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22-487: PKZIP is a file archiving computer program , notable for introducing the popular ZIP file format. PKZIP was first introduced for MS-DOS on the IBM-PC compatible platform in 1989. Since then versions have been released for a number of other architectures and operating systems. PKZIP was originally written by Phil Katz and marketed by his company PKWARE, Inc starting in 1986. The company bears his initials: "PK". By

44-537: A "tape_archiver" command, abbreviated ta , which was perhaps the forerunner of the Unix command tar . The Unix tools ar , tar , and cpio act as archivers but not compressors. Users of the Unix tools use additional compression tools, such as gzip , bzip2 , or xz , to compress the archive file after packing or remove compression before unpacking the archive file. The filename extensions are successively added at each step of this process. For example, archiving

66-632: A US$ 25 registration fee (US$ 47 with manual). To help ensure the interoperability of the ZIP format, Phil Katz published the original .ZIP File Format Specification in the APPNOTE.TXT documentation file. PKWARE continued to maintain this document and periodically published updates. Originally only bundled with registered versions of PKZIP, it was later available on the PKWARE site. The specification has its own version number, which does not necessarily correspond to

88-578: A collection of files with tar and then compressing the resulting archive file with gzip results a file with .tar.gz extension. This approach has two goals: This approach, however, has disadvantages too: The built-in archiver of Microsoft Windows as well as third-party archiving software, such as WinRAR and 7-zip , often use a graphical user interface . They also offer an optional command-line interface , while Windows itself does not. Windows archivers perform both archiving and compression. Solid compression may or may not be offered, depending on

110-403: A gzip replacement. It produces considerably smaller files (especially for source code and other structured text), but at the cost of memory and processing time (up to a factor of 4). AdvanceCOMP, Zopfli , libdeflate and 7-Zip can produce gzip-compatible files, using an internal DEFLATE implementation with better compression ratios than gzip itself—at the cost of more processor time compared to

132-405: Is compatible with gzip and speeds up compression by using all available CPU cores and threads. Data in blocks prior to the first damaged part of the archive is usually fully readable. Data from blocks not demolished by damage that are located afterward may be recoverable through difficult workarounds. The tar utility included in most Linux distributions can extract .tar.gz files by passing

154-448: Is less compact than compressed tarballs holding the same data, because it compresses files individually and cannot take advantage of redundancy between files ( solid compression ). The gzip file format is also not to be confused with that of the compress utility, based on LZW, with extension .Z ; however, the gunzip utility is able to decompress .Z files. Various implementations of the program have been written. The most commonly known

176-515: Is normally used to compress just single files. Compressed archives are typically created by assembling collections of files into a single tar archive (also called tarball ), and then compressing that archive with gzip. The final compressed file usually has the extension .tar.gz or .tgz . gzip is not to be confused with the ZIP archive format, which also uses DEFLATE . The ZIP format can hold collections of files without an external archiver, but

198-603: Is the GNU Project's implementation using Lempel-Ziv coding (LZ77). OpenBSD 's version of gzip is actually the compress program, to which support for the gzip format was added in OpenBSD 3.4. The 'g' in this specific version stands for gratis . FreeBSD , DragonFly BSD and NetBSD use a BSD-licensed implementation instead of the GNU version; it is actually a command-line interface for zlib intended to be compatible with

220-527: The z option, e.g., tar -zxf file.tar.gz , where -z instructs decompression, -x means extraction, and -f specifies the name of the compressed archive file to extract from. Optionally, -v ( verbose ) lists files as they are being extracted. zlib is an abstraction of the DEFLATE algorithm in library form which includes support both for the gzip file format and a lightweight data stream format in its API. The zlib stream format, DEFLATE, and

242-466: The lawsuit between SEA and PKWARE, Inc. Although SEA won the suit, it lost the compression war, as the user base migrated to PKZIP as the compressor of choice. Led by some BBS sysops who refused to accept or offer files compressed as .ARC files, users began recompressing any old archives that were currently stored in .ARC format into .ZIP files. The first version was released in 1989, as a DOS command-line tool, distributed under shareware model with

