 7-Zip uses its own 7z archive format, but can read and write several other archive formats.The program can be used from a command-line interface as the command p7zip, or through a graphical user interface that also features shell integration.Most of the 7-Zip source code is under the GNU LGPL license; the unRAR code, however, is under the GNU LGPL with an "unRAR restriction", which states that developers are not permitted to use the code to reverse-engineer the RAR compression algorithm.