View source for Units of information

{{Use dmy dates|date=January 2021|cs1-dates=y}}
{{Short description|Unit of measure for digital data}}
{{Redirect-distinguish|tribit|Tebibit{{!}}tibit|Ternary numeral system{{!}}trit}}
A '''unit of information''' is any [[unit of measure]] of [[digital data]] size. In digital [[computing]], a unit of information is used to describe the capacity of a digital [[digital data storage|data storage]] device. In [[telecommunication]]s, a unit of information is used to describe the throughput of a [[communication channel]]. In [[information theory]], a unit of information is used to measure [[information]] contained in messages and the [[Entropy (information theory)|entropy]] of random variables.

Due to the need to work with data sizes that range from very small to very large, units of information cover a wide range of data sizes. Units are defined as multiples of a smaller unit except for the smallest unit which is based on convention and hardware design. Multiplier prefixes are used to describe relatively large sizes.

For [[binary number|binary]] [[computer hardware|hardware]], by far the most common hardware today, the smallest unit is the [[bit]], a portmanteau of binary digit,<ref name="Mackenzie_1980"/> which represents a value that is one of two possible values; typically shown as 0 and 1. The [[nibble]], 4 bits, represents the value of a single [[hexadecimal]] digit. The [[byte]], 8 bits, 2 nibbles, is possibly the most commonly known and used base unit to describe data size. The [[Word (computer architecture)|word]] is a size that varies by and has a special importance for a particular hardware context. On modern hardware, a word is typically 2, 4 or 8 bytes, but the size varies dramatically on older hardware. Larger sizes can be expressed as multiples of a base unit via [[SI]] [[metric prefixes]] (powers of ten) or the newer and generally more accurate [[IEC]] [[binary prefixes]] (powers of two).

== Information theory ==
[[File:Units of information.svg|thumb|right|384px|Comparison of units of information: [[bit]], [[ternary numeral system|trit]], [[nat (unit)|nat]], [[ban (unit)|ban]]. Quantity of information is the height of bars. Dark green level is the "nat" unit.]]
{{Fundamental info units}}
In 1928, [[Ralph Hartley]] observed a fundamental storage principle,<ref name="Abramson_1963"/> which was further formalized by [[Claude Shannon]] in 1945: the information that can be stored in a system is proportional to the [[logarithm]] of ''N'' possible states of that system, denoted {{nowrap|log<sub>''b''</sub> ''N''}}. Changing the base of the logarithm from ''b'' to a different number ''c'' has the effect of multiplying the value of the logarithm by a fixed constant, namely {{nowrap|1=log<sub>''c''</sub> ''N'' = (log<sub>''c''</sub> ''b'') log<sub>''b''</sub> ''N''}}.
Therefore, the choice of the base ''b'' determines the unit used to measure information. In particular, if ''b'' is a [[positive and negative numbers|positive]] integer, then the unit is the amount of information that can be stored in a system with ''b'' possible states.

When ''b'' is 2, the unit is the [[Shannon (unit)|shannon]], equal to the [[information content]] of one "bit". A system with 8 possible states, for example, can store up to {{nowrap|1=log<sub>2</sub> 8 = 3}} bits of information. Other units that have been named include:
; Base ''b''&nbsp;=&nbsp;3 : the unit is called "[[ternary numeral system|trit]]", and is equal to {{nowrap|log<sub>2</sub> 3}} (≈&nbsp;1.585) bits.<ref name="Knuth"/>
; Base ''b''&nbsp;=&nbsp;10 : the unit is called ''[[decimal]] [[numerical digit|digit]]'', ''[[Hartley (unit)|hartley]]'', ''ban'', ''decit'', or ''dit'', and is equal to log<sub>2</sub>&nbsp;10 (≈ 3.322) bits.<ref name="Abramson_1963"/><ref name="Shanmugam_2006"/><ref name="Jaeger_2007"/><ref name="Kumar_2001"/>
; Base ''b''&nbsp;=&nbsp;''e'', the [[base of natural logarithm]]s : the unit is called a ''[[nat (unit)|nat]]'', ''nit'', or ''nepit'' (from [[John Napier|Neperian]]), and is worth {{nowrap|log<sub>2</sub> ''e''}} (≈&nbsp;1.443) bits.<ref name="Abramson_1963"/>
The trit, ban, and nat are rarely used to measure storage capacity; but the nat, in particular, is often used in information theory, because natural logarithms are mathematically more convenient than logarithms in other bases.

== Units derived from bit ==
Several conventional names are used for collections or groups of bits.

=== Byte ===
Historically, a [[byte]] was the number of bits used to encode a [[character (computing)|character]] of text in the computer, which depended on computer hardware architecture, but today it almost always means eight bits – that is, an [[octet (computing)|octet]]. An 8-bit byte can represent 256 (2<sup>8</sup>) distinct values, such as non-negative integers from 0 to 255, or [[two's complement|signed]] integers from −128 to 127. The [[IEEE&nbsp;1541-2002]] standard specifies "B" (upper case) as the symbol for byte ([[IEC&nbsp;80000-13]] uses "o" for octet in French, but also allows "B" in English). Bytes, or multiples thereof, are almost always used to specify the sizes of computer files and the capacity of storage units. Most modern computers and peripheral devices are designed to manipulate data in whole bytes or groups of bytes, rather than individual bits.

