Hard Disk

A magnetic hard disk unit is an electro mechanical assembly containing flat metal plates coated on both sides with magnetic material. Many such disks are mounted on one spindle with Read/Write heads available for both surfaces of all the disks. The disk assembly is mounted on a disk drive. The disk drive consist of a motor to rotate the disk assembly at high speed of about 3600 revolution per minute.

The magnetic Read-Write heads mounted on arm can move in and out radially on the disk surfaces for reading and writing operation. Data is stored or read on the magnetic recording surface of the disk when the disks rotates at high speed on its axis.

Data bits 0’s and 1’s are stored in the magnetized recording surface of the disks along concentric circle known as tracks, A track is divided into sectors.

The magnetic hard disk drive assembly is connected to and controlled by an electronic circuit called as hard disk controller. The magnetic hard disk memory

The disk controller when it receives the control signals for reading or writing operation, by the computer, it positions the read/write heads on the specified disk and at the specified surface, track there by read/write heads can either read or write when disks rotate at high speed.

The magnetic hard disks are available in the market with variety of storage capacities for example a 20 MB HDD will provide 20 megabytes of storage where 1 byte of storage equals to 8 bits of binary information. Similarly hard disks of 40MB, 80MB, 240MB, 520MB of storage capacity available. Recent technology provides us hard disks of 1 GB and more storage capacity.

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