Disk Partitioning
Partitioning Primer
This article first appeared in the April 2002 edition of Computer Video Magazine, together with reviews of a number of popular partitioning tools.
What is a disk partition?
All Microsoft's operating systems, from DOS onwards, have used the idea of single letters to identify disk drives. A and B are reserved for two diskette drives, and the first hard-disk drive is C. Extra hard drives are identified as D, E, etc.
However, these “hard drives”are not quite the same as the drive units that are screwed into the computer. The space on each physical drive is divided into one or more chunks, called partitions, and the drive letters actually correspond to partitions, not physical units.
Most new PCs are shipped with one hard drive, configured with a single partition occupying all the available space, so the possibility of multiple partitions isn't immediately apparent. It's tempting to describe such a drive as “not partitioned”, but that's not really true. A drive letter always corresponds to a partition, even if there is only one partition on the drive. A drive that really has no partitions (such as a brand-new one) is not even recognised by the operating system.
Why have partitions?
Microsoft's operating systems have always struggled to keep pace with the relentless rise in hard disk capacity. Partitioning was first introduced when DOS was limited to 32 MB per drive, simply to allow bigger physical disks to be divided into multiple drive letters, each 32 MB or less.
Partitioning is currently not required for such reasons, but it is nonetheless very useful as a way of organising hard disk space. It can also be used if you want to boot different operating systems, by installing each system on a separate partition. With the huge drive capacities that are now common, dividing a drive into partitions makes a lot of sense.
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