In many systems, it is desirable to use some form of compression technique in order to handle data. This can be necessary in order to improve upon data requirements for storage, or to facilitate quicker data transfer in case of limited bandwidth. There is no single data compression program that will work for all types of data, nor is there one that will compress all data of a certain type. Data compression techniques and software tend to be quite specialized.

It is important to understand why it is that data compression is not always possible for all files--many hoaxes and unscientific claims notwithstanding. A well-known concept in discrete mathematics called the pigeonhole principle says that if one has more than n items of a certain kind, but only n slots (or pigeonholes) to put them in, then at least one of the slots will have more...