How many methods of data compression are there?

In general, data compression methods can be categorized into three types: static, dynamic and hybrid methods. The so-called static method is that the mapping relationship between the source text set and the code subset is determined before the transmission of the message, and the given message is always represented as the same code word in the message set no matter what time it appears later. Dynamic methods, on the other hand, establish a time-varying mapping between the set of messages and the subset of codes. Dynamic methods are also called adaptive coding, i.e., they constantly modify the pairwise relationship between the set of source messages and the code words in order to better adapt to the change of the set of message characteristics over time. All adaptive methods are one-operation methods, i.e., the source set is scanned only once. Static coding requires two operations: the first to calculate the probabilities and determine the mapping, and the second to transmit the codeword. When an algorithm is neither fully static nor fully dynamic, it is called a hybrid method. A simple hybrid method is a codebook of K static codewords that is consistent for both the sender and the receiver. Each time a message is transmitted, the sender must select one of the pre-agreed K codewords and notify the receiver that it should be decoded.