HDDs document data by magnetizing ferromagnetic material directionally, to correspond to either a 0 or a 1 binary number. They interpret the data back by become aware of the magnetization of the material. A typical HDD drawing consists of a spindle which grasps one or more smooth rounded disks called platters, on top of which the data are confirmed. The platters are made since a non-magnetic material, more often than not aluminum alloy or glass, and are covered with a thin sheet of magnetic material. The platters are rotate at extremely high speeds. Information is inscribed to a platter as it turns around past devices named read-and-write heads that function very close by over the magnetic facade.