=== Nibble ===
A group of four bits, or half a byte, is sometimes called a [[nibble]], nybble or nyble. This unit is most often used in the context of [[hexadecimal]] number representations, since a nibble has the same number of possible values as one hexadecimal digit has.<ref name="Nybble"/>

=== Word, block, and page ===
Computers usually manipulate bits in groups of a fixed size, conventionally called ''[[word (computer architecture)|word]]s''. The number of bits in a word is usually defined by the size of the [[register (computing)|register]]s in the computer's [[CPU]], or by the number of data bits that are fetched from its [[main memory]] in a single operation. In the [[IA-32]] architecture more commonly known as x86-32, a word is 32 bits, but other past and current architectures use words with 4, 8, 9, 12, 13, 16, 18, 20, 21, 22, 24, 25, <!-- 26, not in Beebe! --> 29, 30, 31, 32, 33, 35, 36, 38, 39, 40, 42, 44, 48, 50, 52, 54, 56, 60, 64, 72<ref name="Beebe_2017"/> <!-- 80, not in Beebe! --> bits or others.

Some [[machine instruction]]s and [[computer number format]]s use two words (a "double word" or "dword"), or four words (a "quad word" or "quad").

Computer [[memory cache]]s usually operate on ''[[block (data storage)|block]]s'' of memory that consist of several consecutive words. These units are customarily called ''cache blocks'', or, in [[CPU cache]]s, ''cache lines''.

[[Virtual memory]] systems partition the computer's [[main storage]] into even larger units, traditionally called ''[[page (computer memory)|page]]s''.

=== Multiplicative prefixes ===

A unit for a large amount of data can be formed using either a metric or binary prefix with a base unit. For storage, the base unit is typically byte. For communication throughput, a base unit of bit is common. For example, using the metric ''kilo'' prefix, a [[kilobyte]] is 1000 bytes and a [[kilobit]] is 1000 bits.

Use of metric prefixes is common, but often inaccurate since binary storage hardware is organized with capacity that is a power of 2 {{endash}} not 10 as the metric prefixes are. In the context of computing, the metric prefixes are often intended to mean something other than their normal meaning. For example, 'kilobyte' often refers to 1024 bytes even though the standard meaning of kilo is 1000. Also, 'mega' normally means one million, but in computing is often used to mean 2<sup>20</sup>&nbsp;= {{gaps|1|048|576}}. The table below illustrates the differences between normal metric sizes and the intended size {{endash}} the binary size.

{| class="wikitable"
! Symbol
! Prefix
! Metric size
! Binary size
! Size difference
|-
| k
| kilo
| 1000
| 1024
| 2.40%
|-
| M
| mega
| 1000<sup>2</sup>
| 1024<sup>2</sup>
| 4.86%
|-
| G
| giga
| 1000<sup>3</sup>
| 1024<sup>3</sup>
| 7.37%
|-
| T
| tera
| 1000<sup>4</sup>
| 1024<sup>4</sup>
| 9.95%
|-
| P
| peta
| 1000<sup>5</sup>
| 1024<sup>5</sup>
| 12.59%
|-
| E
| exa
| 1000<sup>6</sup>
| 1024<sup>6</sup>
| 15.29%
|-
| Z
| zetta
| 1000<sup>7</sup>
| 1024<sup>7</sup>
| 18.06%
|-
| Y
| yotta
| 1000<sup>8</sup>
| 1024<sup>8</sup>
| 20.89%
|-
| R
| ronna
| 1000<sup>9</sup>
| 1024<sup>9</sup>
| 23.79%
|-
| Q
| quetta
| 1000<sup>10</sup>
| 1024<sup>10</sup>
| 26.77%
|}

The [[International Electrotechnical Commission]] (IEC) issued a standard that introduces [[binary prefixes]] that accurately represent binary sizes without changing the meaning of the standard metric terms. Rather than based on powers of 1000, these are based on powers of 1024 which is a power of 2.<ref name="IEC80000_2025"/>

{| class="wikitable"
! Symbol
! Prefix
! Example
! Size
|-
| Ki
| kibi
| kibibyte (KiB)
| 2<sup>10</sup>, 1024
|-
| Mi
| mebi
| mebibyte (MiB)
| 2<sup>20</sup>, 1024<sup>2</sup>
|-
| Gi
| gibi
| gibibyte (GiB)
| 2<sup>30</sup>, 1024<sup>3</sup>
|-
| Ti
| tebi
| tebibyte (TiB)
| 2<sup>40</sup>, 1024<sup>4</sup>
|-
| Pi
| pebi
| pebibyte (PiB)
| 2<sup>50</sup>, 1024<sup>5</sup>
|-
| Ei
| exbi
| exbibyte (EiB)
| 2<sup>60</sup>, 1024<sup>6</sup>
|-
| Zi
| zebi
| zebibyte (ZiB)
| 2<sup>70</sup>, 1024<sup>7</sup>
|-
| Yi
| yobi
| yobibyte (YiB)
| 2<sup>80</sup>, 1024<sup>8</sup>
|-
| Ri
| robi
| robibyte (RiB)
| 2<sup>90</sup>, 1024<sup>9</sup>
|-
| Qi
| quebi
| quebibyte (QiB)
| 2<sup>100</sup>, 1024<sup>10</sup>
|}

The [[JEDEC memory standards|JEDEC memory standard]] JESD88F notes that the definitions of kilo (K), giga (G), and mega (M) based on powers of two are included only to reflect common usage, but are otherwise deprecated.<ref name="JEDEC_2018_Terms"/>

