Calling external files (e.g. executables) in C++ in a cross-platform way
<p>I know many have asked this question before, but as far as I can see, there's no clear answer that helps C++ beginners. So, here's my question (or request if you like),</p>

<p>Say I'm writing a C++ code using Xcode or any text editor, and I want to use some of the tools provided in another C++ program. For instance, an executable. So, how can I call that executable file in my code? </p>

<p>Also, can I exploit other functions/objects/classes provided in a C++ program and use them in my C++ code via this calling technique? Or is it just executables that I can call?</p>

<p>I hope someone could provide a clear answer that beginners can absorb.. :p</p>
