File systems

File Systems: 
A filesystem is the methods and data structures that an operating system uses to keep track of files on a disk or partition, that is, the way the files are organized on the disk. 
A file is an entry in a directory. The file may have attributes like name, creator, date, type, permissions etc.
File Structure:
A file has various kinds of structure. Some of them can be :
  1. 1. Simple Record Structure with lines of fixed or variable lengths.
  2. Complex Structures like formatted document or reloadable load files.
  3. No Definite Structure like sequence of words and bytes etc.
Attributes of a File:
  1. Name. It is the only information which is in human-readable form.
  2. Identifier. The file is identified by a unique tag(number) within file system.
  3. Type. It is needed for systems that support different types of files.
  4. Location. Pointer to file location on device.
  5. Size. The current size of the file.
  6. Protection. This controls and assigns the power of reading, writing, executing.
File Access Methods:
  1. Sequential Access:Data is accessed one record right after another is an order.
  2. Direct Access: There are no restrictions, blocks read/written, can be done in any order.
  3. Indexed Sequential Access: It uses an Index to control the pointer while accessing files.