Operating systems devote a lot of code to the most efficient organization of files in a disk drive. A file is an abstract entity, a fiction maintained by the operating system, whereas a sector is somewhat more concrete, since it can be identified as being a particular place on the surface. Many files are longer than one sector so several sectors must be used to store a file. Disk drives and their controllers know nothing of files nor do they care what data the operating system stores inside the sectors, freeing the OS to structure files in any way it wants.