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Hack 51 Format Your Disk

Lay down some awesome data tracks on diskettes, hard drives, Zip disks, or LS-120 cartridges with FORMAT.

Logical drives and drive letters are created by the process of formatting a partition so that it is ready to accept files. Formatting is done by either the DOS FORMAT program, within the Windows 9x-2003 setup processes, or within the Disk Management console in Windows NT-2003. FORMAT provides limited options: it either creates nonbootable disk space, creates a bootable disk, or it can quick-format (erase) a diskette. For hard drives, FORMAT will lay out either NTFS, FAT-16, or FAT-32 file structures, depending on the filesystem of the partition. For 3.5" diskettes, Zip, and LS-120 media, the filesystem will always be FAT-16.

FORMAT also establishes a single partition for portable media such as diskettes, Zip (100 and 250), and LS-120 media because they have limited storage capacity well below 512 MB.

In the process, FORMAT also establishes the logical drives or drive lettering scheme we use to refer to our drives. Although the FORMAT program has more options applicable to various diskette capacities, it is also a very powerful utility when applied to hard drives.

To use all of the features of the FORMAT program, you need to be at a DOS or command prompt. Then follow these steps:

You have to format every partition you want to use for the operating system or data. FORMAT establishes the FAT filesystem and directory space. FORMAT is typically not used on NTFS partitions, which are instead formatted as part of the operating system setup process or with the Disk Management console within Windows (NT, 2000, XP, and 2003 only).

FORMAT provides the following command-line options:

FORMAT drive: [/V[:label]] [/Q] [/F:size] [/B | /S] [/C]

FORMAT drive: [/V[:label]] [/Q] [/T:tracks /N:sectors] [/B | /S] [/C]

FORMAT drive: [/V[:label]] [/Q] [/1] [/4] [/B | /S] [/C]

FORMAT drive: [/Q] [/1] [/4] [/8] [/B | /S] [/C]

The purposes of these options are as follows:

/V[ :label]

Specifies the volume label.

/Q

Performs a quick format.

/F :size

Specifies the size to format the disk to (such as 160, 180, 320, 360, 720, 1.2, 1.44, or 2.88).

/B

Allocates space on the formatted disk for system files.

/S

Copies system files to the formatted disk.

/T :tracks

Specifies the number of tracks per disk side.

/N :sectors

Specifies the number of sectors per track.

/1

Formats a single side of a floppy disk.

/4

Formats a 5.25-inch 360 K floppy disk in a high-density drive.

/8

Formats eight sectors per track.

/C

Tests clusters that are currently marked "bad."

FORMAT under Windows 2000 and XP offers some additional command-line options:

/FS :filesystem

Specifies the type of the filesystem (FAT, FAT32, or NTFS).

/C(for NTFS only)

Indicates that files created on the new volume will be compressed by default.

/X

Forces the volume to dismount first if necessary. All opened handles to the volume will no longer be valid.

/A :size

Overrides the default allocation unit size. The following default settings are strongly recommended for general use:

• NTFS supports 512, 1,024, 2,048, 4,096, and 8,192 bytes; 16 K, 32 K, and 64 K.

• FAT supports 512, 1,024, 2,048, 4,096, and 8,192 bytes; 16 K, 32 K, and 64 K (128 K or 256 K for sector size greater than 512 bytes).

• FAT-32 supports 512, 1,024, 2,048, 4,096, and 8,192 bytes; 16 K, 32 K, 64 K, (128 K or 256 K for sector size greater than 512 bytes).

Examples of common uses of FORMAT are:

format a:

Erases all the contents of a disk. Commonly used on a diskette that has not been formatted or on a diskette you wish to erase.

format a: /q

Quickly erases all the contents of a floppy diskette.

format a: /s

Formats and makes a diskette bootable.

format c:

Erases all the contents of your hard disk drive. Unless you wish to erase all of your computer's information, this command should not be used. It is also the command used to format a hard drive partition for data use, without being bootable.

format d: /FS:NTFS /A:2048

Formats drive D: with the NTFS filesystem and forces the cluster size to 2 KB. You can accomplish the same thing in the Disk Management console of Windows 2000, XP, and 2003 systems.

5.13.1 Logical Drive Assignments Under DOS

While your system BIOS sees hard drives in the order they are attached to their interface cables and configured by jumpers, DOS dynamically assigns drive letters in a most unusual but quite logical order, alternating between physical/electronic order and partitions found. Drive letter assignments by default first follow physical and then logical/partition order.

For systems with only one partition, it's simple: DOS assigns drive letter C: to the first partition it finds on that drive. If there are more partitions it assigns them drive letter D:, E:, and so on.

For systems with two hard drives, if the first hard drive has only one partition that is assigned drive letter C:, then the first partition on the second hard drive is assigned drive letter D:, and if the second hard drive contains more partitions they are assigned drive letters E:, F:, and so on. Simple enough.

For systems with two hard drives, where the first hard drive has two or more partitions, grab a pencil and paper or head to the nearest white board to map out what happens, or you can refer to Table 5-4. The first partition on the first hard drive is assigned drive letter C:—again, simple enough. The first partition on the second hard drive is assigned drive letter D:—nothing complicated so far. If you have two or more partitions on the first hard drive, they are then assigned drive letters E:, F:, and so on until you run out of partitions or letters. Now that's interesting! If the second hard drive has two or more partitions, the drive letters for the second and all subsequent partitions are assigned in order after the last letter used for the partitions on the first hard drive.

Table 5-4. Logical drive assignments on multiple drives and partitions

Drive letter	One hard drive (any number of partitions)	Two hard drives, (two partitions each)	Two hard drives, (three partitions each)
C:	First partition	First partition of first hard drive	First partition of first hard drive
D:	Second partition	First partition of second hard drive	First partition of second hard drive
E:	Third partition	Second partition of first hard drive	Second partition of first hard drive
F:	Fourth partition	Second partition of second hard drive	Third partition of first hard drive
G:	Fifth partition	None	Second partition of second hard drive
H:	Sixth partition	None	Third partition of second hard drive

Under Windows NT/2000/XP you cannot change the drive letter of the Active boot or system partition, but you may change the drive letters for subsequent partitions within the Disk Management console [Hack #52] .

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