PURPOSE: To take over comments, etc., that a user adds to an old program by automatically generating the specification of a program from the program and distinctively displaying alteration parts when the program is updated.

CONSTITUTION: A specification generation part 3 generates the specification 5 from the new-version program 4. A difference extraction part 6 extracts remarks added to old specification in hypertext form together with their positions and puts them in difference information 7. Then the newly generated specification 5 are compared with the old specification 2 after the remarks are removed and their differences are added to the difference information 7. Then difference patch parts 8 are fitted according to the position information included in the difference information so that the remarks of the old version and difference points are linked with the specification 5 in the hypertext form. A hypertext control part 10 displays the filling difference information.