Of a disk drive. A read/write head that cannot be moved relative to the center of the disk. A large number of these heads are usually incorporated into an assembly so that there is a “head per track”, and such drives may be referred to by this expression. The advantage of a fixed head is that the average access time is reduced to the time for half a revolution since there is no track seek time required. Some drives had both fixed and moveable heads but these are now obsolete.