Winchester - hard disk (HDD - Hard Disk Drive) - the place where all information is stored on the computer - from the operating system to various programs and all kinds of data. The necessary information at the right time is read by the processor from the hard disk and processed and then, if necessary, can be written to the hard drive.
Instructions
Step 1
The design of the hard drive consists of a block of metal discs with a special coating that can memorize and store the effects of a magnetic field. Modern designs consist of 1-3 discs, which are perfectly balanced and have a perfectly flat surface, because the rotation speed is high enough and reaches from 7200 to 10000 rpm, and the positioning accuracy of the heads must be high.
Step 2
To write and read information on the disk, special magnetic heads are used. Most often, two per disc, on both sides. When exposed to current pulses, the heads form a magnetic field and magnetize a portion of the disk with a magnetic moment of a given direction (logical "one" or logical "zero"). The recording process is carried out by applying a current pulse at the required time, the magnetic head is positioned in the right place. When reading information from the disk, the heads react to changes in the magnetic field through the excitation of the current in them. This type of analog signal is read and converted to digital. In this form, it is transmitted to the computer system.
Step 3
Information on a magnetic disk is placed and stored on tracks, in the form of concentrated circles. All magnetic heads of the hard drive make up one common unit. Move from one track of a disc to another at the same time. One head serves one side of the disc. That is, the heads are on the same track over different disks at any given time. Thus, this set of tracks forms a cylinder. Recently, a solenoid actuator has been used to move the magnetic heads. They move around their axis. A coil attached to the back of the head moves them over the surface of the disc using an electromagnet. The contact of the heads to the disk is not allowed; at the moment of disconnection from the power supply, they are taken away from the surface to the side.
Step 4
Each disk track is divided into sectors - the smallest elements of disk space with 512 bytes of information storage. The total memory capacity of the hard drive can be determined by the product of the number of heads, cylinders and sectors. It is also worth considering that in the manufacture of discs, defective sectors and tracks are formed. This process cannot be avoided. These areas are not taken into account during operation. The main thing is that the disk itself has the required total volume.
Step 5
The logical placement of heads, cylinders and sectors is usually different from the physical one and is indicated on the hard drive cover. The parameters are stored on the hard disk by the Setup program, and then the computer works with a logical breakdown. To reconcile the physical and logical values of the device, a special procedure is used - translation of disk parameters. This block is located on the hard drive itself and converts logical corridors into physical ones, which provides access to the desired part of the physical disk.
