On Windows and Mac, there is Microsoft / Apple who decides what is set of OS APIs, and everything outside is external library. In Linux, there is no such autho

On Windows and Mac, there is Microsoft / Apple who decides what is set of OS APIs, and everything outside is external library. In Linux, there is no such authority and therefore no sharp line separating 'core OS' and 'external library'. It is just conglomerate of Linux kernel and independently developed tools and libraries (where each of them is more-or-less optional).