d 4 understanding file strucure

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understanding files structure of hard disk


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What is Files Systems? : What is Files Systems? 1 INTERSOFT TECHNICAL INSTITUTE SURAT EMAIL--INTERSOFT@HOTMAIL.COM The data is stored permanently in different storage media, such as magnetic tapes and optical disks. The operating system provides a uniform logical view of information storage. The operating system abstracts from the physical properties of its storage device to define a logical unit (file). Files are mapped by the operating system onto a physical device.

PowerPoint Presentation : INTERSOFT TECHNICAL INSTITUTE SURAT EMAIL--INTERSOFT@HOTMAIL.COM 2 Some file systems are case sensitive DOS, Windows - Case insensitive n UNIX, Linux - Case sensitive Many OSs support two-part file systems Parts are separated by a period (.) Example: . test.txt,os.pdf,MyClass.java,prog.c Extension indicates something about the file

Types Of Files Systems : Types Of Files Systems Regular files - ones that contain user data. These are either ASCII or binary.. Directories - are systems files which are used to maintain the structure of the file system Character files - related to IO & used to model serial IO devices such as terminals & printers /dev/ tty , /dev/ lp , /dev/net Block files - are used to model disks /dev/hd1, /dev/hd2 INTERSOFT TECHNICAL INSTITUTE SURAT EMAIL--INTERSOFT@HOTMAIL.COM 3

Files - Structure :-- : Files - Structure :-- INTERSOFT TECHNICAL INSTITUTE SURAT EMAIL--INTERSOFT@HOTMAIL.COM 4

DOS File System :-- : DOS File System :-- Make use of File Allocation Table (FAT) Use of 8+3 character file names Attributes Read only, archived, hidden, system 2 versions :-- FAT-12 Max partition size 2MB 4 separate partitions FAT-16 Max partition size 2GB 4 separate partitions INTERSOFT TECHNICAL INSTITUTE SURAT EMAIL--INTERSOFT@HOTMAIL.COM 5

MS-DOS directory entry :-- : MS-DOS directory entry :-- INTERSOFT TECHNICAL INSTITUTE SURAT EMAIL--INTERSOFT@HOTMAIL.COM 6

Maximum partition for different block sizes :-- : Maximum partition for different block sizes :-- INTERSOFT TECHNICAL INSTITUTE SURAT EMAIL--INTERSOFT@HOTMAIL.COM 7

Windows 98 File System :-- : Windows 98 File System :-- Actually came with Windows 95, 2nd release Namely FAT-32 Max partition size 2TB More than 4 partitions File names up to 255 characters Was backward compatible with FAT-16 INTERSOFT TECHNICAL INSTITUTE SURAT EMAIL--INTERSOFT@HOTMAIL.COM 8

Windows 2000 File System :-- : Windows 2000 File System :-- NTFS - New Technology File System Initially used in Windows NT A single partition can be up to 264 bytes File names can be up to 255 Unicode characters File system security is inbuilt Better performance & more reliable Not backward compatible with FAT-16 or FAT-32 INTERSOFT TECHNICAL INSTITUTE SURAT EMAIL--INTERSOFT@HOTMAIL.COM 9

Windows XP System Files:-- : Windows XP System Files:-- INTERSOFT TECHNICAL INSTITUTE SURAT EMAIL--INTERSOFT@HOTMAIL.COM 10

FAT File Allocation Table:-- : FAT File Allocation Table:--

PowerPoint Presentation : INTERSOFT TECHNICAL INSTITUTE SURAT EMAIL--INTERSOFT@HOTMAIL.COM 12 Put the link list allocation entries in memory Advantages Fast random access If one of the blocks in the disk is lost still the rest of the file can be located Full utilization of a single disk block Disadvantages FAT takes some space in memory Fragmentation . Storage efficiency It is not fault tolerant

NTFS New technology files system : NTFS New technology files system The NTFS File System was created in the early 1990s. Microsoft wanted to create a high-quality, high performance, reliable and secure operating system. All the operating systems Microsoft had before Windows XP or Windows 2000 had the power or features needed for Microsoft to take on UNIX or other serious operating systems. One of the biggest weaknesses of MS-DOS and Windows 3.x was that they relied on the FAT file system. INTERSOFT TECHNICAL INSTITUTE SURAT EMAIL--INTERSOFT@HOTMAIL.COM 13

