CHS – Cylinder Head Sector – addressing scheme for hard disk drives. Data is written in sectors on tracks (cylinders) on one side of a platter which is indicated by the head being used. A later Logical Block Address scheme numbers each block from a fixed starting position on a platter and track. Each sector can store 512 bytes and the capacity of the disk drive is given by multiplying the number of sectors by the number of cylinders by the number of heads by 512. See LBA entry.

Disk drive CHS addressing scheme components with an illustrative 6-platter disk drive.