== Size examples ==
* 1&nbsp;bit: Answer to a yes/no question
* 1&nbsp;byte: A number from 0 to 255
* 90&nbsp;bytes: Enough to store a typical line of text from a book
* 512&nbsp;bytes&nbsp;= 0.5&nbsp;KiB: The typical [[disk sector|sector]] size of an old style [[hard disk drive]] (modern [[Advanced Format]] sectors are 4096 bytes).
* 1024&nbsp;bytes&nbsp;= 1&nbsp;KiB: A [[block (data storage)|block]] size in some older [[UNIX]] [[filesystem]]s
* 2048&nbsp;bytes&nbsp;= 2&nbsp;KiB: A [[CD-ROM]] sector
* 4096&nbsp;bytes&nbsp;= 4&nbsp;KiB: A [[memory page]] in [[x86]] (since [[Intel 80386]]) and many other architectures, also the modern [[Advanced Format]] hard disk drive sector size.
* 4&nbsp;kB: About one page of text from a [[novel]]
* 120&nbsp;kB: The text of a typical pocket book
* 1&nbsp;MiB: A 1024×1024 pixel [[bitmap]] image with 256 colors (8&nbsp;bpp color depth)
* 3&nbsp;MB: A three-minute [[song]] (133&nbsp;kbit/s)
* 650–900&nbsp;MB – a CD-ROM
* 1&nbsp;GB: 114 minutes of uncompressed CD-quality audio at 1.4&nbsp;Mbit/s
* 16&nbsp;GB: DDR5 DRAM laptop memory under $40 (as of early 2024) <!-- E.g. (and DDR4 or 3 even cheaper, down to $20): New Samsung 16GB (8GBX2) DDR5 4800 MHz PC5-38400 SODIMM Laptop Memory RAM (M425R1GB4BB0) OEM -->
* 32/64/128&nbsp;GB: Three common sizes of [[USB flash drive]]s
* 1&nbsp;TB: The size of a $30 hard disk (as of early 2024)
* 6&nbsp;TB: The size of a $100 hard disk (as of early 2022)
* 16&nbsp;TB: The size of a small/cheap $130 (as of early 2024) enterprise SAS hard disk drive
* 24&nbsp;TB: The size of $440 (as of early 2024) "video" hard disk drive <!-- Cheapest per TB, that large, I could find: Seagate Skyhawk AI 24TB Video Internal Hard Drive HDD -->
* 32&nbsp;TB: Largest [[hard disk drive]] (as of mid-2024)
* 100&nbsp;TB: Largest commercially available [[solid-state drive]] (as of mid-2024)
* 200&nbsp;TB: Largest solid-state drive constructed (prediction for mid-2022)<!-- Likely never materialized? -->
* 1.6&nbsp;PB (1600&nbsp;TB): Amount of possible storage in one 2U server (world record as of 2021, using 100&nbsp;TB solid-states drives).<!--"use ExaDrive SSDs, including the 100TB capable ExaDrive DC series and QLC-based ExaDrive NL series, in PowerEdge servers. [..] enabling up to 1.2PB of flash in one 2U server. [..]
[As of 2024] As the world’s highest capacity and highest density SSD, ExaDrive offers capacity, energy efficiency, and endurance, thanks to patent-pending architecture. It is available in capacities ranging from 16TB to 100TB, using either SATA or dual-port SAS interfaces, with both TLC and QLC flash models."--><ref>{{Cite web |last=Maleval |first=Jean Jacques |date=2021-02-12 |title=Nimbus Data SSDs Certified for Use With Dell EMC PowerEdge Servers |url=https://www.storagenewsletter.com/2021/02/12/nimbus-data-ssds-certified-by-dell-emc-for-poweredge-servers/ |access-date=2024-05-30 |website=StorageNewsletter |language=en-US}}</ref>
* 1.3&nbsp;ZB: Prediction of the volume of the whole internet in 2016

== Obsolete and unusual units <span class="anchor" id="Crumb"></span><span class="anchor" id="Unibit"></span><span class="anchor" id="Dibit"></span><span class="anchor" id="Quartic digit"></span><span class="anchor" id="Tribit"></span><span class="anchor" id="Triad"></span><span class="anchor" id="Pentad"></span><span class="anchor" id="Hexad"></span><span class="anchor" id="Heptad"></span><span class="anchor" id="Sextet"></span><span class="anchor" id="Declet"></span><span class="anchor" id="Doublet"></span><span class="anchor" id="Quadlet"></span><span class="anchor" id="Octlet"></span><span class="anchor" id="Hexlet"></span><span class="anchor" id="Parcel"></span><span class="anchor" id="Wyde"></span><span class="anchor" id="Tetra"></span><span class="anchor" id="Octa"></span><span class="anchor" id="Combit"></span><span class="anchor" id="Comword"></span> ==

<!-- 
**READ THIS**
This section is intended for unit names that are unusual AND not already included elsewhere in this article AND actually used in serious (!) literature supported by reliable references. Do not include unit names that are intended solely for humor or do not have a reliable reference.
-->

Some notable unit names that are today obsolete or only used in limited contexts. 

* 1 bit: unibit<ref name="Horak_2007_Websters"/><ref name="YourDict_Unibit"/>

* 2 bits: dibit,<ref name="Steinbuch-Wagner_1967"/><ref name="Steinbuch-Weber_1974"/><ref name="Horak_2007_Websters"/><ref name="Bertram_1994"/> crumb,<ref name="Weisstein_Crumb"/> quartic digit,<ref name="CDC_1964"/> quad, semi-nibble, nyp<ref name="Knuth_Nyp"/>

* 3 bits: tribit,<ref name="Steinbuch-Wagner_1967"/><ref name="Steinbuch-Weber_1974"/><ref name="Horak_2007_Websters"/> triad,<ref name="Svoboda_1979"/> triade<ref name="Paul_2013_EE"/><ref name="Böhme_1969"/>

* 4 bits: see [[nibble]]

