You can create maximum 4 primary partitions in one disk.We can set any one partition as active with OS files.
i.e Active Partition loads boot file
Primary partitions can be extended to create unlimited drives in a computer.
- An extended partition is a container that can hold one or more logical drives.
- Logical drives function like primary partitions except that they cannot be used to start an operating system.
- Each hard drive requires one drive letter per partition, and there are 24 drive letters (C-Z) available.
- So you can have up to 24 hard drives, if each one has only one partition.
- A hard drive can have four primary partitions.
- One of them can be an extended partition that contains multiple logical partitions.
Also Look , Why C is default drive ?