Microsoft’s first widely successful operating system for IBM-compatible PCs was MS-DOS.
MS-DOS began as a version of 86-DOS, which Microsoft acquired and adapted after IBM selected it for the IBM PC. IBM released the system under the name PC DOS, while Microsoft marketed related versions to other computer manufacturers as MS-DOS.
The operating system used a command-line interface. Users typed commands to run programs, manage files, and work with disks. Its success helped establish Microsoft as a central software supplier during the rapid expansion of personal computing in the 1980s.
Windows initially operated as a graphical environment that ran on top of DOS. Later Windows releases became increasingly independent, and consumer versions eventually replaced DOS as the visible foundation of Microsoft’s PC platform.