What are the symptoms of Lung Cancer?

Hello, my dad had a cold/flu (not swine flu) for a week and a half. I'm probably sure that his cold is gone (maybe not) but he keeps on coughing like every last 5 seconds... (Dad's a smoker). Is there a probabality that he got Lung Cancer? I'm really worried.. My dad smokes like 4 or 5 cigars a day.. not the whole pack though...