MBR (master boot record) is a piece of code located in the boot sector of the disk, which contains information such as the boot program WindowsDiskSignature. In MBR, WindowsDiskSignature takes 4 bytes (32 bits) to identify the uniqueness of the disk. This value is located in the MBR structure after the boot program, followed by the partition table. It should be noted that MBR only supports four disk partitions at most, and logical disks and disk partitions are not necessarily one-to-one correspondence.