An IC card and card adapters are designed so that the IC card of a specific standard (e.g., MMC standard) is compatible with IC cards and terminals of other standards (e.g., MS card standard and USB terminal standard). In the IC card (MMC), a controller IC, which is connected to a flash memory, includes a voltage pull-down detector, a mode controller, a USB-mode interface controller, a MS-mode interface controller, and an MMC/SD-mode interface controller. The card adapters suffice to have component parts which are easy in formation and low in cost such as wiring lines and resistors. The voltage pull-down detector of the IC card detects the voltage pull-down caused by the resistors, and the mode controller selects the USB-mode interface controller, MS-mode interface controller or MMC/SD-mode interface controller so that the IC card becomes compatible with the corresponding IC card standard.