A program verification system

A program verification system has been developed consisting of three major components. The verification condition generator(which is patterned after the work of Igarashi, London, and Luckham [10]) is used to generate verification conditions from asserted PASCAL programs. The subgoal generator(which is similar to the program described in [2])processes the verification conditions to produce simpler subgoals, a significant number of which it proves using restricted techniques. The subgoal solveris a resolution theorem prover which was developed at NIH by L. Norton [13]. The more powerful techniques of the subgoal solver are used to prove subgoals which the subgoal generator was unable to prove. The verification system has been used to verify a number of programs. These include all but one of the examples from King [11], a Bubble Sort program, and Hoare's FIND program.