understanding file and filnames

A computer file is a block of arbitrary information, or resource for storing information, which is available to a computer program and is usually based on some kind of durable storage. A file is durable in the sense that it remains available for programs to use after the current program has finished. Computer files can be considered as the modern counterpart of paper documents which traditionally were kept in offices' and libraries' files, which are the source of the term.

A filename is a special kind of string used to uniquely identify a file stored on the file system of a computer. Some operating systems also identify directories in the same way. Different operating systems impose different restrictions on length and allowed characters on filenames.

Extension is place deixis that indicates that a location has length or area.

file types
.com
.org


Its important so that we wont have mistakes in Address.

links:
http://en.wikipedia.org/wiki/Computer_file
http://en.wikipedia.org/wiki/Filename
http://www.sil.org/linguistics/GlossaryOfLinguisticTerms/WhatIsExtension.htm