7-Zip - An open Source File Archiver

7-Zip is an open source file archive intended initially for Microsoft Windows which can be used freely. It is distributed under the GNU Lesser General Public License. 7-Zip was zealously established by Igor Pavlov and was begun in the year 1999. The SourceForge.net 2007 community choice awards awarded 7-Zip as the victor for "Technical Design" and "Best Project". As 7-Zip functions with the 7z archive format, it can interpret and write down several new archive formats. This program can be used from a command line interface, graphical user interface, or Windows shell integration.

Almost every computer can use 7-Zip. Even a computer in a commercial organization can use 7-Zip. No registration or payment is required for usingthis program. It is associated to p7zip which is a cross-platform port. The GNU LGPL license brings majority of the source code under it. For Example,the GNU LGPL + unRAR restrictions bring unRAR code under a mixed license. 7-Zip can function in / Vista / XP / 98 / 2000 / 2003/ 2008 Windows 7/ME / NT. UNIX / Linux have a port of the command line version associated to it. 7z format archives is created by default with a 7z file extension in 7-Zip. Every archive includes multiple directories and files. Security or size reduction is accomplished by means of a loaded combination of filters because of container format. These contain encryption filters, compression algorithms, and pre-processors. 7z file format is naturally an open and modular format. The entire filenames are supplied like Unicode.

The source code of the program distributes 7z file format specification officially. 7z file format originates as plain text format in the doc\ subdirectory of the source code distribution. A multiplicity of algorithms is used by the core 7z compressions like LZMA2, LZMA and bzip2. In 7z format it has high compression ratio with LZMA and LZMA2 compression. Igor Pavlov, who made his debut as part of the 7z format developed a quite new system called LZMA. A large LZ-based sliding dictionary is contained in LZMA up to 4 GiB in size and is supported by a range coder.7-zip has an extremely high overhead allocating memory for files even though it supplies file sizes of up to 16 megabytes. The data used for the tests is the main criteria to find the Compression ratio results. 7-zip can be easily compressed to 7z format than to zip format. When compared to zip compatible programs 7-Zip can be easily compressed to zip format.

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GZIP, TAR, 7z, , ZIP and WIM, XZ, BZIP2 etc, are the formats where 7-Zip supports Packing / unpacking. Whereas CAB, CHM ,ARJ, DEB, , FAT, HFS, ISO, LZH, , CPIO, Z, WIM, XAR, CramFS, LZMA, NSIS, SquashFS, UDF, NTFS, RAR, RPM, VHD, and DMG etc, are formats where only Unpacking is supported. 7-Zip provides a compression ratio of 2-10 % for ZIP and GZIP formats which is much better than the ratio supplied through PKZip and WinZip. It has strong AES-256 encryption in 7z and ZIP formats and also has self-extracting capability for 7z format. It can easily integrate with Windows Shell. It is a Powerful File Manager and has Powerful command line version. It can easily be plugged-in for FAR Manager. It has Localizations for 79 languages

If the pathname is very long, about 1 kilobyte or more memory is essential per file. For doing the actual compression, the file listing alone can grow to an order of extent larger than the memory required. Since the memory requirements go beyond the 2 GiB process limit, 32-bit systems cannot compress more than a million or so files in one archive .As such, in 64-bit systems, the process size limitation is not the same. But for defeating this limitation several gigabytes of RAM is required. The machines with less memory cannot open Archives formed on it.

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