Partitioning is one of the necessary steps to prepare a drive for use. It is the process of defining certain areas of the hard disk for the operating system to use as a volume. A volume is a section of the drive with a letter, like C: or D:. All hard drives must be partitioned, even if they will have only one partition called C:.

A partition program writes a master partition boot sector to cylinder 0, head 0, sector 1. The data in this sector defines the start and end locations of each of the other partitions. It also indicates which of these partitions is active, or bootable, thus telling the computer where to look for the operating system.

All systems can handle 24 partitions, either spread out on the same drive or many drives. This means that one can have up to 24 different hard drives, according to DOS. DOS can’t recognize more than 24 partitions, although some other OSes may. The limiting factor is simply the availability of letters. All partitions must have a letter. There are 26 letters, A: and B: are reserved for floppy drives, leaving 24 letters available.

Although there are third party partitioning programs that boast added capabilities, DOS FDISK is the accepted program for partitioning. FDISK sets up the partition in a way optimum for DOS, and allow more than one OS to operate on one system.

FDISK only shows two DOS partitions, the primary partition and the extended partition. The extended partition is divided into logical DOS volumes, each being a separate partition. The minimum partition size is one megabyte, due to the fact that FDISK in DOS 4.0 or later create partitions based on numbers of MB. Partition size is usually limited to 2G. DOS versions earlier than 4.0 allow max partitions of 32MB. Using the Fat32 system under DOS 7 and Windows 95 OSR2, max partition size is kicked up to 2T, or 2,000G.

While FDISK has no trouble recognizing FAT partitions, it will not recognize partitions once formatted with NTFS.  If you wish to make changes to NTFS partitions, it may be easier to use Windows’ Disk Management tool.  NTFS partitions do not delete in FDISK like FAT partitions would.  A zero-fill of the drive may be needed to remove the NTFS partitions if FDISK is the only option.  Note that this will erase all the data on the drive.

How To Partition

The first partition is your primary DOS partition. This is your C: drive and can’t be divided. This is also called the active partition. You can only have one active partition.

The second partition is optional. It is called an extended partition. This is the space left over after the primary partition. Each extended partition must be labeled with a letter D: through Z:. In FDISK, there is one extended partition, with it being divided up into Logical DOS Drives which each have a drive letter.

To start this, type “fdisk” at the A> prompt. If this doesn’t work, it is because your drive is not installed correctly.

First you have to setup a primary DOS partition. Choose Option 1 ( Create DOS partition or Logical DOS drive). Choose Option 1 in the next menu. Now you can make your entire C: drive the primary partition or only a part of it. Many people just make the entire drive one partition just to stay simple. If you want to break from this norm, specify the amount of drive you want to partition in either megabytes or percentage of total drive. If you are using a percentage, be sure to follow the number by a “%” or the computer will think you’re talking MB’s.

Next, you’ll need to make this partition active. Return to the main FDISK menu and choose Option 2 ( Set Active Partition). Follow the prompts.

If you’re going to create an extended partition, choose Option 1 again, but this time choose Option 2 in the next menu ( Create Extended DOS partition). Plug in the percentage of drive to partition for this one. Do not make this partition active. Only one can be active.

After you create an extended partition, you will be given the Create Logical Drives option in the extended partition menu. Follow the on-screen instructions to assign drive letters to your partitions D: through Z:. Keep in mind that D: is often used for the CD-ROM.

After all this is done, you can choose Option 4 ( Display Partition Information) and check your work.

Optional FDISK Functions

FDISK in DOS 5.0 or later is more powerful than most people know. There are several options available with the program that are undocumented in the DOS manuals. The bad news is that these command are unavailable with Windows 95. Instead, you will have to purchase a third party program such as PartitionMagic.

The most useful, in my opinion, is the “/MBR” parameter. This parameter tells FDISK to rewrite the Master Partition boot sector based on the partitions present on the drive, without damaging the partitions on the drive. This is very useful when recovering from a virus that infects the boot sector of the drive. Use it by typing “FDISK /MBR” at the A> prompt.

To back up the partition table onto a floppy diskette, type “MIRROR /PARTN”. This uses the MIRROR program to copy the partition table into a file called PARTNSAV.FIL. This can then be stored on your system disk. To restore this partition info, type “UNFORMAT /PARTN”.