Dot-decimal notation

Dot-decimal notation is a presentation format for numerical data. It consists of a string of decimal numbers, each pair separated by a full stop (dot).

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) numbers separated by dots (full stops). In computer networking, Internet Protocol Version 4 addresses are commonly written using the quad-dotted notation of four decimal integers, ranging from 0 to 255 each.

Dot-decimal notation is a presentation format for numerical data expressed as a string of decimal numbers each separated by a full stop. In computer networking, the term is often used as a synonym of dotted quad notation, or quad-dotted notation, a specific use to represent Internet Protocol Version 4 addresses.

For example, the hexadecimal number 0xFF0000 may be expressed in dot-decimal notation as 255.0.0.

Object identifiers use a style of dot-decimal notation to represent an arbitrarily deep hierarchy of objects identified by decimal numbers.

An Internet Protocol Version 4 (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.

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.

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 of May 1981, in which the IP address was supposed to be enclosed in brackets or represented as a 32bit 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.

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