Editing Coding theory (section)

{{Short description|Study of the properties of codes and their fitness}}
[[File:Hamming.jpg|thumb|A two-dimensional visualisation of the [[Hamming distance]], a critical measure in coding theory]]

'''Coding theory''' is the study of the properties of [[code]]s and their respective fitness for specific applications. Codes are used for [[data compression]], [[cryptography]], [[error detection and correction]], [[data transmission]] and [[computer data storage|data storage]]. Codes are studied by various scientific disciplines—such as [[information theory]], [[electrical engineering]],  [[mathematics]], [[linguistics]], and [[computer science]]—for the purpose of designing efficient and reliable [[data transmission]] methods. This typically involves the removal of redundancy and the correction or detection of errors in the transmitted data.

There are four types of coding:<ref>{{cite book 
|author1=James Irvine |author2=David Harle
|url=https://books.google.com/books?id=ZigejECe4r0C |title=Data Communications and Networks
|date=2002
|page=18
|publisher=John Wiley & Sons
|section=2.4.4 Types of Coding
|quote=There are four types of coding|isbn=9780471808725
}}
</ref>

# [[Data compression]] (or ''source coding'')
# [[Error detection and correction|Error control]] (or ''channel coding'')
# [[Cryptography|Cryptographic coding]]
# [[Line code|Line coding]]

Data compression attempts to remove unwanted redundancy from the data from a source in order to transmit it more efficiently. For example, [[DEFLATE]] data compression makes files smaller, for purposes such as to reduce Internet traffic. Data compression and error correction may be [[Joint source and channel coding|studied in combination]].

Error correction adds useful [[Redundancy (information theory)|redundancy]] to the data from a source to make the transmission more robust to disturbances present on the transmission channel. The ordinary user may not be aware of many applications using error correction. A typical [[Compact Disc Digital Audio|music compact disc]] (CD) uses the [[Reed–Solomon code]] to correct for scratches and dust. In this application the transmission channel is the CD itself. Cell phones also use coding techniques to correct for the [[fading]] and noise of high frequency radio transmission. Data modems, telephone transmissions, and the [[NASA Deep Space Network]] all employ channel coding techniques to get the bits through, for example the [[turbo code]] and [[LDPC code]]s.<!--Kvng RTH-->