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Encyclopedia > Code

In communications, a code is a rule for converting a piece of information (for example, a letter, word, or phrase) into another form or representation, not necessarily of the same type. In communications and information processing, encoding is the process by which information from a source is converted into symbols to be communicated. Decoding is the reverse process, converting these code symbols back into information understandable by a receiver. Communication is a process that allows beings - in particular humans - to exchange information by several methods. ... In mathematics, an operator is a function that performs some sort of operation on a number, variable, or function. ... The ASCII codes for the word Wikipedia represented in binary, the numeral system most commonly used for encoding computer information. ... Vintage German letter balance for home use Look up letter in Wiktionary, the free dictionary. ... A word is a unit of language that carries meaning and consists of one or more morphemes which are linked more or less tightly together, and has a phonetical value. ... Look up phrase in Wiktionary, the free dictionary. ... Communication is a process that allows beings - in particular humans - to exchange information by several methods. ... In general, information processing is the changing (processing) of information in any manner detectable by an observer. ... Process (lat. ... A source is one of the basic concepts of communication and information processing. ...


One reason for coding is to enable communication in places where ordinary spoken or written language is difficult or impossible. For example, a cable code replaces words (e.g., ship or invoice) into shorter words, allowing the same information to be sent with fewer characters, more quickly, and most important, less expensively. Another example is the use of semaphore flags, where the configuration of flags 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. This article does not cite any references or sources. ...


In the history of cryptography, codes were once common for ensuring the confidentiality of communications, although ciphers are now used instead. See code (cryptography). The history of cryptography dates back thousands of years. ... This article is about algorithms for encryption and decryption. ... In the context of cryptography, a code is a method used to transform a message into an obscured form, preventing those not in on the secret from understanding what is actually transmitted. ...

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Codes in communication used for brevity

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 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 words were chosen for various reasons: length, 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 run by Herbert Yardley 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 predates the computer era; an early example is the telegraph Morse code where more frequently-used characters have shorter representations. Techniques such as Huffman coding are now used by computer-based algorithms to compress large data files into a more compact form for storage or transmission. Optical Telegraf of Claude Chappe on the Litermont near Nalbach, Germany Telegraphy (from the Greek words tele (τηλε) = far and graphein (γραφειν) = write) is the long-distance transmission of written messages without physical transport of letters, originally by changing something that could be observed from a distance (optical telegraphy). ... A Code word may refer any of several concepts: For telecommunications senses, see Code word (telecommunication). ... Look up length, width, breadth in Wiktionary, the free dictionary. ... Look up pronunciation in Wiktionary, the free dictionary. ... The Black Chamber, otherwise known as MI-8, was Americas first peacetime cryptanalytic organization and a forerunner of the top-secret National Security Agency. ... Herbert O. Yardley Herbert Osborne Yardley (13 April 1889-7 August 1958) was an American cryptologist most known for his book The American Black Chamber (1931). ... In computer science and information theory, data compression or source coding is the process of encoding information using fewer bits (or other information-bearing units) than an unencoded representation would use through use of specific encoding schemes. ... Optical Telegraf of Claude Chappe on the Litermont near Nalbach, Germany Telegraphy (from the Greek words tele (τηλε) = far and graphein (γραφειν) = write) is the long-distance transmission of written messages without physical transport of letters, originally by changing something that could be observed from a distance (optical telegraphy). ... 1922 Chart of the Morse Code Letters and Numerals Morse code is a method for transmitting telegraphic information, using standardized sequences of short and long elements to represent the letters, numerals, punctuation and special characters of a message. ... In computer science and information theory, Huffman coding is an entropy encoding algorithm used for lossless data compression. ...


An example: the ASCII code

Probably the most widely known data communications code (aka character representation) in use today is ASCII. In one or another (somewhat compatible) version, it is used by nearly all personal computers, terminals, printers, and other communication equipment. Its original version represents 128 characters with seven-bit binary 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 glyphs from essentially all of the world's writing systems (see Unicode and UTF-8). Image:ASCII fullsvg There are 95 printable ASCII characters, numbered 32 to 126. ... The NASA Columbia Supercomputer. ... A computer terminal is an electronic or electromechanical hardware device that is used for entering data into, and displaying data from, a computer or a computing system. ... This does not cite any references or sources. ... The binary numeral system, or base-2 number system, is a numeral system that represents numeric values using two symbols, usually 0 and 1. ... Unicode is an industry standard allowing computers to consistently represent and manipulate text expressed in any of the worlds writing systems. ... UTF-8 (8-bit UCS/Unicode Transformation Format) is a variable-length character encoding for Unicode. ...


