Dot-decimal notation is a presentation format for numerical data. It consists of a string of decimal numbers, using the

full stop The full stop ( Commonwealth English), period (North American English), or full point is a punctuation mark used for several purposes, most often to mark the end of a declarative sentence (as distinguished from a question or exclamation). A ...

(''dot'') as a separation character. A common use of dot-decimal notation is in information technology where it is a method of writing numbers in octet-grouped base-10 (

decimal The decimal numeral system (also called the base-ten positional numeral system and denary or decanary) is the standard system for denoting integer and non-integer numbers. It is the extension to non-integer numbers (''decimal fractions'') of th ...

) numbers. In

computer networking A computer network is a collection of communicating computers and other devices, such as printers and smart phones. In order to communicate, the computers and devices must be connected by wired media like copper cables, optical fibers, or b ...

, Internet Protocol Version 4 (IPv4) addresses are commonly written using the quad-dotted notation of four decimal integers, ranging from 0 to 255 each.

IPv4 address

In computer networking, the notation is associated with the specific use of ''quad-dotted notation'' to represent IPv4 addresses and used as a synonym for ''dotted-quad notation''. 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 Hexadecimal (also known as base-16 or simply hex) is a positional numeral system that represents numbers using a radix (base) of sixteen. Unlike the decimal system representing numbers using ten symbols, hexadecimal uses sixteen distinct symbols ...

''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. This octet-grouped dotted-decimal format may more specifically be called "dotted octet" format, or a "dotted quad address". For example, the address of the loopback interface, usually assigned the host name

localhost In computer networking, localhost is a hostname that refers to the current computer used to access it. The name ''localhost'' is reserved for loopback purposes. It is used to access the network services that are running on the host via t ...

, 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. The first mention of this format in 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. 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 " is last requirement is not intended to specify the complete syntactic form for entering a dotted-decimal host number". An IETF draft intended to define textual representation of IP addresses expired without further activity. 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 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 Hexadecimal (also known as base-16 or simply hex) is a Numeral system#Positional systems in detail, positional numeral system that represents numbers using a radix (base) of sixteen. Unlike the decimal system representing numbers using ten symbo ...

and

octal Octal (base 8) is a numeral system with eight as the base. In the decimal system, each place is a power of ten. For example: : \mathbf_ = \mathbf \times 10^1 + \mathbf \times 10^0 In the octal system, each place is a power of eight. For ex ...

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. 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. A

POSIX The Portable Operating System Interface (POSIX; ) is a family of standards specified by the IEEE Computer Society for maintaining compatibility between operating systems. POSIX defines application programming interfaces (APIs), along with comm ...

-conforming variant of ''inet_aton'', the ''inet_pton()'' function, supports only the four-decimal variant of IP addresses. IP addresses in dot-decimal notation are also presented in

CIDR notation Classless Inter-Domain Routing (CIDR ) is a method for allocating IP addresses for IP routing. The Internet Engineering Task Force introduced CIDR in 1993 to replace the previous classful network addressing architecture on the Internet. Its goal ...

, 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 identifiers 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 Software versioning is the process of assigning either unique ''version names'' or unique ''version numbers'' to unique states of computer software. Within a given version number category (e.g., major or minor), these numbers are generally assig ...

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 Beta (, ; uppercase , lowercase , or cursive ; or ) is the second letter of the Greek alphabet. In the system of Greek numerals, it has a value of 2. In Ancient Greek, beta represented the voiced bilabial plosive . In Modern Greek, it represe ...

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 The Dewey Decimal Classification (DDC) (pronounced ) colloquially known as the Dewey Decimal System, is a proprietary library classification system which allows new books to be added to a library in their appropriate location based on subject. ...

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.

Medicine

Dot-decimal notation is also used to describe illnesses in a language-neutral way. For instance, the

AO Foundation The AO Foundation is a nonprofit organization dedicated to improving the care of patients with musculoskeletal injuries or pathologies and their sequelae through research, development, and education of surgeons and operating room personnel. The AO ...

Orthopaedic Trauma Association Orthopedic surgery or orthopedics ( alternative spelling orthopaedics) is the branch of surgery concerned with conditions involving the musculoskeletal system. Orthopedic surgeons use both surgical and nonsurgical means to treat musculoskeletal ...

(AO/OTA) classification generates numeric codes for describing

broken toe } A broken toe is a type of bone fracture. Symptoms include pain when the toe is touched near the break point, or compressed along its length (as if gently stubbing the toe). There may be bruising, swelling, stiffness, or displacement of the broke ...

s. They run 88 eaning a fracture of the phalanges">phalanges.html" ;"title="eaning a fracture of the phalanges">eaning 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]. So, for instance, 88.5.3.2 means a fracture to the little toe's outermost bone, in the center. There are other classifications for other fractures and dislocations.

References