An Information System is a set of elements each of which is capable of carrying out certain information processing. All the elements performing the task of Information processing together for achieving a desired objective constitute an Information System. A personal computer is an example of Information System. An Information System in general consist of the following units
(1) Logical organizational units
(2) Computer hardware and software
(3) Information related personnels
File System is concerned with the logical organization of Information. File System deals with collection of unstructured and uninterpreted information. Each separately identified collection and information is called the File. A database management system is a file system that performs some structuring of information. We can functionally divide the file system into seven logical phases. They are:-
(a) Accessing methods
(b) Logical file system
(c) Basic file system
(d) File organisation strategy
(e) Allocation system strategy
(f) Device strategy
(g) I/O control system
A Programmer makes a request to read a file. He use a symbolic name. The logical file system accepts the symbolic name and finds the corresponding numeric file identifier. The basic file system takes the numeric file identifier and obtains a file descriptor. The file organisation strategy module uses the file descriptor to determine the physical address. The device strategy module produces the physical I/O commands to access the information (from where it is stored). I/O control system schedules the execution of the physical file commands.
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