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As xref:figu-partitions-partition-table[Disk Drive with Partition Table] shows, the partition table is divided into four sections or four _primary_ partitions. A primary partition is a partition on a hard drive that can contain only one logical drive (or section). Each section can hold the information necessary to define a single partition, meaning that the partition table can define no more than four partitions.
Each partition table entry contains several important characteristics of the partition:
The points on the disk where the partition starts and ends
Whether the partition is "active"
The partition's type
The starting and ending points define the partition's size and location on the disk. The "active" flag is used by some operating systems' boot loaders. In other words, the operating system in the partition that is marked "active" is booted.
The type is a number that identifies the partition's anticipated usage. Some operating systems use the partition type to denote a specific file system type, to flag the partition as being associated with a particular operating system, to indicate that the partition contains a bootable operating system, or some combination of the three.
See xref:figu-partitions-single-part[Disk Drive With Single Partition] for an example of a disk drive with single partition.
Disk Drive With Single Partition
Image of a disk drive with a single partition.
The single partition in this example is labeled as `DOS`. This label shows the *partition type*, with `DOS` being one of the most common ones. The table below shows a list of some of the commonly used partition types and hexadecimal numbers used to represent them.
Partition Types
|Partition Type|Value|Partition Type|Value
|Empty|00|Novell Netware 386|65
|DOS 12-bit FAT|01|PIC/IX|75
|XENIX root|02|Old MINIX|80
|XENIX usr|03|Linux/MINUX|81
|DOS 16-bit <=32M|04|Linux swap|82
|Extended|05|Linux native|83
|DOS 16-bit >=32|06|Linux extended|85
|OS/2 HPFS|07|Amoeba|93
|AIX|08|Amoeba BBT|94
|AIX bootable|09|BSD/386|a5
|OS/2 Boot Manager|0a|OpenBSD|a6
|Win95 FAT32|0b|NEXTSTEP|a7
|Win95 FAT32 (LBA)|0c|BSDI fs|b7
|Win95 FAT16 (LBA)|0e|BSDI swap|b8
|Win95 Extended (LBA)|0f|Syrinx|c7
|Venix 80286|40|CP/M|db
|Novell|51|DOS access|e1
|PReP Boot|41|DOS R/O|e3
|GNU HURD|63|DOS secondary|f2
|Novell Netware 286|64|BBT|ff
Partitions Within Partitions - An Overview of Extended Partitions
In case four partitions are insufficient for your needs, you can use _extended partitions_ to create up additional partitions. You do this by setting the type of a partition to "Extended".
An extended partition is like a disk drive in its own right - it has its own partition table which points to one or more partitions (now called _logical partitions_, as opposed to the four _primary partitions_) contained entirely within the extended partition itself. xref:figu-partitions-extended[Disk Drive With Extended Partition], shows a disk drive with one primary partition and one extended partition containing two logical partitions (along with some unpartitioned free space).
Disk Drive With Extended Partition
Image of a disk drive with an extended partition.