What's the meaning of mining sector
Publish: 2021-05-12 01:08:13
1.
Each track on the disk is equally divided into several arc segments, which are the sectors of the disk
each side of the disk is divided into many tracks, that is, some concentric circles on the surface. The closer to the center, the smaller the circle. Each track is divided into equal parts according to 512 bytes, which is called sector. On the parameter list of some hard disks, you can see the parameter describing the number of sectors of each track. It is usually identified by a range, such as 373-746. This means that the outermost track has 746 sectors, while the innermost track has 373 sectors, so it can be calculated, The capacity of track is 186.5kb to 373kb (190976b -- 381952b)
disk drive should read and write data to disk in sectors. On disk, DOS operating system allocates disk space for files in the unit of cluster. The cluster of hard disk is usually multiple sectors, which is related to the type of disk, DOS version and the size of hard disk partition. Each cluster can only be occupied by one file. Even if there are several bytes in the file, two or more files are not allowed to share one cluster, otherwise it will cause data confusion. This mechanism of taking cluster as the minimum allocation unit makes it relatively easy for hard disk to manage data, but it also causes a waste of disk space, especially when there are a large number of small files. The disk space wasted by a large hard disk can reach hundreds of megabytes
2. Hello, ask you, if the sector event count of remapping is yellow, don't worry too much. It's not caused by physical damage. Generally speaking, there are two reasons: one is that there is a bad channel, but it has been replaced by the backup Sector. Second, when hdtune software detects a certain brand of hard disk, it causes a bug. For example, for Seagate hard disk, even if the new one is detected, it is double yellow.
3. Disdaining the above person for solving the problem here is not to let him find the
sector by himself. Each track on the disk is divided into several arcs, which are the sectors of the disk. When a disk drive reads and writes data to a disk, it should take sectors as the unit. On disk, DOS operating system allocates disk space for files in the unit of cluster. The cluster of hard disk is usually multiple sectors, which is related to the type of disk, DOS version and the size of hard disk partition. Each cluster can only be occupied by one file. Even if there are several bytes in the file, two or more files are not allowed to share one cluster, otherwise it will cause data confusion. This mechanism of taking cluster as the minimum allocation unit makes it relatively easy for hard disk to manage data, but it also causes a waste of disk space, especially when there are a large number of small files. The disk space wasted by a large hard disk can reach hundreds of megabytes
it should be that your disk has a bad track. I can only guess if you check to see if there is a bad track
sector by himself. Each track on the disk is divided into several arcs, which are the sectors of the disk. When a disk drive reads and writes data to a disk, it should take sectors as the unit. On disk, DOS operating system allocates disk space for files in the unit of cluster. The cluster of hard disk is usually multiple sectors, which is related to the type of disk, DOS version and the size of hard disk partition. Each cluster can only be occupied by one file. Even if there are several bytes in the file, two or more files are not allowed to share one cluster, otherwise it will cause data confusion. This mechanism of taking cluster as the minimum allocation unit makes it relatively easy for hard disk to manage data, but it also causes a waste of disk space, especially when there are a large number of small files. The disk space wasted by a large hard disk can reach hundreds of megabytes
it should be that your disk has a bad track. I can only guess if you check to see if there is a bad track
4. Sector number definition: absolute sector and DOS sector
from the previous introction, we can use the cylinder / head / sector to uniquely locate each area on the disk, or the cylinder / head / sector has a one-to-one correspondence with each sector on the disk. Generally, DOS calls the expression of "cylinder / head / sector" as "absolute sector". However, DOS can not directly use absolute sector for information management on disk, but use so-called "relative sector" or "Dos sector"“ "Relative sector" is just a number. For example, the relative sector number of cylinder 140, head 3 and sector 4 is 2757. This number has a one-to-one correspondence with the absolute sector "cylinder / head / sector". When using relative sector number, DOS starts from cylinder 0, head 1, and sector 1
(Note: cylinder 0, head 0, and sector 1 have no DOS sector number, and can not be accessed under DOS, and can only be accessed by calling BIOS). The first DOS sector number is 0, and the remaining sectors on the track are 1 to 16 (SET 17 sectors per track), and then the head number is 2, The number of DOS sector is from 17 to 33. Up to
all heads of the cylinder. Then move to cylinder 1, head 1 and sector 1, and continue to number DOS sectors, that is, continue in the order of sector number, head number and cylinder number (track number)
from the previous introction, we can use the cylinder / head / sector to uniquely locate each area on the disk, or the cylinder / head / sector has a one-to-one correspondence with each sector on the disk. Generally, DOS calls the expression of "cylinder / head / sector" as "absolute sector". However, DOS can not directly use absolute sector for information management on disk, but use so-called "relative sector" or "Dos sector"“ "Relative sector" is just a number. For example, the relative sector number of cylinder 140, head 3 and sector 4 is 2757. This number has a one-to-one correspondence with the absolute sector "cylinder / head / sector". When using relative sector number, DOS starts from cylinder 0, head 1, and sector 1
(Note: cylinder 0, head 0, and sector 1 have no DOS sector number, and can not be accessed under DOS, and can only be accessed by calling BIOS). The first DOS sector number is 0, and the remaining sectors on the track are 1 to 16 (SET 17 sectors per track), and then the head number is 2, The number of DOS sector is from 17 to 33. Up to
all heads of the cylinder. Then move to cylinder 1, head 1 and sector 1, and continue to number DOS sectors, that is, continue in the order of sector number, head number and cylinder number (track number)
5.
