Directory (Computing)

Jai Ganesh · 2025-01-30 17:10:34

Directory (Computing)

Gist

i) Also called folder. an organizing unit in a computer's file system for storing and locating files. In a hierarchical file system, directories can contain child directories subdirectories as well as files.
ii) a description of characteristics of a particular file, as the layout of fields within each record.

In computing, a directory is a file system cataloging structure which contains references to other computer files, and possibly other directories. On many computers, directories are known as folders, or drawers, analogous to a workbench or the traditional office filing cabinet.

Summary

An old-fashioned phone book is a directory, an alphabetical list of the people in your city or town, along with their phone number and address. These days such a directory is more often found online. In computing, a directory is also known as a folder, and it contains information about how data is stored in a computer.

A directory is a unique type of file that contains only the information needed to access files or other directories. As a result, a directory occupies less space than other types of files. File systems consist of groups of directories and the files within the directories.

Directories are used to store, arrange and segregate files on the system. They are majorly used to manage things when there are a large number of files by arranging the code within different directories. A directory, also known as a folder, is a group of files and subdirectories.

A directory is the virtual equivalent of a physical file cabinet. In other words, it's a container for organizing digital data. Unlike a folder, which can only store files, a directory can store files, subdirectories, and other directories.

In computing, a directory is a file system cataloging structure which contains references to other computer files, and possibly other directories. On many computers, directories are known as folders, or drawers, analogous to a workbench or the traditional office filing cabinet.

Details

In computing, a directory is a file system cataloging structure which contains references to other computer files, and possibly other directories. On many computers, directories are known as folders, or drawers, analogous to a workbench or the traditional office filing cabinet. The name derives from books like a telephone directory that lists the phone numbers of all the people living in a certain area.

Files are organized by storing related files in the same directory. In a hierarchical file system (that is, one in which files and directories are organized in a manner that resembles a tree), a directory contained inside another directory is called a subdirectory. The terms parent and child are often used to describe the relationship between a subdirectory and the directory in which it is cataloged, the latter being the parent. The top-most directory in such a filesystem, which does not have a parent of its own, is called the root directory.

The freedesktop.org media type for directories within many Unix-like systems – including but not limited to systems using GNOME, KDE Plasma 5, or ROX Desktop as the desktop environment – is "inode/directory". This is not an IANA registered media type.

Overview

Diagram of a hierarchical directory tree. The root directory is here called "MFD", for Master File Directory. Usually a file can only be in one directory at a time, but here File 2 is hard linked so it appears in two directories.
Historically, and even on some modern embedded systems, the file systems either had no support for directories at all or had only a "flat" directory structure, meaning subdirectories were not supported; there were only a group of top-level directories, each containing files. In modern systems, a directory can contain a mix of files and subdirectories.

A reference to a location in a directory system is called a path.

In many operating systems, programs have an associated working directory in which they execute. Typically, file names accessed by the program are assumed to reside within this directory if the file names are not specified with an explicit directory name.

Some operating systems restrict a user's access only to their home directory or project directory, thus isolating their activities from all other users. In early versions of Unix the root directory was the home directory of the root user, but modern Unix usually uses another directory such as /root for this purpose.

In keeping with Unix philosophy, Unix systems treat directories as a type of file. Caveats include not being able to write to a directory file except indirectly by creating, renaming and removing file system objects in the directory and only being able to read from a directory file using directory-specific library routines and system calls that return records, not a byte-stream.

Folder metaphor

The name folder, presenting an analogy to the file folder used in offices, and used in a hierarchical file system design for the Electronic Recording Machine, Accounting (ERMA) Mark 1 published in 1958 as well as by Xerox Star, is used in almost all modern operating systems' desktop environments. Folders are often depicted with icons which visually resemble physical file folders.

There is a difference between a directory, which is a file system concept, and the graphical user interface metaphor that is used to represent it (a folder). For example, Microsoft Windows uses the concept of special folders to help present the contents of the computer to the user in a fairly consistent way that frees the user from having to deal with absolute directory paths, which can vary between versions of Windows, and between individual installations. Many operating systems also have the concept of "smart folders" or virtual folders that reflect the results of a file system search or other operation. These folders do not represent a directory in the file hierarchy. Many email clients allow the creation of folders to organize email. These folders have no corresponding representation in the filesystem structure.

If one is referring to a container of documents, the term folder is more appropriate. [citation needed] The term directory refers to the way a structured list of document files and folders are stored on the computer. The distinction can be due to the way a directory is accessed; on Unix systems, is usually referred to as a directory when viewed in a command line console, but if accessed through a graphical file manager, users may sometimes call it a folder.

Lookup cache

Operating systems that support hierarchical filesystems (practically all modern ones) implement a form of caching to RAM of recent path lookups. In the Unix world, this is usually called Directory Name Lookup Cache (DNLC), although it is called dcache on Linux.

For local filesystems, DNLC entries normally expire only under pressure from other more recent entries. For network file systems a coherence mechanism is necessary to ensure that entries have not been invalidated by other clients.

Additional Information

In computing, a directory is a file system cataloging structure which contains references to other computer files, and possibly other directories. On many computers, directories are known as folders, or drawers, analogous to a workbench or the traditional office filing cabinet. The name derives from books like a telephone directory that lists the phone numbers of all the people living in a certain area. Files are organized by storing related files in the same directory. In a hierarchical file system (that is, one in which files and directories are organized in a manner that resembles a tree), a directory contained inside another directory is called a subdirectory. The terms parent and child are often used to describe the relationship between a subdirectory and the directory in which it is cataloged, the latter being the parent. The top-most directory in such a filesystem, which does not have a parent of its own, is called the root directory.

A directory is a container that is used to contain folders and files. It organizes files and folders in a hierarchical manner. In other words, directories are like folders that help organize files on a computer. Just like you use folders to keep your papers and documents in order, the operating system uses directories to keep track of files and where they are stored. Different structures of directories can be used to organize these files, making it easier to find and manage them.

Understanding these directory structures is important because it helps in efficiently organizing and accessing files on your computer. Following are the logical structures of a directory, each providing a solution to the problem faced in the previous type of directory structure.

Different Types of Directory in OS
In an operating system, there are different types of directory structures that help organize and manage files efficiently.

Directories in an OS can be single-level, two-level, or hierarchical. To gain a comprehensive understanding of file systems, explore the GATE CS Self-Paced Course which covers operating systems in great detail.

Each type of directory has its own way of arranging files and directories, offering unique benefits and features.These are:

* Single-Level Directory
* Two-Level Directory
* Tree Structure/ Hierarchical Structure
* Acyclic Graph Structure
* General-Graph Directory Structure

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#1 2025-01-30 17:10:34

Directory (Computing)

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