To eliminate the need to secure an additional/changed program for each processor and facilitate restoration of lost setup data caused by a power failure or the like in a processing device with a program-rewritable memory.

A processor 10 transmits a program acquisition request including its own identification information to a host device 20. The host device 20 manages programs to be used by the processor 10 in association with the processor identification information, and transmits the programs associated with the identification information to the processor 10 upon receipt of request from the processor 10 for transmission of the programs. Alternatively, the host device 20 transmits the classification information of the programs upon receipt of request from the processor 10, and transmits the programs associated with the classification upon selection of the classification information by the user. Further, the host device 20 transmits setup data for the processor 10 to the host device 20, which manages the data in association with the identification information and transmits, upon request from the processor, the associated setup data to the processor.