Abstract: When a line is drawn on a screen with a coordinate input pen in a specific shape, the shape of the line drawing is collated with a reference stroke stored in a gesture table. As a result, an edit instruction corresponding to the shape of the line drawing is specified and executed. This function is called a gesture editing function. Here, the coordinate system which is the most suitable for computing the editing position on the screen is selected according to a given edit instruction. Thus, displacement of an editing position due to shaking of the user's hand can be avoided, thereby accurately executing the edit instruction. Moreover, the combination between the reference stroke and the edit instruction in the gesture table can be changed as desired by a key-operation according to the use of the user. Thus, a more convenient gesture editing function for the user can be achieved.