The probabilities of the elements in these memoried messages are dependent on the elements which precede them. Data Compression Overview Data Compression shrinks down a file so that it takes up less space. This is desirable for data storage and data communication. Smaller files are also desirable for data communication, because the smaller a file the faster it can be transferred. A compressed file appears to increase the speed of data transfer over an uncompressed file.
All data is encoded.
This means that the data is originally a combination of elements, e , from some alphabet, A . This combination of elements is a message, M. This message from the alphabet, A , is encoded into the binary alphabet, B . So essentially encoding is just tranferring a message, M, from the alphabet A into the alphabet B . The above example just translates the elements a,b,c,d from the english alphabet, A , into the binary alphabet, B . These elements can also be decoded from the binary alphabet back into the original message which was in the english alphabet.