Abstract Formal program specification and logical analysis are often used for program derivation and proofs of correctness. The basic tools include the logic of predicate calculus and Dijkstra's weakest precondition calculations. Recent work has shown that these tools are also very useful in the maintenance phase of the software life‐cycle. This paper reports experience working with software maintenance teams to apply formal methods. Formal logical analysis is invaluable for isolating defects, determining code corrections, eliminating side‐effects, and code re‐engineering. Logical analysis works well in software maintenance because many defects can be isolated to small segments of code. These small segments can then be analyzed manually or with code analysis tools. The result is lowered software maintenance costs due to the benefits of defect prevention, reduction of code complexity metrics, productivity improvements, and better specifications and documentation. It would be beneficial to use logical code analysis in the earlier phases of the software life‐cycle, such as quality assurance and inspection.

Abstract The techniques of paged virtual memory, commonly employed only in large operating systems, can be provided at the software level by a small collection of primitive procedures. This paper defines the primitives and their implementation. The techniques of applying software virtual memory are also discussed, and these techniques are useful for compilers, database systems, and other applications in which large amounts of random access memory are required. Other benefits of using software virtual memory are transportability, modularity in program design, implementation on mini and microcomputers, and improved speed performance over alternative approaches.

The local adjunct languages (LAL's) and grammars have been defined so as to characterize many aspects of natural and programming languages.