What is file system? How a file is organised in file system? Give few examples?

File system is depending on Operation systems & hard Disk sizes.
At the time 1990 there were only dos which supports only FAT16 (File allocation table)
Upto MS-DOS 6.22 & Windows 3.1 & 3.11 It works only on FAT16
FAT16 Has it's limitation that it can't support more than 2.1 GB partition at a time.
After that windows 95 & Windows 98
That supported FAT16 & FAT32 only.
Windows NT supports
FAT16 as well as It develops new file systems HPFS i.e. (High Performance File System)

Later i.e. is called as NTFS (New Technology File System)
NTFS is now a largest support for us.

FAT16-File Allocation Table 16-bit Supports upto DOS6.22 Windows 3.1/3.11/95/98
FAT32-File Allocation Table 32-bit Supports Windows 95/98/Windows 2000/xp/2003
HPFS-High Performance Fils System Supports NT/2000/xp/2003
NTFS-New Technoloy File System Supports NT/2000/xp/2003

collectioon of related files stored in a perticuler location is called file syetem.there three types of file system i disk based filesystem and 2 is network based file system and the other one is virtual based filre system. for examole in diskbased file system is

fat      file allocation table
ntfs:  new technologiy file system
ufs:   unix file system
jfs :   journal file system
hpfs: hiperformance file system