This hour focused on the Unix hierarchical file system. You’ve learned the organization of a hierarchical file system, how Unix differs from Macintosh and DOS systems, and how Unix remembers preferences with its hidden dot files. This hour also explained the difference between relative and absolute filenames, and you’ve learned about the . and .. directories. You learned four new commands: env to list your current environment, echo to show a particular value, cd to change directories, and pwd to find your present working directory location.