The root directory is identified by a single character: slash (/). To name one of the major directories directly under root, type slash (/) to represent root, followed by the directory's own name, as in /usr. The slash in front of usr tells you that usr is a subdirectory of root.
/u or /user user directory/bin binary directory
/dev device directory
/etc miscellaneous directory (usually system files)
/tmp temporary directory
The home directory on the central Unix Service (DXCERN) is: /u/gg/userid/ where gg refers to the user's computing group code and userid is the login name and for AFS it is /afs/cern.ch/user/X/userid where X is the first letter of the login-name.