7-Zip
Encyclopedia : 7 : 7Z : 7ZI : 7-Zip
7-Zip is a file archiver predominantly for the Microsoft Windows operating system. It operates either as a command line program or with a graphical user interface. It also features integration with the Windows shell environment. 7-Zip is free software, developed by Igor Pavlov and distributed under the GNU Lesser General Public License (LGPL). It is a competitor to the market-leading WinZip and WinRAR programs, both of which are closed source. It offers a special 64-bit version for Windows XP Professional x64 Edition. In the form of p7zip, 7-Zip has been ported for use on Unix-like systems such as Linux and FreeBSD.
The project was started in 2000 and the latest stable version is 4.42, released on May 14, 2006. Beta versions of 7-Zip are frequently made available.
The 7z compression format
The 7-Zip program supports a variety of archive formats, the default being its own 7z format.
By default, the program creates 7z archives, with file extension .7z, using the LZMA algorithm for compression. This relatively new format allows the program to achieve a very high compression ratio, comparable to other popular high compression formats such as RAR (which is based on proprietary algorithms).
7z files have the MIME-type application/x-7z-compressed.
Other supported formats & algorithms
7-Zip supports a number of other compression (and non-compression) archive formats. These supported formats include ZIP, Microsoft cabinet (CAB) files, RAR, ARJ, gzip, bzip2, LHA, tar, cpio, rpm and Debian deb archives. As of version 4.42, 7-Zip also supports ISO CD/DVD images.7-Zip can also open any file format that uses a supported compression method. For instance, it is possible to open MSI files in 7-Zip that include the files to be installed with the file itself (otherwise, the files are stored in CAB files, also supported). This makes 7-Zip a good tool to check if a file is an archive.
For ZIP and gzip files, 7-Zip uses a modified implementation of the DEFLATE algorithm that is tuned for higher compression levels at the expense of speed. This implementation is also used in the AdvanceCOMP tools.
The native 7z file format is an open, modular architecture which allows it to contain files compressed using different algorithms. Filenames are stored as Unicode.
Features
7-Zip supports many features that may not be found in popular commercial compression software.
- For 7z format files, 7-Zip supports 256-bit AES encryption of both files and the 7z directory structure, preventing users without the password from even seeing the archive contents.
- 7-Zip flexibly supports volumes of dynamically variable sizes, useful for backups on removable media such as writable CDs and DVDs.
- When in 2-panel mode, 7-Zip can be considered a basic orthodox file manager.
- Multithreading support.
- Special 64-bit version with support for large memory maps for faster compressing.
See also
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External links
- [7-Zip Home]
- [Project: 7-Zip] - 7-Zip's SourceForge project page.
- [7zX] - 7z compressor for Mac OS X
- [p7zip] - a port of 7-Zip for Unix-like systems
- [MaximumCompression.com], a site providing test results from compression of various file types using different compression tools (including 7-Zip)
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