1 floppy drive formatting ©richard goldman february, 2001
TRANSCRIPT
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Floppy DriveFormatting
©Richard GoldmanFebruary, 2001
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The First StepLow Level Format (LLF)
Tracks are placed on the disk.
Tracks are divided into sectors.
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The First StepLow Level Format (LLF)
Prefixes are added to each sector – Including: Sector I.D.
Cylinder Number Head Number Sector Number
Sector ID CRC (Cyclic Redundancy Checking )
Gaps
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The First StepLow Level Format (LLF)
Suffixes are added to each sector – Including: Buffer area and Gaps Data CRC
The data areas are filled with F6h ()
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Low Level FormatTracks are placed on the disk
Track
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Low Level FormatTracks are divided into sectors
Sectors
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Low Level FormatPrefixes are added to each sector
Prefix - Including:
Sector I.D.Cylinder NumberHead NumberSector Number
Sector ID CRCGaps
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Low Level FormatSuffixes are added to each sector
Suffix – Including:
Buffer areaData CRCGaps
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Low Level FormatThe data areas are filled with ’s
Data Area
Note:
ASCII Character -
Binary – 1111 0110
Hexadecimal – F6h
Decimal – 264
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The Second StepMaster Boot Record (MBR) The first sector of the disk is used
to store the MBR. Cylinder 0 Head 0 Sector 1
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Master Boot RecordMBR
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1.44MB FloppyMaster Boot Record Information
Bytes per Sector
Sectors per Cluster
Number of FAT’s
Size of the Root Directory
Number of Sectors
Medium Descriptor byte
Size of FAT
Sectors per Track
Number of Heads
Number of Hidden Sectors
Program to Load OS
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Bytes per Sector 512 bytes
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Sectors per Cluster 1 Sector
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Number of FAT’s 2 FAT’s
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Size of the Root Directory 7808 Bytes (224 Records X 32 Bytes/Record)
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Number of Sectors 2880 Sectors (18 Sectors X 80 Tracks X 2 Heads)
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Medium Descriptor byte Type of material used to make
disk.
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Size of FAT Uses FAT12 Uses 12 Binary digit number to
identify each cluster. Example:
0000 0000 0001 = first cluster
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Sectors per Track 18 Sectors
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Number of Heads 2 Heads
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Number of Hidden Sectors Includes the number of sectors
used by the MBR, Root Directory, and the two FATs.
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Program to Load OS A program that attempts to load
the operating system. If IO.SYS in not found on the disk a “Non-system disk error” is given.
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The Third StepFile Allocation Table (FAT) Two FATs are created in the space
immediately following the MBR.
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File Allocation TablesMBR
FAT 1
FAT 2
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File Allocation Table The FAT is a table of all the sectors
available for use on the disk. The FAT has one column of information:
A sequential list of all the data clusters on the disk.
(The sectors used for the MBR, FATs, and Root directory are not included.)
FAT 12 is used on floppy disks. This means each cluster is identified with a
12 bit binary number in the FAT.
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000 001
001 002
002 003
003 FFF
004 005
005 FFF
006 009
007 FF7
008 FF7
009 00A
00A FFF
00B A2E
Cluster
Number
FAT Information
Continues
Each entry points to the next cluster in chain of clusters that make up a file.
The last cluster in the chain is marked with FFFh
(1111 1111 1111)
Known bad clusters are marked with FF7h
(1111 1111 0111)
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The Fourth StepRoot Directory The Root Directory is created
in the space immediately following the second FAT.
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Root DirectoryMBR
FAT 1
Root Directory
FAT 2
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Root Directory The Root Directory is a table
that contains a list of all files and subdirectories in the “Root” or first directory on the disk.
A 3 ½ inch High Density (HD) floppy disk can hold a maximum of 224 entries.
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ContentsRoot Directory
File Name
File Extension
Attribute – R, A, S, H, File/Subdirectory, Volume Label
Time – Created/Updated
Date – Created/Updated
Starting Cluster
File Size
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Maximum Number ofRoot Directory Entries
Drive File System Max Entries
3.5” Floppy - HD
FAT12 224
Hard Drive FAT16 512
Hard Drive FAT32 Unlimited
Hard Drive NTFS Unlimited
The use of LFNs can reduce the number of entries.
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Deleting a File The first letter of the file name is
replaced with the lower case Greek letter sigma () in the Directory.
The FAT entry is replaces with 000. The data on the disk is NOT deleted. The data will remain on the disk until it
is overwritten by another write process. It may be possible recover “Deleted”
data with undelete utilities.