A communication system in which data stored in a memory card mounted in a host apparatus, such as a digital camera, can be sent to an external apparatus with ease without relying on operations carried out on the host apparatus. The memory card includes a communication control section controllable by the external apparatus so that data can be read out from a memory of the memory card and sent to the external apparatus in accordance with control executed by the external apparatus. Even if the host apparatus is a mobile apparatus such as a digital camera, picture data stored by the digital camera in the memory card can be sent to the external apparatus by wireless communication without the need to change the digital camera serving as the mobile apparatus specially by, for example, installing driver software. That is to say, the memory card can be applied to contemporary digital cameras.