The topmost directory — the only one that is not inside another directory — is called the root, or (more commonly) just “root”.
On Unix systems, the name of the root directory is
On Windows, use
\ instead of
Because root is at the top, every file in the file system is below root.
Note: “root” is also the username of the top administrator or superuser account on Unix systems. That’s not the same as the root directory.
This is because they are both the root of their tree hierarchies: all files in the file system are below root; all users (in terms of groups and permissions) are below the root user.