I would like to know What is the exact meaning of primary partitions? Why it is named so? and why it is restricted to 4?What is meant by extended partitions? Why it is named so? and what is the possible number of extended partitions in the hard disk?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?
Meaning of hard disk drive software partitions?
partition
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 detailsIn 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.