PURPOSE: To move data between the windows and smoothly cancel it in a multiwindow system.

CONSTITUTION: The method for data movement between the windows stores the fact that the operation contents in a before-movement data saving step and a before-movement data deletion step and a process at a movement destination are successive, in a process at a movement source in a movement source process storage step. In a movement destination process storage step, the fact that the process at the movement source is taken over and the operation contents in a moved data fetch step, are stored. The canceling method deletes data moved from a movement-destination window according to the storage contents of the movement destination process storage step and reports that to a canceling process at the movement source. The canceling process at the movement source copies data from a buffer for restoration to the movement source window according to the storage contents of the movement source process storage step. Consequently. the data movement is canceled by one operation and the data can be restored to its original state.