A personal computer connected to a USB port of a printer through a
management table managing writing on an ordinary storage region in FLASH
ROM recognizes the ordinary storage region in the FLASH ROM of the
printer as a removable drive which is a USB mass storage class device.
Accordingly, an execution file of an application program stored in a
portion of the ordinary storage region in the FLASH ROM can be read with
a usual access from the personal computer, enabling the application
program to be executed without being installed. When the application
program is executed on the personal computer, periodic accesses are made
to the ordinary storage region of the printer, and when an access fails,
the application program is terminated.