View source for Dot-decimal notation

{{Short description|Presentation format for numerical data}}
'''Dot-decimal notation''' is a presentation format for numerical data. It consists of a string of decimal numbers, using the [[full stop]] (''dot'') as a [[Decimal separator#Digit grouping|separation character]].<ref>{{cite web |title=Gepunktete Dezimalschreibweise |url=https://techplugged.com/de/Glossar/punktierte-Dezimalschreibweise/ |website=Techplugged |language=de}}</ref>

A common use of dot-decimal notation is in information technology where it is a method of writing numbers in [[octet (computing)|octet]]-grouped base-10 ([[decimal]]) numbers.<ref>{{cite web |title=What is Dotted Decimal Notation? - Definition from Techopedia |url=https://www.techopedia.com/definition/30265/dotted-decimal-notation |website=Techopedia.com |language=en}}</ref> In [[computer networking]], [[IPv4 address|Internet Protocol Version 4 (IPv4) addresses]] are commonly written using the '''quad-dotted notation''' of four decimal integers, ranging from 0 to 255 each.<ref name=IBM>{{cite web |title=IPv4 and IPv6 address formats |url=https://www.ibm.com/docs/en/ts3500-tape-library?topic=functionality-ipv4-ipv6-address-formats |website=www.ibm.com |language=en-us|quote=An IPv4 address has the following format: x . x . x . x where x is called an octet and must be a decimal value between 0 and 255. Octets are separated by periods. An IPv4 address must contain three periods and four octets. The following examples are valid IPv4 addresses:{{br}}    1 . 2 . 3 . 4{{br}}    01 . 102 . 103 . 104}}</ref>

==IPv4 address==
[[Image:IPv4 address structure and writing systems-en.svg|right|300px|thumb|An IP address (version 4) in both dot-decimal notation and [[binary code]]]]

In computer networking, the notation is associated with the specific use of ''quad-dotted notation'' to represent IPv4 addresses<ref>{{cite web
|url=http://searchsmb.techtarget.com/sDefinition/0,,sid44_gci211994,00.html
|title=Dot address
|publisher=TechTarget
|access-date=2010-11-18
}}</ref> and used as a synonym for ''dotted-quad notation''.<ref>{{cite web
|url=http://www.encyclopedia.com/doc/1O12-dotteddecimalnotation.html
|title=Dotted Decimal Notation
|publisher=encyclopedia.com
}}{{dl|fix-attempted=yes|date=August 2021}}</ref> Dot-decimal notation is a presentation format for numerical data expressed as a string of decimal numbers each separated by a full stop. For example, the [[hexadecimal number]] ''0xFF000000'' may be expressed in dot-decimal notation as ''255.0.0.0''.

An IPv4 address has 32 bits. For purposes of representation, the bits may be divided into four octets written in decimal numbers, ranging from 0 to 255, concatenated as a character string with full stop delimiters between each number.<ref name=IBM>{{cite web |title=IPv4 and IPv6 address formats |url=https://www.ibm.com/docs/en/ts3500-tape-library?topic=functionality-ipv4-ipv6-address-formats |website=www.ibm.com |language=en-us|quote=An IPv4 address has the following format: x . x . x . x where x is called an octet and must be a decimal value between 0 and 255. Octets are separated by periods. An IPv4 address must contain three periods and four octets. The following examples are valid IPv4 addresses:{{br}}    1 . 2 . 3 . 4{{br}}    01 . 102 . 103 . 104}}</ref> This octet-grouped dotted-decimal format may more specifically be called "dotted octet" format,<ref name="ipaddr-text-rep" /> or a "dotted quad address".<ref>{{cite web |title=Definition of dot address |url=https://www.pcmag.com/encyclopedia/term/dot-address |website=PCMAG |language=en}}</ref>

For example, the address of the [[loopback]] interface, usually assigned the host name [[localhost]], is 127.0.0.1. It consists of the four octets, written in binary notation: ''01111111'', ''00000000'', ''00000000'', and ''00000001''. The 32-bit number is represented in hexadecimal notation as ''0x7F000001''.

No formal specification of this textual IP address representation exists.<ref name="ipaddr-text-rep" /> The first mention of this format in [[Request for Comments|RFC]] documents was in RFC 780 for the [[Mail Transfer Protocol]] published May 1981, in which the IP address was supposed to be enclosed in brackets or represented as a 32-bit decimal integer prefixed by a pound sign. A table in RFC 790 (''Assigned Numbers'') used the dotted decimal format, zero-padding each number to three digits.<ref name="ipaddr-text-rep">{{cite IETF
 |title= Textual Representation of IPv4 and IPv6 Addresses
 |draft= draft-main-ipaddr-text-rep-02
 |last= Main
 |first= Andrew
 |date=23 February 2005
 |publisher=[[Internet Engineering Task Force|IETF]]
}}</ref> RFC 1123 (''Requirements for Internet Hosts – Application and Support'') of October 1989 mentions a requirement for host software to accept "IP address in dotted-decimal ("#.#.#.#") form", although it notes "[t]his last requirement is not intended to specify the complete syntactic form for entering a dotted-decimal host number".<ref name="host-requirements">{{cite IETF
 |title= Requirements for Internet Hosts -- Application and Support
 |url=https://tools.ietf.org/html/rfc1123
 |last= Braden
 |first= Robert
 |date=1 October 1989
 |publisher=[[Internet Engineering Task Force|IETF]]
 |section=2.1
}}</ref> An IETF draft intended to define textual representation of IP addresses expired without further activity.<ref name="ipaddr-text-rep" />

