Ever wonder what those .zip extensions on PC files mean? Well, in the Mac world we have .sit and .sea, which refer to a method of compression. ZipIt for the Mac OS lets you compress files in the ZIP format, as well as decompress files you may come across that are zipped up. The ZIP format is the most commonly used compression method available for DOS and Windows users. Version 1.4 adds the ability to create self-extracting archives on the Mac and PC, and there are numerous bug fixes designed to make this a more reliable compression program.