Cylinder-head-sector, also known as CHS, was an early method for giving addresses to each physical block of data on a hard disk drive. In the case of floppy drives, for which the same diskette medium can be low-level formatted to different capacities, this is still true. Although
CHS values no longer have a direct physical relationship to the data stored on disks, pseudo
CHS values (
which can be translated by disk electronics or software) are still being used by many utility programs.