U type, operating system, file system,
            and character set, and hence can be used for interchange;

          * Can be produced or consumed, even for an arbitrarily long
            sequentially presented input data stream, using only an a
            priori bounded amount of intermediate storage, and hence can
            be used in data communications or similar structures such as
            Unix filters;

          * Can use a number of different compression methods;

          * Can be implem