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[[Truncated binary encoding]] is a straightforward generalization of fixed-length codes to deal with cases where the number of symbols ''n'' is not a power of two. Source symbols are assigned codewords of length ''k'' and ''k''+1, where ''k'' is chosen so that ''2<sup>k</sup> < n ≤ 2<sup>k+1</sup>''.
[[Huffman coding]] is a more sophisticated technique for constructing variable-length prefix codes. The Huffman coding algorithm takes as input the frequencies that the code words should have, and constructs a prefix code that minimizes the weighted average of the code word lengths. (This is closely related to minimizing the entropy.) This is a form of [[lossless data compression]] based on [[entropy encoding]].
Some codes mark the end of a code word with a special "comma" symbol, different from normal data.<ref>[http://www.imperial.ac.uk/research/hep/group/theses/JJones.pdf "Development of Trigger and Control Systems for CMS"] by J. A. Jones: "Synchronisation" p. 70</ref> This is somewhat analogous to the spaces between words in a sentence; they mark where one word ends and another begins. If every code word ends in a comma, and the comma does not appear elsewhere in a code word, the code is prefix-free. However, modern communication systems send everything as sequences of "1" and "0" – adding a third symbol would be expensive, and using it only at the ends of words would be inefficient. [[Morse code]] is an everyday example of a variable-length code with a comma. The long pauses between letters, and the even longer pauses between words, help people recognize where one letter (or word) ends, and the next begins. Similarly, [[Fibonacci coding]] uses a "11" to mark the end of every code word.
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