formula of logical sector number LBA:
LBA (logical sector number) = number of heads × Sectors per track × Current cylinder number + sectors per track × If CHS = 0 / 0 / 1, LBA = 255 × sixty-three × 0 + 63 × 0 + 1 – 1 = 0
that is to say, physical 0 cylinder 0 head 1 sector is logical 0 sector
The whole hard disk is generally composed of many disks. Each disk is "cut" into a fan like a watermelon. At the same time, it is divided into many concentric circles along the radius direction, which is the legendary track. Each track is cut into many fan areas by the fan, which are called sectors (sectors are the smallest units of information read and written from the disk, Generally, the size is 512 bytes). The same radius tracks on different disks form a cylinder. These are physical concepts of disks. You can know them. With these concepts, you can calculate the capacity of the disk:
number of heads × Number of tracks (cylinders) × Number of sectors per channel × Number of bytes per sector
L number of heads: each disk generally has two sides, one corresponding to one head and two heads in total
L number of tracks: tracks are numbered from the outer ring to the inner ring of the disk, 0 track, 1 track... Concentric circles close to the spindle are used to dock the magnetic head and do not store data
L cylinder number: the number of the same track
lnumber of sectors: each track is divided into many sectors, and each track has the same number of sectors
lnumber of platters: the number of platters
as shown in the figure:
data location on the hard disk
each sector can store 128 × 2 (n = 0.1.2.3) bytes of data (generally 512b). The sector is the smallest unit of data storage. As can be seen from the figure above, the sector area of the outer ring is larger than that of the inner ring. Why the amount of data stored is the same? This is because the density of magnetic material used in the inner and outer rings is different. But now the hard disk has adopted the same density material used in the inner and outer rings to store data, In order to rece the waste of "large area and small data" At this time, the number of sectors of the internal and external tracks will be different, and the specific details will be omitted)
with sector, cylinder and head, it is obvious that the data can be located. This is one of the data location (addressing) methods. CHS (also known as 3D) is very effective for the early disks (as shown in the figure above). You know which head to use, Read which sector on the cylinder is OK. The capacity of hard disk supported by CHS mode is limited. 8bit is used to store the head address, 10bit is used to store the cylinder address, and 6bit is used to store the sector address, In this way, using CHS to address a hard disk, the maximum capacity is 256 * 1024 * 63 * 512b = 8064 MB (1MB = 1048576b) (if 1MB = 1000000b, it is 8.4GB)
but now many hard disks use the same density disks, which means that the number of sectors on the inner and outer tracks is different, the number of sectors increases, the capacity increases, and 3D is difficult to locate and address. A new addressing mode: LBA (logical block addressing). In LBA address, the address no longer represents the actual physical address (cylinder, head and sector) of the actual hard disk. LBA addressing mode transforms CHS, a three-dimensional addressing mode, into a one-dimensional linear addressing mode. It transforms the C / h / s number of all physical sectors of the hard disk into a linear number through certain rules. The system efficiency is greatly improved, and the cumbersome head / cylinder / sector addressing mode is avoided. When accessing the hard disk, the hard disk controller converts the logical address into the physical address of the actual hard disk
In LBA, sector numbers start from 0formula of logical sector number LBA:
LBA (logical sector number) = number of heads × Sectors per track × Current cylinder number + sectors per track × If CHS = 0 / 0 / 1, LBA = 255 × sixty-three × 0 + 63 × 0 + 1 – 1 = 0
that is to say, physical 0 cylinder 0 head 1 sector is logical 0 sector
6. Each track on the disk is equally divided into several arc segments, which are the sectors of the disk. The basic unit of hard disk reading and writing is sector
1. Introction
each side of the disk is divided into many tracks, that is, some concentric circles on the surface. The closer to the center, the smaller the circle. Each track is divided into equal parts according to 512 bytes, which is called sector. On the parameter list of some hard disks, you can see the parameter describing the number of sectors of each track. It is usually identified by a range, such as 373-746. This means that the outermost track has 746 sectors, while the innermost track has 373 sectors, so it can be calculated, The capacity of tracks ranges from 186.5kb to 373kb (190976b -- 381952b)
when the disk drive reads and writes data to the disk, it should take the sector as the unit. On disk, DOS operating system allocates disk space for files in the unit of cluster. The cluster of hard disk is usually multiple sectors, which is related to the type of disk, DOS version and the size of hard disk partition. Each cluster can only be occupied by one file. Even if there are several bytes in the file, two or more files are not allowed to share one cluster, otherwise it will cause data confusion. This mechanism of taking cluster as the minimum allocation unit makes it relatively easy for hard disk to manage data, but it also causes a waste of disk space, especially when there are a large number of small files. The disk space wasted by a large hard disk can reach hundreds of megabytes
