Top 10 hard drive troubleshooting strategies

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1. Familiar with the use of basic operation commands/shortcuts in CAD
Most people know this. The Ancients cloud: Practice makes perfect. The basic commands and quick icons are the most familiar ones in CAD, and they should be well mastered, so I will not discuss them in detail.

Ii. Modify the Acad. PGP File
　　
We all know that the line command can be simplified to L when the command is input. Why? Because there is an encrypted file named Acad. PGP in AutoCAD that defines the line command
To open the file. Find "these examples include most frequently used
Commands. you can define the shorthand for the following lines of text, remember that its left column is the short command text implementation you can modify according to your needs (of course, you are familiar with English
It is the default command in the right column. Do not modify it at will. I believe this will increase your speed.

3. Operations on graphical points
Click it. Have you used it? When you click a graph with the left mouse button, many boxes are displayed on the graph. You can perform some basic editing operations by controlling the click. For example, copy, move, and change the layer of the image. In addition, different images have special operations. For example, a straight line has an extension operation.

4. Use a large number of modification commands
　　
For the CAD Drawing staff, a figure 60% -- 70% is modified, only 30% -- 40% is the drawing, which regularly backs up data at work, is to ensure system crash and hard disk loss
An important way to restore data in a timely manner after the fault occurs. Therefore, we should develop a good habit of backing up data frequently at work. In addition, you also need to learn how to save the hard disk when the hard disk fails, or extract from the bad area
Produce useful data to minimize the loss.

I. Hard Disks are not recognized by the System

The system cannot be started from the hard disk, nor can it be started from disk A into disk C. The existence of the hard disk cannot be found by using the automatic monitoring function in CMOS. Most of these failures occur on the connection cable or IDE port.
The failure of the hard disk itself is unlikely. You can re-plug the hard disk cable or change the IDE port and cable to perform replacement tests, and the fault will soon be detected. If the new hard disk is not accepted
The common cause is the master-slave jumper on the hard disk. If an IDE hard disk is connected to two hard disk devices online, the master-slave relationship should be clearly identified.

Ii. faults caused by CMOS

Whether the hard disk type in CMOS is correct directly affects the normal use of the hard disk. All current machines support "Ide auto
Detect, which can automatically detect the hard disk type. When the hard disk type is wrong, sometimes the system cannot be started, sometimes the system can be started, but a read/write error occurs. For example, the hard disk type in CMOS is smaller
The actual disk capacity, the sectors behind the hard disk will not be able to read and write, if the status is multi-partition, then individual partitions will be lost. There is another important cause of failure. Because the current ide supports the logical parameter type, the hard disk can
"Normal, LBA, large" and so on are used. If data is installed in normal mode and changed to another mode in CMOS, a read/write error occurs on the hard disk, because of its ing
The original hard disk location cannot be read because the link has changed.

Iii. startup failure caused by the Main Boot Program

The primary boot program is located in the primary Boot Sector of the hard disk. It is mainly used to check the correctness of the hard disk partition, determine the active partition, and hand over the boot right to the DoS or other active partition.

Operating System. If the program is damaged, it cannot be booted from the hard disk, but the hard disk can be read and written after being started from the soft drive or optical drive. The troubleshooting method is relatively simple. The fdisk with a higher DOS version is the most
Convenience. When the system runs with parameters/MBR, the Main Boot Program of the hard disk will be directly replaced (overwritten. In fact, the Main Boot Sector of the hard disk is created by this program. fdisk. EXE contains the complete hard disk.
The main Bootstrap program. Although the DOS version is constantly updated, the Main Boot Program of the hard disk remains unchanged, from Dos 3.x to ipvs.
95 dos, as long as you find a DOS boot disk to start the system and run this program to repair.

4. startup Fault Caused by Partition Table Error

Partition Table errors are serious hard disk errors. Different levels of errors may cause different losses. If there is no active partition flag, the computer cannot start. However, you can read and write the hard disk after the drive or the Drive boot system. You can use fdisk to reset the active partition for repair.

