If you program in REALbasic, these classes allow you to create and read .zip files. ZIP files are the most popular compression archive format on DOS/Windows systems. Compatible with programs such as: WinZip, PKZip, ZipIt, Aladdin Expander and Stuffit DropZip. Another nice feature is that one can create and read "snapshot" archives, for incremental backups of the same set of files and folders.
Source code included.