How does a write-readhead function?
The write-readhead (head) makes it able to write and read on the magnetic layer of the hard disk. In common, modern hard disks have two to eight heads: exactly two per magnetic disk. Normally the heads fly on a thin layer of air above the magnetic surface that originates in the rotation of the disk. If the head touches the magnetic layer, one speaks about a headcrash. Even a piece of dust of only a few nanometers may reach enough to cause a headcrash. Opening of the hard disk by non-experts may cause considerable damage. In modern disks the heads can position themselves within one or two milliseconds.
