Automatic Program Verification Ii : Verifying Programs by Algebraic and Logical Reduction

Methode for verifying progroms uritten in a higher level programming language are deviled and imp!em-nted. The system can verify programs uritten in a subset of PASCAL, which may have data structures and control structures such as WHILE, REPEAT. FOR, PROCEDURE. FUNCTION and COROUTINE. The process of creation of verification conditions is an extension of the work done by Igarashi, London and Luckham uhich is based on the deductive theory by Hoare. Verification conditions are proved using specialized simplification and proof techniques, which consist of an arithmetic simplifie-, equality replacement rules, fast algorithm for simplifying formulas using prepositional truth value evaluation, and a depth first proof search process. The basis of deduction mechanism used in this proven is Gentzen-type formal system. Several sorting programs including Floyd's TREES0RT3 and Hoare's FIND are verified. It is shoun that the resulting arr.iy is not only ue I I-ordered but also a permutation of the input array. This rfiearch was supported in pari by (he Advanced Research Projects Agency of the Office of the Secretary of Defence under contract DAHC I5-75-C0435. The view and conclusiors contained in this document are those of the author and should not be interprtttd as necessarily representing the official policies, either expressed or implied, of the Advanced Research Projects Agency or the US Government. Reproduced in the USA. Avauaole from the National Technical Information Service, Springfield Virginia 22/5/. i^ . ■ ■ ■ -■---■ — ■ mmmmtmttm. •a^MOd