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I would like to know

  1. What is the exact meaning of primary partitions? Why it is named so? and why it is restricted to 4?

  2. What is meant by extended partitions? Why it is named so? and what is the possible number of extended partitions in the hard disk?

  3. What is mean by logical partitions? Why it is named so? How it is calculated?

What are the advantages of these software partitioning?

Is it it possible to install OS(Linux/windows) in all partitions ? If no, why?

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closed as off topic by xenoterracide Oct 16 '10 at 3:22

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This is probably a question for Super User; I don't think any part of it is Linux-specific –  Michael Mrozek Oct 15 '10 at 21:59
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2 Answers 2

up vote 1 down vote accepted

Hard drives have a built-in partition table on the MBR. Due to the structure of that table the drive is limited to four partitions. These are called primary partitions.

You can have more partitions by creating virtual ( called logical ) partitions on one of the four primary partitions. There is a limit of 24 logical partitions.

The partition you choose to split into logical partitions is called the extended partition, and as far I understand you can have only one.

The advantage to logical partitions is quite simply that you can have more than 4 partitions on a disk.

You should be able to install any OS on all of the partitions.

See this page for more details

In the current IBM PC architecture, there is a partition table in the drive's Master Boot Record (section of the hard dirve that contains the commands necessary to start the operating system), or MBR, that lists information about the partitions on the hard drive. This partition table is then further split into 4 partition table entries, with each entries corresponding to a partition. Due to this it is only possible to have four partitions. These 4 partitions are typically known as primary partitions. To overcome this restriction, system developers decided to add a new type of partition called the extended partition. By replacing one of the four primary partitions with an extended partition, you can then make an additional 24 logical partitions within the extended one.

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Not clear! Can you please little bit technical? –  Renjith G Oct 15 '10 at 21:42
    
updated my answer, is that what you were looking for? –  Stefan Oct 15 '10 at 21:59
    
some what..but i want to get more technical details. For example: "Due to the structure of that table the drive is limited to four partitions"How the structure look like? Why it restricts to 4 only? Now the technology has grown and why didn't they change it to n ? Meaning there should be a good/superb logic(may be bitwise) behind that restriction...I am interested in that.. –  Renjith G Oct 15 '10 at 22:27
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We can only have 4 Primary partitions because of the Master Boot Record being 512 bytes. 64 of those bytes are available for the partition Table. A primary partition takes 16 bytes. The other 446 bytes are used for the rest of the MBR.

If you want a really technical answer, you can read the Wikipedia article, http://en.wikipedia.org/wiki/Master_boot_record

It has images of the MBR and a breakdown of each sections functions, as well as the breakdown of the Partition table and each sections functions.

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