Shrink, Reduce, and Implode: The Legacy Zip Compression Methods
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. While the earlier methods are not in themselves relevant today, the techniques involved are still both interesting and relevant. For example, the first method used LZW compression, which popularised dictionary compression, gained notoriety due to patent issues, and is still widely used in GIF files. 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.