This operating system originally began life as QDOS, created by computer company Seattle Computer Products in 1980. Microsoft would eventually purchase the system for $50k and license it to IBM.
MS-DOS 1.0 was released in 1981 for IBM-PCs. The latest version is MS-DOS 6.22, released in 1994. Originally, IBM and Microsoft produced different versions of the software, although they were largely identical. It is reputed that IBM found over 300 bugs in the code and wound up re-writing much of it. Most OEM’s that used it also changed it’s name until Microsoft later insisted it not be changed. IBM was the only company that refused to do so. While it is not commonly used by itself today, it still can be accessed from most of the current versions of Windows.