Introduction to the Unix command line
Most popular Operating Systems (OS), like Microsoft Windows and Mac OS X, offer primarily (but not exclusively) graphical interfaces. The user interacts with files and programs by pointing and clicking with a mouse. Unix, which is considerably older than Windows or OS X, offers (multiple) graphical interfaces, but Unix originally presented a command line interface. The user interacts with the OS by typing commands at a text prompt and reading textual output from programs. The command line interface is alive and well in Unix today, and many Unix users consider it the most powerful and efficient system for basic operations like navigating around the file system.