The disk surface is divided into tracks. into tracks. 1.
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The disk surface is divide The disk surface is divide into tracks. into tracks. 1
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Transcript of The disk surface is divided into tracks. into tracks. 1.
The disk surface is dividedThe disk surface is divided into tracks.into tracks.
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Track 0Track 0
Track 1Track 1
Track 79Track 79
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Side 1,Track 0Side 1,Track 0
Side 2,Track 0Side 2,Track 0
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Most hard drives have multiple platters.Most hard drives have multiple platters.
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Platter1, Track1Platter1, Track1
Platter2, Track1Platter2, Track1
Platter3, Track1Platter3, Track1
Platter4, Track1Platter4, Track1
The eight track 1’s are referred to The eight track 1’s are referred to collectively as “Cylinder 1.”collectively as “Cylinder 1.”
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Read\WriteHead
Read\WriteHead PlatterPlatter
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One Sector =512 Bytes
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Cluster
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ClusterClusterClusterCluster
The smallest unit of disk space that the The smallest unit of disk space that the operating system can allocate to a file. operating system can allocate to a file.
It consists of one or more sectors.It consists of one or more sectors.
Generally, the larger the disk drive; the Generally, the larger the disk drive; the more sectors per cluster.more sectors per cluster.
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File Allocation Table (FAT)File Allocation Table (FAT)File Allocation Table (FAT)File Allocation Table (FAT)
OS’s road map to the diskOS’s road map to the disk
How the OS keeps track of which How the OS keeps track of which clusters belong to which filesclusters belong to which files
How the OS keeps track of bad sectorsHow the OS keeps track of bad sectors
TwoTwo copies maintained and kept up to copies maintained and kept up to date.date.
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FormattingFormattingFormattingFormatting
Low Level FormattingLow Level Formatting - Performed by - Performed by the Drive Manufacturer.the Drive Manufacturer.
High Level FormattingHigh Level Formatting - Performed - Performed by the PC User via the FORMAT by the PC User via the FORMAT Command.Command.
Blank Disk Sectors and tracks defined
Low-Level Formatting
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Low Level FormattingLow Level FormattingLow Level FormattingLow Level Formatting
Performed at the factory.Performed at the factory.
Converts the single blank surface into Converts the single blank surface into tracks and sectors.tracks and sectors.
Finds and remaps bad spots on the disk Finds and remaps bad spots on the disk so that the operating system can avoid so that the operating system can avoid them.them.
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High Level FormattingHigh Level FormattingHigh Level FormattingHigh Level Formatting
Originally performed by the vendor of Originally performed by the vendor of the computer.the computer.
Creates boot record, FAT, and the root Creates boot record, FAT, and the root directory.directory.
Performed with the FORMAT Performed with the FORMAT command.command.
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PartitioningPartitioningPartitioningPartitioning
Makes the hard disk compatible with Makes the hard disk compatible with the OSthe OS
Prepares hard disk for high-level Prepares hard disk for high-level formatformat
Divides hard disk into partitions or Divides hard disk into partitions or makes it one large partitionmakes it one large partition
Performed with the FDISK utilityPerformed with the FDISK utility
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FAT and FAT 16FAT and FAT 16FAT and FAT 16FAT and FAT 16
DOS, Win 95, Win 98DOS, Win 95, Win 98
2 GB Maximum Partition2 GB Maximum Partition
32 KB Cluster @ 2 GB32 KB Cluster @ 2 GB
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VFAT VFAT VFAT VFAT
Win 95 and Win 98Win 95 and Win 98
2 GB Maximum Partition2 GB Maximum Partition
32 K Cluster @ 2 GB32 K Cluster @ 2 GB
Long File NamesLong File Names
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FAT 32FAT 32FAT 32FAT 32
Win 95, Win 98, Win MEWin 95, Win 98, Win ME
2 TB Maximum Partition2 TB Maximum Partition
4 KB Cluster @ 2 GB4 KB Cluster @ 2 GB
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The File Allocation Table The File Allocation Table contains a 16-bit entry for every contains a 16-bit entry for every
cluster on the disk. cluster on the disk.
The File Allocation Table The File Allocation Table contains a 16-bit entry for every contains a 16-bit entry for every
cluster on the disk. cluster on the disk.
For this reason, the system is For this reason, the system is called FAT16. called FAT16.
For this reason, the system is For this reason, the system is called FAT16. called FAT16.
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However, 16-bits can represent However, 16-bits can represent only 65,536 clusters.only 65,536 clusters.
However, 16-bits can represent However, 16-bits can represent only 65,536 clusters.only 65,536 clusters.
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The FAT16 system used by MS-The FAT16 system used by MS-
DOS and Windows 3.X is DOS and Windows 3.X is
limited to 65,536 clusters.limited to 65,536 clusters.
