An Acronym for Cylinder, Head, Sector.
The classic HardDisk sector addressing mode where a sector is identified by a coordinate for each of the axes.
CHS was conceived at a time when 10MB was the average capacity of a HardDisk. Nowadays, the ranges available for the coordinates of each axis have become insufficient to express the actual location of a sector, so CHS addresses have long ceased to correspond to the actual location of a sector. Performance considerations also play a role here. In practice, CHS addresses are therefore translated by the HardDisk's electronics to map them to the real position of a sector.