In computer science, what does "DOS" stand for?

In computer science, “DOS” stands for Disk Operating System. The term describes an operating system designed to manage files and programs stored on disk-based media, including floppy disks and hard drives.

DOS is a broad name rather than one single product. Before and during the early personal-computer era, systems such as Apple DOS, Commodore DOS, Atari DOS, and TRS-DOS used the abbreviation. The term became especially associated with MS-DOS and IBM PC DOS after IBM introduced the IBM Personal Computer in 1981.

MS-DOS provided a command-line environment in which users typed commands to list files, change directories, launch programs, and copy data. Its command interpreter, COMMAND.COM, became familiar to generations of PC users. DOS was eventually displaced for everyday desktop use by graphical operating systems, especially Microsoft Windows.

A common mix-up is confusing the computing term with DoS, meaning denial-of-service, a type of cyberattack. The capitalization and context distinguish them: DOS refers to disk-based operating systems, while DoS refers to a network availability attack.