PURPOSE: To improve the operability for updating a file of a computer, and to execute the synchronization for updating the file.

CONSTITUTION: Inter-host synchronous telegraphic message means 13, 23 and 33 are connected to other computers by on-line and constitute a system, and transmit and receive a telegraphic message in order to synchronize file updating of other computers. In the case a file updating abnormality notice is received from this inter-host synchronous telegraphic message means, cancellation confirming means 16, 26 and 36 output a file updating cancellation request to the inter-host synchronous telegraphic message means. File updating means 14, 24 and 34 input a file updating request or a file updating cancellation request from the inter-host synchronous telegraphic message means, and execute updating of a file or a cancellation of updating.