AC is a transaction code generated by ICC, and GENERATE AC is a process by which ICC makes transaction decisions. That is to say, every time the terminal executes a transaction, it must send this command to ICC for transaction decision-making (such as rejecting the transaction or requesting online authorization) to decide whether to accept the transaction and how to accept it. Before the terminal sends GENERATE AC, it first goes through a terminal behavior analysis process. The result of the analysis is to decide what kind of AC request needs to be sent to ICC: online authorization (ONLINE), offline rejection (REJECT OFFLINE) or offline authorization ( APPROVE OFFLINE). After receiving the command and processing it, ICC returns its decision result, which is the AC value.