View source for PKZIP


{{Short description|File archiving software}}
{{Use mdy dates|date=January 2017}}
{{primary sources|date=July 2008}}
{{Infobox software
|logo                    = 
|screenshot              = Pkzip-2.04g-dos.png
|screenshot size         = 250px
|caption                 = PKZIP 2.04g for DOS, circa 1993
|collapsible             = 
|author                  = [[Phil Katz]]
|developer               = PKWARE Inc
|released                = <!-- {{Start date|YYYY|MM|DD}} -->
|discontinued            = 
|latest release version  = 
|latest release date     = <!-- {{Start date and age|YYYY|MM|DD}} -->
|latest preview version  = 
|latest preview date     = <!-- {{Start date and age|YYYY|MM|DD}} -->
|programming language    = 
|operating system        = 
|platform                = 
|size                    = 
|language                = 
|genre                   = archiving and data compression tool
|license                 = [[proprietary software|proprietary]]
|website                 = http://www.pkware.com/
}}

'''PKZIP''' is a [[File archiver|file archiving]] [[computer program]], notable for introducing the popular [[ZIP (file format)|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".

==History==
[[File:PKZIP floppy.jpg|thumb|PKZIP on a [[floppy disk]]]]
By the 1970s, file archiving programs were distributed as standard utilities with operating systems.  They include the [[Unix utilities]] ar, shar, and [[tar (computing)|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 (software)|compress]] and others.

Other archivers also appeared during the 1980s, including [[ARC (file format)|ARC]] by System Enhancement Associates, Inc. (SEA), Rahul Dhesi's [[Zoo (file format)|ZOO]], Dean W. Cooper's DWC, [[LHA (file format)|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 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 [[Bulletin board system|BBS]] [[sysop]]s 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 a US$25 registration fee (US$47 with manual).

==.ZIP file format==
{{Main|ZIP (file format)}}

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.<ref name="Buchholz, JMU, 2015"/> Originally only bundled with registered versions of PKZIP, it was later available on the PKWARE site.<ref name="Buchholz, JMU, 2015"/>

The specification has its own version number, which does not necessarily correspond to 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.

==Compatibility==
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.

==Patents==
Shrinking uses dynamic [[Lempel–Ziv–Welch|LZW]], on which [[Unisys]] held patents. A patent for the Reduce Algorithm had also been filed on June 19, 1984, long before PKZIP was produced.<ref>{{cite web|url=http://www.faqs.org/faqs/compression-faq/part1/section-7.html|title=comp.compression Frequently Asked Questions (part 1/3)Section - [8] What about patents on data compression algorithms?|work=faqs.org|access-date=October 4, 2007|archive-date=May 13, 2008|archive-url=https://web.archive.org/web/20080513135306/http://www.faqs.org/faqs/compression-faq/part1/section-7.html|url-status=live}}</ref>

==See also==
* [[Comparison of file archivers]]
* [[List of archive formats]]
* [[PKLite]]

==References==
{{Reflist|refs=
<ref name="Buchholz, JMU, 2015">{{Cite web |url=https://users.cs.jmu.edu/buchhofp/forensics/formats/pkzip.html |title=The structure of a PKZip file |last=Buchholz |first=Florian |year=2006 |website=[[James Madison University]] |access-date=September 30, 2020 |url-status=live |archive-url = https://web.archive.org/web/20150412205749/https://users.cs.jmu.edu/buchhofp/forensics/formats/pkzip.html |archive-date=April 12, 2015 |quote=This document describes the on-disk structure of a PKZip (Zip) file. The documentation currently only describes the file layout format and meta information but does not address the actual compression or encryption of the file data itself. This documentation also does not discuss Zip archives that span multiple files in great detail. This documentation was created using the official documentation provided by PKWare Inc.}}</ref>
}}

==External links==

===Official===
* {{Official website|http://www.pkware.com/}}, PKWARE
* [http://www.pkware.com/business_and_developers/compression/ PKZIP from PKWARE] {{Webarchive|url=https://web.archive.org/web/20060313041206/http://www.pkware.com/business_and_developers/compression/ |date=March 13, 2006 }}
* [http://www.pkware.com/index.php?option=com_content&task=view&id=43&Itemid=90 PKZIP 2.50 for DOS]
* [http://www.pkware.com/business_and_developers/security/ SecureZIP from PKWARE] {{Webarchive|url=https://web.archive.org/web/20060313041315/http://www.pkware.com/business_and_developers/security/ |date=March 13, 2006 }}
* [http://www.pkware.com/documents/casestudies/APPNOTE.TXT APPNOTE]

===Other===
* [http://www.securezip.com/ SecureZIP Homepage]
* [http://www.esva.net/~thom/philkatz.html Commentary from SEA owner about Phil Katz, the lawsuit, and his death]
* [http://www.bbsdocumentary.com/library/CONTROVERSY/LAWSUITS/SEA/ CONTROVERSY: LAWSUITS: SEA vs. PKWARE]
** [http://www.bbsdocumentary.com/library/CONTROVERSY/LAWSUITS/SEA/judgment.txt Judgment in favor of SEA in ''SEA v. PKWARE and Phil Katz'']
* [https://web.archive.org/web/20070822125354/http://www.practicalpc.co.uk/computing/how/pkzip_dos.htm How to Use PKZIP From the Command Line]

{{Compression Software Implementations}}
{{Authority control}}

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[[Category:Data compression software]]
[[Category:File archivers]]
[[Category:Windows compression software]]