To provide a portable phone that can reduce the system cost.

The mobile phone of a simple/high performance type that incorporates only a required minimum memory function in addition to a usual communication function for radio wave transmission reception, consists of a high frequency unit section (RF) 1, a low frequency unit section (base band) 2, a liquid crystal display section 3, an MPU 4 for system control, an ASIC(Application Specific Integrated Circuit) 6 interfacing an MMC 5 being an external storage device, and a DRAM 7 or the like. Since the portable phone has only to incorporate only a boot loader by a boot program especially, no flash memory is required, the boot program is built in the MPU 4 as a ROM 8. Since the-interface capability of the MPU 4 is enhanced, only the interface between the MMC 5 and the DRAM 7 is supported to reduce the cost.