Asynchronous shell and multicore


I’m currently designing a crossplatform application for which I’m planning to use the cp and the xcopy command in multiple asynchronous shells (mode1). And it raises a few questions. I’ve searched the forum but couldn’t find a relevant thread for a couple of them:

Will each shell execute in a different core or will all the shells execute in the same core the parent application is running or do I need to use a helper console app?
Is there a system app/tool to know on which core a process is running with Mac OS and/or Windows?