Archive file

An archive file is a file that is composed of one or more files along with metadata that can include source volume and medium information, file directory structure, error detection and recovery information, file comments, and usually employs some form of lossless compression. Archive files may be encrypted in part or as a whole. Archive files are used to collect multiple data files together into a single file for easier portability and storage, or simply to compress files to use less storage space.

Computer archive files are created by file archiver software, optical disc authoring software, or disk image software that uses an archive format determined by that software. The file extension or file header of the archive file are indicators of the file format used.

Archive files are sometimes accompanied by separate parity archive (PAR) files that allow for additional error detection and recovery, particularly in recovery of missing files in a multi-file archive.

In operating systems that distinguish different file types by filename extensions, archive extensions include .zip, .rar, .7z, and .tar, (of these examples, .tar is the only non-compressed format). Java also introduced a whole family of archive extensions such as .jar and .war ('j' is was Java and 'w' is for web). They are used to exchange entire byte-code deployment. Sometimes they are also used to exchange source codes and other text/html/xml files. By default they are all compressed.

History

Archive files were originally used to store important files on alternate media, such as tapes, for preservation and recoverability^{[citation needed]}. Archive files are now commonly used for transferring files and for software distribution & installation.

See also

• File archiver
• Archive format
• Disk image
• Optical disc image