How did the Windows 95 user interface code get brought to the Windows NT code base?

After the release of Windows 95, with its brand new and incredibly influential graphical user interface, it was only a matter of time before this new taskbar, Start menu, and everything else would make its way to Microsoft’s other operating system line, Windows NT. The development of Windows 95 more or less lined up with that of Windows NT 3.5, but it wouldn’t be until Windows NT 4.0, released a little less than a year after Windows 95, that NT, too, would have the brand new user interface.

Raymond Chen has published a blog post detailing the cooperation and interplay between the Windows 95 and Windows NT teams, and, as always with Chen, it’s a joy to read.

Members of the Windows 95 user interface team met regularly with members of the Windows NT user interface team to keep them aware of what was going on and even get their input on some ideas that the Windows 95 team were considering. The Windows NT user interface team were focused on shipping Windows NT, but they appreciated being kept in the loop.

During the late phases of the development of Windows 95, the Windows NT side of the house took a more active role in bringing the Windows 95 user interface to Windows NT.

↫ Raymond Chen at The Old New Thing

Chen details there was a lot of code-sharing, to the point where the Windows 95 version of the GUI contained NT-specific code, and vice versa. This code-sharing was quite a lot less elegant than today with tools like git, since Microsoft’s own internal source code system called SLM (pronounced ‘slime’) did not support branches, so they had to regularly perform three-way merges manually.

It was a different time, for sure.

Anyway, it’s amazing how much of this ancient Microsoft lore could’ve been lost to time, or shrouded in mystery, if it wasn’t for someone like Raymond Chen regularly sharing the stories from Microsoft’s past.