UUID (Universally unique identifier)

botond published 2019/12/22, v - 15:45 time

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Overview

The universally unique identifier (UUID) is a 128-bit number used to identify information in computer systems. The term globally unique identifier (GUID) is also used, usually in software created by Microsoft.

When produced using standard methods, UUIDs are unique for practical purposes. Their uniqueness does not depend on any central registry or coordination between the parties creating the UUIDs - unlike most other numbering systems. Although the probability of recurrence of UUIDs is not zero, it is close enough to be negligible.

This way, anyone can create a UUID to identify something that can be sure that that ID has not yet been created to identify something else. Information marked with UUIDs by independent parties can later be merged into a single database or transmitted over the same channel for a negligible chance of duplication.

UUIDs are widespread, with many computer platforms supporting their creation and processing of their textual representation.

 

 

history

UUIDs were originally created by Apollo Network Computing System (NCS)and then Open Software Foundation (OSF) in a distributed computing environment (Distributed Computing Environment, DCE) were used. The initial design of the DCE UUID was based on NCS UUIDs, inspired by (64-bit) unique identifiers Domain / OSwas also used in, which was also developed by Apollo Computer. Later, the Microsoft Windows platform adopted the DCE design, which it named as GUIDs (globally unique identifiers). The RFC 4122 registered one URN namespace for UUIDs, and repackaged previous specifications with the same technical content. What RFC 4122 recommended IETFpublished as a standard ITU also standardized UUIDs based on earlier standards and early versions of RFC 4122.

 

format

In regular text representation, UUID is represented as 32 hexadecimal numbers separated by dashes divided into five parts in 8-4-4-4-12 character length format. This gives you a total of 36 characters, including dashes. For example:

502c2f96-7b2c-ed5d-67ed-5b416fed4cd8

Microsoft GUIDs are sometimes displayed in brackets. e.g.:

{502c2f96-7b2c-ed5d-67ed-5b416fed4cd8}

This format should not be confused with the Windows Registry format, which is similar in parentheses.

Time stamps, MAC addresses and random numbers are used to produce them.

 

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