In-depth analysis of Microsoft system formatting conflicts

For Microsoft operating systems, formatting often happens. However, there are also many problems in the formatting process. In the face of problems in formatting, many friends feel overwhelmed. After encountering the problem of formatting conflicts, this friend actively researches and even explores the things behind the problem through experiments. This is a practice worth advocating to learn about computers.

If a friend asks, "I formatted the C drive after I started it with a DOS boot disk. After I restarted it, I still entered the operating system of the C drive. Instead, all the content on the d drive disappeared ." You will not hesitate to answer: "That's because your C drive is converted to the NTFS format when it is installed or installed, while the C drive in the NTFS format is invisible in the real DOS mode, therefore, the C disk you see and formatted in DOS is actually the D disk in win." As a matter of fact, the fact that NTFS-format partitions do not recognize the drive letter in real DOS mode is already the knowledge of most friends.

However, if I ask, "I formatted the D disk after I started it with a DOS boot disk. After I restarted it, the hard disk could not enter the system. After checking that the data on the d disk was still there, the data on the C disk would be gone ." I believe it will get confused. Next we will use an experiment to solve this fault. For convenience, for win2000 (nt5.0), WINXP (nt5.1), and win2003 (nt5.2), we will refer to "NT System" below "; the "dos boot disk" refers to the DOS boot disk (msdos7.1) of Win98, which we currently use most frequently ). In order to avoid confusion on the drive letter when the problem is clearly stated and the fault we target, the partition format of the hard disk is also set to the most common FAT32 format.

Now we are doing experiments in a standard format.

Step 1: Start the DOS boot disk and use fdisk to partition the hard disk: Primary partition (drive C), extended partition, logical partition 1 (drive D), logical partition 2 (drive E) and activate the primary partition. After the restart, format the three partitions in format. (This step can also be performed by PQ or DM)

Step 2: continue to use the NT System disc to start the installation system to drive C.

Step 3: Enter the NT System after installation. Open my computer, right-click drive D, and select "format" (the file format is still FAT32 ). After formatting, copy a few files to drive d to view the formatting result.

Step 4: Start the system with a DOS disk after restart, and format the D disk with the format command: A:/> Format D: Or a:/> Format D:/Q

Step 5: restart. fault: all data on drive C is lost, and drive D files still exist.

Analysis: as long as the operations in step 3 are skipped and no fault occurs, we will start from the beginning and end of step 3. After step 2 is executed, we will not rush to step 3, instead, use the DOS boot disk to start and debug the data of the 0-Sector D disk to view the changes in its BPB table (some unaffected BPB table data is not described here)

A:/> debug
-L 100 3 0 1
-D 11C L4
B7 72 13 02
-Q

The hexadecimal value displayed in the preceding operation is defined as the number of special hidden sectors in the BPB table. The differences between the FAT32 and fat16 formats are described below:

In FAT32 format: this value is the number of sectors from the start sector of the Logical Disk to the first partition table (also known as the primary boot sector or the hard disk 0-bar 0-way 1-sector, the partition size is different.

In fat16 format: this value is the number of sectors of the starting sector of the Logical Disk relative to the partition table of the disk (each Logical Disk corresponds to a partition table). The value is generally fixed, it is equivalent to the number of sectors per head in the hard disk parameter. The current number of sectors per head in the hard disk is 63, I .e., the hexadecimal 3f, which is embodied in the BPB table as 3f 00.

In actual use, we found that this four-byte value is not related to the active Partition Boot system and formatting, but other read/write operations have no adverse effect.

Write down the four bytes in the BPB table and proceed with Step 3. In Step 4, the format operation is not performed first after the DOS disk is started, use DEBUG again to check the execution result of step 3:

A:/> debug
-L 100 3 0 1
-D 11C L4
3f 00 00 00
-Q

We found that the value was rewritten by the format of the NT System as fat16, the format command in the DOS boot disk uses this value to determine the start position of the Logical Disk when formatting partitions in the FAT32 format, after being rewritten to 3f 00 00, it will be exactly the same as the starting position of our c drive. Now, after you run format D: or format D:/Q, the files on your drive C can only be viewed by the data recovery software.

Here we also found a strange phenomenon in the NT system. If you are familiar with the compilation, you can use DEBUG in the command prompt of the NT System to query the Virtual DOS version number, which is version 5.0, in real DOS mode, msdos5.0 only supports fat16, but does not support FAT32. I believe that when formatting a partition in FAT32 format, it is related to entering four bytes in the BPB table.

Not just formatting in the window of the NT System, also, formatting during the installation of the NT System and formatting in the console will convert the value in the bpb table of the FAT32 format partition to the fat16 standard, this leaves a hidden danger to friends who are used to dealing with problems in DOS. You must be careful when formatting non-primary partitions in FAT32 format in real DOS mode. In the example above, even if the drive C has been converted to the NTFS format (format D: Format C :), it is hard to escape. From time to time on the Internet, my friends may mention this kind of fault. I hope you will learn from the experiment and analysis above.

Prevention: if you do not know whether the FAT32 format logical partition on your machine or your friend has been formatted by the NT System, if you really need to format it in real DOS mode, run the Sys command First (four bytes in the BPB table that affects the format mentioned above) and then run the format command to reduce unnecessary losses. In the fourth step above, if we run a:/> sys D: And then a:/> Format D:/Q, We can correctly format the D disk.