In computing

Computing

Computing is usually defined as the activity of using and improving computer hardware and software. It is the computer-specific part of information technology...

, a directory structure is the way an operating system

Operating system

An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...

's file system

File system

A file system is a means to organize data expected to be retained after a program terminates by providing procedures to store, retrieve and update data, as well as manage the available space on the device which contain it. A file system organizes data in an efficient manner and is tuned to the...

 and its files are displayed to the user. Files are typically displayed in a Hierarchical tree structure.

File names and extensions

A filename

Filename

The filename is metadata about a file; a string used to uniquely identify a file stored on the file system. Different file systems impose different restrictions on length and allowed characters on filenames.A filename includes one or more of these components:...

 is a special kind of string used to uniquely identify a file stored on the file system of a computer. Before the advent of 32-bit

32-bit

The range of integer values that can be stored in 32 bits is 0 through 4,294,967,295. Hence, a processor with 32-bit memory addresses can directly access 4 GB of byte-addressable memory....

 operating systems, file names were typically limited to short names (6 to 14 characters in size). Modern operating systems now typically allow much longer filenames (more than 250 characters per pathname

Path (computing)

A path, the general form of a filename or of a directory name, specifies a unique location in a file system. A path points to a file system location by following the directory tree hierarchy expressed in a string of characters in which path components, separated by a delimiting character, represent...

 element).

Windows, DOS, and OS/2

In DOS

DOS

DOS, short for "Disk Operating System", is an acronym for several closely related operating systems that dominated the IBM PC compatible market between 1981 and 1995, or until about 2000 if one includes the partially DOS-based Microsoft Windows versions 95, 98, and Millennium Edition.Related...

, Windows

Microsoft Windows

Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...

, and OS/2

OS/2

OS/2 is a computer operating system, initially created by Microsoft and IBM, then later developed by IBM exclusively. The name stands for "Operating System/2," because it was introduced as part of the same generation change release as IBM's "Personal System/2 " line of second-generation personal...

, the root directory is "drive:\", for example, the root directory is usually "C:\". The directory separator is usually a "\", but the operating system also internally recognizes a "/". Physical and virtual drives are named by a drive letter, as opposed to being combined as one. This means that there is no "formal" root directory, but rather that there are independent root directories on each drive. However, it is possible to combine two drives into one virtual drive letter, by setting a hard drive into a RAID

RAID

RAID is a storage technology that combines multiple disk drive components into a logical unit...

 setting of 0.

Common Windows directory structure

$Recycle.Bin: Recycle folder (hidden)
Boot: Boot folder (hidden, since Windows Vista)
Documents and Settings: User folders (up to Windows XP, legacy and hidden since Windows Vista)
inetpub: IIS folder (if installed)
PerfLogs: created by Windows Performance Information and Tools
Program Data: Program data (hidden, since Windows Vista)
Program Files: Program files
Program Files (x86): Program files for x86 (32 bit) programs on a x64 Windows
Recovery: System recovery informations (hidden)
System Volume Information: Part of system restore (hidden)
Users: User folders (since Windows Vista)
Windows: Windows folder

Unix

Unix

Unix

Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...

 and Unix-like

Unix-like

A Unix-like operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification....

 operating systems use Filesystem Hierarchy Standard

Filesystem Hierarchy Standard

The Filesystem Hierarchy Standard defines the main directories and their contents in Linux operating systems. For the most part, it is a formalization and extension of the traditional BSD filesystem hierarchy....

as the common form for their directory structures. All files and directories appear under the root directory "/", even if they are stored on different physical devices.