# file system

> concrete format or program for storing files and directories on a data storage device

**Wikidata**: [Q174989](https://www.wikidata.org/wiki/Q174989)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/File_system)  
**Source**: https://4ort.xyz/entity/file-system

## Summary
A file system is a concrete format or program used by an operating system to control how data is stored and retrieved. It organizes files and directories on a data storage device, such as a hard drive or flash drive, providing a hierarchical structure for managing information. Without a file system, data placed on a storage medium would be one large, unusable body of information.

## Key Facts
- **Classification:** A file system is an operating system component and a subclass of disk storage format, data store, and filestore.
- **Function:** It provides a concrete format for storing files and directories on a data storage device.
- **Structure:** Most modern file systems are hierarchical, organizing computer files into nested directories.
- **Distinctions:** A file system is different from a virtual file system (which is an abstraction layer), a volume (a logical storage area), and a file format (the structure of an individual file).
- **Types:** There are many specialized types of file systems, including journaling, cryptographic, flash, clustered, and network file systems.
- **Example (ext):** The extended file system, a historical Linux file system, was created in April 1992.
- **Example (HFS):** Apple's Hierarchical File System (HFS) was introduced on September 17, 1985. Its successor, HFS Plus, was developed on January 19, 1998.

## FAQs
### Q: What is the difference between a file system and a virtual file system?
A: A file system is a concrete program or format for storing data on a device. A virtual file system is an abstraction layer on top of a concrete file system, providing a consistent interface for applications to access different types of file systems.

### Q: What are some common types of file systems?
A: File systems are often categorized by their features. Common types include journaling file systems (which improve reliability after a crash), cryptographic file systems (for security), flash file systems (optimized for flash memory), and network file systems (for accessing files over a network).

### Q: Is a file system the same as a volume or a file format?
A: No. A file system is the method of organizing files on a storage device. A volume is a single accessible storage area with a single file system. A file format defines the structure of data within a single file (e.g., JPEG, PDF), not how multiple files are organized on a disk.

## Why It Matters
The file system is a fundamental and indispensable component of modern computing. It acts as the organizational backbone for all data on a storage device, translating the physical placement of bits into a logical, hierarchical structure of files and folders that users and applications can understand and navigate. Without it, an operating system could not locate, read, write, or manage data, rendering storage devices useless.

The evolution of file systems has been critical to advancements in computing. Specialized types solve specific problems: journaling file systems (e.g., SFS) prevent data corruption from power failures, cryptographic file systems (e.g., EFS) provide essential data security, and clustered file systems (e.g., CXFS) enable high-performance computing by allowing multiple machines to share storage. The file system is the invisible yet essential layer that makes persistent data storage reliable, efficient, and accessible.

## Notable For
- **Hierarchical Organization:** File systems are primarily known for organizing data into a tree-like structure of nested directories (folders), which is a universally understood method for managing files.
- **Specialized Variants:** The concept has been adapted into numerous specialized classes to meet specific technical needs, such as journaling file systems for crash recovery, flash file systems for solid-state drives, and cryptographic file systems for data security.
- **Operating System Integration:** It is a core component of an operating system, responsible for managing all file-related operations on a storage volume.
- **User-Space Implementation:** Through interfaces like FUSE (Filesystem in Userspace), file systems can be created and run by non-privileged users without modifying the operating system's kernel, enabling rapid development and experimentation.
- **Abstraction of Physical Storage:** A file system abstracts the physical details of a storage device, allowing users and applications to work with logical files and directories without needing to know where the data is physically located on the disk.

## Body
### Definition and Purpose
A file system is a concrete format and set of programs that an operating system uses to manage files and directories on a data storage device. It is an instance of an operating system component and a subclass of a `disk storage format`. Its primary purpose is to organize data in a structured way, allowing for efficient storage, retrieval, and management. It is distinct from a `virtual file system`, which serves as an abstraction layer, and from a `volume`, which is the logical storage area a file system is applied to.

### Types of File Systems
File systems can be categorized based on their design, features, and intended use case.
- **Hierarchical File System:** Organizes files in a tree structure of nested directories. This is the most common model.
- **Journaling File System:** Keeps a log, or "journal," of changes that have not yet been committed to the main file system. This allows for faster recovery and less data corruption in the event of a system crash or power failure.
- **Log-structured File System:** Writes all modifications sequentially to a circular buffer called a log, which can improve write performance.
- **Flash File System:** A class of file systems, such as UBIFS (introduced in 2008), designed specifically for the characteristics of flash memory.
- **Cryptographic File System:** Uses cryptographic principles to provide security and encryption for stored files.
- **Network File System:** A protocol that allows a computer to access files over a network as if they were on a local storage device.
- **Clustered File System:** A decentralized file system where multiple machines can access and manage data on a shared storage device. An example is CXFS, designed by Silicon Graphics in 1994.
- **Record-oriented filesystem:** Stores data as collections of records rather than as an unstructured stream of bytes.

### Notable Implementations
- **extended file system (ext):** A historical file system for Linux, first released in April 1992.
- **Hierarchical File System (HFS):** Developed by Apple for macOS and introduced on September 17, 1985.
- **HFS Plus:** An updated version of HFS, also developed by Apple, released on January 19, 1998.
- **Unix File System (UFS):** A file system used by many Unix and Unix-like operating systems.
- **Smart File System (SFS):** A journaling file system used on Amiga computers, created in 1998.
- **Encrypting File System (EFS):** A feature in Microsoft Windows that provides filesystem-level encryption.
- **WinFS:** A relational file system developed for the Windows operating system.

## Schema Markup
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## References

1. Freebase Data Dumps. 2013
2. Quora
3. National Library of Israel Names and Subjects Authority File
4. KBpedia
5. [OpenAlex](https://docs.openalex.org/download-snapshot/snapshot-data-format)