FAT File System in Hard Disk

The abbreviation for FAT is File Allocation Table which is a file system used for MS-DOS and used for consumer versions of Microsoft Windows including Windows. The FAT file system is relatively uncomplicated, because it is a popular format for floppy disks. Moreover, FAT is used to support virtually all existing operating systems for personal computers, and that, it is often used to share data between several operating systems booting on the same computer. It is used on solid-state memory cards and other similar devices. The most common implementations have a serious drawback in when files are deleted and new files written to the media.

FAT16:

The FAT 16 was developed in the year 1987 with the removal of the 16 bit counter of disk sectors. In 1988 the improvement became generally available through MS-DOS 4.0. The partition size was now limited by the 8-bit signed count of sectors per cluster, which could reach a maximum power-of-two value of 64. Windows NT increased the maximum cluster size to 64K by considering the sector per cluster count as unsigned. However the resulting format was not compatible with any other FAT implementation of the time and generated really huge internal fragmentation anyway.

Windows 98 also supported reading and writing this variant but its disk utilities didn't work with it. The FAT are used for older systems, and for small partitions on modern systems, uses a 16-bit binary number to hold cluster numbers. When you see someone refer to a volume generically, they are usually referring to FAT16, because it is the de facto standard for hard disks, even with FAT32 now more popular than FAT16. A volume using FAT16 can hold a maximum of 65,526 clusters, which is 2^16 less a few values (again for reserved values in the FAT). FAT16 is used for hard disk volumes ranging in size from 16 MB to 2,048 MB. VFAT is a variant of FAT16.

FAT32:

The latest type of FAT version is FAT32 which is supported by Windows, including Windows 98 and Windows 2000. FAT32 uses a 28-bit binary cluster and is still enough to permit huge volumes. The size of the FAT grows very large. In order to overcome the volume size limit of FAT16 while still allowing DOS real-mode code to handle the format without unnecessarily reducing the available conventional memory, Microsoft decided to implement a newer generation of FAT, known as FAT32, with 32-bit cluster numbers, of which 28 bits are currently used. FAT32 partitions can be created by other means.

FAT32 was introduced with Windows 95 OSR2, although reformatting was needed to use FAT32 advantages, and DriveSpace 3 never supported it. Windows 98 introduced a utility to convert existing hard disks from FAT16 to FAT32 without loss of data. The maximum possible file size for a FAT32 volume is 4 GB minus 1 byte. For most users, this has become the most nagging limit of FAT32 for using the video capture and editing applications can easily exceed this limit, as can the system swap file fails.

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