Disk operating system (DOS),
Definition of Disk operating system (DOS):
Original operating system for the IBM Personal computer (IBM PC) which made its debut in 1981. Published by then fledgling Microsoft, it was known first as IBM DOS and, when IBM tried to develop an advanced version as its own operating system (named OS/2), as MS DOS.
Meaning of Disk operating system (DOS) & Disk operating system (DOS) Definition