UNIX system files are organized in a hierarchy; their structure is often described as an inverted tree. At the top of this tree is the root directory, the source of the entire file system. It is designated by a / (slash). All other directories and files descend and branch out from root, as shown in the following figure:
Directory tree from root
The following section provides brief descriptions of the root directory and the system directories under it, as shown in an earlier figure.