In communications systems, the altering of the characteristics of a signal to make the signal more suitable for an intended application, such as optimizing the signal for transmission, improving transmission quality and fidelity, modifying the signal spectrum, increasing the information content, providing errordetection and/or correction, and providing data security (Note: A single coding scheme usually does not provide more than one or two specific capabilities. Different codes have different sets of advantages and disadvantages.)
In communications and computer systems, implementing rules that are used to map the elements of one set onto the elements of another set, usually on a one-to-one basis
The digital encoding of an analog signal and, conversely, decoding to an analog signal
The on-line textbook: Information Theory, Inference, and Learning Algorithms (http://www.inference.phy.cam.ac.uk/mackay/itila/), by David MacKay, contains chapters on data-compression codes (including symbol codes such as Huffman codes, and arithmetic codes); hash codes (which are used for verifying data integrity and for rapid information recall); error-correcting codes (including elementary error-correcting codes, the theoretical limits of error-correction, and the latest state-of-the-art error-correcting codes, including low-density parity-check codes, turbo codes, and digital fountain codes).
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.
Codewords 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,...
Morsecode 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 telegraphcode using dots and dashes which was the forerunner of Morsecode.
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