Not sure where you have been all my life, but the DOS 'where' cmd tells me which .exe is being pointed to (for example) when compiling so i don't have to guess:
for example, 'where fxc'.
“The sciences do not try to explain, they hardly even try to interpret, they mainly make models. By a model is meant a mathematical construct which with the addition of certain verbal interpretations describes observed phenomena. The justification of such a model construct is solely and precisely that it is expected to work.” John Von Neumann