3.1 was an app on dos.
Discussion
If that is how you respond to me we need to first define operating system and application.
Hard to define when all executables are basically the same structure. In the case of windows 3.1, the os that was booted up was dos. All the exception handlers etc. the ui was an app started by a batch file ran by dos. And it was replaceable. If the dos that was in 3.1 is the os you refer too, you are right. Very solid. The windows apps, not so much.