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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.