Data Compression The Complete Reference 3rd

Compressing data is done by changing its representation from inefficient (i.e., long) to efficient (short). Compression is thus possible only because data is normally represented in the computer in a format that is longer than absolutely necessary. The reason that inefficient (long) data representations are used is that they make it easier to process the data, and data processing is more common and more important than data compression. The ASCII code for characters is a good example of a data representation that is longer than absolutely necessary. It uses 7-bit codes because fixed-size codes are easy to work with. A variable-size code, however, would be more efficient, since certain characters are used more than others and so could be assigned shorter codes.