Hard disk
Hard disk is a complex, self-controlled device, whose complexity and functional structure can be compared to that of a computer. It contains a control processor, memory and operating system located in inaccessible areas of the disk. Similarly to computers, at the start it introduces the operating system to its RAM memory and allows access to user data only afterward.
The hard disk consists of data plates (aluminum or glass circular plate covered with a thin magnetic layer), reading/writing heads, an actuator mechanism, motor and control electronics. There are electronics amplifying signals to external electronics near the heads inside the disk.
During disk startup, the actuator head mechanism is released after plates start turning at a given speed. The heads moved from the parking area (situated on the inner edge of plates or outside, depending on the type of the disk) to the plate, information is read from the service tracks, calibration is carried out and the disk is ready to operate. The heads float on an air cushion above the plates with a speed over 100 km/h at a distance 1000 times shorter than the diameter of a human hair.
