interrupt 5 when input 0 = 1           'if input D0 is high, the programme will stop everything else and turn on the fan
label_5:
            out %xxx1x000           'Turn on output Q4
            if input 0 = 1 then goto label_5    'check if input D0 is still high
            out %xxx0xxxx
            return              'return to main programme if D0 is low