Wikimedia Commons has media related to Disk operating systems.

A disk operating system is an operating system component that deals with high-level disk-IO such as providing the abstraction of a file system resident on a disk storage system (made up of hard disks and/or floppy disk drives). Disk Operating System is often abbreviated by the three-letter acronym DOS and used as a suffix for specific operating system names. This was common among mainframe computers, and also to home and personal computers of the 1970s and 80s.