A file system is a process that manages how and where data on a storage disk, typically a hard disk drive (HDD), is stored, accessed and managed. It is a logical disk component that manages a disk's internal operations as it relates to a computer and is abstract to a human user.
Regardless of type and usage, a disk contains a file system and information about where disk data is stored and how it may be accessed by a user or application. A file system typically manages operations, such as storage management, file naming, directories/folders, metadata, access rules and privileges.
Commonly used file systems include File Allocation Table 32 (FAT 32), New Technology File System (NTFS) and Hierarchical File System (HFS).
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Computers use particular kinds of file systems to store and organize data on media, such as a hard drive or flash drive, or the CDs, DVDs, and BDs in an optical drive.
A file system can be thought of as an index or database containing the physical location of every piece of data on the device. The data is usually organized in folders called directories, which can contain other folders and files.
Any place that a computer or other electronic device stores data employs some type of file system. This includes your Windows computer, your Mac, your smartphone, your bank's ATM—even the computer in your car!
Getty Images / Csaba Bajko PhotographyThe Microsoft Windows operating systems have always supported various versions of the FAT file system. FAT stands for File Allocation Table, a term that describes what it does: maintains a table of each file's space allocation.
In addition to FAT, all Windows operating systems since Windows NT support a newer file system called NTFS—New Technology File System. For Windows NT, the NT stood for new technology.
All modern versions of Windows also support exFAT, which is designed for flash drives.
ReFS (Resilient File System) is a newer file system for Windows 11, 10, and 8 that includes features not available with NTFS, but it's currently limited in several ways. You can see which versions of Windows support each version of ReFS in this table.
A file system is set up on a drive during a format. See How to Format a Hard Drive for more information.
Files on a storage device are kept in sectors. Sectors marked as unused can store data, typically in groups of sectors called blocks. It's the file system that identifies the size and position of the files, as well as which sectors are ready to be used.
Over time, because of the way the file system stores data, writing to and deleting from a storage device causes fragmentation because of the gaps that inevitably occur between different parts of a file. A free defrag utility can help fix that.
Without a structure for organizing files, it not only would be next to impossible to remove installed programs and retrieve specific files, but no two files could exist with the same name because everything might be in the same folder (which is one reason folders are so useful).
What's meant by files with the same name is like an image, for example. The file IMG123.jpg can exist in hundreds of folders because each folder is used to separate the file, so there isn't a conflict. However, files can't bear the same name if they're in the same directory.
A file system doesn't just store the files but also information about them, like the sector block size, fragment information, file size, attributes, file name, file location, and directory hierarchy.
Some operating systems other than Windows also take advantage of FAT and NTFS, but many kinds of file systems dot the operating-system horizon, like HFS+ used in Apple product like iOS and macOS. Wikipedia has a comprehensive list of file systems if you're more interested in the topic.
Sometimes, the term "file system" is used in the context of partitions. For example, saying "there are two file systems on my hard drive" doesn't mean that the drive is split between NTFS and FAT, but that there are two separate partitions that use the same physical disk.
Most applications you come into contact with require a file system in order to work, so every partition should have one. Also, programs are file system-dependant, meaning you can't use a program on Windows if it was built for use in macOS.
A file system is not the same as a system file.
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For most users, the file system is the most visible aspect of an operating system. It provides the mechanism for on-line storage of and access to both data and programs of the operating system and all the users of the computer system. The file system consists of two distinct parts: a collection of files, each storing related data, and a directory structure, which organizes and provides information about all the files in the system. File systems live on devices, which we explore fully in the following chapters but touch upon here. In this chapter, we consider the various aspects of files and the major directory structures. We also discuss the semantics of sharing files among multiple processes, users, and computers. Finally, we discuss ways to handle file protection, necessary when we have multiple users and we want to control who may access files and how files may be accessed.
Computers can store information on various storage media, such as magnetic disks, magnetic tapes, and optical disks. So that the computer system will be convenient to use, the operating system provides a uniform logical view of information storage. The operating system abstracts from the physical properties of its ...
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