A system using a tape cassette (1) with a memory (4) as a recording medium is provided. In the memory (4) provided in the tape cassette (1) used in the system, there is formed a storage area where instruction/object information in which an instruction to be executed by a required device is stated in addition to a storage area where management information for managing recording to or playback from the tape cassette (1) is stated. At an information processor (10, 40 or 50), instruction/object information is acquired from the memory (4) and processed to provide a control corresponding to the content of the instruction/object information. A device to make some action on the tape cassette (1) can thus have a higher operability and extensibility.