PURPOSE: To shorten processing time and to simplify data transmission routine for an image-supplying device in which images are printed with printing modes being switched over.

CONSTITUTION: A memory area that is only for data reception is maintained in a memory of an image-supplying device, and the said memory area is made such that is not initialized by a program that processes individual printing mode. Therefore, initialization of the memory area only for the data reception is not necessary when switching from one mode to another one is made, and the image-supplying device does not need to be off-line to a host computer, resulting in shortening of processing time. As erasion of received contents occurring whenever the switching over of the mode is made can be prevented by arrangements as mentioned above, sending of necessary data (such as command for processing of mode) from the host computer to the image-supplying device can be made without regard to confirmation to be made on completion of the switching over of the mode.