This disclosure discloses a printer comprising a USB port, memory, a printing device, and a processor configured to control the printing device and the memory, wherein the regular storage area includes a first memory area, and at least a second memory area in which at least an instruction file including the print data, and wherein, the processor executes a plurality of processing while concurrently performing at least one processing thereof, the plurality of processing including file write processing for updating a content of original instruction file stored in the second memory area by writing the instruction file in the second memory area, update preparation processing for enabling to be updated later a content of the instruction file stored in the second memory area, and print processing for making the printing device execute printing of print data corresponding to the instruction file written in the second memory area.