For example, DOS, Windows, OS/2, Macintosh and Unix-based operating systems (OSes) all have file systems in which files are placed somewhere in a hierarchical (tree) structure. A file is placed in a directory (folder in Windows) or subdirectory at the desired place in the tree structure.
File systems specify conventions for naming files, including the maximum number of characters in a name, which characters can be used and, in some systems, how long the file name suffix can be. A file system also includes a format for specifying the path to a file through the structure of directories.
File systems and the role of metadata
File systems use metadata to store and retrieve files. Some examples of metadata tags include:
- Date created
- Date modified
- File size
An example of a file system that capitalizes on metadata is OS X, the OS used by Macintosh hardware. It allows for a number of optimization features, including file names that can stretch to character counts of 255.
File system access
File systems can also restrict read and/or write access to a particular group of users. Passwords are the easiest way to do this.
File systems definition evolves
The file systems definition can also refer to the part of an OS or an added-on program that supports a file system. Examples of such add-on file systems include the Network File System (NFS) and the Andrew file system (AFS).