There are a wide variety of compression methods in use. You can tell which method was used by the last one to three letters at the end of a file. Here are some of the more common ones and what you'll need to un- compress the files they create (most of these decompression programs can be located through archie).
.txt or .TXT By itself, this means the file is a document, rather than a program.
.ps or .PS A PostScript document (in Adobe's page description language). You can print this file on any PostScript capable printer, or use a previewer, like GNU project's GhostScript.
.doc or .DOC Another common "extension" for documents. No decompression
is needed, unless it is followed by:
.Z This indicates a Unix compression method. To uncompress,
type
uncompress filename.Z
and hit enter at your host system's command line. If the file is a compressed text file, you can read it online by instead typing
zcat filename.txt.Z |more
u16.zip is an MS-DOS program that will let you download such a file and uncompress it on your own computer. The Macintosh equivalent program is called MacCompress (use archie to find these).
.zip or .ZIP These indicate the file has been compressed with a common MS-DOS compression program, known as PKZIP (use archie to find PKZIP204.EXE). Many Unix systems will let you un-ZIP a file with a program called, well, unzip.