The FAT16 system used by MS-The FAT16 system used by MS-
DOS and Windows 3.X is DOS and Windows 3.X is
limited to 65,536 clusters.limited to 65,536 clusters.
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Because of this limitation, cluster Because of this limitation, cluster
size increases as disk size size increases as disk size
increases. increases.
Because of this limitation, cluster Because of this limitation, cluster
size increases as disk size size increases as disk size
increases. increases.
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FAT 16FAT 16Disk SizeDisk Size vs. Cluster Size vs. Cluster Size
FAT 16FAT 16Disk SizeDisk Size vs. Cluster Size vs. Cluster Size
16 - 127 MB16 - 127 MB
128 - 255 MB128 - 255 MB
256 - 511 MB256 - 511 MB
512 - 1023 MB512 - 1023 MB
1024 - 2047 MB1024 - 2047 MB
2048 bytes2048 bytes
4096 bytes4096 bytes
8192 bytes8192 bytes
16,384 bytes16,384 bytes
32,768 bytes32,768 bytes
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No matter how small the file, No matter how small the file, FAT allocates the entire cluster.FAT allocates the entire cluster.
No matter how small the file, No matter how small the file, FAT allocates the entire cluster.FAT allocates the entire cluster.
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A short text file might require A short text file might require only 1000 bytes.only 1000 bytes.
A short text file might require A short text file might require only 1000 bytes.only 1000 bytes.
But on a 2 GB drive, the cluster But on a 2 GB drive, the cluster size is 32,768 bytes.size is 32,768 bytes.
But on a 2 GB drive, the cluster But on a 2 GB drive, the cluster size is 32,768 bytes.size is 32,768 bytes.
In this example, 31,768 bytes are In this example, 31,768 bytes are wasted.wasted.
In this example, 31,768 bytes are In this example, 31,768 bytes are wasted.wasted.
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The wasted bytes are called The wasted bytes are called “cluster overhang.”“cluster overhang.”
The wasted bytes are called The wasted bytes are called “cluster overhang.”“cluster overhang.”
Cluster overhang causes a lot of Cluster overhang causes a lot of wasted space.wasted space.
Cluster overhang causes a lot of Cluster overhang causes a lot of wasted space.wasted space.
The larger the hard drive, the The larger the hard drive, the greater the wasted space.greater the wasted space.
The larger the hard drive, the The larger the hard drive, the greater the wasted space.greater the wasted space.
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Windows 98 has a way of Windows 98 has a way of overcoming this problem.overcoming this problem.Windows 98 has a way of Windows 98 has a way of overcoming this problem.overcoming this problem.
Windows 98 uses a system called Windows 98 uses a system called Virtual File Allocation Table or Virtual File Allocation Table or
VFAT.VFAT.
Windows 98 uses a system called Windows 98 uses a system called Virtual File Allocation Table or Virtual File Allocation Table or
VFAT.VFAT.
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In order to maintain backwards In order to maintain backwards
compatibility with earlier files, compatibility with earlier files,
Windows 98 accommodates Windows 98 accommodates
FAT16 files.FAT16 files.
In order to maintain backwards In order to maintain backwards
compatibility with earlier files, compatibility with earlier files,
Windows 98 accommodates Windows 98 accommodates
FAT16 files.FAT16 files.
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At the same time, Windows 98 At the same time, Windows 98
has updated the FAT system to a has updated the FAT system to a
new FAT32 system.new FAT32 system.
At the same time, Windows 98 At the same time, Windows 98
has updated the FAT system to a has updated the FAT system to a
new FAT32 system.new FAT32 system.
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Advantages of FAT32Advantages of FAT32Advantages of FAT32Advantages of FAT32
Smaller cluster sizesSmaller cluster sizes
Support for larger hard disksSupport for larger hard disks
Improved reliabilityImproved reliability
Flexible partitioningFlexible partitioning
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FAT32FAT32Disk SizeDisk Size vs. Cluster Size vs. Cluster Size
FAT32FAT32Disk SizeDisk Size vs. Cluster Size vs. Cluster Size
16 MB - 8 GB16 MB - 8 GB
8 - 16 GB8 - 16 GB
16 - 32 GB16 - 32 GB
Over 32 GBOver 32 GB
4096 bytes4096 bytes
8192 bytes8192 bytes
16,384 bytes16,384 bytes
32,768 bytes32,768 bytes
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Windows 98 comes with a utility Windows 98 comes with a utility
called called Drive Converter (FAT32)Drive Converter (FAT32)
that converts FAT16 partitions that converts FAT16 partitions
into FAT32 Partitions.into FAT32 Partitions.
Windows 98 comes with a utility Windows 98 comes with a utility
called called Drive Converter (FAT32)Drive Converter (FAT32)
that converts FAT16 partitions that converts FAT16 partitions
into FAT32 Partitions.into FAT32 Partitions.
