Microsoft today released the source code for early versions of MS-DOS and Word for Windows, nearly 33 and 31 years after their respective debuts.

Microsoft Research engineer and managing director Roy Levin announced the release in a blog post, explaining that Microsoft has given permission to the Computer History Museum (CHM) to make the code publicly available for the first time. The CHM is releasing code from MS-DOS versions 1.1 and 2.0, and the 1990 version of Word for Windows.

MS-DOS source code

For more information, read the CHM press release.