Disk Operating System

Disk Operating System (specifically) and disk operating system (generically), most often abbreviated as DOS, refer to an operating system software used in most computers that provides the abstraction and management of secondary storage devices and the information on them (e.g., file systems for organizing files of all sorts). Such software is referred to as a disk operating system when the storage devices it manages are made of rotating platters, such as floppy disks or hard disks.

In the early days of microcomputers, computer memory space was often limited, so the disk operating system was an extension of the operating system. This component was only loaded if needed. Otherwise, disk access would be limited to low-level operations such as reading and writing disks at the sector-level.

In some cases, the disk operating system component (or even the operating system) was known as DOS.

Sometimes, a disk operating system can refer to the entire operating system if it is loaded off a disk and supports the abstraction and management of disk devices. Examples include DOS/360 and FreeDOS. On the PC compatible platform, an entire family of operating systems was called DOS.