in order to find and manage sectors, it is necessary to number sectors. The sector number starts from track 0, the starting sector is sector 1, followed by sector 2 and sector 3. After the sector number of track 0 ends, the starting sector number of track 1 accumulates until the last sector (sector n) of the last track. For example, if a hard disk has 1024 tracks and each track is divided into 63 sectors, the sector number of track 0 is 1-63, the starting sector number of track 1 is 64, and the last sector number of the last track is 64512. There are some differences between hard disk and floppy disk in sector numbering. In one track of floppy disk, sector numbers are arranged once, i.e. 1, 2, 3... N sectors. Due to the high speed of the hard disk, the head must transmit the data to the microcomputer after reading and writing the data of a sector, which takes a time. However, the hard disk continues to rotate at a high speed. When the data transmission is completed and the head reads and writes the second sector, the disk has already rotated to another sector. Therefore, in the early hard disk, the sector number was arranged according to a certain interval coefficient
Second, bad sectors
sectors that cannot be accessed normally or read and written correctly in the hard disk are called baddirector. A sector can store 512bytes of data. If any byte in a sector cannot be read or written correctly, the sector is baddirector. In addition to storing 512bytes, there are dozens of bytes in each sector of the hard disk, including ID, check value and other information. An error in any byte of this information will cause the sector to become bad. For example, in low-level formatting, each sector is assigned a number, written in the ID. If there is an error in the ID part, the sector will not be accessible, then the sector belongs to baddirector. Some badectors can correct this by rewriting this information with low-level formatting.
1. Introction
each side of the disk is divided into many tracks, that is, some concentric circles on the surface. The closer to the center, the smaller the circle. Each track is divided into equal parts according to 512 bytes, which is called sector. On the parameter list of some hard disks, you can see the parameter describing the number of sectors of each track. It is usually identified by a range, such as 373-746. This means that the outermost track has 746 sectors, while the innermost track has 373 sectors, so it can be calculated, The capacity of tracks ranges from 186.5kb to 373kb (190976b -- 381952b)
when the disk drive reads and writes data to the disk, it should take the sector as the unit. On disk, DOS operating system allocates disk space for files in the unit of cluster. The cluster of hard disk is usually multiple sectors, which is related to the type of disk, DOS version and the size of hard disk partition. Each cluster can only be occupied by one file. Even if there are several bytes in the file, two or more files are not allowed to share one cluster, otherwise it will cause data confusion. This mechanism of taking cluster as the minimum allocation unit makes it relatively easy for hard disk to manage data, but it also causes a waste of disk space, especially when there are a large number of small files. The disk space wasted by a large hard disk can reach hundreds of megabytes
in order to find and manage sectors, it is necessary to number sectors. The sector number starts from track 0, the starting sector is sector 1, followed by sector 2 and sector 3. After the sector number of track 0 ends, the starting sector number of track 1 accumulates until the last sector (sector n) of the last track. For example, if a hard disk has 1024 tracks and each track is divided into 63 sectors, the sector number of track 0 is 1-63, the starting sector number of track 1 is 64, and the last sector number of the last track is 64512. There are some differences between hard disk and floppy disk in sector numbering. In one track of floppy disk, sector numbers are arranged once, i.e. 1, 2, 3... N sectors. Due to the high speed of the hard disk, the head must transmit the data to the microcomputer after reading and writing the data of a sector, which takes a time. However, the hard disk continues to rotate at a high speed. When the data transmission is completed and the head reads and writes the second sector, the disk has already rotated to another sector. Therefore, in the early hard disk, the sector number was arranged according to a certain interval coefficient
Second, bad sectors
sectors that cannot be accessed normally or read and written correctly in the hard disk are called baddirector. A sector can store 512bytes of data. If any byte in a sector cannot be read or written correctly, the sector is baddirector. In addition to storing 512bytes, there are dozens of bytes in each sector of the hard disk, including ID, check value and other information. An error in any byte of this information will cause the sector to become bad. For example, in low-level formatting, each sector is assigned a number, written in the ID. If there is an error in the ID part, the sector will not be accessible, then the sector belongs to baddirector. Some badectors can correct this by rewriting this information with low-level formatting.
