** Start of listing of h.cc **
#include <iostream>

main()
{
  std::cout << "Content-type: text/plain;charset=us-ascii\n\n";
  std::cout << "hello, world\n";
}
** End of listing of h.cc **

Here is the directory entry for that source file:
-rw-------  1 rem  user  129 Feb 28  2007 h.cc
   ^ Note user execute permission *not* needed for source files.

That gets compiled to a.out, but then renamed to something.cgi
so that it will be usable by remote users via CGI:
-rwx------  1 rem  user  4842 Feb 28  2007 h-c++.cgi
   ^ Note user execute permission needed for all CGI programs.
(because compiled C++ is native machine code run directly on machine)