Transcript Format - Floppy Disk - Pioneer Pacific College

Floppy Drive
Formatting
©Richard Goldman
February, 2001
1
The First Step
Low Level Format (LLF)
Tracks are placed on the disk.
 Tracks are divided into sectors.

2
The First Step
Low 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
3
The First Step
Low Level Format (LLF)

Suffixes are added to each sector –
Including:
Buffer area and Gaps
 Data CRC


The data areas are filled with F6h ()
4
Low Level Format
Tracks are placed on the disk
Track
5
Low Level Format
Tracks are divided into sectors
Sectors
6
Low Level Format
Prefixes are added to each sector
Prefix - Including:

Sector I.D.
Cylinder Number
Head Number
Sector Number

Sector ID CRC
Gaps

7
Low Level Format
Suffixes are added to each sector
Suffix – Including:

Buffer area
Data CRC
Gaps

8
Low Level Format
The data areas are filled with ’s
Data Area
Note:
ASCII Character -

Binary – 1111 0110
Hexadecimal – F6h
Decimal – 264
9
The Second Step
Master Boot Record (MBR)

The first sector of the disk is used to
store the MBR.



Cylinder 0
Head 0
Sector 1
10
Master Boot Record
MBR
11
1.44MB Floppy
Master 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
12
Bytes per Sector

512 bytes
13
Sectors per Cluster

1 Sector
14
Number of FAT’s

2 FAT’s
15
Size of the Root Directory


7808 Bytes
(224 Records X 32 Bytes/Record)
16
Number of Sectors


2880 Sectors
(18 Sectors X 80 Tracks X 2 Heads)
17
Medium Descriptor byte

Type of material used to make disk.
18
Size of FAT



Uses FAT12
Uses 12 Binary digit number to identify
each cluster.
Example:

0000 0000 0001 = first cluster
19
Sectors per Track

18 Sectors
20
Number of Heads

2 Heads
21
Number of Hidden Sectors

Includes the number of sectors used by
the MBR, Root Directory, and the two
FATs.
22
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.
23
The Third Step
File Allocation Table (FAT)

Two FATs are created in the space
immediately following the MBR.
24
File Allocation Tables
MBR
FAT 1
FAT 2
25
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.
26
FAT
Information
000
001
001
002
002
003
004
005
003
FFF
005
FFF
006
007
008
009
FF7
FF7
009
00A
Continues 00B
00A
FFF
A2E
Cluster
Number
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)
27
The Fourth Step
Root Directory

The Root Directory is created in the
space immediately following the
second FAT.
28
Root Directory
Root
Directory
MBR
FAT 1
FAT 2
29
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.
30
Contents
Root Directory
File Name
File Extension
Attribute – R, A, S, H, File/Subdirectory, Volume Label
Time – Created/Updated
Date – Created/Updated
Starting Cluster
File Size
31
Maximum Number of
Root 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.
32
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.
33