Phil Katz’s ZIP Program
An archiving tool originally written by the late Phil Katz, and marketed by his company PKWARE, Inc.
The first version of PKZIP appeared in 1989.
It was a DOS command-line tool and was distributed as shareware with a $25 registration fee.
PKZIP 1 used three different compression algorithms, colourfully referred to as “shrinking”, “reducing” and “imploding” which were chosen based on the characteristics of the file being compressed.
Although popular at the time, files in PKZIP 1 format are now rare, and many modern unzip tools are unable to handle “shrinking” and “reducing”, although “imploding” is usually supported.