i had about 30min at the end to go back and look over what i had done missed and i spent basically all that time on this (and i dont care what my exam strategy is like) The only Logic error i could see is that the system could not be turned off without a card having been enetered. While there was no card in the machine the while loop was never exited and so even if system_on was changed elsewhere the system couldn't shut down until a card was entered. There were a number of errors in the algorithm but they were all syntax, ie switched_on and system_on so i dont think this is what they are refering to, its not a hell of a lot you would have to write to change the algortihm, and although SDD people SUCK at writing exams i am sure they were after a 'logic' error, and i dont remember who said it but i think that the algorithm lined up with the structure diagram almost perfectly. OH and for software people they have a whole stack of initialisations and setting booleans that are just a waste of time