Hard Disk is also called as hard drive, HDD (Hard Disk Drive), Fixed Disk .It is used as a secondary storage device, they are a non-volatile memory (Data is not lost when power is off) They are cheapest and faster device which is used for data storage. This days hard disk comes in huge data storage capacity such as 160 GB (Giga Byte),250 GB, 500GB ,1TB (TeraByte),2TB.they have a rotation speed of 7200 rpm ,9200 rpm (Revolution Per minute),15000 rpm and the access speed of hard drives are approx 1000 kb per second.
Hard Disk Drive
Computer Hard disk was first introduced in 1956 for IBM.They are the most crucial part of the computer system where all the important data has been stored almost permanently. As when you built your new computer you install operating system in hard disk if they fails your computer stops responding.
Hard drives are made up of rigid materials, it has a disk-shaped platter made up of aluminum or glass and is coated with a thin layer of magnetic material the platters are hard and cannot be bend, therefore, are called as fixed disk. The Sizes of disk platters vary from 1 to 14 inches in diameter.
HDD record data by magnetizing ferromagnetic material directionally to represent either 0 and 1 in a binary form.
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How Hard Disk Works?
A hard drive consists of spinning disk with heads that move over the disk and stores data in tracks and sectors. The head read and write in a form of rings often called as Tracks, which are further divided and are called as sectors, which can store up to 512 bytes.
This Fixed Disk have multiple disks and are called as platters, they are arranged on top of each other and they spin accordingly, each of the two sides are manufactured to store data, many Fixed Disk has more than 2 platters which result in four or six ,some hard drives have 12 platters and 24 sides plus 24 heads which are used to read and write. The aligned tracks on each side of every platter together make up a cylinder.
A Hard Drive has one head per platter with all heads mounted on a common arm, the head moves fast with vigorous speed across the disk, they are mounted on a rack which is called as actuator. Most of the hard disk speed entirely depends upon their rotation speed before many hard disks rotate at 3600 rpm which was a constant speed at that time but as the technology developed many manufacturers build hard disk with more revolution speed.
Many of the modern day drives spin the platters at 4200 rpm, 7200 rpm, 10,000 rpm, and 15000 rpm. Which stands out the reasons for faster hard drive speed which can in turn access the data faster? The heads in most hard disk drives do not (and should not!) touch the platters during normal operation. When the heads are powered off, however, in most drives they land on the platters as they stop Spinning. While the drive is running, a very thin cushion of air keeps each head suspended a short
While the hard drive is in working position you are advised not to touch the platters and head while in moving position this action can seriously damage your hard drive.
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Types of hard drives?
There are mainly two types of hard drives ::
• IDE (Integrated Device Electronics) also known as PATA or ATA or E-IDE
• SATA (Serial Advanced Technology Attachment) or Serial-ATA