GNU rzip is a compression program for large files that is released under the GNU General Public License version 2 or later. Data compression or bit-rate reduction involves encoding information using fewer bits than the original file, thus reducing use of data storage or transmission capacity. rzip functionality is similar to gzip or bzip2 but it performs better on very large files containing very long distance redundancies, thus producing better compression ratios. There are two steps in the compression program in rzip. In the first step, the program finds and encodes from the input file large amounts of duplicated data over a very long distance (900 MB). The second step employs bzip2 to compress the output from the first stage. bzip2 is a compressor for single files that uses a standard compression algorithm (Burrows-Wheeler) to convert frequently-recurring character sequences into strings of identical letters. It compresses data blocks with size between 100 kB and 900 kB, then applies move-to-front transform and Huffman coding.