibank's data centers that used the basic data unit nabble.Template:Fact

In the early 1980s, the alternative spelling nybble reflected the spelling of byte, as noted in editorials of Kilobaud and Byte.Template:Fact

Usage

Nibble is used to describe the amount of memory used to store a digit of a number stored in packed decimal format (BCD) within an IBM mainframe. This technique is used to make computations faster and debugging easier. An 8-bit byte is split in half and each nibble is used to store one decimal digit. The last (rightmost) nibble of the variable is reserved for the sign. Thus a variable which can store up to nine digits would be "packed" into 5 bytes. Ease of debugging resulted from the numbers' being readable in a hex dump where two hex numbers are used to represent the value of a byte, as Template:Math. For example, a five-byte BCD value of 31 41 59 26 5C represents a decimal value of +314159265.Template:Fact

Historically, nybble was used in many cases for a group of bits greater than 4. On the Apple II, much of the disk drive control and group-coded recording was implemented in software. Writing data to a disk was done by converting 256-byte pages into sets of 5-bit (later, 6-bit) nibbles and loading disk data required the reverse.[13][14][15] Moreover, 1982 documentation for the Integrated Woz Machine refers consistently to an "8 bit nibble".[16] The term byte once had the same ambiguity and meant a set of bits but not necessarily 8, hence the distinction of bytes and octets or of nibbles and quartets (or quadbits). Today, the terms byte and nibble almost always refer to 8-bit and 4-bit collections, respectively, and are very rarely used to express any other sizes.Template:Fact

Value representation

A nibble-sized value can be represented in different numeric bases:

Binary Decimal Hexadecimal
Template:Mono 0 0
Template:Mono 1 1
Template:Mono 2 2
Template:Mono 3 3
Template:Mono 4 4
Template:Mono 5 5
Template:Mono 6 6
Template:Mono 7 7
Template:Mono 8 8
Template:Mono 9 9
Template:Mono 10 A
Template:Mono 11 B
Template:Mono 12 C
Template:Mono 13 D
Template:Mono 14 E
Template:Mono 15 F

Low and high nibbles

The low and high nibbles of a byte are its two halves, which are the least and the most significant bits within the byte, respectively. In a graphical representation of bits within a byte, the leftmost bit could represent the most significant bit (MSB), corresponding to ordinary decimal notation in which the digit at the left of a number is the most significant. In such an illustration, the four bits on the left end of the byte form the high nibble, and the remaining four bits form the low nibble.[17] For example,

Template:Math

the high nibble is Template:Math (Template:Math), and the low nibble is Template:Math (Template:Math). The total value is Template:Math (Template:Math).

See also

References

Template:Reflist

External links

  • Script error: No such module "citation/CS1".

Template:Computer Storage Volumes

  1. ↑ a b c Cite error: Invalid <ref> tag; no text was provided for refs named Intel_1974_MCS-40
  2. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Hall_1980
  3. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Warren_2013
  4. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named esr
  5. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Carr_1959
  6. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Speiser_1965
  7. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Puzman_2012
  8. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Horak_2007_Websters
  9. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Brewster_1994
  10. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Courbis_1989
  11. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Intro_CPP_1997
  12. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Intel_1973_MCS-4
  13. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Lechner_1982_Beneath_Apple_DOS
  14. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Lechner_1985_Beneath_Apple_ProDOS
  15. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named CP_1989_CopyII
  16. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Apple_1982_IWM
  17. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Baccala_1997
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