![]() ![]() Since Katz had implemented and made various improvements to the algorithm in his PKArc program, it was natural to use that experience when creating his new file format. (For more history, see the previous article.)Īrc used a compression algorithm called LZW. Following a legal dispute with the original program's creators, the "Arc Wars", Katz created his own file format: the Zip file. Phil Katz started out in the compression business by creating his own version of the then-popular Arc program, which he called PKArc. Who provided valuable feedback on drafts of this article. Let's do data compression like it's 1989! All the code is available in hwzip-2.1.zip. The previous article is not required reading, but provides useful background for readers without previous knowledge about Zip files. This article describes and implements the Shrink, Reduce, and Implode compression methods. From a historical perspective, the older methods allow us to trace the evolution from the roots of PKZip to the Deflate method that we use today. For example, the first method used LZW compression, which popularized dictionary compression, gained notoriety due to patent issues, and is still widely used in GIF files. ![]() While the earlier methods are not in themselves relevant anymore, the techniques involved are still both interesting and relevant. #JASON SUMMERS LODE RUNNER 2 ZIP FILE#Zip files support many different compression methods, however, and although Deflate is the one most commonly used today, it was not added until several years after the introduction of the Zip file format. I was fascinated by the subject: the magic of data compression, and how this truly ubiquitous file format works. Last year I wrote a long article about Zip files, covering the history, describing the Deflate compression method in great detail, and showing the implementation of a simple Zip program. ![]()
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