Sector

This military-sounding term is the basic structure of magnetic disk storage. By putting data into chunks scattered over a disk, disk controllers make it possible for bits of data to be found independently of the rest of the data they may rest with. A central index keeps track of where everything is, but data can be accessed independently of the surrounding data. Magnetic tape required searching through a long line of data to reach the needed information, and CD-ROMs have similar problems because they store information in one long groove. Sectoring allows quick and random access to any information on a disk.