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This calculator is designed to take in the number of letters in the alphabet and the number of letters in the message and calculate the amount of information that the message contains. The Hartley formula is based on the assumption that all messages are equiprobable and that each symbol in the alphabet is equally likely to appear in any position in the message.
That is, we have an alphabet A of which letters we make up a message:
The number of possible variants of different messages:
where N — the possible number of different messages; m — number of letters in the alphabet; n — the number of letters in a message.
Then the Hartley's formula is defined as:
where I — the amount of information, bits.
The Hartley's formula was proposed by Ralph Hartley in 1928 as one of the scientific approaches for message evaluation. The Hartley Information Calculator is useful in information theory, cryptography, and other fields where the amount of information contained in a message needs to be quantified.