On the Uncertainty in the Correctness of Computer Programs

The use of digital computers in critical process control systems requires the formal assessment of the system reliability. Failures can be due to either component malfunctions or design faults. Only the latter are relevant in evaluating software reliability. Although it is preferable to prove whether the program meets its specification, this is not yet practical for real-time control programs. Further, the specification itself can be incorrect or incomplete due to the complex requirements.