* 5 bits: pentad, pentade,<ref name="Speiser_1965"/>

* 6 bits: byte (in early [[IBM]] machines using [[Binary Coded Decimal|BCD alphamerics]]), hexad, hexade,<ref name="Speiser_1965"/><ref name="Steinbuch_1962"/> sextet<ref name="Svoboda_1979"/>

* 7 bits: heptad, heptade<ref name="Speiser_1965"/>

* 8 bits: [[octad (computing)|octad]],<ref name="Williams_1969">{{cite book |title=British Commercial Computer Digest: Pergamon Computer Data Series |author-first=R. H. |author-last=Williams |publisher=[[Pergamon Press]] |date=1969-01-01 |isbn=1-48312210-7 |id=978-148312210-6 }}</ref> [[octade (computing)|octade]]<ref name="Philips_1971">{{cite web |title=Philips – Philips Data Systems' product range – April 1971 |publisher=[[Philips]] |date=1971 |url=http://www.intact-reunies.nl/pdf/product1971.pdf |archive-url=https://web.archive.org/web/20150917144504/http://www.intact-reunies.nl/pdf/product1971.pdf |url-status=usurped |archive-date=17 September 2015 |access-date=2015-08-03}}</ref>

* 9 bits: nonet,<ref name="Crispin_2005"/> rarely used

* 10 bits: declet,<ref name="IEEE754-2008"/><ref name="Muller_2010"/><ref name="Erle_2008"/><ref name="Kneusel_2015"/> decle<ref name="Zbiciak"/>

* 12 bits: [[slab (unit)|slab]]<ref name="NCR_315_EDPS"/><ref name="Bardin_1963"/><ref name="Schneider_1970"/>

* 15 bits: parcel (on [[CDC 6600]] and [[CDC 7600]])

* 16 bits: doublet,<ref name="IEEE1754-1994"/> wyde,<ref name="Knuth"/><ref name="Knuth_MMIX"/> parcel (on [[Cray-1]]), chawmp (on a 32-bit machine)<ref name="Raymond_HackerDict">{{cite book |last1=Raymond |first1=Eric S. |title=The New Hacker's Dictionary |date=1996 |publisher=MIT Press |isbn=0262680920 |page=333 |edition=3}}</ref>

* 18 bits: chomp, chawmp (on a 36-bit machine)<ref name="Raymond_HackerDict"/>

* 32 bits: quadlet,<ref name="IEEE1754-1994"/><ref name="ParNum_1999"/><ref name="Nicoud_1999"/> tetra<ref name="Knuth_MMIX"/>

* 64 bits: octlet,<ref name="IEEE1754-1994"/> octa<ref name="Knuth_MMIX"/>

* 96 bits: bentobox (in [[ITRON project|ITRON OS]])

* 128 bits: hexlet,<ref name="IEEE1754-1994"/><ref name="SEDMS_1999"/> [[paragraph (Intel)|paragraph]] (on [[Intel x86]] processors)<ref name="Intel_1980_8086FU-UG"/><ref name="Dewar-Smosna_1990"/>

* 256 bytes: [[page (computer memory)|page]] (on Intel 4004,<ref name="Intel_1973_MCS-4"/> [[Intel 8080|8080]] and 8086 processors,<ref name="Intel_1980_8086FU-UG"/> also many other 8-bit processors&nbsp;– typically much larger on many 16-bit/32-bit processors)

* 6 trits: [[tryte]]<ref name="Brousentsov_Tryte"/>

* combit, comword<ref name="Telefunken_1979"/><ref name="US4319227_1"/><ref name="US4319227_2"/>

== See also ==
* [[File size]]
* [[ISO 80000-13]] (Quantities and units – Part 13: Information science and technology)

