Hard-Disk Drives

The hard drive, also called the hard disk or fixed disk, is the primary storage unit of the computer. It is always labeled the C drive. Additional drives are labeled after it as the D, E, F, etc. It has several read/write heads that read and record data magnetically on platters, a stack of rotating disks inside the hard drive. Hard drive is important for the following reasons:

*  It stores programs that must be installed to the hard drive before they can be used.
*  It stores data files that can be accessed later.
*  It organizes files like a file cabinet so they can be accessed more easily.
The Hard Drive can store a large amount of computer data on it. Many advancements have made it possible to store a large amounts of data in a small space. The hard drive’s speed is discussed in terms of access time. This is the speed at which the hard drive finds data. The average access time
is measured in milliseconds. One millisecond equals 1/1000 of a second. The average drives had 9 to 14 ms access time. The lower the access time the faster the hard drive. The capacity, or amount of information that a hard drive can store, is measured in bytes. Today many computers come with 20-
80 GB (Giga Byte=1,000 Mega Bytes) hard drives.

Types of Hard Drives

(1)  Bournolli has a mechanism that acts as a fly wheel. When the HD spins the disk follows gravities course and is lifted up a few centimeters causing the Read/Write heads to touch. When it stops spinning, the HD will fall back down the few centimeters.
(2) Magnetic Optical Drive has the best storage capacity. It has the same principles as the Bournolli, but is mixed with the Compact Disc technology so that the Read/Write head puts data in order and the laser reads off of it.

(3) Standard Magnetic Drive The standard magnetic drive is less complex and less expensive than the others. It stores data with a read/write head which sends a pulse of electricity through causing the magnetic films electrons to line up in a certain way.