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Zip (File Format)

Zip (File Format)

ZIP is an archive format of a file. It ensures lossless data compression through a variety of compression algorithms, though DEFLATE is the most widely used. A .ZIP file typically contains one or more files that have been compressed. This format created in 1989 by Phil Katz was first used in PKWARE, Inc.'s PKZIP utility instead of the previous ARC compression format by Thom Henderson. Currently many software utilities support the .ZIP format. For example, versions of Microsoft Windows have had built-in .ZIP support (under the name "compressed folders") since 1998. Apple has added built-in .ZIP support to Mac OS X 10.3 (via BOMArchiveHelper, now Archive Utility). Also most free operating systems feature built in support for .ZIP like Windows and Mac OS X do.

.ZIP files typically use the file extensions ".zip" or ".ZIP". When searching a file system, users will spot graphical icons representing .ZIP files


Zip (File Format) Phil Katz

Phil Katz of PKWARE created the .ZIP file format after Systems Enhancement Associates (SEA) sued his company for using the archiving products that were derivatives of SEA's ARC archiving system. The name "zip" which means "move at high speed" was introduced by Robert Mahoney, Katz's friend. This name implies that the new product would be much faster than ARC or any other compression formats that existed at that time. The first version of .ZIP File Format Specification was part of PKZIP 0.9 package under the file APPNOTE.TXT in 1989. The .ZIP file format was released into the public domain


ZIP file is an archive that allows contained files to be compressed and stored using many different methods, or just stored without being compressed. Since the .ZIP files are compressed individually users can easily extract them, or add new ones, without compressing or decompressing to the entire archive.

A directory is placed at the end of a .ZIP file so that .ZIP readers could load the list of files without reading the entire .ZIP archive. .ZIP archives can also contain additional data not related to the .ZIP archive. This function of a .ZIP archive makes it a self-extracting archive. As the catalog is stored at the end it is possible to hide a zipped file by appending it to another file, for example, a GIF image file.

The .ZIP format employs a 32-bit CRC algorithm with two copies of the directory structure of the archive to ensure better protection against data loss.


Zip (File Format) Zip and Rar

There are several .ZIP tools available, and a number of .ZIP libraries for different programming fields, with licenses used for commercial and open source. For example, WinZip is run on Windows while WinRAR, IZarc, Info-ZIP, 7-Zip, PeaZip, B1 Free Archiver and DotNetZip are used on other platforms. Some of the tools mentioned above feature library or programmatic interfaces.

The examples of open source development libraries are libzip and Info-ZIP. For Java: Java Platform, Standard Edition includes the package "" for standard .ZIP files; the Zip64File library supports large files of over 4 GB; and there is Apache Ant tool, a more complete implementation under the Apache Software License

The Info-ZIP implementations also support Unix file system features, including support for symbolic links, user and group IDs, file permissions, as well as the error correction capabilities built into the .ZIP compression format.

Versions of Microsoft Windows also contain support for .ZIP compression in Explorer known as "Compressed Folders" feature. Unfortunately not all .ZIP features are supported by the Windows Compressed Folders function. For example, AES Encryption and Unicode entry encoding don't support the Compressed Folders feature in Windows versions released prior Windows 8.

In 2006 Microsoft Office implemented the zip archive format for their Office Open XML .docx, .xlsx, .pptx, etc. files, but it became the default file format with Microsoft Office 2007.