7. The inside of the hard disk is a metal disk. The circular disk is divided into several fan-shaped areas, which are called sectors. Several sectors make up the whole disk. Why divide sectors? Is the need of logical data, can better manage the hard disk space. Take the disk center as the center of the circle, divide the disk into several concentric circles, and each "line" dividing the circle is called the track. The disk in the hard disk has two surfaces, which can store data. However, there is often more than one disk in the hard disk, and there are usually two disks. Then, the tracks at the same position in the two disks form a "cylinder". As many tracks in the disk, there are as many cylinders. Both sides of the disk can store data. To read it, there must be a magnetic head. Therefore, each side has a magnetic head, and a disk has two magnetic heads. The above is the technical terms of hard disk: sector, track, cylinder and head. Storage capacity of hard disk = number of heads × Number of tracks (cylinders) × Sectors Per Trark × Bytes per sector. Tracks are numbered from 0 to 0 in sequence from the outside to the inside. The number of sectors on each track is determined ring hard disk formatting. In addition, it can be seen from the figure that the number of sectors on the inner track is equal to the number of sectors on the outer track.
8. Track
when the disk rotates, if the head remains in a position, each head will draw a circular track on the disk surface, which is called track
cylinder
in a disk group composed of multiple disks, a cylinder is composed of tracks at the same radius
magnetic area
each track on the disk is equally divided into several arc segments, which are the magnetic area (sector) of the hard disk. The first magnetic area of the hard disk is called the boot sector
as for the following problems, I don't quite understand. It didn't help.
when the disk rotates, if the head remains in a position, each head will draw a circular track on the disk surface, which is called track
cylinder
in a disk group composed of multiple disks, a cylinder is composed of tracks at the same radius
magnetic area
each track on the disk is equally divided into several arc segments, which are the magnetic area (sector) of the hard disk. The first magnetic area of the hard disk is called the boot sector
as for the following problems, I don't quite understand. It didn't help.
9. DOS management structure of hard disk
1. Number of tracks, sectors, cylinders and heads
the most basic component of hard disk is hard metal coated with magnetic media, and the number of disks varies with the capacity of hard disk. Each disc has two sides, which can
record information. Disk is divided into many fan-shaped areas, each area is called a sector, each sector can store 128 × 2 (n = 0.1.2.3). In DOS
each sector is 128 × The second power of 2 = 512 bytes. On the surface of the disk, the center of the disk is the center of the circle. Concentric circles with different radii are called tracks. In a hard disk, a cylinder composed of tracks of different disks with the same radius is called a cylinder. Track and cylinder are circles representing different radii. In many cases, track and cylinder can be used interchangeably. As we know, each magnetic disk has two faces, and each face has a head. It is customary to use the head number to distinguish them. Sector, track (or cylinder) and the number of heads constitute the basic parameters of hard disk structure. With these
parameters, the capacity of hard disk can be obtained. The basic calculation formula is:
storage capacity = number of heads × Number of tracks (cylinders) × Sectors Per Trark × The key points are as follows: (1) there are several disks in the hard disk, two faces in each disk, and one head in each face
(2) the disk is divided into several sectors, namely sectors
(3) concentric circles with different radii of the same disk are magnetic tracks
(4) cylindrical surfaces with the same radii of different disks, namely cylindrical surfaces
(5) formula: storage capacity = number of heads × Number of tracks (cylinders) × Sectors Per Trark × (6) information records can be expressed as follows: ×× Track (cylinder), ×× Magnetic head, ×× Sector
2. Cluster
"cluster" is the smallest unit allocated by DOS. When creating a very small file, such as a byte, it does not occupy only one byte of disk space,
but occupies the whole cluster. DOS depends on different storage media (such as floppy disk, hard disk), different capacity of hard disk, cluster size is not the same. The size of the cluster can be obtained in a block called disk
parameter (BPb). The concept of cluster only applies to data area
this point: (1) "cluster" is the smallest unit that dos allocates
(2) different storage media, different capacity hard disks, different DOS versions, the cluster size is also different
(3) the concept of cluster is only applicable to data area
3. Sector number definition: absolute sector and DOS sector
