A directory is a file system catalogue structure that contains the references to the computer files and other directories.
Files are organized by storing related files in the same directory. There are many ways to display the directories in the system. The most common is the hierarchical file system in which all the directories and files are stored in tree format. A directory stored inside another directory is called a subdirectory. This relationship is termed as parent and child between a directory and subdirectory. The top most directory is called as root directory. To display all the directories in the UNIX and Linux based OS, ls command is used to list all the directories in the system. ???????