Answer
The conclusion is: $\therefore$ this program is not correct.
Work Step by Step
Universal modus tollens: $\forall x,$ if $P(x)$ then $Q(x).$
~$Q(a)$, for a particular a,
$\therefore$ ~$P(a).$
In this case P(x) is: a computer program x is correct.
Q(x) is: compilation of the computer program x does not produce error messages.
a is "this program."
Therefore ~$P(a)$ is: this program is not correct.