A popular implementation of IP networking, originating in [[4.2BSD]], contains a function ''inet_aton()'' for converting IP addresses in character string representation to internal binary storage. In addition to the basic four-decimals format and 32-bit numbers, it also supported intermediate syntax forms of ''octet.24bits'' (e.g. 10.1234567; for [[Classful network|Class A]] addresses) and ''octet.octet.16bits'' (e.g. 172.16.12345; for Class B addresses). It also allowed the numbers to be written in [[hexadecimal]] and [[octal]] representations, by prefixing them with 0x and 0, respectively. These features continue to be supported in some software, even though they are considered as non-standard.<ref name="ipaddr-text-rep" /> This means addresses with a component written with a leading zero digit may be interpreted differently in programs that do or do not recognize such formats.<ref>{{cite web
|url = http://support.microsoft.com/kb/115388
|title = Ping and FTP resolve IP address with leading zero as octal
|publisher = Microsoft Support
|archive-url = https://web.archive.org/web/20061206211851/http://support.microsoft.com/kb/115388
|archive-date = 2006-12-06
}}</ref>

A [[POSIX]]-conforming variant of ''inet_aton'', the ''inet_pton()'' function, supports only the four-decimal variant of IP addresses.<ref>{{man|3|inet_pton|die.net}}</ref>

IP addresses in dot-decimal notation are also presented in [[CIDR notation]], in which the IP address is suffixed with a slash and a number, used to specify the length of the associated routing prefix. For example, 127.0.0.1/8 specifies that the IP address has an eight-bit routing prefix, and therefore the subnet mask ''255.0.0.0''.

==OIDs==
[[Object identifier]]s use a style of dot-decimal notation to represent an arbitrarily deep hierarchy of objects identified by decimal numbers. They may also use textual words separated by dots, like some computer languages (see inheritance).

==Version numbers==
Software releases are often given [[version number]]s in dot-decimal notation, with the first digit designating major revisions and the smaller ones progressively more minor releases. Version numbers with a leading zero, say "0.1.8", conventionally indicate that the software is still in [[beta software|beta]] and does not yet have complete features.

==Libraries==
Libraries use notation systems consisting of decimal numbers separated by dots, such as the older [[Dewey Decimal Classification]] and the [[Universal Decimal Classification]], to classify books and other works by subject. The UDC additionally codes works with ''multiple'' dot-decimal topics, separated by colons.<ref>{{cite book |last1=Taylor |first1=Arlene G. |title=Introduction to Cataloging and Classification |date=2005 |publisher=preprint, to be published by Libraries Unlimited in2006 |edition=10th |url=https://sites.pitt.edu/~agtaylor/articles/ICC10DeweyChapter.pdf |chapter=15: Decimal Classification}}</ref>

==Medicine==
{{Image frame|content=
<gallery mode=packed heights=200>
File:Phalanges of left foot - animation01.gif
File:Phalanges of left foot - animation02.gif
</gallery>
Toe bones or [[phalanges of the foot]].
{{legend|red|[[Distal phalanges]] of the foot}}
{{legend|yellow|[[Middle phalanges]] of the foot}}
{{legend|lime|[[Proximal phalanges]] of the foot}}
|border=no|align=right}}
Dot-decimal notation is also used to describe illnesses in a language-neutral way. For instance, the [[AO Foundation]]/[[Orthopaedic Trauma Association]] (AO/OTA) classification generates numeric codes for describing [[broken toe]]s.<ref name=halprox/> They run '''88'''[meaning a fracture of the [[phalanges]]]'''.'''[number-code of toe, with the big toe=1 and the little toe=5]'''.'''[number-code of phalanx, counting 1-3 outwards from the foot]'''.'''[number-code of location on the bone, with 1 being the inner end, 3 the outer, and 2 in-between].<ref name=halprox/> So, for instance, '''88.5.3.2''' means a fracture to the little toe's outermost bone, in the center.<ref name=halprox>{{cite journal |last1=Godoy-Santos |first1=AL |last2=Giordano |first2=V |last3=Cesar |first3=C |last4=Sposeto |first4=RB |last5=Bitar |first5=RC |last6=Wajnsztejn |first6=A |last7=Sakaki |first7=MH |last8=Fernandes |first8=TD |title=Hallux Proximal Phalanx Fracture in Adults: An Overlooked Diagnosis |journal=Acta Ortopedica Brasileira |date=November 2020 |volume=28 |issue=6 |pages=318–322 |doi=10.1590/1413-785220202806236612 |pmid=33328790 |pmc=7723381 }}</ref> There are other classifications for other fractures and dislocations.<ref>{{cite journal |last1=Meinberg |first1=EG |last2=Agel |first2=J |last3=Roberts |first3=CS |last4=Karam |first4=MD |last5=Kellam |first5=JF |title=Fracture and Dislocation Classification Compendium-2018 |journal=Journal of Orthopaedic Trauma |date=January 2018 |volume=32 Suppl 1 |pages=S1–S170 |doi=10.1097/BOT.0000000000001063 |pmid=29256945|s2cid=39138324 }}</ref>

==See also==
* {{Section link|IPv6 address|Representation}}
* [[ISO 2145]]
* [[Decimal section numbering]]

==References==
{{Reflist}}

{{DEFAULTSORT:Dot-Decimal Notation}}
[[Category:Network addressing]]