The bibliographical definition of an edition includes all copies of a book printed “from substantially the same setting of type,” including all minor typographical variants. The numbering of book editions is a special case of the wider field of revision control. The traditional conventions for numbering book editions evolved spontaneously for several centuries before any greater applied science of revision control became important to humanity, which did not occur until the era of widespread computing had arrived (when software and electronic publishing came into existence). The old and new aspects of book edition numbering (from before and since the advent of computing) are discussed below.