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A file archiver combines a number of files together into one archive file, or a series of archive files, for easier transportation or storage. Many file archivers use lossless data compression in order to reduce the archive's size. A computer file is a collection of information that is stored in a computer system and can be identified by its full path name. ...
Lossless data compression is a class of data compression algorithms that allows the exact original data to be reconstructed from the compressed data. ...
The most basic archivers just take a list of files and concatenate their contents sequentially into the archive. In addition the archive must also contain some information about at least the names and lengths of the originals, so that proper reconstruction is possible. Most archivers also store meta-data about a file that the operating system provides, such as timestamps, ownership and access control. Metadata can refer to a number of things: Metadata (computing) Metadata (corporation) This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ...
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The process of making an archive file is called archiving or packing. Reconstructing the original files from the archive is termed unarchiving, unpacking or extracting.
Popular archive formats
Ubiquitous amongst Unix and Unix-like operating systems is the tar file format ("tape archive"). Originally intended for transferring files to and from tape, it is still used on disk-based storage to combine files before they are compressed. Other Unix-originated formats include ar and shar. Unix or UNIX is a computer operating system originally developed in the 1960s and 1970s by a group of AT&T Bell Labs employees including Ken Thompson, Dennis Ritchie, and Douglas McIlroy. ...
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In computing, the tar file format is a type of archive file format: the Tape ARchive format. ...
The archiver (also known simply as ar) is a UNIX utility that maintains groups of files as a single archive file. ...
For the Forgotten Realms fictional goddess see Shar (goddess). ...
On Windows platforms, the most widely-used archive format by far is ZIP; other popular formats are RAR and ACE. On Amigas, the standard archive format is LHA, while on Apple Macintosh computers, StuffIt is among the most common. Microsoft Windows is a family of operating systems by Microsoft for use on personal computers, although versions of Windows designed for servers, embedded devices, and other platforms also exist. ...
The ZIP file format is the most widely-used compressed file format in the IBM PC world. ...
RAR 2. ...
In computing, ACE is a proprietary data compression archive file format with superior compression compared to the ZIP file format, but at the cost of a lower compression speed. ...
The original Amiga (1985) The Amiga is a family of home/personal computers originally developed by Amiga Corporation (motto: ) as an advanced home entertainment and productivity machine. ...
LHA is a freeware compression utility and associated file format. ...
The first Macintosh computer, introduced in 1984, upgraded to a 512K Fat Mac. The Macintosh or Mac, is a line of personal computers designed, developed, manufactured, and marketed by Apple Computer. ...
StuffIt is a family of software utilities for archiving and compressing files on the Apple Macintosh, Microsoft Windows and Linux platforms: Macintosh users in particular utilise the software. ...
Unix Unlike integrated archival and compression tools like ZIP and RAR, the Unix tools ar, tar, cpio (for "archiver", "tape archiver" and "copy in/out" respectively) act as archivers but not compressors. Users of the Unix tools typically add compression by compressing the result of packing (and uncompressing before unpacking), most often using the gzip or bzip2 programs. In fact modern tar programs include an option to automatically call a (de)compression program, so that it looks just as if tar itself could handle compressed archives. This approach has two advantages: Unix or UNIX is a computer operating system originally developed in the 1960s and 1970s by a group of AT&T Bell Labs employees including Ken Thompson, Dennis Ritchie, and Douglas McIlroy. ...
gzip is short for GNU zip, a GNU free software replacement for the Unix compress program. ...
bzip2 is an open source data compression algorithm and program developed by Julian Seward. ...
- It follows the Unix toolbox concept that each program should accomplish a single but well-done task. Once a better compressor is developed, users may use that immediately, without having to give up their archiver.
- Since the whole archive is compressed, redundancy between archived files can be detected and eliminated. An archiver compressing each archived file in isolation cannot exploit these inter-file redundancies.
Its main disadvantage is that extracting one file from a compressed archive requires all the files before it to be decompressed, which may take many minutes for a large archive. Altering the underlying archive is even more inconvenient, requiring the entire file to be uncompressed, altered and then recompressed. Archivers with integrated compression perform these operations much more quickly. The Unix philosophy is a set of cultural norms and philosophical approaches to developing software based on the experience of leading developers of the Unix operating system. ...
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