What are the differences between NTFS and FAT system?

Windows 95, 98, and ME all use a file system called FAT. (Windows 95 in the original edition used FAT16; the later versions of Windows 95, 98, and ME could also use FAT32.) FAT stands for File Allocation Table, which is a portion of the hard drive that keeps track of the possibly many scattered segments making up any given file, which could be distributed all over the drive because of fragmentation. Windows NT introduced the NTFS (New Technologies File System), and both Windows 2000 and XP can also use this.
FAT is by far the most simplistic of the file systems supported by Windows NT. The FAT file system is characterized by the file allocation table (FAT), which is really a table that resides at the very "top" of the volume. To protect the volume, two copies of the FAT are kept in case one becomes damaged. In addition, the FAT tables and the root directory must be stored in a fixed location so that the system's boot files can be correctly located.

A disk formatted with FAT is allocated in clusters, whose size are determined by the size of the volume. When a file is created, an entry is created in the directory and the first cluster number containing data is established. This entry in the FAT table either indicates that this is the last cluster of the file, or points to the next cluster.

Updating the FAT table is very important as well as time consuming. If the FAT table is not regularly updated, it can lead to data loss. It is time consuming because the disk read heads must be repositioned to the drive's logical track zero each time the FAT table is updated.

There is no organization to the FAT directory structure, and files are given the first open location on the drive. In addition, FAT supports only read-only, hidden, system, and archive file attributes. === === From a user's point of view, NTFS continues to organize files into directories, which, like HPFS, are sorted. However, unlike FAT or HPFS, there are no "special" objects on the disk and there is no dependence on the underlying hardware, such as 512 byte sectors. In addition, there are no special locations on the disk, such as FAT tables or HPFS Super Blocks.

The goals of NTFS are to provide: * Reliability, which is especially desirable for high end systems and file servers * A platform for added functionality * Support POSIX requirements * Removal of the limitations of the FAT and HPFS file systems
FAT cannot save files which has size about and more 4 GB. NTFS is better protected from virus and hackers attackes. FAT is working faster but not siginificantly.