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. (Note: to change your default shell, send an email message to csstaff@cs.princeton.edu. You can determine your shell by printing the SHELL environment variable with 'echo $SHELL' Users of csh The environment setting files for csh are .login, .logout, and .cshrc. Every new csh user will automatically have these three files in their top-level directory. The file .login serves the purpose of trying to recognize your terminal type and setting up your computing environment. If you have some familiarity with the UNIX operating system, you are welcome to modify these files. As the comments in the files indicate, we ask that you do not remove or comment out the line sourcing the common department files in /usr/local/etc. If you have somehow configured your environment into a strange state and wish to revert back to the initial department default configuration, you can do so by copying the default .login, .logout and .cshrc files from the directory '/usr/local/etc'. The files are named login.initial, logout.initial, and cshrc.initial, respectively. Users of bash The environment setting file for bash is .bashrc. Every new bash user will automatically have this file in their top-level directory. It serves the purpose of trying to recognize your terminal type and setting up your computing environment. If you have some familiarity with the UNIX operating system, you are welcome to modify this file. As the comments in the file indicate, we ask that you do not remove or comment out the line sourcing the common department files in /usr/local/etc. If you have somehow configured your environment into a strange state and wish to revert back to the initial department default configuration, you can do so by copying the default .bashrc file from the directory '/usr/local/etc'. The file is named bashrc.initial.