Fault-tolerant programs and their reliability

The authors review and extend available techniques for achieving fault-tolerant programs. The representation of the techniques is uniform and is illustrated by simple examples. For each technique a fault tree has been developed to derive failure probability from the probabilities of the basic fault events. This allows the subsequent analysis of program-failure causes and the reliability modeling of computer programs. Numerical examples are given to support the comparison of the reviewed techniques. The models can be used to evaluate numerical values of program reliability in a relatively simple way. The models deal with program reliability for a single run, which seems more practical and straightforward than dealing with distributions as for hardware systems. Evaluations obtained by using models correspond to those used in the literature; however, the authors´ procedures are computationally simpler