"How do I start a process in the background?"

needs to also mention that any use of
system("echo", "a", "b", "c")
will have to be rewritten
system("echo a b c &")
(and not e.g.,
system("echo&", "a", "b", "c")
system("echo", "a", "b", "c", "&")
system("echo&", "a", "b", "c&")
etc.), or else the user will never guess.