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.
One reason for coding is to enable communication in places where ordinary spoken or written language is difficult or impossible. For example, semaphore, where the configuration of flags held by a signaller or the arms of a semaphore towerencodes 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.
Coding, Encoding, Decoding
In general the term coding describes the procedure defining the transformation of symbols from
one set of symbols to another one. For that a coding specification or code will be applied.
The steps for processing some original data can be differentiated into encoding and decoding.
The encoding process denotes the coding into a particular destination format, e.g. converting a bitmap graphic into a JPEG file.
The decoding process denotes the reverse process related to this format; for example the conversion
of the JPEG file back into a proper format. Encoding and decoding always refer to their common denominator, in this case the JPEG format.
For lossless data compresion both the original and the decoded data are identical; the
coding process is called reversible. That is not neccessarily the case for any compression procedure. GIF for example is only able to represent 256 different colours. Any further colour information will be lost during encoding.  |
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