)A sequence of symbols and names that identifies a file. Every file has a name, called a filename, so the simplest type of pathname is just a filename. If you specify a filename as the pathname, the operating system looks for that file in your current working directory. However, if the file resides in a different directory, you must tell the operating system how to find that directory. You do this by specifying a path that the operating system must follow.
The pathname always starts from your working directory or from the root directory. Each operating system has its own rules for specifying paths. In DOS systems, for example, the root directory is named \, and each subdirectory is separated by an additional backslash. In UNIX, the root directory is named /, and each subdirectory is followed by a slash. In Macintosh environments, directories are separated by a colon.