== References ==
{{reflist|refs=
<ref name="Abramson_1963">{{cite book |author-first=Norman |author-last=Abramson |date=1963 |title=Information theory and coding |publisher=[[McGraw-Hill]]}}</ref>
<ref name="Mackenzie_1980">{{cite book |url=https://textfiles.meulie.net/bitsaved/Books/Mackenzie_CodedCharSets.pdf |title=Coded Character Sets, History and Development |series=The Systems Programming Series |author-last=Mackenzie |author-first=Charles E. |date=1980 |edition=1 |publisher=[[Addison-Wesley Publishing Company, Inc.]] |isbn=978-0-201-14460-4 |lccn=77-90165 |page=xii |access-date=2019-08-25 |archive-url=https://web.archive.org/web/20160526172151/https://textfiles.meulie.net/bitsaved/Books/Mackenzie_CodedCharSets.pdf |archive-date=May 26, 2016 |url-status=live |df=mdy-all }}</ref>
<ref name="Knuth">{{cite book |author-first=Donald Ervin |author-last=Knuth |author-link=Donald Ervin Knuth |title=The Art of Computer Programming: Seminumerical algorithms |title-link=The Art of Computer Programming |volume=2 |publisher=[[Addison Wesley]]}}</ref>
<ref name="Shanmugam_2006">{{cite book |author=Shanmugam |date=2006 |title=Digital and Analog Computer Systems}}</ref>
<ref name="Jaeger_2007">{{cite book |author-first=Gregg |author-last=Jaeger |date=2007 |url=https://www.springer.com/physics/quantum+physics/book/978-0-387-35725-6 |title=Quantum information: an overview}}</ref>
<ref name="Kumar_2001">{{cite book |author-first=I. Ravi |author-last=Kumar |date=2001 |title=Comprehensive Statistical Theory of Communication}}</ref>
<ref name="Beebe_2017">{{cite book |author-first=Nelson H. F. |author-last=Beebe |title=The Mathematical-Function Computation Handbook – Programming Using the MathCW Portable Software Library |chapter=Chapter I. Integer arithmetic |date=2017-08-22 |location=Salt Lake City, UT, US |publisher=[[Springer International Publishing AG]] |edition=1 |lccn=2017947446 |isbn=978-3-319-64109-6 |doi=10.1007/978-3-319-64110-2 |page=970|s2cid=30244721 }}</ref>
<ref name="IEC80000_2025">{{cite ISO standard |id=IEC 80000-13:2025 |title=Quantities and units – Part 13: Information science and technology |edition=2.0 |date=February 2025 |csnumber=87648}}</ref>
<ref name="JEDEC_2018_Terms">{{cite web |publisher=JEDEC Solid State Technology Association |title=Dictionary of Terms for Solid State Technology – 7th Edition |id=JESD88F|pages=100,118,135|date=February 2018 |url=https://www.jedec.org/standards-documents/docs/jesd-88c |access-date=2021-06-25}}</ref>
<ref name="Nybble">[http://dictionary.reference.com/browse/nybble ''Nybble''] at dictionary reference.com; sourced from Jargon File 4.2.0, accessed 2007-08-12</ref>
<ref name="YourDict_Unibit">{{cite web |title=Unibit |url=http://www.yourdictionary.com/unibit#computer}}</ref>
<ref name="Steinbuch-Wagner_1967">{{cite book |title=Taschenbuch der Nachrichtenverarbeitung |language=de |editor-first1=Karl W. |editor-last1=Steinbuch |editor-link1=Karl W. Steinbuch |editor-first2=Siegfried W. |editor-last2=Wagner |date=1967 |orig-date=1962 |edition=2 |publisher=[[Springer-Verlag OHG]] |publication-place=Berlin / Heidelberg / New York |location=Karlsruhe, Germany |id=Title No. 1036 |lccn=67-21079 |pages=835–836}}</ref>
<ref name="Steinbuch-Weber_1974">{{cite book |title=Taschenbuch der Informatik – Band III – Anwendungen und spezielle Systeme der Nachrichtenverarbeitung |language=de |editor-first1=Karl W. |editor-last1=Steinbuch |editor-link1=Karl W. Steinbuch |editor-first2=Wolfgang |editor-last2=Weber |editor-first3=Traute |editor-last3=Heinemann |date=1974 |orig-date=1967 |edition=3 |volume=3 |<!--work=Taschenbuch der Nachrichtenverarbeitung |-->publisher=[[Springer Verlag]] |location=Karlsruhe / Bochum |publication-place=Berlin / Heidelberg / New York |isbn=3-540-06242-4 |lccn=73-80607 |pages=357–358}}</ref>
<ref name="Horak_2007_Websters">{{cite book |title=Webster's New World Telecom Dictionary |author-first=Ray |author-last=Horak |publisher=[[John Wiley & Sons]] |date=2007 |isbn=9-78047022571-4 |page=402 |url=https://books.google.com/books?id=L18YaEomzjMC&pg=PA402}}</ref>
<ref name="Bertram_1994">{{cite book |title=Theory of magnetic recording |author-first=H. Neal |author-last=Bertram |publisher=[[Cambridge University Press]] |edition=1 |date=1994 |isbn=0-521-44973-1 |id=9-780521-449731 |quote=[...] The writing of an impulse would involve writing a dibit or two transitions arbitrarily closely together. [...]}}</ref>
<ref name="Weisstein_Crumb">{{cite web |title=Crumb |author-first=Eric. W. |author-last=Weisstein |author-link=Eric Weisstein |publisher=[[MathWorld]] |url=http://mathworld.wolfram.com/Crumb.html |access-date=2015-08-02}}</ref>
<ref name="Paul_2013_EE">{{cite book |title=Elektrotechnik und Elektronik für Informatiker – Grundgebiete der Elektronik |language=de |author-first=Reinhold |author-last=Paul |date=2013 |publisher=[[B.G. Teubner]] Stuttgart / [[Springer Verlag|Springer]] |isbn=978-3-32296652-0 |volume=2 |url=https://books.google.com/books?id=-fzKBgAAQBAJ |access-date=2015-08-03}}</ref>
