PKZIP is an archiving tool originally written by Phil Katz and marketed by his company PKWARE, Inc. The common "PK" prefix used in both PKZIP and PKWARE stands for "Phil Katz".
File compression routines date back to at least the 1960s: IBM had a compression program called SQUOZE that was commonly used to pack programs on the 709 and 7090 mainframes as part of the SHARE operating system.
By 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.
Other archivers also appeared during the 1980s, including 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 the ARC lawsuit between System Enhancement Associates (SEA), Inc. and PKWARE, Inc. Although SEA won the suit, it literally lost the compression war as the user base in protest switched to PKZIP as the compressor of choice. Led by 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. Within a year of SEA's victory, an estimated more than 95% of files available for downloading from BBS systems worldwide were compressed using PKZIP.
The first version was released in 1989 as a DOS command-line tool, distributed under shareware model with a $25US registration fee ($47US with manual).
PKZIP 0.8 (1989-01-11) initial version
PKZIP 0.9 (1989-02-10) supported Reducing algorithm (from SCRNCH by Graeme McRae) with 4 compression settings and shrinking. In addition to PKZIP and PKUNZIP, it also included ZIP2EXE, which required an external self-extracting executable header created by MAKESFX from the PKZIP executable package.
PKZIP 0.92 (1989-03-06): In addition to bug fixes, PKZIP included an option to automatically choose the best compression method for each file. New tools included with PKZIP include PKZipFix.
PKZIP 1.01 (1989-07-21) added Implode compression, while Reduced files can only be extracted from ZIP archive. Imploding was chosen based on the characteristics of the file being compressed. New utility included Thomas Atkinson's REZIP conversion utility (part of ZIP-KIT). PKZIP's default compression behavior was changed from fastest (Shrink) to best (Implode). Supported platforms include OS/2, DOS.
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