Programming the System

"While C++ can prevent mistakes, it can not prevent frauds."

Bjarne Stroustrup (The C++ Programming Language)

This is true for all the real world systems ofcourse. So what is the solution ? Why do what programmers do.Good old bug fixing here and there, along with using good desing patterns.
I think engineers in generals and programmers in particular should make good economists, but reverse may not be true.