霍夫曼编码使用变长编码表对源符号（如文件中的一个字母）进行编码，其中变长编码表是通过一种评估来源符号出现机率的方法得到的，出现机率高的字母使用较短的编码，反之出现机率低的则使用较长的编码，这便使编码之后的字符串的平均长度、期望值降低，从而达到无损压缩数据的目的。(Huffman Hoffman uses a variable length encoding encoding encoding table of source symbols (such as file in a letter) for encoding, variable length encoding table which is through an evaluation method of source symbol appears likely to be the probability high letters use short encoding, and now the low probability of using longer encoding, which would make the average length of string encoding after the lowering of expectations, so as to achieve the purpose of lossless data compression.)