from the previous introction, we can use cylinder / head / sector to uniquely locate each area on the disk, or cylinder / head / sector has a one-to-one correspondence with each sector on the disk. Generally, DOS calls "cylinder / head / sector" as "absolute sector". But DOS can't directly use absolute sector for information management on disk, instead it uses so-called "relative sector" or "Dos sector"“ "Relative sector" is just a number, such as cylinder 140, head 3 and sector 4. The corresponding relative sector number is 2757. This number has a one-to-one correspondence with the absolute sector "cylinder / head / sector". When using relative sector number, DOS starts from cylinder 0, head 1, and sector 1 (Note: cylinder 0, head 0, and sector 1 have no DOS sector number, and can not be accessed in DOS, and can only be accessed by calling BIOS). The first DOS sector number is 0, and the remaining sectors on the track are 1 to 16 (SET 17 sectors per track), followed by 17 sectors with head 2 and cylinder 0, The formed DOS sector numbers range from 17 to 33. All heads up to the cylinder. Then move to cylinder 1, head 1 and sector 1 and continue to number DOS sectors, that is, assign DOS sector numbers continuously according to the increasing sequence of sector number, head number and cylinder number (track number)
formula: record DH - head number of the first DOS sector
DC - cylinder number of the first DOS sector
DS - sector number of the first DOS sector
ns - number of sectors per track
NH - total head number of disk
then the relative sector number rs of a sector (cylinder C, head h, sector s) is:
rs = NH × NS × C－DC＋NS × H-dh) + (s-ds)
If RS, DC, DH, DS, NS and NH are known, then
s = (RS mod NS) + DS
H = ((RS div NS) mod NH) + DH
C = ((RS div NS) div NH) + DC
main points: (1) the absolute sector represented by cylinder / head / sector is also called physical disk address
(2) the relative sector or DOS sector represented by a single number, (3) conversion formula between relative sector and absolute sector
4. Partition of DOS disk area
a formatted hard disk can be divided into main boot record (MBR), DOS boot record (DBR), file assignment table (fat) according to the function of recorded data, BD: boot directory and data area. The first five important information are on the outer track of the disk. The reason is that the circumference of the outer ring is always larger than that of the inner ring, which means that the storage density of the outer ring is smaller and the reliability is higher< Key points: (1) the whole hard disk can be divided into MBR, DBR, fat, BD and data area
(2) MBR, DBR, fat, and BD are located outside the disk
5. MBR
MBR is located at cylinder 0, head 0 and sector 1 of the first physical sector (absolute sector) of the hard disk. Because DOS starts from cylinder 0, head 1 and sector 1, MBR does not belong to DOS sector and DOS cannot be accessed directly. MBR contains the main bootloader and partition table of hard disk. The partition table has four partition record areas. A record area is a table that records information about partitions. It is continuously stored from the master boot record offset address 01beh, and each partition record area occupies 16 bytes
format of partition table
number of bytes occupied by offset meaning of partition table entries
00 boot indicator 1b
01 partition boot record head number 1b
02 partition boot record sector and cylinder number 2B
04 system indicator 1b
05 partition end head number 1b
06 partition end sector and cylinder number 2B
08 partition front sector number 4B
0C The total number of sectors in the partition is 4B
there can only be one active partition in the four partitions, namely disk C. The flag is 80h at the first byte of the partition table. If 00h, it means inactive partition. For example:
80 01 00 0b Fe 3F 81 3F 00 00 00 C3 DD 1F 00
00 01 82 05 Fe BF 0C 02 de 1F 00 00 00 e 90 61 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00. It does not belong to DOS sector,
(2) main boot record is divided into main boot program and partition table of hard disk
6. DBR
DBR is located in cylinder 0, head 1 and sector 1, namely logical sector 0. DBR is divided into two parts: Dos bootloader and BPb (BIOS parameter block). The DOS boot program completes the location and loading of
DOS system files (io.sys, MSDOS. Sys), and BPb is used to describe the disk information of this DOS partition. BPb is located at the DBR offset 0Bh, with a total of 13 bytes. It contains the parameters used in logical format, which can be used by DOS to calculate the file allocation table on disk, the starting address of directory area and data area, and the three words after BPb to provide some parameters used in physical format (low format). The bootloader or device driver converts the disk logical address (DOS sector number) to the physical address (absolute
sector number) according to the information. BPb format
serial number offset address meaning
1 03h-0ah OEM number
2 0bh-0ch bytes per sector
