Comma codes are codes where each symbol is a string of 1s followed by a 0, except the last symbol which is all 1s. As a special case we have We have the Kraft sum and we have exactly met the condition. It is easy to see the general comma code meets the Kraft inequality with exact equality. If the Kraft sum is less than 1, then there is excess signaling capacity, since another symbol could be included, or some existing one shortened, and thus the average code length would be less. Note if the Kraft inequality is met, that does not mean the code is uniquely decodable, only there exists a code
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