An external device is configured to be directly connected to an image forming device. The external device includes an image storage unit configured to store therein image data. The external device further includes a setting unit configured to issue a plurality of output commands of the image data to an image forming device based on a total number of images to be output by the image forming device and a specified mode indicative of a number of images to be output onto one side of a medium. The external device further includes a communication unit configured to transmit the image data based on the plurality of output commands to the image forming device.