FAT Full Form

Introduction

In this article, we are going to have a detailed description and understanding of File Allocation Table (FAT), it is a type of file system that was developed by Microsoft to maintain small disks and a number of simple folder structures. The file system is named as File Allocation Table because a table is used to track the sequential order of clusters as well as to understand how this series of clusters are associated together through their analogous files.

This Story also Contains

1. Introduction
2. Full form of FAT
3. The Naming of FAT
4. Uses of FAT
5. Types of FAT
6. Advantages and Disadvantages of FAT
7. Limitations of FAT

Full form of FAT

FAT stands for File Allocation Table. It is a table that is conserved via the Operating System on a hard disk that issues a map of the clumps in which files have been categorized. The operating system generates a FAT entry for each and every new file that tracks every cluster’s location and its sequential arrangement. When we look through a file, the operating system (OS) reconstructs the file into clusters and then locates it as an absolutely new and fresh file. FAT has been designed to help out the hard drives and their subdirectories.

The Naming of FAT

FAT has been discovered into three generations, FAT12, FAT16, and FAT 32. FAT16 is the actual and real representation of FAT file systems with 2 to the power 16 (2^16) bit cluster entries.

FAT32 is the representation of FAT file systems with 2 to the power 32 (2^32) bit cluster entries Values remain piled up in the Disk parameter block that can be used to identify the file structures.

Another form of FAT is VFAT where optional extension types for long file names are stored. VFAT can be used to work on top of any FAT file system. The Volumes which are used by VFAT file systems can be read on other operating systems, which prohibits any VFAT file system extension.

The popular type of file system (FAT12, FAT16, and FAT32) can be determined by the width of the cluster entries in the FAT file systems.

Uses of FAT

The File Allocation Table was first invented in DOS and Windows 9x, via hard disks. In 1993, when Microsoft introduced its new file system, NTFS FAT was only applicable to the Windows NT platform. The usage of FAT was through hard drives. FAT became the standard for all home users until the period of the invention of NT-based Windows XP in 2001.

Types of FAT

1. 8-bit FAT8

Marc Donald outlined and executed the original and real FAT file system based on a sequence of discussions between McDonald’s and Bill Gates. It was initiated with 8-bit table elements in 1977 and 1978. In 1978, The FAT file system was also in use in Microsoft’s Z80 platforms. Three FATs were supported by the Standalone Disk BASIC. Moreover, MIDAS has also been prepared to support 10-bit, 12-bit, and 16-bit FAT variants.

2. 12-bit FAT12

Through the entries of 12-bit for the cluster address, FAT12 is being used. Some of the values were restrained for marking the termination of a series of clusters and for marking unsuitable disk areas. The maximum number of sequential clusters was restricted to 4078. To retain disk space, two and three consecutive 8-bit bytes were used by 12-bit FAT entries on the disk, to be in need of manipulation to unpack the 12-bit values. This was adequate for the original floppy disk drives and small hard disks of about 32 megabytes. The FAT 6B version was available with DOS 3.31 which supported the 32-bit sector operating system and raised the volume size limit.

3. 16-bit FAT16

Cluster addresses were now raised to 16-bit, allowing the increase for up to 65,526 clusters. The cluster addresses were 16 bits yet this format was not commonly recognized as FAT16.

MS-DOS 3.0 to MS-DOS 3.30 could even access FAT12 partitions under 15 MB but needed all 16 MB-32 MB partitions for FAT16, so this could not access MS-DOS 2.0 partitions in this sequential size range. MS-DOS 3.31 and higher than this could easily access 16 MB-32 MB FAT12 partitioning.

The FAT16B improvement became more normally accessible through DOS 3.31, PC DOS 4.0, OS/2 1.1, and MS-DOS 4.0. The limitation on partition size is indicated by the 8-bit signed count of sectors per sequential order of cluster which originally had the highest power of two values of 64. The standard hard disk sector size of 512 bytes gives access to a maximum of 32 KB cluster size.

4. 32-bit FAT32

To overcome the size limitation of the FAT16 file system, Microsoft created a new version of the file system called FAT32 which reinforced an increase in the number of possible sequential clusters. This could be used to reuse most of the existing code to raise the conventional memory to less than 5 KB under DOS. Windows 98 introduced the practicality to convert existing hard disks from FAT16 to FAT32 without the loss of data.

The latter type was also named FAT32X to indicate the utilization of the LBA disk approach instead of CHS. On such partitions, there are CHS-related geometry entries namely the CHS in the MBR and the maximum number of sectors per track, and the maximum number of heads in the EBPB record may accommodate no misleading values.

Advantages and Disadvantages of FAT

Advantages:

• Fat utilizes the whole disk block for data.

• Any successive blocks lost are not caused by a bad disk block

• FAT provides random access although it is not too fast.

• In each file operation, only FAT needs to be negotiated.

Disadvantages:

• A FAT entry is needed by each block.

• FAT size may be very huge based on the number of FAT entries.

• The number of FAT entries can be turned down by raising the block size but leading to an increase in Internal Fragmentation.

Limitations of FAT

• There are multiple partitions in FAT that are not subsidized or identified.

• Multiple active file handling is permitted and authorized only for files opened in the reading mode

• The maximum path length for FAT is 260 bytes only.

• UTF 16 and UTF 8 are not supported or identified by FAT.