How to do data loss to help you find it back

Many users will encounter such problems, the data loss caused by the damage of the hard disk, there are many important data loss, what should I do, in fact, the data can be recovered Today, this tutorial will share with you how to recover the data in the hard disk. Let's take a look.

Main Boot Sector

The main boot sector is located on the 0 track 0 cylinder 1 sector of the entire hard disk, including the hard disk master boot record MBR (Main Boot Record) and partition table DPT (Disk Partition Table). The role of the master boot record is to check the partition table is correct and determine which partition is the boot partition, and at the end of the program, the boot program of the partition (that is, the operating system boot sector) is loaded into memory for execution. As for the partition table, many people know that the beginning flag of 80H or 00H, with 55AAH as the end mark, a total of 64 bytes, is located at the very end of this sector. It is worth mentioning that the MBR is generated by a partitioning program (such as DOS's Fdisk.exe). Different operating systems may have different sectors. If you have this intention, you can write one yourself, as long as it can complete the above tasks, which is why you can achieve multi-system startup (saying off topic: just because this master boot record is easy to write, it appears A lot of boot sector viruses).

Operating system boot sector

OBR (OS Boot Record) is the operating system boot sector, usually located on the hard disk 0 track 1 cylinder 1 sector (this is for DOS For those systems that boot in multiple boot mode, they are located in the first sector of the corresponding primary/extended partition. It is the first sector that the operating system can directly access. It also includes a bootloader and a called This partition parameter record table for BPB (BIOS Parameter Block). In fact, each logical partition has an OBR, and its parameters vary depending on the size of the partition and the type of operating system. The main task of the bootloader is to determine whether the first two files in the root directory of the partition are the boot files of the operating system (such as MSDOS or IO.SYS and MSDOS.SYS of Win9x/Me originating from MSDOS). If so, the first file is read into memory and control is given to the file. The BPB parameter block records the starting sector, ending sector, file storage format, hard disk media descriptor, root directory size, FAT number, allocation unit (Allocation Unit, formerly called cluster), etc. of the partition. Important parameters. OBR is generated by an advanced formatter (such as DOS's Format.com).

File Allocation Table

FAT (File Allocation Table) is a file addressing system for DOS/Win9x systems. For data security, FAT generally does two, second. FAT is the backup of the first FAT, and the FAT area is immediately after the OBR, and its size is determined by the size of the partition and the size of the file allocation unit. There have been many choices about the format of FAT. Microsoft's DOS and Windows use the FAT12, FAT16 and FAT32 formats we are familiar with, but otherwise there is no FAT in other formats, like Windows NT, OS/2, UNIX/Linux, Novell. I have my own way of managing files.

Directory area

DIR is short for Directory, which is the root directory area. DIR is immediately after the second FAT table. Only FAT can't locate the file on disk. FAT must also be The DIR fit can accurately locate the location of the file. The DIR records the starting unit (which is the most important) of each file (directory), the attributes of the file, and so on. When locating the file location, the operating system can know the specific location and size of the file on the disk according to the starting unit in the DIR and the FAT table. After the DIR area, it is the real data storage area, namely the DATA area.