A state constraint is a programming construct designed to restrict a program's domain of definition. It can be used to decompose a program pathwise, i.e. dividing the program into subprograms along the control flow, as opposed to dividing the program across the control flow when the program is decomposed into functions and procedures. As a result, a program consisting of one or more execution paths of another program can be constructed and manipulated. The author describes the idea involved, examines the properties of state constraints, establishes a formal basis for pathwise decomposition and discusses their uses in program simplification, testing and verification.>

It is argued that real-time system design can be made a more credible research subject and can attract more attention from academic researchers if it is possible to do significant experimentation with computing facilities commonly found in a university. This may be accomplished by: (1) compiling and publishing interesting problems found in real-world systems; (2) developing system design courses with nontrivial programming projects; (3) developing simulators of real-time system problems that are capable of exercising the experimental real-time systems; and (4) making common software components available for research and teaching.>

Abstract This paper describes a software im plementation strategy that allows the programmer to construct a running version of a program early in its development. In general, the first version of the program only works for a subset of the intended input domain. The subset is defined by a number of constraints placed on the program by the programmer. The program can be completed by removing the constraints one at a time. In the process, each new part added to the program can be validated independently. Software tools can be built to facilitate the validation process.

Abstract A software simulator can be built to facilitate debugging and testing of real‐time programs. This paper describes a simulator designed to operate in three modes: simulation, debugging and process monitoring. In the simulation mode, it simulates a Z80‐based microcomputer and can be used to execute programs written in the Z80‐assembler language. In the debugging mode, it provides facilities for interactive debugging on the instruction level. The simulator's unique feature is the process monitoring mode. It displays the activities among processes being executed concurrently under the control of a real‐time executive and thus allowing direct observation of dynamic program behaviour at the process level.

This paper describes a verification rule for loop programs, and shows how it can be used in conjunction with the invariant-relation theorem to facilitate verification of programs.

A data flow anomaly in a program iB an indication that a programming error might have been committed. This paper descibes a method for detecting such an anomiay by means of program instrumentation. The method is conceptually simple, easy to use, easy toimplement on a computer, and can be applied in conjunction with a conventional program test to achieve increased error-detection capability.