Code

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Code

In communication

Communication

Communication is commonly defined as "the imparting or interchange of thoughts, opinions, or information by speech, writing, or signs...",, 1: an act or instance of transmitting and 3 a: "a process by which information is exchanged between individuals through a common system of symbols, signs, or beha...
s, a code is a rule

Operator

In mathematics, an operator is a function which operates on another function. Often, an "operator" is a function which acts on functions to produce other functions ; or it may be a generalization of such a function, as in linear algebra, where some of the terminology reflects the origin of the subject in operations on the functions which ar...
for converting a piece of information

Information

Information as a Conveyed concept has a diversity of meanings, from everyday usage to technical settings. Generally speaking, the concept of information is closely related to notions of constraint, communication, control system, data, form, instruction, knowledge, Meaning , stimulation, pattern, perception, and knowledge representation....
(for example, a letter

Letter (alphabet)

A letter is an element in an alphabetic system of writing, such as the Greek alphabet and its descendants. Each letter in the written language is usually associated with one phoneme in the spoken form of the language....
, word

Word

A word is a unit of language that represents a concept which can be expressively communication with Meaning . A word consists of one or more morphemes which are linked more or less tightly together, and has a phonetic value....
, phrase

Phrase

In grammar, a phrase is a group of words that functions as a single unit in the syntax of a Sentence .For example the house at the end of the street is a phrase....
, or gesture

Gesture

A gesture is a form of non-verbal communication made with a part of the body, used instead of or in combination with verbal communication. The language of gesture allows individuals to express a variety of feelings and thoughts, from contempt and hostility to approval and affection....
) into another form or representation (one sign

Sign

A sign is an entity which signifies another entity. A natural sign is an entity which bears a causal relation to the signified entity, as thunder is a sign of storm....
into another sign), not necessarily of the same type. In communications and information processing

Information processing

Information processing is the change of information in any manner detectable by an observation. As such, it is a Process which describes everything which happens in the universe, from the falling of a rock to the printing of a text file from a digital computer system....
, encoding is the process by which information from a source

Communication source

A source or sender is one of the basic concepts of communication and information processing. Sources are objects which encode message data and Transmission the information, via a channel , to one or more observations ....
is converted into symbols to be communicated. Decoding is the reverse process, converting these code symbols back into information understandable by a receiver.

One reason for coding is to enable communication in places where ordinary spoken or written language is difficult or impossible.

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Encyclopedia

In communication

Communication

Operator

Information

Letter (alphabet)

Word

Phrase

In grammar, a phrase is a group of words that functions as a single unit in the syntax of a Sentence .For example the house at the end of the street is a phrase....
, or gesture

Gesture

Sign

Information processing

Communication source

Flag semaphore

Modern semaphore The newer flag semaphore system uses two short poles with square flags, which a signalman holds in different positions to signal letters of the alphabet and numbers....
held by a signaller or the arms of a semaphore tower encodes parts of the message, typically individual letters and numbers. Another person standing a great distance away can interpret the flags and reproduce the words sent.

In the history of cryptography

History of cryptography

The history of cryptography begins thousands of years ago. Until recent decades, it has been the story of what might be called classical cryptography ? that is, of methods of encryption that use pen and paper, or perhaps simple mechanical aids....
, codes were once common for ensuring the confidentiality of communications, although cipher

Cipher

In cryptography, a cipher is an algorithm for performing encryption and decryption — a series of well-defined steps that can be followed as a procedure....
s are now used instead. See code (cryptography)

Code (cryptography)

In cryptography, a code is a method used to transform a message into an obscured form, preventing those who do not possess special information, or key , required to apply the transform from understanding what is actually transmitted....
.

Codes in communication used for brevity

A cable code replaces words (e.g., ship or invoice) into shorter words, allowing the same information to be sent with fewer characters

Character (computing)

In computer and machine-based telecommunications terminology, a character is a unit of information that roughly corresponds to a grapheme, grapheme-like unit, or symbol, such as in an alphabet or syllabary in the written language form of a natural language....
, more quickly, and most important, less expensively.