<ref name="Böhme_1969">{{cite book |title=Programmierung von Prozeßrechnern |language=de |author-first1=Gert |author-last1=Böhme |author-first2=Werner |author-last2=Born |author-first3=B. |author-last3=Wagner |author-first4=G. |author-last4=Schwarze |editor-first=Jürgen |editor-last=Reichenbach |orig-date=1969 |date=2013-07-02 |series=Reihe Automatisierungstechnik |volume=79 |publisher={{ill|VEB Verlag Technik|de}} Berlin, reprint: [[Springer Verlag]] |url=https://books.google.com/books?id=T-S0BgAAQBAJ |isbn=978-3-663-00808-8 |doi=10.1007/978-3-663-02721-8 |id=9/3/4185}}</ref>
<ref name="Speiser_1965">{{cite book |author-first=Ambrosius Paul |author-last=Speiser |author-link=Ambrosius Paul Speiser |location=[[Eidgenössische Technische Hochschule Zürich|ETH Zürich]], Zürich, Switzerland |title=Digitale Rechenanlagen – Grundlagen / Schaltungstechnik / Arbeitsweise / Betriebssicherheit |language=de |trans-title=Digital computers – Basics / Circuits / Operation / Reliability |edition=2 |date=1965 |orig-date=1961 |publisher=[[Springer-Verlag]] / [[IBM]] |lccn=65-14624 |id=0978 |pages=6, 34, 165, 183, 208, 213, 215}}</ref>
<ref name="Steinbuch_1962">{{cite book |title=Taschenbuch der Nachrichtenverarbeitung |language=de |editor-first=Karl W. |editor-last=Steinbuch |editor-link=Karl W. Steinbuch |date=1962 |edition=1 |publisher=[[Springer-Verlag OHG]] |location=Karlsruhe, Germany  |publication-place=Berlin / Göttingen / New York |lccn=62-14511 |page=1076}}</ref>
<ref name="Svoboda_1979">{{cite book |title=Advanced Logical Circuit Design Techniques |author-first1=Antonín |author-last1=Svoboda |author-link1=Antonín Svoboda (computer scientist) |author-first2=Donnamaie E. |author-last2=White |date=2016 |orig-date=2012, 1985, 1979-08-01 |edition=retyped electronic reissue |publisher=[[Garland STPM Press]] (original issue) / WhitePubs Enterprises, Inc. (reissue) |lccn=78-31384 |isbn=0-8240-7014-3<!-- 1990 1st issue |ISBN=978-0-8240-7014-4 1990 1st issue --> |url=http://www.donnamaie.com/Advanced_logic_ckt/Advanced_Logical_Circuit_Design_Techniques%20sm.pdf |access-date=2017-04-15 |url-status=live |archive-url=https://web.archive.org/web/20170414163013/http://www.donnamaie.com/Advanced_logic_ckt/Advanced_Logical_Circuit_Design_Techniques%20sm.pdf |archive-date=2017-04-14}} [http://www.donnamaie.com/<!-- https://web.archive.org/web/20170415220158/http://www.donnamaie.com/ -->][https://books.google.com/books?id=g3uzAAAAIAAJ]</ref>
<ref name="Crispin_2005">{{cite IETF |author-last=Crispin |author-first=Mark R. |author-link=Mark Crispin |rfc=4042 |title=UTF-9 and UTF-18 Efficient Transformation Formats of Unicode |date=April 1, 2005}}</ref>
<ref name="IEEE754-2008">{{cite book |<!--journal=IEEE STD 754-2008 |-->date=2008-08-29 |pages=1–70 |isbn=978-0-7381-5752-8<!--E-ISBN --> |doi=10.1109/IEEESTD.2008.4610935 |url=https://ieeexplore.ieee.org/document/4610935 |access-date=2016-02-10 |title=IEEE Standard for Floating-Point Arithmetic }}</ref>
<ref name="Muller_2010">{{cite book |author-last1=Muller |author-first1=Jean-Michel |author-last2=Brisebarre |author-first2=Nicolas |author-last3=de Dinechin |author-first3=Florent |author-last4=Jeannerod |author-first4=Claude-Pierre |author-last5=Lefèvre |author-first5=Vincent |author-last6=Melquiond |author-first6=Guillaume |author-last7=Revol |author-first7=Nathalie |author7-link=Nathalie Revol|author-last8=Stehlé |author-first8=Damien |author-last9=Torres |author-first9=Serge |title=Handbook of Floating-Point Arithmetic |date=2010 |publisher=[[Birkhäuser]] |edition=1 |isbn=978-0-8176-4704-9<!-- print --> |doi=10.1007/978-0-8176-4705-6 |lccn=2009939668<!-- |ISBN=978-0-8176-4705-6 (online), ISBN 0-8176-4704-X (print) -->|url=https://cds.cern.ch/record/1315760 }}</ref>
<ref name="Erle_2008">{{cite thesis |author-last=Erle |author-first=Mark A. |title=Algorithms and Hardware Designs for Decimal Multiplication |location=Lehigh University |date=2008-11-21 |publication-date=2009 |isbn=978-1-10904228-3 |id=1109042280 |url=https://books.google.com/books?id=_4OKPgcPfEYC |access-date=2016-02-10}}</ref>
<ref name="Kneusel_2015">{{cite book |title=Numbers and Computers |author-first=Ronald T. |author-last=Kneusel |publisher=[[Springer Verlag]] |date=2015 |isbn=9783319172606 |id=3319172603 |url=https://books.google.com/books?id=FPlICAAAQBAJ |access-date=2016-02-10}}</ref>
<ref name="Zbiciak">{{cite web |url=http://spatula-city.org/~im14u2c/intv/jzintv-1.0-beta3/doc/utilities/as1600.txt |title=AS1600 Quick-and-Dirty Documentation |author-first=Joe |author-last=Zbiciak |access-date=2013-04-28}}</ref>
<ref name="NCR_315_EDPS">{{cite web |url=http://www.thecorememory.com/NCR_315_EDPS.pdf |title=315 Electronic Data Processing System |publisher=[[NCR Corporation|NCR]] |date=November 1965 |id=NCR MPN ST-5008-15 |access-date=2015-01-28 |url-status=live |archive-url=https://web.archive.org/web/20160524113545/http://www.thecorememory.com/NCR_315_EDPS.pdf |archive-date=2016-05-24}}</ref>
