Definition
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| Byte offset | Number of bytes | Description | Value |
|---|---|---|---|
| 0 | 440 | Boot code used to launch the operating system | |
| 440 | 4 | Drive signature (hexadecimal string) | |
| 444 | 2 | 00 00 | |
| 446 | 64 | Master partition table (four 16-byte entries to describe partitions). | |
| 510 | 2 | Marker to notate the end of the MBR | 55 AA |
Partition tables
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The MBR partition table is comprised of four 16-byte entries that define the size, type, and location of logical volumes on the disk. Partition tables identify the type and location of partitions on the device. a disk and conform to a standard layout regardless of the operating system. Each 16-byte entry in the MBR partition table includes the following information:
- Boot indicator
- Starting CHS address
- Partition type ID
- Endinging CHS address
- Starting LBA address
- Number of sectors in the partition
The following table further describes the fields in each 16-byte entry in the partition table (offsets are shown from the start of the partition entry, not the start of the MBR):
| Byte offset | Number of bytes | Description | Value |
|---|---|---|---|
| 0 | 1 | Boot indicator - Indicates whether the volume is the active partition (i.e., bootable). 00 for "do not use for booting" and 80 for "active partition." | 00 or 80 |
| Starting CHS address (3 bytes) | |||
| 1 | 1 | Starting head | |
| 2 | 6 bits | Starting sector - uses bits 0-5. Bits six and seven are used by the starting cylinder field | |
| 2 | 10 bits | Starting cylinder - uses 1 byte in addition to the upper two bits from the starting sector field to make up the cylinder value. The starting cylinder is a 10-bit number, with a maximum value of 1023 | |
| 4 | Partition type (file system ID) | ||
| Ending CHS address (3 bytes) | |||
| 5 | 1 | Ending head | |
| 6 | 6 bits | Ending sector -uses bits 0-5. Bits six and seven are used by the ending cylinder field. | |
| 6 | 10 bits | Ending cylinder - uses 1 byte in addition to the upper two bits from the ending sector field to make up the cylinder value. The ending cylinder is a 10-bit number, with a maximum value of 1023 | |
| 8 | 4 | Relative sectors (LBA offset to the partition) - The offset from the beginning of the disk to the beginning of the logical volume. Used to locate partitions larger than 8.4 GB. | |
| 12 | 4 | Total sectors (length of the partition) - Total number of sectors in the logical volume | |
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Microsoft. Master boot record. https://technet.microsoft.com./en-us/library/cc976786.aspx.
NTFS.com. Hard drive partition. partition table. http://www.ntfs.com/partition-table.htm.