Windows File system ( FAT and NTFS)

This article explains about the Windows File System. The family of Windows operating systems mostly use two major types of file systems i.e. FAT ( File Allocation Table) and NTFS ( New Technology File System). Before going to discuss about FAT and NTFS, let us know what actually the file system is:

What is a file system:

A file system in a computer is a method of storing and organizing data or files in a secondary storage media like hard disk, floppy disk, optical drive, etc. Every data in a computer is saved as a file. A file is a collection of data saved as a single unit and each file is identified by its file name. A file can be in the form of image, document, video, audio, etc. The collection of such files constitute a directory or a folder.

The operating system employs the files system to manage and organize these files and directories on the storage media. A file can not be stored in a single large space of the hard disk. It is logically divided into smaller sizes of clusters. Different file system utilizes different sizes of clusters. A file may occupy one or more clusters to store its data on the hard disk.

There are many different types of operating systems that employ their own different types of file systems. Windows File system largely uses FAT and NTFS for its different variants of operating systems. Now let us discuss FAT and NTFS in details:

File Allocation Table (FAT):

FAT file system is introduced by Microsoft for disk operating system (DOS) to manage files and directories on the hard drives and other storage media. FAT maintains a table or an index that describes the cluster allocation to the files and directories on the hard drive.

When a file is written on a hard disk, it occupies one or more clusters depending on the size of the file. When file size is greater than the cluster size, it occupies more than two clusters. But, multiple clusters occupied by file may not be adjacent to each other. However, it may be distributed across the hard disk.

In order to keep a record of which file occupies how many clusters, the FAT system maintains a table containing files and clusters location. Hence, when a file is to be retrieved or read, it is the job of the operating system to fetch the file from different cluster locations by looking at the FAT table.

FAT has three different variants:

  • FAT 12
  • FAT 16
  • FAT 32

FAT 12:

  • It is the oldest version of the FAT system.
  • It was originally introduced by Microsoft for Disk Operating System (DOS).
  • It is specially designed for storing data on a floppy drives.
  • It uses 12-bit file allocation table entry.
  • FAT16 supports up to 16MB of partition volume for 4 kb of cluster size and 32 MB of partition volume for 8kB of cluster size.
  • The maximum data clusters supported by FAT 12 is up to 4087 clusters.

FAT 16:

  • FAT 16 was introduced in 1984.
  • It supports 16-bit file allocation table entry.
  • The cluster size depends on the different types of operating system used.
  • It supports maximum partition size from 2 GB to 16GB. However, 16 GB of partition size is possible only 256 kb of cluster size.
  • The maximum data clusters supported by FAT32 is from 4087 to 65536.
  • FAt 16 is extensively used by operating systems such as MS-DOS, Windows 95, Windows 98, Windows NT, Windows 2000 and some variants of UNIX OS.


  •  FAT32  was introduced in 1995.
  • It was s major improvement to the previous FAT system.
  • It has overcome the limitations of older FAT 16  file system and supports media with higher storage space.
  • It supports 32-bit file allocation table entry.
  • It can support up to 2 Tera bytes of partition volume.
  • It supports maximum single file size up to 4 GB.
  • The hard drive formatted with FAT 32 can accomodate data clusters from 65526 to 268,435,456.
  • FAT 32 is more robust and has better performance as compared to the previous FAT system.

NTFS (New Technology File System):

NTFS file system is used by Windows NT operating system for managing and storing files on a hard drive. NTFS has several advantages over FAT file system. NTFS suppports efficient use of disk space, supports metadata and improved data structures. The major features of NTFS file system are :

  • It was introduced 1993 and employed with Windows NT 3.1.
  • NTFS supports file compression, thereby increasing the storage space.
  • It enables security access control by placing permissions on files and folders.
  • The biggest advantage of NTFS file system is fault tolerance. In case disk failure, it automatically recovers from errors without displaying any error messages.
  • It provides journaling facility by keeping logs and audits of modified files in MFT ( Master File Table).
  • Cluster size varies from 512 bytes to 64 kbytes.
  • Theoritically, maximum volume supported by NTFS is 256 kbytes.
  • Maximum file size can be 2 Terabytes

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