1. File System.doc - File System Management in Operating...

File System Management in Operating System
One of the major responsibilities of the Operating System (OS) is file management. A file can
be "free formed", indexed or structured collection of related bytes/information having meaning
only to the one who created it. Or in other words an entry in a directory is the file. The file may
have attributes like name, creator, type, date, permissions etc.
File Structure
A file has various kinds of structure; and
a defined structure should be according to a
required format that the operating system can understand.
Some of them can be:

Simple Record Structure: which is made up of lines of fixed or variable lengths?

Complex Structures: these are like formatted documents or reloadable load files.

No Definite Structure: this looks like sequence of words and bytes etc.
Attributes of a File
Attributes are factors used in keeping track of files in an operating system. A file has
attributes, which vary from one operating system to another, but typically consist of the
following attributes of a file:

File’s Name: It is the only information which is in human-readable form. It’s essentially
the name of a file

Identifier: The file is usually identified by a unique tag (ID number usually in
figures— 123..) within the file system.

Type : It is needed for systems that support different types (.doc, .txt etc) of files.

Location : It is a pointer to a device and the location (stored) of the file on the device.

Size . It is the current size of the file ex. 2048 Kb.

Protection : This controls (access control information) and assigns the power of reading,
writing, executing i.e. a file can be “READ ONLY”, R/W or W.

Time and date: This gives information about the time and dates when operations
like creation, last access time, modification , deletion etc. of the file took place.

User identification (ID) . This is the identification given to the creator or user of the file
Operations on a File
The following include the operations performed on files

a) Creating a file : to create a file, there should be space in the system then you enter the
new file
b) Writing a file : is writing a content or information to a file system
c) Reading a file : In this case the system gives information of just reading a file
d) Reposition of a file : Is searching for a file
e) Delete File : It is the deletion of a file from a file system
f) Truncating a File : It is the deletion of the contents of a file but keeping the attributes of
that file
Open File
To perform file operation, we first have to open the file. Many OS maintain a data
structure kind of property called open file table which contains information (properties)
about the currently opened file. Several pieces of information associated with an open
file may include:
File pointer: Records the current position of file, which enables the accessibility
of the next block for the next read/write process.