Define file management system?

File Management:

An important part of a computer's operating system is the file management system.  A file may be a document created in word, excel, or other software, or it may be an executable file. The file management part of an operating system has four basic functions.

1. To allocate space on the storage device to hod each file stored, and to de-allocate space when a file is deleted. 
2. To keep track of the allocation units occupied by each file, files may be split over several allocation units, not necessary constigous. A file may initially occupy one unit of 512 bytes, and then when updated by a user, need extra space which may have to be found some where else on the disk. 
3. To control file access rights and permissions. 
4. To map logical file addresses to physical disk addresses, for example a physical drive may be split into several  logical drives C, D, E, F and G. 

Files containing programs and data are located secondary-storage devices. The operating system records the storage location of all files. If you move, rename, or delete a file, the operating system manages such changes and help you locate and gain access to it for example, you can copy, or duplicate, files and programs from one disk to another. You can back up, or make duplicate copy of the contents of a disk. You can erase or remove from a disk  any files or programs that are no-longer useful. You can rename, or give new file names to the files on a disk.