Ever wondered what the insides of Microsoft’s operating systems look like? Now’s your chance, as Microsoft has released the source code for both MS-DOS and the original Word for Windows.

Both have been released to the Computer History Museum, in a bid to help scholars understand how those iconic pieces of software were built. “We think preserving historic source code such as these two programs is key to understanding how software has evolved from primitive roots to become a crucial part of our civilisation,” said Len Shustek, chairman of the museum.
Microsoft has made the source code of two versions of MS-DOS available: MS-DOS v1.1 and MS-DOS 2.0. MS-DOS 1.1 has less than 300KB of source code, reflecting the limited hardware it was designed to run on in the early 1980s.
The source code for Word for Windows – first released in 1989 – can be downloaded here.
Both sets of source code are released for non-commercial use, although anyone hoping to build a business out of two pieces of software from the 1980s should probably have a rethink, anyway.
The Computer History Museum has the source code for several other landmark pieces of software, including the first version of Photoshop and Apple II DOS.