Primary / extended partition
The partition table in the partition sector of the
MBR can contain at most four entries. This could be either only primary
partitions (max. four) or exactly one extended partition and up to
three primary partitions. This convention allows, for example, that on
a second hard disk only one extended partition is created.
Primary partition:
A primary partition is completely defined by its entry in the partition table.
This entry contains the information about the beginning and end of the partition,
the type of the partition and the position of the accompanying boot sector.
Extended partition:
In the case of an extended partition the entry in the partition table of the MBR
describes only the space reserved for the extended partition. This space can
be split in up to 24 logical drives. Logical drives can be created only inside
an extended partition. In simple words, the extended partition represents the
space reserved for the logical drives. The partition entry in the MBR points
to the partition sector of the first logical partition, which resides directly at the
beginning of the extended partition.
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