A Heuristic Approach to Program Verification

We present various heuristic techniques for use in proving the correctness of computer programs. The techniques are designed to obtain automatically the "inductive assertions" attached to the loops of the program which previously required human "understanding" of the program''s performance. We distinguish between two general approaches: one in which we obtain the inductive assertion by analyzing predicates which are known to be true at the entrances and exits of the loop ($underline{top-down}$ approach), and another in which we generate the inductive assertion directly from the statements of the loop ($underline{bottom-up}$ approach).