Code can be used for brevity. When telegraph messages were the state of the art in rapid long distance communication, elaborate commercial codes which encoded complete phrases into single words (commonly five-letter groups) were developed, so that telegraphers

Telegraphy

Telegraphy is the long-distance transmission of written messages without physical transport of letters. Radiotelegraphy or wireless telegraphy transmits messages using radio....
became conversant with such "words" as BYOXO ("Are you trying to weasel out of our deal?"), LIOUY ("Why do you not answer my question?"), BMULD ("You're a skunk!"), or AYYLU ("Not clearly coded, repeat more clearly."). Code word

Code word

In telecommunication, a code word is an element of a code. Each code word is a sequence of symbols assembled in accordance with the specific rules of the code and assigned a unique meaning ....
s were chosen for various reasons: length

Length

Length is the long dimension of any object. The length of a thing is the distance between its ends, its linear extent as measured from end to end....
, pronounceability, etc. Meanings were chosen to fit perceived needs: commercial negotiations, military terms for military codes, diplomatic terms for diplomatic codes, any and all of the preceding for espionage codes. Codebooks and codebook publishers proliferated, including one run as a front for the American Black Chamber

Black Chamber

The Black Chamber, otherwise known as MI-8 or Cipher Bureau, was the United States' first peacetime cryptanalytic organization, and a forerunner of the National Security Agency....
run by Herbert Yardley

Herbert Yardley

Herbert Osborne Yardley was an American cryptologist best known for his book The American Black Chamber . The title of the book refers to MI-8, the cryptographic organization of which Yardley was the founder and head....
between WWI and WWII. The purpose of most of these codes was to save on cable costs. The use of data coding for data compression

Data compression

In computer science and information theory, data compression or source coding is the process of encoding information using fewer bits than an code representation would use through use of specific encoding schemes....
predates the computer era; an early example is the telegraph

Telegraphy

Morse code

Morse code is a type of character encoding that transmits telegraphic information using rhythm. Morse code uses a standardized sequence of short and long elements to represent the alphanumeric, punctuation and special characters of a given message....
where more frequently-used characters have shorter representations. Techniques such as Huffman coding

Huffman coding

In computer science and information theory, Huffman coding is an entropy encoding algorithm used for lossless data compression. The term refers to the use of a variable-length code table for encoding a source symbol where the variable-length code table has been derived in a particular way based on the estimated probability of occurrence for...
are now used by computer-based algorithm

Algorithm

In mathematics, computing, linguistics and related subjects, an algorithm is a sequence of finite instructions, often used for calculation and data processing....
s to compress large data files into a more compact form for storage or transmission.

An example: the ASCII code

Probably the most widely known data communications code (aka character representation) in use today is ASCII

ASCII

American Standard Code for Information Interchange , is a coding standard that can be used for interchanging information, if the information is expressed mainly by the written form of English words....
. In one or another (somewhat compatible) version, it is used by nearly all personal computer

Computer

A computer is a machine that manipulates Data according to a list of Code .The first devices that resemble modern computers date to the mid-20th century , although the computer concept and various machines similar to computers existed earlier....
s, terminals

Computer terminal

A computer terminal is an electronic or electromechanical computer hardware device that is used for entering data into, and displaying data from, a computer or a computing system....
, printers

Computer printer

File:Lexmark X5100 Series.jpgIn computing, a printer is a peripheral which produces a hard copy of documents stored in computer file form, usually on physical print media such as paper or Transparency ....
, and other communication equipment. It represents 128 characters

Character (computing)

Binary numeral system

The binary numeral system, or notation with a radix of 2. Owing to its straightforward implementation in digital electronic circuitry using logic gates, the binary system is used internally by all modern computers....
numbers—that is, as a string of seven 1s and 0s. In ASCII a lowercase "a" is always 1100001, an uppercase "A" always 1000001, and so on. Successors to ASCII have included 8-bit characters (for letters of European languages and such things as card suit symbols), and in fullest flowering have included characters from essentially all of the world's writing systems (see Unicode

Unicode

Unicode is a computing industry standard allowing computers to consistently represent and manipulate Character expressed in most of the world's writing systems....
and UTF-8

UTF-8

UTF-8 is a Variable-width encoding character encoding for Unicode. It is able to represent any character in the Unicode standard, yet the initial encoding of byte codes and character assignments for UTF-8 is backward compatibility with ASCII....
).

