File systemSee Filing system for this term as it is used in libraries and offices\n---- In computing, a file system is a method for storing and organizing computer files and the data they contain to make it easy to find and access them. File systems may use a storage device such as a hard disk or CD-ROM and involve maintaining the physical location of the files, or they may be virtual and exist only as an access method for virtual data or for data over a network (e.g. NFS). More formally, a file system is a set of abstract data types that are implemented for the storage, hierarchical organization, manipulation, navigation, access, and retrieval of data.
File systems and operating systems\nMost operating systems provide a file system, as a file system is an integral part of any modern operating system. Early microcomputer operating systems' only real task was file management - a fact reflected in their names (see DOS and QDOS). Because of this, there needs to be an interface provided by the operating system software between the user and the file system. This interface can be textual (such as provided by a command line interface, such as the Unix shell) or graphical (such as provided by a graphical user interface, such as a file browsers). If graphically, the metaphor of the folder, containing documents, other files, and nested folders is often used (see also: directory and folder).File systems under Unix\nUnix and Unix-like operating systems assigns a device name to each device, but this is not how the files on that device are accessed. Unix creates a virtual file system, which makes all the files on all the devices appear to exist under the one hierachy. This means, in Unix, there is one root directory, and every file existing on the system is located under it somewhere. Furthermore, the Unix root directory does not have to be in any physical place. It might not be on your first hard drive - it might not even be on your computer. Unix can use a network shared resource as its root directory. To gain access to files on another device, you must first inform the operating system where in the directory tree you would like those files to appear. This process is called mounting a file system. For example, to access the files on a CD-ROM, informally, one must tell the operating system "Take the file system from this CD-ROM and make it appear under the directory /mnt". The directory given to the operating system is called the mount point - in this case it is /mnt. The /mnt directory exists on all Unix systems, and it is intended specifically for use as a mount point for temporary media like floppy disks or CDss. It may be empty, or it may contain subdirectories for mounting individual devices. Generally, only the administrator (i.e. root user) may authorize the mounting of file systems. At least one and perhaps many file systems are automatically mounted (automounting) by Unix at boot time. The system administrator can control which file systems are mounted at boot time, and can pre-determine the mount points for specific file systems. The sysadmin can also designate some file systems that may be mounted by normal users, and can specify when mounted file systems are checked for errors and backed up. All this information is stored in the file /etc/fstab, which anyone can read to discover what file systems are available and mountable by users.File systems under Plan 9\nPlan 9 was originally designed to extend some of Unix's good points, and to introduce some new ideas of its own. With respect to file systems, the Unix system of treating things as files was continued, but in Plan 9, everything is treated as a file, and accessed as a file would be. Secondly, the underlying 9P protocol was used to ensure that the difference between a file existing on a remote system and a file existing on a local system was basically nil (possibly modulo a perceptible difference in latency). This had the advantage that a device or devices, represented by files, on a remote computer, could be used as though it were the local computer's own device(s). This means that under Plan 9, multiple file servers provide access to devices, classing them as special file systems. Everything on a Plan 9 system has, then, an abstraction as a file. For example, FTP connections are not handled by a dedicated program, but instead the ftpfs server mounts the remote hierachy as part of the local filesystem hierachy, and is accessed as if the remote files were local.File systems under Windows\nMicrosoft Windows developed from an earlier operating system (MS-DOS which in turn was based on CP/M-80, which took many ideas from still earlier operating systems, notably several from DEC), and has added both file system and user interface ideas from several other sources since its first release (Unix, OS/2, etc). As such, Windows makes use of modified versions of the simple FAT and HPFS file systems, FAT32 and NTFS respectively. Older versions of the FAT file system had file name length limits, plus had restrictions on the maximum size of FAT-formatted disks or partitions. NTFS allowed Unix-style user based permission control, and inherited HPFS's automatic fragmentation control, which was a problem for FAT-based file systems. Both FAT32 and NTFS make use of drive letters in order to distinguish the physical location of files on a disk. For example, the path C:\\WINNT\\ represents a directory WINNT on the drive represented by the letter C. The C drive is most commonly used for the primary hard disk, on which Windows is installed and from which it boots. This "tradition" has become so so firmly ingrained that bugs came about in older versions of Windows which made assumptions that the drive that the operating system was installed on was C). The tradition of using "C" for the drive letter can be traced to MS-DOS, where the letters A and B were reserved for up to two floppy disk drives. Since Windows interacts with the user with a graphical user interface, its literature (help files, icon labels, ...) all refer to a "directory" as a folder which contains files. Network locations can be mapped to drive letters: for example, Z: could represent a location on a different server. Newer file systems, such as WinFS, aim to move beyond the folder metaphor and into more general categories, with greater use of metadataSee also\n* File extension\n* List of file systems \n* UnionFSExternal links\n* Filesystem Specifications and Technical Whitepapers \n\n\n\n\n\n |
||||
"Too many pieces of music finish too long after the end." - Igor Stravinsky (1882-1971) |
