history of computers
A hard disk drive (sometimes abbreviated as Hard drive, HD, or HDD) is a non-volatile memory hardware device that permanently stores and retrieves information. There are many variations, but their sizes are generally 3.5" and 2.5" for desktop and laptop computers respectively. A hard drive consists of one or more platters to which data is written using a magnetic head, all inside of an air-sealed casing. Internal hard disks reside in a drive bay, connect to the motherboard using an ATA, SCSI, or SATA cable, and are powered by a connection to the PSU (power supply unit).
A hard drive can be used to store just about any type of data, including pictures, music, videos, and text documents. Computers have a hard drive and use it to store files for the operating system and software that run on the computer, as well as files created or downloaded to the computer by a user.