Operating Systems: Concepts and Terminologies
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by Joydip Kanjilal
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File and I/O Management

This is the module of the Operating System that is responsible for creating and/or deleting files in the file system and managing the input and output of data in the file system.

File System

A File System refers to the arrangement in a secondary storage that is done by the Operating System for the purpose of data storage and retrieval.  The File System of any two Operating Systems is not identical.  The following are the names of the Operating Systems and the respective file systems that they follow.

·         DOS                                       : FAT File System

·         Windows 9x                            : VFAT

·         Windows XP/NT/2000/2003       : NTFS

·         Windows Vista                        : NTFS

·         UNIX                                     : UFS (UNIX File System)

·         Linux                                     : Ext II File System

Note: Windows Vista is now built on the NTFS file system.  Windows Future Storage (WinFS), a relational database based data storage engine, is currently under development and will be introduced later as a free add-on for Windows Vista in late 2006.

Root File System

The Root File System specifies the information related to the files on the disk or the secondary storage.  Typical contents include the following.

·         Name of the file

·         Starting Cluster Number

·         Size of the file

·         Date and Time stamp

·         File Permissions

File Control Block

A File Control Block (FCB) is a data structure that contains information related to the files that are present on a File System.  Even though the contents of the FCB would vary from one Operating System to another, the following are the common parts that it contains.

·         Name of the file

·         Location

·         Size of the file

·         Date and Time stamp

Disk Fragmentation and De-Fragmentation

The files created in the secondary storage are created and deleted as needed.  Allocation of the clusters for a file in the file system is non–contiguous.  The Operating System maintains a free cluster list to keep track of the clusters that are available for use or re-use.  Due to deletions of one or more files in the file system, the clusters that are allocated to a file are not in sequence, but rather they are scattered all over the disk with free clusters or holes in between.  This concept is known as disk fragmentation.  The disk de-fragmentation tools available are responsible for compacting or arranging the clusters of a file contiguously in the disk.


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User Comments

Title: OS   
Name: Anil gopal
Date: 2006-12-18 7:44:54 AM
Comment:
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Title: operating system concepts   
Name: shashi
Date: 2006-11-16 11:40:25 AM
Comment:
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Title: OS   
Name: Anuj
Date: 2006-10-04 2:53:45 AM
Comment:
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Title: os   
Name: rajesh
Date: 2006-08-10 10:01:12 AM
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Title: HI   
Name: Hardik
Date: 2006-08-07 8:44:54 AM
Comment:
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Title: os   
Name: saravanan
Date: 2006-08-07 1:29:43 AM
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