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264-537: The original timestamps , file attributes or access control lists. 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 . An early archiver was the Multics command archive , descended from the CTSS command of the same name, which was a basic archiver and performed no compression. Multics also had

286-543: The "g" of gzip is derived). Version 0.1 was first publicly released on 31 October 1992, and version 1.0 followed in February 1993. The decompression of the gzip format can be implemented as a streaming algorithm , an important feature for Web protocols , data interchange and ETL (in standard pipes ) applications. gzip is based on the DEFLATE algorithm, which is a combination of LZ77 and Huffman coding . DEFLATE

308-485: The 1970s, file archiving programs were distributed as standard utilities with operating systems. They include the Unix utilities ar, shar, and tar . These utilities were designed to gather a number of separate files into a single archive file for easier copying and distribution. These archives could optionally be passed through a stream compressor utility, such as compress and others. Other archivers also appeared during

330-488: The 1980s, including ARC by System Enhancement Associates, Inc. (SEA), Rahul Dhesi's ZOO , Dean W. Cooper's DWC, LHarc by Haruhiko Okomura and Haruyasu Yoshizaki and ARJ which stands for "Archived by Robert Jung". The development of PKZIP was first announced in the file SOFTDEV.DOC from within the PKPAK 3.61 package, stating it would develop a new and yet unnamed compression program. The announcement had been made following

352-430: The GNU implementations' options. These implementations originally come from NetBSD , and support decompression of bzip2 and the Unix pack format. An alternative compression program achieving 3-8% better compression is Zopfli . It achieves gzip-compatible compression using more exhaustive algorithms, at the expense of compression time required. It does not affect decompression time. pigz , written by Mark Adler,

374-596: The PKZIP version numbers, especially with PKZIP 6 or later. At various times, PKWARE adds preliminary features that allows PKZIP products to extract archives using advanced features, but PKZIP products that create such archives won't be available until the next major release. Although popular at the time, ZIP archives using PKZIP 1.0 compression methods are now rare, and many unzip tools such as 7-Zip are able to read and write several other archive formats. Shrinking uses dynamic LZW , on which Unisys held patents. A patent for

396-477: The Reduce Algorithm had also been filed on June 19, 1984, long before PKZIP was produced. File archiver Basic archivers just take a list of files and concatenate their contents sequentially into archives. The archive files need to store metadata, at least the names and lengths of the original files, if proper reconstruction is possible. More advanced archivers store additional metadata, such as

418-558: The form of headers and trailers. Still, the gzip format is sometimes recommended over zlib because Internet Explorer does not implement the standard correctly and cannot handle the zlib format as specified in RFC 1950. zlib DEFLATE is used internally by the Portable Network Graphics (PNG) format. Since the late 1990s, bzip2 , a file compression utility based on a block-sorting algorithm, has gained some popularity as

440-575: The gzip file format were standardized respectively as RFC 1950, RFC 1951, and RFC 1952. The gzip format is used in HTTP compression , a technique used to speed up the sending of HTML and other content on the World Wide Web . It is one of the three standard formats for HTTP compression as specified in RFC 2616. This RFC also specifies a zlib format (called "DEFLATE"), which is equal to the gzip format except that gzip adds eleven bytes of overhead in

462-433: The product: Windows itself does not support it; WinRAR and 7-zip offer it as an option that can be turned on or off. Gzip gzip is a file format and a software application used for file compression and decompression . The program was created by Jean-loup Gailly and Mark Adler as a free software replacement for the compress program used in early Unix systems, and intended for use by GNU (from which

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484-452: Was intended as a replacement for LZW and other patent -encumbered data compression algorithms which, at the time, limited the usability of the compress utility and other popular archivers. "gzip" is often also used to refer to the gzip file format, which is: Although its file format also allows for multiple such streams to be concatenated (gzipped files are simply decompressed concatenated as if they were originally one file), gzip

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