sec·tor / ˈsektər/ • n. 1. an area or portion that is distinct from others. ∎ a distinct part or branch of a nation's economy or society or of a sphere of activity such as education: the industrial and commercial sector the Muslim sector of the village. ∎ Mil. a subdivision of an area for military operations. ∎ Comput. a subdivision of a track on a magnetic disk.2. the plane figure enclosed by two radii of a circle or ellipse and the arc between them.3. a mathematical instrument consisting of two arms hinged at one end and marked with sines, tangents, etc., for making diagrams.DERIVATIVES: sec·tor·al / -rəl/ adj.
A disk may be soft-sectored or hard-sectored. In soft-sectoring, the size and position of the sectors is determined by the control electronics and software: disk drives generate an index signal once per revolution of the disk, and when this is received from the drive unit all the sectors of a track are written in one continuous operation. On a hard-sectored disk, the start of each sector is related to a sector signal generated by the disk drive and is positively related to the position of the disk. Hard-sectoring can achieve higher packing of sectors since it is not necessary to have large intersector gaps to accommodate speed variations.