PURPOSE: To easily generate a program using algorithm in accordance with the purpose of a designer such as computing accuracy and execution speed, etc., by selecting one program module out of plural program modules corresponding to the purpose when software is designed.

CONSTITUTION: Firstly, the designer selects the symbol of control algorithm desired to generate by an input means 14. Thereby, the symbol is displayed on a screen retrieved from a graphic symbol file 4 by a graphic symbol retrieval means 5. Following that, a selected graphic symbol is connected to a graphic screen. Thence, the attribute of respective graphic symbol is inputted, and also, one of the plural program modules registered for the graphic symbols is selected. At this time, the attribute of the graphic symbol is inputted by a program module selecting means 15, and also, an attribute input form to select one of the plural program modules is displayed on the screen.