7z
Encyclopedia : 7 : 7Z : 7Z : 7z
7z is a compressed archive file format that supports several different data compression algorithms. The format was initially implemented by the 7-Zip archiver; both the file format and 7-Zip's implementation are publicly available under the GNU LGPL licence.
The MIME type of 7z is application/x-7z-compressed.
Contents
Features and enhancements
The 7z format provides the following main features:- Open, modular architecture (which allows any compression, conversion, or encryption method to be used)
- High compression ratio (depending on which compression method is used)
- Strong AES-256 encryption
- Large file support (up to approximately 16 exabytes)
- Unicode file names
- Support for solid compression
- Compression of archive headers
Encryption
The 7z format supports encryption with the AES algorithm with a 256-bit key. The key is generated from a user-supplied passphrase using an algorithm based on the SHA-256 hash algorithm (a large number of iterations are used to make a brute-force search for the passphrase more difficult).Compression methods
The format's open architecture allows additional compression methods to be added to the standard.The following methods are defined in the current version:
- LZMA - Improved and optimized version of LZ77 algorithm, using Markov chains/entropy coding and Patricia tries.
- PPMD - Dmitry Shkarin's 2002 PPMdH (PPMII/cPPMII) with small changes: PPMII is an improved version of the 1984 PPM compression algorithm (prediction by partial matching).
- BCJ - Converter for 32-bit x86 executables, see LZMA. Compresses target addresses of near jumps and calls.
- BCJ2 - Converter for 32-bit x86 executables, see LZMA. Jump, call and conditional jump targets addresses are compressed separately.
- Bzip2 - Standard Burrows-Wheeler transform algorithm. Bzip2 uses (faster) Huffman coding, while Bzip is using (stronger) arithmetic coding.
- DEFLATE - Standard LZ77-based algorithm (also used in ZIP and gzip formats.)
Implementations
The following archiving software currently support the 7z archive format:- 7-Zip and p7zip
- 7zX
- Ark
- ExtractNow
- EZ 7z
- File Roller
- IZArc
- PowerArchiver
- QuickZip
- SimplyZip
- Squeez
- TUGZip
- WinRAR
- WinZip
- ZipGenius
See also
- redirect
External links
- [7z Format] — general description about the 7z archive format
- [7-Zip] — the original file archiver for Microsoft Windows
- [7zX] - 7z compressor for Mac OS X. This utility has some unique features: it can create safe 7-Zip archives (.s7z), that will preserve Macintosh resource forks and Spotlight metadata, and Self Extracting Archives that will open on any computer with Mac OS X 10.3 or newer even if the user doesn't have a 7-Zip tool.
- [p7zip] — a port of 7-Zip for Unix-like systems
- [Dmitry Shkarin (Institute for Dynamics of Geospheres, Moscow, Russia) 2002: PPM: One Step to Practicality]
From Wikipedia, the Free Encyclopedia. Original article here. Support Wikipedia by contributing or donating.
All text is available under the terms of the GNU Free Documentation License See Wikipedia Copyrights for details.