3.4. MBR disk partitions

The partition table is stored at the very start of the disk, before any file system or user data.

For a more clear example, the partition table is shown as being separate in the following diagrams.

图 3.2. Disk with MBR partition table

As the previous diagram shows, the partition table is divided into four sections of four unused primary partitions. A primary partition is a partition on a hard disk drive that contains only one logical drive (or section). Each logical drive holds the information necessary to define a single partition, meaning that the partition table can define no more than four primary partitions.

Each partition table entry contains important characteristics of the partition:

The starting and ending points define the size and location of the partition on the disk. Some of the operating systems boot loaders use the active flag. That means that the operating system in the partition that is marked "active" is booted.

The type is a number that identifies the anticipated usage of a partition. Some operating systems use the partition type to:

The following diagram shows an example of a drive with a single partition. In this example, the first partition is labeled as DOS partition type:

图 3.3. Disk with a single partition