Definition
Hard Disk
A mechanical hard disk organizes data physically across rotating platters using a movable arm with read/write heads.
Physical Structure
Platters
Circular disks coated with magnetic material. Data is stored on both sides.
Tracks
Concentric circles on a platter side where data is recorded.
Sectors
Fixed-size segments (typically 512 bytes or 4KB) dividing each track. The smallest physical unit of transfer.
Cylinders
The set of all tracks at the same distance from the center across all platter surfaces. Moving the arm to a cylinder accesses multiple tracks without further movement.
Addressing
CHS (Cylinder-Head-Sector)
Historical addressing scheme using physical coordinates.
LBA (Logical Block Addressing)
Modern scheme addressing sectors as a linear sequence (). The controller maps LBA to physical CHS coordinates.