Dot-decimal notation

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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.

Definition and use[edit]

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 0xFF0000 is expressed in dot-decimal notation as 255.0.0.

In computer networking, the term is often used as a synonym of dotted quad notation,[1] or quad-dotted notation, a specific use to represent Internet Protocol Version 4 addresses. [2]

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

IPv4 address[edit]

An IP address (version 4) in both dot-decimal notation and binary code

An Internet Protocol Version 4 (IPv4) address consists of 32 bits, which may be divided into four octets, 8 bits each. These four octets are written in decimal numbers, ranging from 0 to 255, and are concatenated as a character string with full stop delimiters between number.

For example, the address of the loopback interface, usually assigned the host name localhost, is It consists of the four binary octets 01111111, 00000000, 00000000, and 00000001, forming the full 32-bit address.

Note: has an 8 (significant) bit mask and thus refers to an entire block of addresses all beginning with "127." . See CIDR notation.


In information technology, an integer number that starts with the digit 0 is often interpreted as a number in octal representation. Therefore, if an IP address component is written with a leading 0 digit, it may be interpreted incorrectly by some utility programs.[3] For example, the representation, when parsed as octal, would be equivalent to the decimal notation[note 1]

See also[edit]


  1. ^ Similarly, standard IP addresses can be written with a leading 0x to mean a hexadecimal address: pinging 133.45.0xEE.0x10 pings the decimal address


  1. ^ "Dotted Decimal Notation". 
  2. ^ "Dot address". TechTarget. Retrieved 2010-11-18. 
  3. ^ "Ping and FTP resolve IP address with leading zero as octal". Microsoft Support. Retrieved 2010-03-01.