PURPOSE: To provide the data input output device being able to use a memory efficiently and to simplify its management.

CONSTITUTION: This device is provided with a file address memory 14 storing the presence of each file in a file memory 13, a head address and a final address, and when data are written newly, a file write control circuit 8 is used to write the data sequentially to a succeeding idle area of the final file in the file memory 13 and when data are deleted, a file delete control circuit 10 is used at first to set data representing the presence of a file in the file address memory 14 to no file and a file transfer control circuit 12 is used in the standby state of the system to transfer data of succeeding files to the area set to be no file in the file memory 13.