3 0dh sectors per cluster
4 0eh-0fh reserved sectors
5 10h fat backups
6 11h-12h root directory entries
7 13h-14h total sectors
8 15h description media
9 16h-17h sectors per fat
10 18h-19h sectors per disk Number of trace sectors
number of 11 1ah-1bh heads
number of 12 1ch-1fh special hidden sectors
number of 13 20h-23h total sectors
number of 14 24h-25h physical drives
number of 15 26h extended boot visa
16 27h-2ah volume serial number
17 2bh-35h volume label
18 36h-3dh file system number
DOS boot record formula:
file allocation table ≡ reserved sectors Number
root directory ≡ number of reserved sectors + number of fat × Number of sectors per fat
data area ≡ root directory logical sector number + (32 × Number of directory entries in root directory + (bytes per sector-1)) div bytes per sector
absolute sector number ≡ logical sector number + implied sector number
sector number ≡ (absolute sector number mod sectors per track) + 1
head number ≡ (absolute sector number div sectors per track) mod head number
track number ≡ (absolute sector number div sectors per track) div head number
key points: (1) DBR is located in cylinder 0, head 1, sector 1, and its logical sector number is 0
(2) DBR contains DOS bootloader and BPb
(3) BPb is very important, from which the logical address and physical address can be calculated
7. File allocation table
file allocation table is the main component of DOS file organization structure. We know that the most basic unit of DOS allocation is cluster. The file allocation table reflects the usage of clusters on the hard disk. You can know the usage of any cluster by looking up the file allocation table. When DOS allocates space to a file, it always scans fat first, finds the first available cluster, allocates the space to the file, and fills the cluster number of the cluster in the corresponding section of the directory. The cluster number chain is formed. Fat is a table that records the cluster number of files. The first two fields of fat are reserved fields, which are 3 bytes for FAT12 and 4 bytes for fat. The first byte is used to describe the media, and the rest is FFH. The media format is the same as BPb<
the 8-bit meaning of the first byte:
7 65 4 3 21 0
└ - - - ┘踋┌ 0 is not double-sided
Set 1 ū└
ū└ 1 double-sided
ū┌ 0 is not 8 sector
ū└
└ 1 is 8 sector
ū┌ 0 is not replaceable
└
└ 1 is replaceable
FAT12 structure meaning
FAT16 meaning
000h 0000H available
ff0h-ff6h-fff0h-fff6h reserved
ff7h fff7h bad
ff8h-fffh fff8h-ffffffffh file last cluster
ff8h ××× H ×××× H file next cluster
for FAT16, the cluster number × 2 as the offset address, take out a word from fat, that is the field in fat
logical sector number = data area starting logical sector number + (cluster number-2) × The number of sectors in each cluster
cluster number = (logical sector number - starting logical sector number of data area) div number of sectors in each cluster + 2
key points: (1) fat reflects the usage of all clusters on the hard disk, and records the specific location (cluster) of files in the hard disk
(2) the first cluster number of the file (in the directory table) and the cluster number of the fat file are linked together to form a "cluster number chain" of the file, and the root of the damaged file is the "cluster number chain"
(3) the cluster number can be used to calculate the logical sector number. On the contrary, the cluster number can also be calculated from the logical sector number. The formula is as follows
(4) fat is located after DBR, and its DOS sector number starts from 1
8. File directory
file directory is another important part of DOS file organization structure
1. Number of tracks, sectors, cylinders and heads
the most basic component of hard disk is hard metal coated with magnetic media, and the number of disks varies with the capacity of hard disk. Each disc has two sides, which can
record information. Disk is divided into many fan-shaped areas, each area is called a sector, each sector can store 128 × 2 (n = 0.1.2.3). In DOS
each sector is 128 × The second power of 2 = 512 bytes. On the surface of the disk, the center of the disk is the center of the circle. Concentric circles with different radii are called tracks. In a hard disk, a cylinder composed of tracks of different disks with the same radius is called a cylinder. Track and cylinder are circles representing different radii. In many cases, track and cylinder can be used interchangeably. As we know, each magnetic disk has two faces, and each face has a head. It is customary to use the head number to distinguish them. Sector, track (or cylinder) and the number of heads constitute the basic parameters of hard disk structure. With these
parameters, the capacity of hard disk can be obtained. The basic calculation formula is:
storage capacity = number of heads × Number of tracks (cylinders) × Sectors Per Trark × The key points are as follows: (1) there are several disks in the hard disk, two faces in each disk, and one head in each face