<ref name="Bardin_1963">{{cite journal |author-last=Bardin |author-first=Hillel |date=1963 |title=NCR 315 Seminar |journal=Computer Usage Communique |volume=2 |number=3 |url=http://www.thecorememory.com/NCR_315_Seminar.pdf |url-status=live |archive-url=https://web.archive.org/web/20160524113611/http://www.thecorememory.com/NCR_315_Seminar.pdf |archive-date=2016-05-24}}</ref>
<ref name="Schneider_1970">{{cite book |title=Datenverarbeitungs-Lexikon |language=de |trans-title=Lexicon of information technology |author-first=Carl |author-last=Schneider |date=2013 |orig-date=1970 |publisher=[[Springer Fachmedien Wiesbaden GmbH]] / [[Betriebswirtschaftlicher Verlag Dr. Th. Gabler GmbH]] |location=Wiesbaden, Germany |edition=softcover reprint of hardcover 1st |isbn=978-3-409-31831-0<!-- softcover reprint |ISBN=3-663-13618-3 / {{ISBN|978-3-663-13618-7}} (ebook) ebook --> |doi=10.1007/978-3-663-13618-7 |pages=201, 308 |url=https://books.google.com/books?id=3aN9BwAAQBAJ |access-date=2016-05-24 |quote=[...] ''slab'', Abk. aus ''syllable''&nbsp;= Silbe, die kleinste adressierbare Informationseinheit für 12 bit zur Übertragung von zwei Alphazeichen oder drei numerischen Zeichen. ''(NCR)'' [...] Hardware: Datenstruktur: NCR 315-100&nbsp;/ NCR 315-RMC; Wortlänge: Silbe; Bits: 12; Bytes: –; Dezimalziffern: 3; Zeichen: 2; Gleitkommadarstellung: fest verdrahtet; Mantisse: 4 Silben; Exponent: 1 Silbe (11 Stellen&nbsp;+ 1 Vorzeichen) [...] [''[[slab (unit)|slab]]'', abbr. for ''[[syllable (linguistics)|syllable]]''&nbsp;= syllable, smallest addressable information unit for 12 bits for the transfer of two alphabetical characters or three numerical characters. ''(NCR)'' [...] Hardware: Data structure: [[NCR 315-100]]&nbsp;/ [[NCR 315-RMC]]; [[Word length]]: [[Syllable (computing)|Syllable]]; [[Bit]]s: 12; [[Byte]]s: –; [[Decimal digit]]s: 3; Characters: 2; [[Floating point format]]: hard-wired; [[Significand]]: 4 syllables; [[Exponent]]: 1 syllable (11 digits + 1 prefix)]}}</ref>
<ref name="IEEE1754-1994">{{cite book |<!--journal=IEEE STD 1754-1994 |-->publisher=[[The Institute of Electrical and Electronics Engineers, Inc.]] |isbn=1-55937-428-4 |doi=10.1109/IEEESTD.1995.79519 |url=https://ieeexplore.ieee.org/document/478092 |access-date=2016-02-10 |pages=5–7 |date=1995 |title=IEEE Standard for a 32-bit Microprocessor Architecture }} (NB. The standard defines doublets, quadlets, octlets and hexlets as 2, 4, 8 and 16 [[byte]]s, giving the numbers of [[bit]]s (16, 32, 64 and 128) only as a secondary meaning. This might be important given that bytes were not always understood to mean 8 bits ([[octet (computing)|octet]]s) historically.)</ref>
<ref name="Knuth_MMIX">{{cite book |author-first=Donald Ervin |author-last=Knuth |author-link=Donald Ervin Knuth |<!--work=[[The Art of Computer Programming]] |-->title=Fascicle 1: MMIX |orig-date=1999 |date=2004-02-15 |location=[[Stanford University]] |publisher=[[Addison-Wesley]] |edition=0th printing, 15th |url=http://profs.scienze.univr.it/~manca/storia-informatica/mmix.pdf |access-date=2017-03-30 |url-status=live |archive-url=https://web.archive.org/web/20170330001534/http://profs.scienze.univr.it/~manca/storia-informatica/mmix.pdf |archive-date=2017-03-30}}</ref>
<ref name="ParNum_1999">{{cite conference |author-first1=László |author-last1=Böszörményi |author-first2=Günther |author-last2=Hölzl |author-first3=Emaneul |author-last3=Pirker |title=Parallel Cluster Computing with IEEE1394–1995
|work=Proceedings: Lecture Notes in Computer Science 1557 |editor1-first=Peter |editor1-last=Zinterhof |editor2-first=Marian |editor2-last=Vajteršic |editor3-first=Andreas |editor3-last=Uhl
|conference=Parallel Computation: 4th International ACPC Conference including Special Tracks on Parallel Numerics (ParNum '99) and Parallel Computing in Image Processing, Video Processing, and Multimedia |location=Salzburg, Austria |date=February 1999 |publisher=[[Springer Verlag]] |publication-place=Berlin, Germany}}</ref>
<ref name="Nicoud_1999">{{cite book |author-first=Jean-Daniel |author-last=Nicoud |<!--work=Traité d'électricité de l'École polytechnique fédérale de Lausanne |-->volume=14 |language=fr |date=1986 |edition=2 |title=Calculatrices |publisher=Presses polytechniques romandes |location=Lausanne |isbn=2-88074054-1 <!--|ISBN=978-2-88074054-2 --> |url=https://books.google.com/books?id=3hGZ2qxxby8C&pg=PR3}}</ref>
<ref name="SEDMS_1999">{{cite conference |conference=Symposium on Experiences with Distributed and Multiprocessor Systems (SEDMS) |title=Proceedings |volume=4 |publisher=[[USENIX Association]] |date=1993}}</ref>
