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Monday, September 25, 2000
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Files are under FATís supervision

THE computer world evolved by leaps and bounds during the past decade. During this period, technology changed by several generations. It was only during this period, the personal computers became popular. Right from PC XT to Pentium III and Athelon, several milestones were created in computer hardware segment.

This era also saw a sweeping change in operating systems, as Microsoft Windows got popular during this period. Today, we have several operating systems, like Windows 95, 98, NT, 2000 Linux, Unix and MacOS.

Normally, a big question looms in the minds of computer users as to what file allocation table is and what function it performs. Basically, file allocation table or FAT is a table that is maintained by operating system (Windows 95/98/NT/ 2000) on the hard disk and contains information about the cluster where a file is being stored. A cluster is a basic unit of storage on a hard disk.


Whenever something is written on a computer, it is saved as a file and stored in the form of a cluster(s) on the hard disk, which may not necessarily adjoin each other and thus may actually be spread across the hard disk. A cluster size is normally of 2048 bytes, 4096 bytes or 8192 bytes.

The function of a file allocation table is that the operating system creates an entry for any new file stored on the hard disk, which records the location of the clusters and also their sequential order. One cluster can save only one file and therefore there could be wastage of disk space.

During the first half of the last decade, 16-bit file allocation tables were used, which were maintained by DOS and early versions of Windows 95 (OSR2). It had a normal cluster size of 2048 bytes and thus limited the hard disk size to 128 MB. However, the later versions of Windows and DOS version 5 and above used the 16-bit FAT entry by having separate file allocation tables for up to 4 partitions and supported up to 2 GB storage space of hard disk. With the increasing storage capacities, the 32-bit file allocation tables were introduced.

Today, we have hard disks of very high capacities that are divided into one or more partitions, so that each partition can work independently. Hence, the benefit of having one or more operating system on a computer is also possible. These partitions are formatted by file systems, which are mainly, FAT 16, FAT 32 and NTFS.

Since, today the hard disks available are of capacity higher than 2 GB, thus normally 32-bit file allocation tables have become very common. If a hard disk of less than 2 GB is still in use, then 16-bit file allocation tables are good enough. Moreover, in case the hard disk capacity is 4.3 GB or 6 GB, and one goes in for three partitions, in these cases also, the FAT partition can serve the purpose. The FAT partition is well supported by Window 3.1, Window 95 and Windows 98 operating systems in above-mentioned conditions of hard disk storage space and partitions.

Since FAT had its limitation of storage space, thus with the increase in the size of hard disk, FAT also enhanced its system known as VFAT (virtual file allocation table). Thus, the virtual file allocation table system works on 32-bit configuration and creates an interface between the file allocation tables and applications. The input and output process is much faster with this system. It also has the advantage of using big file names, as it can keep them in additional block of directory.

Improvement in FAT file system continued with the introduction of FAT 32 file system, and is supported by Window 98 and Window 2000 operating systems. Use of FAT 32 is advisable if the size of partition is 2 GB or more ( up to 2 tetrabytes). Special feature of this system is that it can save the disk space with the use of smaller clusters. An 8 GB hard disk can have small clusters of 4 KB. This helps in saving precious disk space. Such a benefit was not available in the earlier FAT systems.

FAT 32 also provides backup copy of all main system areas, so in case of any damage, Windows can recreate the directory structure. It has a large and efficient storage capacity. In addition to above benefits, loading of program is also much faster. It works on 32-bit configuration. In Window 98, user can upgrade FAT-to-FAT 32 system with the help of graphical drive converter utility. For this one has to press start>program>accessories>system tool>drive converter.

However, Windows NT users have yet another option in the form of an NT file system (NTFS). NTFS is the file system used by Windows NT and Windows 2000 for storing and retrieving files on a hard disk. Basically, NT file system is equivalent to OS2 high performance file system and the normal FAT used by Windows 95/98. NT file system is considered better than FAT, as it has many qualities besides those common with FAT 32 system.

The NTFS can thus work with the hard disk having very large capacities even in terabytes. Similar to FAT 32, the NTFS can also be used for formatting partition of more than 2 GB. This file system provides excellent safety to files as well as directories. In case of disk failure, it provides transaction log facility. Information about a fileís cluster and other data is stored with each cluster and not just in a governing table, as is the case in FAT. When a file is saved in the NTFS, its record is maintained in the master file table, which helps in locating various clusters of file, if required.

The NTFS also supports the facility of disk compression, whereby files and directories that are not very commonly used, are compressed automatically, which keeps precious resources free for more productive uses. It can efficiently and safely handle large-sized files and supports long file names as well as "8 by 3 names". The NTFS also supports name based on unicode.

Window NT and Window 2000 can work with the NTFS. It is rather suggested that Window 2000 should use this file system, as it helps in encryption and decryption of a file. Point to be kept in mind is that Windows 2000 can either support FAT/FAT 32 or NTFS, at a time.

ó SR

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