(GNU ZIP) A popular compression program in the Unix world that is also available for Windows and Mac. Using the .GZ file extension, gzip compresses only a single file and is therefore often used in combination with the Unix "tar" utility when more than one file must be compressed. Tar combines multiple files into one archive, and gzip compresses that single archive, creating a file with the extension .TAR.GZ."Gunzip" is the gzip decompression utility, and it decompresses archives compressed with gzip or the Unix pack and compress commands. Many have lamented the fact that gzip includes the word "zip" because gzip cannot decompress files compressed with PKZIP. It was named that way because gzip uses one of the algorithms in PKZIP. However, in contrast, many PKZIP utilities can decompress gzip files. For more information, visit www.gzip.org. See archive formats.