What is a directory?
A directory (also known as a folder) is an IT element that can contain files.
Imagine a large dresser containing drawers in which files or other drawers are stored. A directory can in fact contain:
Using the example of the dresser, the largest entity containing other entities is the dresser: it cannot be found in a drawer!
In IT language, this entity is known as the root directory (sometimes simply referred to as "root"): it is the lowest-level entity since it can contain files or directories but cannot itself be contained in a directory!
It is designated by "\" (in Windows environment) or by "/" (in UNIX/Linux environment). There is only one root in the UNIX system and one for each partition in Microsoft Windows.
A directory containing another directory is known as a "parent directory". When moving from a directory to a parent directory, the latter is designated by "..." on most systems (type "cd..." in DOS or UNIX to access a parent directory).
Let us look at the layout of a directory system in Windows 95:
In this example directory2 is the parent of directory20 and directory 21. "directory2" in relation to "directory20" will be designated "..." The root (d:\) in relation to "directory20" will be designated "..\.." since they are separated by two relationships.
The concept of path
The path is the succession of directories starting from the root and leading to the required file. In Windows systems, a path will be written x:\directory1\directory2\ whereas in a Unix system it will be written /directory1/directory2/.