Microsoft developed MS-DOS with IBM in the early 1980s, and the operating system became the foundation of the IBM PC software ecosystem.
IBM approached Microsoft in 1980 about providing an operating system for its forthcoming personal computer. Microsoft acquired rights to 86-DOS from Seattle Computer Products, adapted it, and supplied it to IBM as PC DOS; Microsoft also marketed its own version as MS-DOS.
MS-DOS was a command-line operating system designed for x86-based personal computers. Users entered text commands to launch programs, manage files, and configure the system, unlike later graphical Windows environments.
MS-DOS is sometimes called simply DOS, but DOS was a broader family of disk operating systems. IBM PC DOS and Microsoft MS-DOS were closely related versions distributed under different branding.