If a partition type is incorrect, the loss of a partition may occur. The fourth byte of the partition table is the partition type value. Normally, the basic DOS partition value larger than 32 MB is 06, and the extended DOS partition value is 05. Many people use this type of value to encrypt a single partition and restore the original correct type value to restore the partition to normal.

The partition table contains other data used to record the start or end address of the partition. Damage to the data will cause confusion or loss of the partition. The available method is to re-write the data in the backup partition table, you can also obtain partition table data from other hard disks of the same type and with the same partition status.

The recovery tool can use tools such as nu for easy operation. Of course, you can also use DEBUG for operations, but the operations are cumbersome and risky.

V. Fault with incorrect partition valid flag

There is also an important part in the Main Boot Sector of the hard disk, that is, the last two bytes: "55aa", which is a valid symbol of the sector. When the disk, floppy disk, or disc is started
Test the two bytes. If the two bytes exist, the hard disk exists. Otherwise, the hard disk is not recognized. This can be used for the encryption technology of the entire hard disk, and the debug method can be used for recovery. In addition, when the DOS Boot Sector
If the boot flag is not displayed, the system startup will be shown as "mmissing Operating System ". The convenient method is to use the following common repair methods for the dossystem.

6. startup Fault Caused by DOS boot System

The dos boot system consists of the DOS Boot Sector and the DOS system file. System files include IO. sys, msdos. sys, and command. com.
Command. com is a DOS shell file, which can be replaced by other similar files, but is a required file for DOS Startup by default. In Windows
In the dossystem carried by 95, msdos. sys is a text file that is required to start Windows, but this file is not used only when DOS is started. When a DOS boot error occurs
Use the Sys C: Command to send the system to the boot system of the disk or CD to fix the fault, including the Boot Sector and system files.

VII. read/write failures caused by fat tables

The fat table records the storage address of the hard disk data. Each file has a set of fat chains to specify the address of the cluster to store. Corruption of the fat table means the loss of file content. Fortunately, the DOS system
Two fat tables are provided. If the current fat table is damaged, use the second one to overwrite and fix it. However, the fat table length of disks of different specifications and the address of the second fat table are not fixed.
So you must find the correct position for the repair. Some tool software such as Nu has such repair functions and is very convenient to use. Debug can also be used to achieve this operation, that is, its m life is used.
Move the second fat table to the first table. If the second fat table is damaged, the hard disk cannot be restored to the original state, but the file data is still stored in the hard disk data area.
Run the chkdsk or Scandisk command to fix the issue and finally obtain the *. Chk file. This is the loss of the sector data of the fat chain. If it is a text file, you can extract the complete or part of the file from it.
Content.

VIII. Guide Fault Caused by directory Table Corruption

The directory table records the file name and other data in the hard disk. The most important one is the starting cluster number of the file. Because the directory table does not have the automatic backup function, if the directory is damaged, a large number of files will be lost.
. One method to reduce the loss is to use the chkdsk or Scandisk program to recover the *. Chk file from the hard disk. Because the directory table is damaged, only the first cluster number is lost.
A *. Chk file is a complete file. Change it to the original name to restore most files.

9. Data Recovery during accidental deletion of partitions

After the hard disk partition is deleted using fdisk, the data on the hard disk disappears completely. When the hard disk is not formatted, it is displayed as an invalid drive. If you know how fdisk works
You will know that fdisk only rewrites the content in the primary Boot Sector of the hard disk (0-side, 0-way, 1-sector). Specifically, it deletes the partition table information of the hard disk, the data in any partition on the hard disk is not changed.
Change. You can recover the original partition and data by following the preceding solution to partition table errors. If you have already formatted the partition, you can restore the partition according to the following method after the partition is restored.
Zone data.

10. recover accidentally formatted Hard Disk Data

In a high version of DOS, the format formatting operation creates disk information for restoring formatting by default. In fact, the DOS Boot Sector and FAT partition table of the disk are used.
And all contents of the Directory table are copied to the last several sectors of the disk (because the following sectors are rarely used), and the content in the data area is not changed at all. In this way, run the unformat command to restore
. In addition, DOS also provides a miror command to record the information of the current disk for formatting or restoration after deletion. This method is also effective.