FAT/NTFS Comparison:-- : FAT/NTFS Comparison:-- 14 FAT32 ( vFAT ) NTFS Systems Windows98, NT5 NT4, NT5 Maximal volume size Almost unlimited Almost unlimited Maximal files count Almost unlimited Almost unlimited File name Long names (up to 255 chars), system character set. Long names (up to 255 chars), unicode character set. File attributes Basic set All that programmers want Security No Yes (capability of physical encryption, starting from NT5.0) Compression No Yes Fault tolerance Low Fully (automatic) Economy Improved (small clusters) Maximal Performance Penalty for big volumes Very effective for all volume sizes

How data store in hard disk in fat:-- : How data store in hard disk in fat:-- INTERSOFT TECHNICAL INSTITUTE SURAT EMAIL--INTERSOFT@HOTMAIL.COM 15

Linked allocation :-- : Linked allocation :-- INTERSOFT TECHNICAL INSTITUTE SURAT EMAIL--INTERSOFT@HOTMAIL.COM 16

Linked allocation Cont..:-- : Linked allocation Cont..:-- Advantages Every disk block can be used No space is lost due to fragmentation Disadvantages Random access is slow Amount of data stored will not be powers of 2 If the link is lost rest of the file can’t be Located INTERSOFT TECHNICAL INSTITUTE SURAT EMAIL--INTERSOFT@HOTMAIL.COM 17

Attributes of files systems:-- : Attributes of files systems:-- A files includes set of other characteristics than just name & an extension some common attributes Owner - current owner of file Creator - ID of the person who created the file Protection - who can access &who can’t access Read only flag - can it be modified or not Hidden flag - display or not when listed Archive flag - to be backed up or not Last modified date , Created date, etc. INTERSOFT TECHNICAL INSTITUTE SURAT EMAIL--INTERSOFT@HOTMAIL.COM 18

File - Operations :-- : File - Operations :-- Different systems allow operations to store & retrieve data from files Create - create a new file with no data & set initial attributes Delete - remove the file from system freeing up disk space Open - before using a files must be open Read - after opening a file data can be read Write - after opening a file data can be written INTERSOFT TECHNICAL INSTITUTE SURAT EMAIL--INTERSOFT@HOTMAIL.COM 19

PowerPoint Presentation : Append - after opening a file data can be written to the end of the file Close - when all the access is finished file must be closed Seek - used in random access a file Get attributes - get the attributes of a file Set attributes - set the attributes of a file Rename - change the name or the extension of a file INTERSOFT TECHNICAL INSTITUTE SURAT EMAIL--INTERSOFT@HOTMAIL.COM 20

NTFS File attributes:-- : NTFS File attributes:-- Resident attributes Stored in the MFT itself Filename and timestamp always resident Nonresident attributes File information too large to fit in the MFT Allocated to clusters like file data INTERSOFT TECHNICAL INSTITUTE SURAT EMAIL--INTERSOFT@HOTMAIL.COM 21

NTFS File attributes Cont..:-- : NTFS File attributes Cont..:-- INTERSOFT TECHNICAL INSTITUTE SURAT EMAIL--INTERSOFT@HOTMAIL.COM 22

NTFS File attributes cont..:-- : NTFS File attributes cont..:-- INTERSOFT TECHNICAL INSTITUTE SURAT EMAIL--INTERSOFT@HOTMAIL.COM 23

Deleting NTFS FILES:-- : Deleting NTFS FILES:-- When a file is deleted in Windows XP, 2000, or NT: NTFS renames file Moves it to Recycle Bin in a unique subfolder Information on original path and file name stored in Info2 file (control file for the Recycle Bin) Date/time of deletion and other info INTERSOFT TECHNICAL INSTITUTE SURAT EMAIL--INTERSOFT@HOTMAIL.COM 24

PowerPoint Presentation : When file is deleted via DOS: Associated clusters designated as free $Bitmap file marked to show new available space File attribute record in MFT marked to indicate it’s available Inodes and VCN/LFN cluster numbers removed from MFT. NTFS is more efficient than FAT: Reclaiming deleted space Deleted files are overwritten more quickly INTERSOFT TECHNICAL INSTITUTE SURAT EMAIL--INTERSOFT@HOTMAIL.COM 25

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