You get a "Command not found" message from Unix.

Either the program is not installed, or the PATH variable in your environment is not pointing to it.

Let's assume the program you want to execute is called "foo".

• Type "whereis foo" and see if you get a path name. If you do, you can invoke it using a full path name (e.g. /usr/local/bin/foo) or add the path to your PATH variable in your .cshrc file, then "source ~/.cshrc; rehash"
• Do a full disk search: "find / -name foo -print" and see if you get a hit. Then, as above, invoke it using a full path name or add it to your PATH variable in your .cshrc.
• You have located the program, and your .cshrc seems correct. Type "source ~/.cshrc; rehash" and try again. If this doesn't work, invoke it using the full path name, e.g. /usr/local/bin/foo.