Hard Disk Drive (HDD)

A hard disk drive (HDD), (sometimes called hard disk or hard drive) is a device used for storing and retrieving data. A hard disk in modern computers contains several gigabytes of storage. HDD consists of one or more rotating disks (platters) covered with magnetic material. A set of disks store their information in concentric circles (tracks). They are recorded electromagnetically. The disks are paired with magnetic heads. They are organized on a moving arm, which read and write data to the platters as the disk spins. Data is accessed in a random-access manner. Any of a read/write operation requires data locating. This is called a seek. Access time usually takes milliseconds. Data are divided into a number of sections called sectors. Each sector is assigned an address that defines where data is stored. This address is called a Logical Block Address (LBA). In fact, a computer reads information from the hard drive as scanning of the magnetic polarities on the platter. One side of the magnetic polarity is 0, and the other is 1. Reading this as binary code, the computer can understand what the data is on the platter.