<ref name="Intel_1980_8086FU-UG">{{cite book |title=8086 Family Utilities – User's Guide for 8080/8085-Based Development Systems |chapter=1. Introduction: Segment Alignment |id=Order Number: 9800639-04 |edition=A620/5821 6K DD |version=Revision E |date=May 1982 |orig-date=1980, 1978 |publisher=[[Intel Corporation]] |location=Santa Clara, California, US |page=1-6<!-- This is a single page! --> |url=http://bitsavers.trailing-edge.com/pdf/intel/ISIS_II/9800639-04E_8086_Famility_Utilities_Users_Guide_May82.pdf |access-date=2020-02-29 |url-status=live |archive-url=https://web.archive.org/web/20200229032355/http://bitsavers.trailing-edge.com/pdf/intel/ISIS_II/9800639-04E_8086_Famility_Utilities_Users_Guide_May82.pdf |archive-date=2020-02-29}}</ref>
<ref name="Intel_1973_MCS-4">{{cite book |title=MCS-4 Assembly Language Programming Manual – The INTELLEC 4 Microcomputer System Programming Manual |chapter=Terms And Abbreviations / 4.1 Crossing Page Boundaries |edition=Preliminary |publisher=[[Intel Corporation]] |date=December 1973 |location=Santa Clara, California, US |id=MCS-030-1273-1 |pages=v, ((2-6)), ((4-1)) |url=http://bitsavers.trailing-edge.com/components/intel/MCS4/MCS-4_Assembly_Language_Programming_Manual_Dec73.pdf |access-date=2020-03-02 |url-status=live |archive-url=https://web.archive.org/web/20200301235541/http://bitsavers.trailing-edge.com/components/intel/MCS4/MCS-4_Assembly_Language_Programming_Manual_Dec73.pdf |archive-date=2020-03-01 |quote=[...] [[Bit]] – The smallest unit of information which can be represented. (A bit may be in one of two states I 0 or 1). [...] [[Byte]] – A group of 8 contiguous bits occupying a single memory location. [...] [[Character (computing)|Character]] – A group of 4 contiguous bits of data. [...] programs are held in either ROM or program RAM, both of which are divided into [[page (computer memory)|page]]s. Each page consists of 256 8-bit locations. Addresses 0 through 255 comprise the first page, 256-511 comprise the second page, and so on. [...]}} (NB. This [[Intel 4004]] manual uses the term ''character'' referring to ''4-bit'' rather than 8-bit ''data'' entities. Intel switched to use the more common term ''[[nibble]]'' for 4-bit entities in their documentation for the succeeding processor [[Intel 4040|4040]] in 1974 already.)</ref>
<ref name="Brousentsov_Tryte">{{Cite web |author-last=Brousentsov |author-first=N. P. |author-last2=Maslov |author-first2=S. P. |author-last3=Ramil Alvarez |author-first3=J. |author-last4=Zhogolev |author-first4=E. A. |title=Development of ternary computers at Moscow State University |url=http://www.computer-museum.ru/english/setun.htm |access-date=2010-01-20}}</ref>
<ref name="Telefunken_1979">{{cite patent |inventor1-first=Christopher W. |inventor1-last=Malinowski |inventor2-first=Heinz |inventor2-last=Rinderle |inventor3-first=Martin |inventor3-last=Siegle |assign=[[AEG-Telefunken]] |title=Three-state signaling system |gdate=1982-03-09 |fdate=1979-10-16 |pridate=1979-06-02 |country=US|number=4319227}}<!-- US4319227A, US 06/085335, CA1175526A1, DE2922595A1, DE2922595C2, --></ref>
<ref name="US4319227_1">{{cite web |title=US4319227 |work=Google |url=https://patents.google.com/patent/US4319227}}</ref>
<ref name="US4319227_2">{{cite web |title=US4319227 |work=Patentimages |url=http://patentimages.storage.googleapis.com/pdfs/US4319227.pdf}}</ref>
<ref name="Dewar-Smosna_1990">{{cite book |title=Microprocessors – A Programmer's View |author-first1=Robert Berriedale Keith |author-last1=Dewar |author-link1=Robert Berriedale Keith Dewar |author-first2=Matthew |author-last2=Smosna |date=1990 |edition=1 |publisher=[[McGraw-Hill Publishing Company]] |location=[[Courant Institute]], [[New York University]], New York, US |isbn=0-07-016638-2 |lccn=89-77320 |page=85}} (xviii+462 pages)</ref>
<ref name="CDC_1964">{{cite book |title=Control Data 8092 TeleProgrammer: Programming Reference Manual |date=1964 |id=IDP 107a |publisher=[[Control Data Corporation]] |location=Minneapolis, Minnesota, US |url=http://bitsavers.org/pdf/cdc/809x/IDP107a_8092pgmRef_1964.pdf |access-date=2020-07-27 |url-status=live |archive-url=https://web.archive.org/web/20200525053524/http://bitsavers.org/pdf/cdc/809x/IDP107a_8092pgmRef_1964.pdf |archive-date=2020-05-25}}</ref>
<ref name="Knuth_Nyp">{{cite book |author-first=Donald Ervin |author-last=Knuth |author-link=Donald Ervin Knuth |title=The Art of Computer Programming: Cobinatorial Algorithms part 1 |title-link=The Art of Computer Programming |volume=4a |publisher=[[Addison Wesley]]}}</ref>
}}

== External links ==
* [http://people.csail.mit.edu/jaffer/MIXF/MIXF-08 Representation of numerical values and SI units in character strings for information interchanges]
* [http://www.bit-calculator.com Bit Calculator]{{snd}}Make conversions between bits, bytes, kilobits, kilobytes, megabits, megabytes, gigabits, gigabytes, terabits, terabytes, petabits, petabytes, exabits, exabytes, zettabits, zettabytes, yottabits, yottabytes.
* [http://www.cl.cam.ac.uk/~mgk25/information-units.txt Paper on standardized units for use in information technology]
* [https://www.gbmb.org/ Data Byte Converter]
* [https://www.dataunitconverter.com/ High Precision Data Unit Converters]

{{Computer Storage Volumes}}

{{DEFAULTSORT:Units of Information}}
[[Category:Units of information| ]]