Topic summary
Disk operating system
A disk operating system (DOS) is a computer operating system that requires a hard disk (HDD), floppy disk, solid-state drive (SSD), or other direct-access storage device as secondary storage. A DOS provides a file system and a means for loading and running programs stored on the disk.
The term is now historical, as most if not all operating systems for general-purpose computers now require direct-access storage devices as secondary storage.