HARD DRIVES, PARTITIONS, & LOGICAL DRIVES UNDER VARIOUS OPERATING SYSTEMS
A hard disk is organized so that one or more operating systems can save or retrieve files you stored there. To do this, each disk is divided into partitions and each partition is further subdivided into many small numbered fixed-size data blocks called sectors. Partitions come in six varieties: active, bootable, extended, installable, primary, and startable. DOS, Windows 9x. and Windows XP have active, primary, and extended partitions. OS/2 has installable, startable, bootable, primary, and extended partitions.
Types of Hard Drive Partitions
Active => Under DOS and Windows 9.x, this refers to the primary partition containing the operating system that will be in control when the computer is turned on ("booted up"). This drive will always be assigned drive letter C:. There can be only one active partition.
Bootable=> Partitions where the computer looks for an operating system to start the computer under. Under DOS, this would be the partition where the computer will find COMMAND.COM, AUTOEXEC.BAT, CONFIG.SYS, etc.. On a machine with multiple operating systems installed, youll have more than one bootable partition.
Extended => An area outside the primary partitions in which you can create multiple logical drives. There can only be one extended partition on a drive. You dont explicitly create the extended partition: its whats left after youve created all your primary partitions. Information in this partition can be shared among the operating systems.
Installable => Under OS/2 this is the partition where the installation program will install the OS/2 operating system. After installation, this partition becomes a bootable partition.
Primary => Usually holds an operating system. All versions of DOS must reside in a primary partition of the first hard drive in your system. OS/2s Boot Manager requires one. OS/2 itself can reside in either a primary or an extended partition. Usually operating systems in primary partitions cannot share data with operating systems in other partitions. OS/2 is an exception to this rule of thumb; its "DOS-compatible".
Startable=> Under OS/2 the partition that will be in control of the computer at boot-up, usually the boot manager primary partition. Only one partition on a hard disk can be designated as startable.
You can divide your disk into a maximum of four partitions. So you can have a maximum of four primary partitions or up to three primary partitions plus one extended partition. You could have a disk with two primary and one extended partition. However, most of the time youll see one primary and one extended partition on a hard drive.
What are Logical Drives? What Do They Have To Do With Hard Drive Partitions?
You can explicitly further subdivide the extended partition into one or more "logical drives"; when you have a single hard drive system but you have "drives" listed which reside on that hard drive, those are "logical drives." For instance, suppose that under Windows 9.x you have a C:, a D, an E, and an F "drive" listed in your My Computer folder. If the F: drive is a CD, then C: is on the active, primary partition, then D: and E: are logical drives in the extended partition. Remember, logical drives can only exist in an extended partition
You can think of logical drives as virtual or imaginary in some sense. You can have as many logical drives as you want up to 23 (drive letters D: to Z:); you decide how to divide up the extended partition. Logical Drives within extended partitions are shareable. Any data installed in the logical drive can be used by an operating system running from any other active logical drive on the system, if the file formats are compatible.
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