Special Account Files (shell environment)
Certain file names (files beginning with a ".") will not appear on your screen when you type the 'ls' command. However, you can see these file names by typing the command 'ls -a'. Some of these files serve special purposes such as setting up your computing environment when you login. The actual files used depend on your default shell. Your default shell was specified when your account was created. Common choices for the shell are csh or bash.
