<*theory*> A measure of the disorder of a system. Systems tend
to go from a state of order (low entropy) to a state of
maximum disorder (high entropy).

The entropy of a system is related to the amount of information it contains. A highly ordered system can be described using fewer bits of information than a disordered one. For example, a string containing one million "0"s can be described using run-length encoding as [("0", 1000000)] whereas a string of random symbols (e.g. bits, or characters) will be much harder, if not impossible, to compress in this way.

Shannon's formula gives the entropy H(M) of a message M in bits:

H(M) = -log2 p(M)Where p(M) is the probability of message M.

Last updated: 1998-11-23

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entity « entity-relationship diagram « entity-relationship model « **entropy** » Entry Sequenced Data Set » enumerated type » enumeration

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Copyright Denis Howe 1985