DOS Format

DOS Format

To format an unformatted floppy fresh from the box, put it into drive A or B and type:

         format a:   or   format b:

and answer the prompts.

FLOPPY DISK SIZES
There are four floppy disk capacities:

   Diameter  Capacity  Name
   5.25"     1.2MB     High density
   5.25"     360KB     Low density (Double Density)
    3.5"    1.44MB     High density
    3.5"     720KB     Low density (Double Density)

Higher-density drives can read and write low-density disks. But to format a low-density disk in a high-density drive, you must modify the command as follows.

FORMATTING 5.25" DISKS
To format a 360K disk in a 1.2M drive, type:

    format a: /4         All versions
    format a: /f:360     DOS 4.01 and up

Caution!
360K disks formatted on very early 1.2MB drives may cause reading problems.

FORMATTING 3.5" DISKS
To format a 720KB disk in a 1.44MB drive, type:

    format a: /n:9 /t:80  All versions
    format a: /f:720      DOS 4.01 and up

To format a 1.44M disk in a 2.88M drive, type:

             format a: /f:1.44

REFORMATTING A FLOPPY (As of DOS 5)
The /q switch causes Format to bypass checking for bad sectors. To quickly reformat a formatted disk that you know is OK, type:

             format a: /q

Previous to DOS 5, the format program completely formatted a floppy losing all data if previously formatted. As of DOS 5, Format creates a "safe format" by saving additional data on the disk. This takes a bit longer but allows the disk to be unformatted. Since you will not have to unformat blank disks, you can format "unconditional" and speed up the format process with the /u switch:

             format a: /u

Also previous to DOS 5, any bad sector on a diskette eliminated the entire track. As of 5, only that sector is marked as bad.

CREATING A BOOTABLE FLOPPY
To format a floppy and make it "bootable" by copying DOS from the hard disk onto it, type:

             format a: /s

The DOS COMMAND.COM file is also necessary on the bootable floppy. Starting with DOS 5, the Format command copies COMMAND.COM to the floppy automatically. In DOS 4.01 and earlier, you have to copy COMMAND.COM manually.

Formatting a Hard Disk Is Three Steps

         WHAT YOU DO         WHAT YOU USE
   1. Low-level format    Low-level format program
   2. Create partitions   FDISK.EXE program
   3. High-level format   FORMAT.COM program

LOW-LEVEL FORMAT
All IDE hard disks and most SCSI disks are already low-level formatted at the factory. Sometimes the SCSI host adapter (controller card) requires that a low-level format be performed on each new SCSI drive that is added to the system. Read the instructions that come with your host adapter to be sure. The low-level SCSI format utility is typically built into the host adapter and is launched by pressing a certain key immediately after the computer is turned on.

CREATE PARTITIONS WITH FDISK
Every hard disk must be partitioned after it is low-level formatted. Even if one drive letter serves the entire disk, you must use the Fdisk utility to create a primary partition for that disk. If your DOS version cannot support the full size of the disk, or if you want to divide up your disk for your own storage reasons, you first make a primary partition and then an extended partition for the logical drives to reside in.

          DOS       Disk size
          Version   Supported
          3.3       32MB
          4.0       512MB
          5.0       2GB
          6.0       2GB

To Fdisk your C: drive, boot the computer with a bootable floppy in drive A:, which also contains the FDISK.EXE program. At the A: prompt, type:

               A:\>fdisk

Select from the options. In Fdisk, drives are not letters, they are numbered (1, 2, etc.). In Fdisk, the active partition is the one you boot from and is assumed to be the C: drive. If it is not, you can change that in Fdisk.

If you want to Fdisk a second or subsequent hard disk, load Fdisk from the C: drive:

               C:\>fdisk

HIGH-LEVEL FORMAT
The final step is to run the Format command for each logical drive (C:, D:, etc.). This step creates the directory structure and FAT tables and places startup data in the boot sector.

To format your C: drive, boot the computer with a bootable floppy in drive A:, which also contains the FORMAT.COM program. Use the /s switch to transfer DOS to the hard disk as soon as the formatting is completed. To format drive C, type:

             A:\>format c: /s

To format a second or subsequent hard drive, load Format from your C: drive. For example, to format drive D:, type:

             C:\>format d: