File system

In computing, a file system or filesystem (often abbreviated to FS or fs) governs file organization and access. A local file system is a capability of an operating system that services the applications running on the same computer. A distributed file system is a protocol that provides file access between networked computers.

A file system provides a data storage service that allows applications to share mass storage. Without a file system, applications could access the storage in incompatible ways that lead to resource contention, data corruption and data loss.

There are many file system designs and implementations – with various structure and features and various resulting characteristics such as speed, flexibility, security, size and more.

File systems have been developed for many types of storage devices, including hard disk drives (HDDs), solid-state drives (SSDs), magnetic tapes and optical discs.

A portion of the computer main memory can be set up as a RAM disk that serves as a storage device for a file system. File systems such as tmpfs can store files in virtual memory.

A virtual file system provides access to files that are either computed on request, called virtual files (see procfs and sysfs), or are mapping into another, backing storage.

From c. 1900 and before the advent of computers the terms file system, filing system and system for filing were used to describe methods of organizing, storing and retrieving paper documents. By 1961, the term file system was being applied to computerized filing alongside the original meaning. By 1964, it was in general use.

A local file system's architecture can be described as layers of abstraction even though a particular file system design may not actually separate the concepts.