Disk Operating System (DOS) is an early operating system that runs from a disk drive, primarily used in the 1980s and early 1990s. DOS manages hardware and software resources, providing an interface for users to run programs, manage files, and execute commands via a command-line interface (CLI). MS-DOS, developed by Microsoft, became widely popular and formed the foundation for early versions of Windows. Although DOS is no longer widely used, it played a crucial role in the development of personal computing, influencing subsequent operating systems and still being used for low-level system tasks in specific environments.