If, at the time of any error, the value of $ETRAP is non-empty, GT.M proceeds as if the next instruction to be excuted were the first one on "the next line" and the code on that next line would be the same as the text in the value of $ETRAP. Furthermore, GT.M behaves as if the line following "the next line" looks like:

	QUIT:$QUIT "" QUIT
	

When a value is assigned to $ETRAP, the new value replaces the previous value. If the value of $ZTRAP is a non-empty one, $ZTRAP is implicitly NEWed, and the value of $ZTRAP becomes equal to the empty string; this ensures that at most one of $ETRAP and $ZTRAP is not the empty string.