A file with one of these suffixes or file extensions (e.g., “myfile.zip”) has been saved (encoded) in a special compressed format. The “.hqx” and “.zip” and “.sit” formats all are “lossless” — the content and quality of the file’s data are preserved exactly.
Why are these formats used? The first three were invented to correctly transfer data files across the Internet, between different services and computers. They also permit transferring several files in a single “attachment” or archive. Zip’d files, and to a greater degree Stuff’d files, are smaller than uncompressed files. (JPEG or “.jpg” files already are compressed, however.)
The “.pdf” format, established by Adobe, stands for “portable document format.” The PDF format preserves the content and layout of highly formatted documents across all types of computers. For example, a 3-column newsletter will look the same on a PC and Mac. The quality of embedded images and other items may vary, depending on how the PDF document was prepared.
Viewing PDF files requires downloading Adobe’s free Adobe Reader program (or a PDF browser plug-in). Most new computers come with Adobe Reader pre-installed. On Mac OS X systems, the Preview program also can open and read PDF files.
Most modern computers can automatically convert (decode) “.hqx” and “.zip” files so that your word processor, for example, can view the files normally. However, “.sit” (or “.sitx”) files require the free StuffIt Expander or StuffIt Standard program to decompress them.