No, I really did mean backward compatibility. Specifically, I was thinking of the degree to which MS have supported even very old (by IT standards) APIs and file formats and protocols even in much newer (again by IT standards) systems over the years, and the lengths they have sometimes gone to in order to maintain that support despite the potentially breaking changes not even being their fault in many cases.

However, I would also agree that they are better at forward compatibility than a lot of other major software developers today.