Abstract: A printer including: a printhead; and a processor that controls the printhead. The processor, when data including print data of one transaction is received from an external device, acquires from the received data the print data and a first error detection code the external device calculated from the print data, calculates a second error detection code from the acquired printer, determines whether or not the first error detection code and the second error detection code match, and sends to the external device evaluation result data indicating the evaluation result. When the first error detection code and second error detection code match, the processor prints by the printhead based on the acquired print data; and when first error detection code and second error detection code do not match, discards the received data.

Abstract: A printer including: a printhead; and a processor that controls the printhead. The processor, when data including print data of one transaction is received from an external device, acquires from the received data the print data and a first error detection code the external device calculated from the print data, calculates a second error detection code from the acquired printer, determines whether or not the first error detection code and the second error detection code match, and sends to the external device evaluation result data indicating the evaluation result. When the first error detection code and second error detection code match, the processor prints by the printhead based on the acquired print data; and when first error detection code and second error detection code do not match, discards the received data.