You learned that much of today's software adds an application-specific filename extension to the files you save. Suppose you receive a file that has an unfamiliar extension. What software should you use to view the file? On the Web you'll find a list of filename extensions in alphabetical order at www.crosswinds.net/san-marino/~jom/filex/extensio.htm. You can also connect to a great Web reference called The PC Guide at www.pcguide.com/ref/hdd/file/fat-c.html that includes plenty of information on filenames and extensions.