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Using FDISK 125
Using FDISK
FDISK is the partitioning utility used with MS-DOS, Windows 95,
and above and has equivalents in all other operating systems. In
most cases with SCSI and all cases with IDE drives, it’s the first software
program you run after you physically install a hard disk and
properly detect it in the BIOS.
FDISK is used to set aside disk space (or an entire physical drive) for
use by an operating system, and to specify how many and what
size the logical drives will be within that space. By default, the MS-
DOS and Windows 9x versions of FDISK prepares a single physical
drive as a single drive letter (up to the limits listed), but FDISK can
also be used to create multiple drives. By not preparing all of a hard
disk’s capacity with FDISK, you can use the remaining room on the
hard disk for another operating system.
Drive-Letter Size Limits
We’ve already considered the physical drive size limits caused by
BIOS limitations and how to overcome them. Those limits define
the maximum size a physical hard drive can be. However, depending
on the version of Windows in use (and with any version of MS-
DOS), it might be necessary to subdivide a hard drive through the
use of FDISK to allow its full capacity to be used through the creation
of multiple logical drive letters.
The original release of Windows 95 and all versions of MS-DOS
from DOS 3.3x support FAT16, which allows no more than 65,536
files per drive and a single drive letter no more than 2.1GB in size.
Thus, a 6GB hard disk prepared with MS-DOS or the original
Windows 95 must have at a minimum three drive letters and could
have more (see Figure 4.14). The primary disk partition (C: on a
single drive system) can be bootable and contains only a single
drive letter. An extended partition, which cannot be bootable, contains
the remainder of the drive letters (called logical DOS drives in
most versions of FDISK).
Large Hard Disk Support
If you use the Windows 95B or above (Win95 OSR 2.x), Windows
98, or Windows Me versions of FDISK with a hard drive greater
than 512MB, FDISK offers to enable large hard disk support.
Choosing to enable large hard disk support provides several benefits:
• You can use a large hard disk (greater than 2.1GB) as a single
drive letter; in fact, your drive can be as large as 2TB and still
be identified by a single drive letter. This is because of the
FAT-32 file system, which allows for many more files per
drive than FAT-16.