(2) the disk is divided into several sectors, namely sectors
(3) concentric circles with different radii of the same disk are magnetic tracks
(4) cylindrical surfaces with the same radii of different disks, namely cylindrical surfaces
(5) formula: storage capacity = number of heads × Number of tracks (cylinders) × Sectors Per Trark × (6) information records can be expressed as follows: ×× Track (cylinder), ×× Magnetic head, ×× Sector
2. Cluster
"cluster" is the smallest unit allocated by DOS. When creating a very small file, such as a byte, it does not occupy only one byte of disk space,
but occupies the whole cluster. DOS depends on different storage media (such as floppy disk, hard disk), different capacity of hard disk, cluster size is not the same. The size of the cluster can be obtained in a block called disk
parameter (BPb). The concept of cluster only applies to data area
this point: (1) "cluster" is the smallest unit that dos allocates
(2) different storage media, different capacity hard disks, different DOS versions, the cluster size is also different
(3) the concept of cluster is only applicable to data area
3. Sector number definition: absolute sector and DOS sector
from the previous introction, we can use cylinder / head / sector to uniquely locate each area on the disk, or cylinder / head / sector has a one-to-one correspondence with each sector on the disk. Generally, DOS calls "cylinder / head / sector" as "absolute sector". But DOS can't directly use absolute sector for information management on disk, instead it uses so-called "relative sector" or "Dos sector"“ "Relative sector" is just a number, such as cylinder 140, head 3 and sector 4. The corresponding relative sector number is 2757. This number has a one-to-one correspondence with the absolute sector "cylinder / head / sector". When using relative sector number, DOS starts from cylinder 0, head 1, and sector 1 (Note: cylinder 0, head 0, and sector 1 have no DOS sector number, and can not be accessed in DOS, and can only be accessed by calling BIOS). The first DOS sector number is 0, and the remaining sectors on the track are 1 to 16 (SET 17 sectors per track), followed by 17 sectors with head 2 and cylinder 0, The formed DOS sector numbers range from 17 to 33. All heads up to the cylinder. Then move to cylinder 1, head 1 and sector 1 and continue to number DOS sectors, that is, assign DOS sector numbers continuously according to the increasing sequence of sector number, head number and cylinder number (track number)
formula: record DH - head number of the first DOS sector
DC - cylinder number of the first DOS sector
DS - sector number of the first DOS sector
ns - number of sectors per track
NH - total head number of disk
then the relative sector number rs of a sector (cylinder C, head h, sector s) is:
rs = NH × NS × C－DC＋NS × H-dh) + (s-ds)
If RS, DC, DH, DS, NS and NH are known, then
s = (RS mod NS) + DS
H = ((RS div NS) mod NH) + DH
C = ((RS div NS) div NH) + DC
main points: (1) the absolute sector represented by cylinder / head / sector is also called physical disk address
(2) the relative sector or DOS sector represented by a single number, (3) conversion formula between relative sector and absolute sector
4. Partition of DOS disk area
a formatted hard disk can be divided into main boot record (MBR), DOS boot record (DBR), file assignment table (fat) according to the function of recorded data, BD: boot directory and data area. The first five important information are on the outer track of the disk. The reason is that the circumference of the outer ring is always larger than that of the inner ring, which means that the storage density of the outer ring is smaller and the reliability is higher< Key points: (1) the whole hard disk can be divided into MBR, DBR, fat, BD and data area
(2) MBR, DBR, fat, and BD are located outside the disk
5. MBR
MBR is located at cylinder 0, head 0 and sector 1 of the first physical sector (absolute sector) of the hard disk. Because DOS starts from cylinder 0, head 1 and sector 1, MBR does not belong to DOS sector and DOS cannot be accessed directly. MBR contains the main bootloader and partition table of hard disk. The partition table has four partition record areas. A record area is a table that records information about partitions. It is continuously stored from the master boot record offset address 01beh, and each partition record area occupies 16 bytes
format of partition table
number of bytes occupied by offset meaning of partition table entries
00 boot indicator 1b
01 partition boot record head number 1b
02 partition boot record sector and cylinder number 2B
04 system indicator 1b
05 partition end head number 1b
06 partition end sector and cylinder number 2B
08 partition front sector number 4B
0C The total number of sectors in the partition is 4B
there can only be one active partition in the four partitions, namely disk C. The flag is 80h at the first byte of the partition table. If 00h, it means inactive partition. For example:
80 01 00 0b Fe 3F 81 3F 00 00 00 C3 DD 1F 00
00 01 82 05 Fe BF 0C 02 de 1F 00 00 00 e 90 61 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00. It does not belong to DOS sector,
(2) main boot record is divided into main boot program and partition table of hard disk
6. DBR
DBR is located in cylinder 0, head 1 and sector 1, namely logical sector 0. DBR is divided into two parts: Dos bootloader and BPb (BIOS parameter block). The DOS boot program completes the location and loading of
DOS system files (io.sys, MSDOS. Sys), and BPb is used to describe the disk information of this DOS partition. BPb is located at the DBR offset 0Bh, with a total of 13 bytes. It contains the parameters used in logical format, which can be used by DOS to calculate the file allocation table on disk, the starting address of directory area and data area, and the three words after BPb to provide some parameters used in physical format (low format). The bootloader or device driver converts the disk logical address (DOS sector number) to the physical address (absolute
sector number) according to the information. BPb format
serial number offset address meaning
1 03h-0ah OEM number
2 0bh-0ch bytes per sector
3 0dh sectors per cluster
4 0eh-0fh reserved sectors
5 10h fat backups
6 11h-12h root directory entries
7 13h-14h total sectors
8 15h description media
9 16h-17h sectors per fat
10 18h-19h sectors per disk Number of trace sectors
number of 11 1ah-1bh heads
number of 12 1ch-1fh special hidden sectors
number of 13 20h-23h total sectors
number of 14 24h-25h physical drives
number of 15 26h extended boot visa
16 27h-2ah volume serial number
17 2bh-35h volume label
18 36h-3dh file system number
DOS boot record formula:
file allocation table ≡ reserved sectors Number
root directory ≡ number of reserved sectors + number of fat × Number of sectors per fat
data area ≡ root directory logical sector number + (32 × Number of directory entries in root directory + (bytes per sector-1)) div bytes per sector
absolute sector number ≡ logical sector number + implied sector number
sector number ≡ (absolute sector number mod sectors per track) + 1
head number ≡ (absolute sector number div sectors per track) mod head number
track number ≡ (absolute sector number div sectors per track) div head number
key points: (1) DBR is located in cylinder 0, head 1, sector 1, and its logical sector number is 0
(2) DBR contains DOS bootloader and BPb
(3) BPb is very important, from which the logical address and physical address can be calculated
7. File allocation table
file allocation table is the main component of DOS file organization structure. We know that the most basic unit of DOS allocation is cluster. The file allocation table reflects the usage of clusters on the hard disk. You can know the usage of any cluster by looking up the file allocation table. When DOS allocates space to a file, it always scans fat first, finds the first available cluster, allocates the space to the file, and fills the cluster number of the cluster in the corresponding section of the directory. The cluster number chain is formed. Fat is a table that records the cluster number of files. The first two fields of fat are reserved fields, which are 3 bytes for FAT12 and 4 bytes for fat. The first byte is used to describe the media, and the rest is FFH. The media format is the same as BPb<
the 8-bit meaning of the first byte:
7 65 4 3 21 0
└ - - - ┘踋┌ 0 is not double-sided
Set 1 ū└
ū└ 1 double-sided
ū┌ 0 is not 8 sector
ū└
└ 1 is 8 sector
ū┌ 0 is not replaceable
└
└ 1 is replaceable
FAT12 structure meaning
FAT16 meaning
000h 0000H available
ff0h-ff6h-fff0h-fff6h reserved
ff7h fff7h bad
ff8h-fffh fff8h-ffffffffh file last cluster
ff8h ××× H ×××× H file next cluster
for FAT16, the cluster number × 2 as the offset address, take out a word from fat, that is the field in fat
logical sector number = data area starting logical sector number + (cluster number-2) × The number of sectors in each cluster
cluster number = (logical sector number - starting logical sector number of data area) div number of sectors in each cluster + 2
key points: (1) fat reflects the usage of all clusters on the hard disk, and records the specific location (cluster) of files in the hard disk
(2) the first cluster number of the file (in the directory table) and the cluster number of the fat file are linked together to form a "cluster number chain" of the file, and the root of the damaged file is the "cluster number chain"
(3) the cluster number can be used to calculate the logical sector number. On the contrary, the cluster number can also be calculated from the logical sector number. The formula is as follows
(4) fat is located after DBR, and its DOS sector number starts from 1
8. File directory
file directory is another important part of DOS file organization structure
10. Disk is divided into many fan-shaped areas, each area is called a sector, each sector can store 128 × 2 (n = 0.1.2.3).
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