Hard disks use rigid, metallic platters that are stacked on top of one another.
Store and organize files using tracks, sectors, and cylinders.
Susceptible to head crash.
Head crash occurs when read-write head makes contact with the hard disk’s surface or with particles on its surface. Internal hard disks are located inside the system unit. Internal are used to store programs and data files. External hard disks are removable. They are used to complement internal hard disk. Performance enhancement: Disk caching to improve hard disk performance, redundant arrays of inexpensive disks (RAID) to expand storage and to improve access speed, file compression and decompression to increase capacity.