MS-DOS stands for Microsoft Disk Operating System and is an operating system developed by Microsoft in the 1980s. It was the most commonly used operating system on IBM PC compatible computers during the 1980s and early 1990s. MS-DOS was the main operating system used by millions of people around the world until the introduction of Windows 95. MS-DOS was designed to be a simple operating system that could be used with minimal technical knowledge. It was also designed to be compatible with existing hardware, making it easy to install and use.