To economize a memory by storing the maximum number of executable files, storing the executing statuses of the files, storing the number of the executing statuses to write in each unit time and storing the executing statuses written in each unit time.

A writing number storing part 33 stores the number of the executing statuses to write in each unit time in a telemetry storing part 34 by an executing status reading/writing means 23. The means 23 writes a telemetry in the part 34 in a range without exceeding the number of pieces stored in the part 33. Depending on the quantity of executing form files under simultaneous execution, the writing frequency of the executing statuses into one executing form file is increased or reduced. However, this frequency is adjusted by increasing/reducing the number of the executing statuses stored in the part 33.