7-Zip
From Wikipedia, the free encyclopedia
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 7-Zip, in Windows Vista |
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| Developed by | Igor Pavlov |
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| Initial release | 2000 |
| Stable release | 4.65 (2009-2-3) [+/−] |
| Preview release | 4.66 alpha (2009-3-22) [+/−] |
| Written in | C++, C |
| Operating system | Microsoft Windows |
| Available in | 69 languages, including Brazilian Portuguese, Czech, English, French, German, Italian, Japanese, Russian, Simplified Chinese, and Spanish |
| Type | File archiver |
| License | GNU Lesser General Public License with unRAR restriction[1] |
| Website | http://www.7-zip.org/ |
7-Zip is an open source file archiver designed originally for Microsoft Windows. 7-Zip operates primarily with the 7z archive format, as well as being able to read and write to several other archive formats. A user can use the command line interface, graphical user interface, or Windows shell integration. 7-Zip began in 2000 and is actively developed by Igor Pavlov. It is related to a cross-platform port, p7zip.
Unlike WinZip and WinRAR programs, which are distributed under proprietary licenses, 7-Zip is distributed under the GNU Lesser General Public License. 7-Zip was the winner of the SourceForge.net 2007 community choice awards for "Technical Design" and for "Best Project".[2]
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[edit] Formats
[edit] The 7z archive format
By default, 7-Zip creates 7z format archives, with a .7z file extension. Each archive can contain multiple directories and files. As a container format, security or size reduction are achieved using a stacked combination of filters. These can consist of pre-processors, compression algorithms, and encryption filters.
The core .7z compression uses a variety of algorithms, the most common of which are bzip2 and LZMA. Developed by Igor Pavlov, LZMA is a relatively new system, making its debut as part of the 7z format. LZMA consists of a large LZ-based sliding dictionary up to 4 GiB in size, backed by a range coder.
LZMA compression ratios tend to be very efficient. Compressed sizes are comparable to other high-gain compression formats, including RAR or ACE, both of which are proprietary.
The native 7z file format is open and modular. All filenames are stored as Unicode.
[edit] Other supported formats
7-Zip supports a number of other compression, and non-compression, archive formats. Supported formats include:
Packing/Unpacking of ZIP, gzip, bzip2, tar
Unpacking only: Microsoft cabinet (CAB) files, RAR, ARJ, Z, LHA, cpio, smzip, JAR, ISO CD/DVD images (7Zip version 4.42 and up), rpm and Debian deb archives.
7-Zip is able to open some MSI files, allowing access to the meta-files within along with the main contents. Some Microsoft CAB (LZX compression) and NSIS (LZMA) installer formats can be opened, making 7-Zip a good tool to check if a given binary file is in fact an archive.
When compressing ZIP or gzip files, 7-Zip uses a home-brewed DEFLATE encoder which is often able to achieve higher compression levels than the more common DEFLATE implementation of zlib, at the expense of compression speed. The 7-Zip deflate encoder implementation is available separately as part of the AdvanceCOMP suite of tools.
[edit] Variations
In the form of p7zip, the command line version has been ported for use on Unix-like systems including Linux, FreeBSD and Mac OS X. There are several GUI frontends for p7zip such as Q7Z. An alternate GUI for 7-Zip on Windows, #7Z, has been released by the same developers.[3]
Two command line versions are provided: 7z.exe, using external libraries; and a stand-alone executable 7za.exe containing built-in modules. However, 7za's compression/decompression support is limited to 7z, ZIP, gzip, bzip2, Z and tar formats. A 64-bit version is available for 64-bit editions of Windows, with support for large memory maps leading to faster compression. All versions support multi-threading.
A freeware application based on the 7-Zip engine, jZip, is available for Microsoft Windows. Its stated focus is an easier, more streamlined user interface than 7-Zip.
[edit] Features
7-Zip supports many features, some which may not be found in popular commercial compression software.
- For encryption, 7z archives support the 256-bit AES cipher. Encryption can be enabled for both files and the 7z directory structure. When the directory structure is encrypted, users are required to supply a password to see the filenames contained within the archive, unless only the data was encrypted but not the filenames. WinZip-developed AES encryption standard is also available in 7-Zip to encrypt ZIP archives with AES 256-bit, but it doesn't offer filename encryption like in 7z archives.[4]
- 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.
- Multiple CPU / core / threading settings can be configured.
- Ability to attempt to open EXE files as archives. (Useful for decompressing data from inside many "SetUp" or "Installer" or "Extract" type programs without having to launch them)
- Ability to browse and extract data from ISO data images/archives.
- 7-Zip has the ability to unpack archives with corrupted filenames, renaming the files as required.
- 7-Zip has the ability to create self-extracting archives although cannot do so for multi-volume archives.
[edit] See also
[edit] Notes
[edit] External links
- 7-Zip 7-Zip Home
- SourceForge.net: 7-Zip
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