Codes to detect or correct errors

Codes may also be used to represent data in a way more resistant to errors in transmission or storage. Such a "code" is called an error-correcting code, and works by including carefully crafted redundancy with the stored (or transmitted) data. Examples include Hamming code

Hamming code

In telecommunication, a Hamming code is a linear code error-correcting code named after its inventor, Richard Hamming. Hamming codes can detect up to two simultaneous bit errors, and correct single-bit errors; thus, reliable communication is possible when the Hamming distance between the transmitted and received bit patterns is less than or e...
s, Reed–Solomon, Reed–Muller, Bose–Chaudhuri–Hochquenghem

BCH code

In coding theory the BCH codes form a class of parameterised Error detection and correction which have been the subject of much academic attention in the last fifty years....
, Turbo

Turbo code

In electrical engineering and digital communications, turbo codes are a class of high-performance error-correcting code developed in 1993 which are finding use in deep space satellite telecommunication and other applications where designers seek to achieve maximal information transfer over a limited-bandwidth communication link in the prese...
, Golay

Golay code

Golay code may refer to:* Binary Golay code* Ternary Golay codeExcess long comment to prevent listing on...
, Goppa

Goppa code

In mathematics, an algebraic geometric code , otherwise known as a Goppa code, is a general type of linear code constructed by using an algebraic curve over a finite field ....
, low-density parity-check code

Low-density parity-check code

In information theory, a low-density parity-check code is an error correcting code, a method of transmitting a message over a signal noise transmission channel....
s, and space–time code

Space–time code

A space–time code is a method employed to improve the reliability of data transmission in wireless using multiple transmit antenna . STCs rely on transmitting multiple, redundancy copies of a data stream to the receiver in the hope that at least some of them may survive the transmission medium between transmission and reception in a...
s. Error detecting codes can be optimised to detect burst errors, or random errors.

Codes and acronyms

Acronyms and abbreviations can be considered codes, and in a sense all language

Language

A language is a form of symbol communication in which elements are combined to represents something other than themselves. Language can also refer to the use of such systems as a general phenomenon....
s and writing systems are codes for human thought. Occasionally a code word achieves an independent existence (and meaning) while the original equivalent phrase is forgotten or at least no longer has the precise meaning attributed to the code word. For example, '30' was widely used in journalism

Journalism

Journalism is the craft of conveying news, descriptive material and editorial via a widening spectrum of Media . These include newspapers, magazines, radio and television, the internet and, more recently, the cellphone....
to mean "end of story", and it is sometimes used in other contexts to signify "the end".

Coupon Codes

In marketing

Marketing

Marketing is defined by the American Marketing Association as the activity, set of institutions, and processes for creating, communicating, delivering, and exchanging offerings that have value for customers, clients, partners, and society at large....
, coupon

Coupon

In marketing a coupon is a ticket or document that can be exchanged for a financial discounts and allowances or rebate when purchasing a product ....
codes can be used for a financial discount or rebate when purchasing a product from an internet retailer. Coupon codes are also referred to as "promotional codes," "promotion codes," "discount codes," "key codes," "promo codes," "shopping codes," "voucher codes" or "source codes."

Gödel code

In mathematics

Mathematics

Mathematics is the study of quantity, structure, space, change, and related topics of pattern and form. Mathematicians seek out patterns whether found in numbers, space, natural science, computers, imaginary abstractions, or elsewhere....
, a Gödel code was the basis for the proof of Gödel's incompleteness theorem. Here, the idea was to map mathematical notation

Mathematical notation

A mathematical notation is a system of symbolic representations of mathematical objects and ideas. Mathematical notations are used in mathematics and the physical sciences, engineering and economics....
to a natural number

Natural number

In mathematics, a natural number can mean either an element of the Set = *n = = ? = ? ...
(a Gödel number

Gödel number

In mathematical logic, a G?del numbering is a function that assigns to each symbol and well-formed formula of some formal language a unique natural number, called its G?del number....
).*

Code

Codes in communication used for brevity

An example: the ASCII code

Codes to detect or correct errors

Codes and acronyms

Coupon Codes

Gödel code

See also