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7-Zip
7-Zip Logo
7-Zip.png
7-Zip
Developer(s) Igor Pavlov
Initial release 2000
Stable release 4.65 / February 3, 2009; 13 month(s) ago (2009-02-03)
Preview release 9.11 beta / March 15, 2010; 0 day(s) ago (2010-03-15)
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 www.7-zip.org

7-Zip is an open source file archiver designed originally for Microsoft Windows. 7-Zip operates with the 7z archive format, and can read and write to several other archive formats. The program can be used from a 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.

7-Zip is distributed under the GNU Lesser General Public License. It was the winner of the SourceForge.net 2007 community choice awards for "Technical Design" and for "Best Project".[2]

Contents

Formats

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, LZMA2, 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 GB in size, backed by a range coder.

The native 7z file format is open and modular. All filenames are stored as Unicode.[3]

The official 7z file format specification is distributed with the program's source code. The specification can be found in plain text format in the doc\ subdirectory of the source code distribution.

Other supported formats

7-Zip supports a number of other compression, and non-compression, archive formats including:

Packing/unpacking of ZIP, gzip, bzip2, tar and, in betas for version 9, xz.

Unpacking only: Microsoft cabinet (CAB) files, RAR, MSLZ, SWF, FLV ARJ, Z, LHA, cpio, smzip, JAR, ISO CD/DVD images (7Zip version 4.42 and up), DMG, HFS, rpm and Debian deb archives.

According to the 7-Zip website, since version 4.65 (from 2009-02-03), 7-Zip can unpack the following formats in addition to the formats it fully supports: ARJ, CAB, CHM, CPIO, DEB, DMG, HFS, ISO, LZH, LZMA, MSI, NSIS, RAR, RPM, UDF, WIM, XAR and Z.

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, meaning that 7-Zip can be used to check if a binary file is an archive. Similarly, some executable programs (.EXEs) may be opened as archives and have their contents extracted by 7-Zip.

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.

Variants

In the form of p7zip, the command line version has been ported for use on Unix-like systems including Linux, FreeBSD, Mac OS X and AmigaOS 4. 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.[4] Also a GUI for Mac OS X is available at the name of keka.[5]

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.

Features

7-Zip supports many features, including:

  • 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 as in 7z archives.[6]
  • 7-Zip supports volumes of dynamically variable sizes, allowing use for backups on removable media such as writable CDs and DVDs.
  • When in 2-panel mode, 7-Zip can be used as a basic orthodox file manager.
  • Multiple CPU / core / threading settings can be configured.
  • Ability to attempt to open EXE files as archives, allowing the decompression of data from inside many "SetUp" or "Installer" or "Extract" type programs without having to launch them
  • 7-Zip can unpack archives with corrupted filenames, renaming the files as required.
  • 7-Zip can create self-extracting archives although cannot do so for multi-volume archives.

Version numbering scheme change

After version 4.65, 7-Zip switched to a "Year.Revision" version numbering scheme, similar to the one used by Ubuntu and some other projects. The first release under the new scheme was 9.07 beta. The large jump was met with some criticisms.[7] Though it should be noted that this appears to be from a single person.

See also

Notes

External links








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