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 codes, Reed–Solomon, Reed–Muller, Bose–Chaudhuri–Hochquenghem, Turbo, Golay, Goppa, Gallager Low-density parity-check codes, and space–time codes. Error detecting codes can be optimised to detect burst errors, or random errors. It has been suggested that this article or section be merged with Forward error correction. ... In telecommunication, a Hamming code is a linear error-correcting code named after its inventor, Richard Hamming. ... Reed-Solomon error correction is an error-correcting code that works by oversampling a polynomial constructed from the data. ... The Reed-Muller codes are a family of linear error-correcting codes used in communications. ... A BCH (Bose, Ray-Chaudhuri, Hocquenghem) code is a much studied code within the study of coding theory and more specifically error-correcting codes. ... In electrical engineering and digital communications, turbo codes are a class of recently-developed high-performance error correction codes finding use in deep space satellite communications and other applications where designers seek to achieve maximal information transfer over a limited-bandwidth communication link in the presence of data-corrupting noise. ... A Golay code can be binary or ternary. ... In mathematics, a Goppa code is a general type of linear code constructed by using an algebraic curve X over a finite field . ... Robert G. Gallager (born May 29, 1931 in Philadelphia, PA) is an American computer scientist known for his work on information theory and communications networks. ... A low-density parity-check code (LDPC code) is an error correcting code, a method of transmitting message over a noisy transmission channel. ... A space–time code (STC) is a method employed to improve the reliability of data transmission in wireless communication systems using multiple transmit antennas. ...


Codes and acronyms

Acronyms and abbreviations can be considered codes, and in a sense all languages 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 to mean "end of story", and it is sometimes used in other contexts to signify "the end". It has been suggested that this article or section be merged with Backronym and Apronym (Discuss) Acronyms and initialisms are abbreviations, such as NATO, laser, and ABC, written as the initial letter or letters of words, and pronounced on the basis of this abbreviated written form. ... This article does not cite any references or sources. ...


Gödel code

In mathematics, a Gödel code was the basis for the proof of Gödel's incompleteness theorem. Here, the idea was to map mathematical notation to a natural number (a Gödel number). Euclid, Greek mathematician, 3rd century BC, as imagined by by Raphael in this detail from The School of Athens. ... In formal number theory a Gödel numbering is a function which assigns to each symbol and formula of some formal language a unique natural number called a Gödel number (GN). ... Kurt Gödel Kurt Gödel [kurt gøːdl], (April 28, 1906 – January 14, 1978) was a logician, mathematician, and philosopher of mathematics. ... In mathematical logic, Gödels incompleteness theorems are two celebrated theorems proved by Kurt Gödel in 1931. ... Mathematical notation is used in mathematics, and throughout the physical sciences, engineering, and economics. ... In mathematics, a natural number can mean either an element of the set {1, 2, 3, ...} (i. ... This article or section may be confusing or unclear for some readers, and should be edited to rectify this. ...


See also

United States Government Code: A form of communication used by government personnel to communicate their wishes for kickbacks. This is a list of coding-related terms derived from the Glossary of Telecommunication Terms published as Federal Standard 1037C. Please see the Federal Standard article for copyright-related issues, as not all parts of the source document are in the public domain. ...


  Results from FactBites:
 
Code - Wikipedia, the free encyclopedia (749 words)
In communications, a code is a rule for converting a piece of information (for example, a letter, word, or phrase) into another form or representation, not necessarily of the same type.
Code words were chosen for various reasons: length, 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,...
In mathematics, a Gödel code was the basis for the proof of Gödel's incompleteness theorem.
Encyclopedia4U - Morse code - Encyclopedia Article (1539 words)
Morse code is an early form of digital communication, however unlike modern binary digital codes that use just two states (commonly represented as 1 and 0), it uses five - dot, dash, short gap (between each letter), medium gap (between words) and long gap (between sentences).
The code may transmitted as an audio tone, a steady radio signal switched on and off (known as continuous wave, or CW), an electrical pulse down a telegraph wire, or as a mechanical or visual signal (e.g.
On January 8, 1838 Alfred Vail demonstrated a telegraph code using dots and dashes which was the forerunner of Morse code.
  More results at FactBites »

 
 

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