This paper uses a single model to analyze the effects of both hardware and software on
system reliability. A unified model of hardware and software reliability is developed using
Markov modeling. Then the effect of hardware and software failures is studied using the
model. The model incorporates concepts from both hardware and software reliability
modeling. Examples of both simplex (nonredundant) and redundant architectures are
analyzed using the model.<>

Developing complex systems to meet the demands of the current military and commercial
marketplaces requires careful architectural design to ensure optimal robustness within the
expected use environment. Modeling the reliability of systems that combine hardware and
software elements to achieve needed system functionality has been difficult or impossible
due to the paucity of techniques for including software and the effects of software failures
into system reliability models. This paper reports on and extends the research into system …