hmm and where is its use, at least on Windows were a screensaver is just a renamed exe?
a windows screensaver must accept 3 switches:
/p - preview
/c - configuration
/s - start normally.
It must also prevent multiple instances of itself from launching.
In preview mode, it is passed the handle of the preview window upon which the screensaver is expected to draw a small example.
Whilst it's true that you can just rename an exe, there's a little more to it.