Microsoft open-sources “the earliest DOS source code discovered to date”

Several times in the last couple of decades, Microsoft has released source code for the original MS-DOS operating system that kicked off its decades-long dominance of consumer PCs. This week, the ...
ZDNet

Microsoft finally open sources DOS 1.0 - and it's so much more than the code

PC-DOS 1.00 would lead to Microsoft becoming computing's top dog Microsoft continues to embrace open source. The source code and annotations provide insight into the operating system's earliest days.