On: Why has Plan 9 chosen statically linked binaries i...

[int_19h]

To be even more specific, it happened because apps dumped DLLs into shared system directories instead of bundling them alongside the app binary. Since on Windows, each app has its own directory, it's easy to bundle in a way that doesn't mess up other apps.

[__d → int_19h]

It became so once the DLL search path was changed to put the .exe file's containing folder first.

Prior to that, the system dirs were searched first, which was the trigger for the DLL hell issue.

[int_19h → __d]

I mean, if all apps avoided writing to the global folders (i.e. reserve it for OS-managed components), there wouldn't be an issue even with the old arrangement.

But not even Microsoft's own products respected that in practice.