Universal code: Difference between revisions

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{{self reference|"Universal code of conduct" redirects here. For the code of conduct that applies to Wikimedia projects, see [[:Foundation: Universal Code of Conduct]].}}

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'''Universal Code''' can refer to:

* [[Universal code (data compression)]], a prefix used to map integers onto binary codewords

* [[Universal Code (biology)]], another term for genetic code, the set of rules living cells to form proteins

* An alternate term for a [[Universal law]], the concept that principles and rules governing human behaviour can gain legitimacy by demonstrating universal acceptability, applicability, translation, and philosophical basis of those rules

* [[Universal code (ethics)]], the belief that a system of ethics can apply to every sentient being

* [[Universal Product Code]], a barcode symbology system widely used in Australia, Europe, New Zealand, North America, and other countries for tracking trade items

* [[Universal code (typography)]], a standard set of characters in typography

* [[Universal code (cartography)]], another term for the Natural Area Code, a geocode system for identifying a ___location on or in the volume of space around Earth

{{Disambig}}

==Data compression==

In [[data compression]],

a universal code maps the integers (representing messages) onto self-delimiting binary codewords.

Longer binary codewords are mapped to less probable messages.

(Self-delimiting codes are also called [[prefix-free code]]s or "instantaneously decodable" codes).

Unlike other compression codes such as [[Huffman coding]] or [[fixed-length code]]s, universal codes do not require the receiver or the transmitter to know the maximum integer (number of potential messages) ahead of time.

Universal codes include:

* [[Unary coding]]

* [[Elias gamma coding]]

* [[Elias delta coding]]

* [[Elias omega coding]]

* [[Delta code]]

* [[Fibonacci coding]]

* [[Golomb coding]]

* [[Rice coding]]

[[Huffman coding]], [[range encoding]], and [[arithmetic encoding]] (when it can be used) gives at least as good, and often better compression than any universal code.

However, universal codes are useful when Huffman coding cannot be used -- for example, when one does not know the exact probability of each message, but only knows their ranking (this message is more probable than that message).

Universal codes are also useful when Huffman codes are inconvenient. For example, when the transmitter but not the receiver knows the probabilities of the messages, Huffman coding requires an overhead of transmitting those probabilities to the receiver. Using a universal code does not have that overhead.

Each universal code, like each other self-delimiting (prefix-free) binary code, has its own "implied probability distribution". If a set of messages happens to have a probability distribution similar enough to that implied by some universal code, then the Huffman code for that set of messages will be equivalent to that universal code. Since universal codes are simpler and faster to encode and decode than Huffman codes (which is, in turn, simpler and faster than [[range encoding]] and [[arithmetic encoding]]), the universal code would be preferable in cases where the codes are equivalent.

[http://www.cs.tut.fi/~albert/Dev/pucrunch/]

Some codes such as Elias delta coding and Huffman are "asymptotically optimal", while others such as Elias gamma coding are not.

[http://www.ics.uci.edu/~dan/pubs/DC-Sec3.html]

==Biology==

In [[biology]], "universal code" is short for the idea of the "universal [[genetic code]]".

In all known living creatures, instructions for making proteins are encoded in DNA. Three bases of DNA (the "codon") select an amino acid. In the 1960s, biologists and chemists worked out which particular amino acid is selected by each codon -- the [[genetic code]]. They were surprised to discover that this code was the same for every living creature they investigated -- plant, animal, bacteria, etc.

This evidence supports the hypothesis of [[Common descent]].

(In the 1990s, it was discovered that the genetic code was not universal after all -- quite a few organisms use genetic codes that have one or two differences from what was once thought to be the universal code, now called the "canonical code" --

[http://evolvingcode.net/uni_code.php], [http://www.mcb.harvard.edu/BioLinks/gencode.html],

[http://swift.cmbi.kun.nl/swift/future/aainfo/gencode.html]

).

See also the [[International Code of Zoological Nomenclature]].

==Law==

In [[law]], a universal code is a law that applies everywhere on Earth.

==Ethics==

In ethics, a "universal code of ethics" is a system of ethics that can apply to every human. See [[Michael E. Berumen]], [[James Harrison Rigg]].

==Etiquette==

In [[etiquette]], a "universal code of etiquette" ...

==Marketing==

In marketing and package design, "universal code" may refer to the [[Universal Product Code]] [[bar code]]. EAN-UCC assigns each company a manufacturer code (from 00000 to 99999). Each manufacturer assigns a unique (to that manufacturer) product code to each of its products (from 00000 to 99999).

This allows up to 9 999 999 999 unique products, which is expected to be more than enough for the forseeable future.

[http://www.howstuffworks.com/upc.htm HowStuffWorks]

==Typography==

In [[typography]], the "universal code" may refer to the

[[Unicode]] [[Universal character set]],

or one of its encodings such as [[UTF-32]].

(In particular, the [[ASCII]] code is not universal because there are many letters it does not encode).

==Cartography==

In [[cartography]], a "universal code" is a code that can indicate any ___location on Earth, such as "latitude and longitude", or the [[Natural Area Code]].

==Post code==

A "post code" of the [http://upu.int/ Universal Postal Union]

==CD==

"Universal Code" is also the title of a CD by Dan Handrabur.

==INSPSC==

* [[UNSPSC]]

{{disambig}}