This project is using the phrase &quot;system call&quot; idiosyncratically &#x2F; incorrectly: by it they mean &quot;calls to the system() function&quot;, not &quot;low-level OS facilities&quot;. POCO and ACE seem to be about actual system calls (network programming, threads, pipes, etc.) They&#x27;re for very different purposes.<p>libcox is for when your existing code would do something like system(&quot;uname&quot;) or system(&quot;ls&quot;) (... except not even with system(), with popen() or something), and you want it portable to Windows.