ABSTRACT
This chapter identifies the similarities and differences between hardware and software reliability. It discusses the differences as well as similarities in the software and hardware failure processes, and describes software error, fault, and failure. It is very important to understand exactly what a software failure is before reading the other chapters and even before comparing software reliability to hardware reliability. Software failures are software faults that cause a system failure. Some software faults may be software failures, but all software failures are software faults and thus software errors. Hardware failures are hardware faults that cause a system failure. System failures may be classified as software or hardware or other. The mechanism for a hardware failure versus a software failure is not the same; however, both hardware and software failures have the effect of a degradation of the system. Software fails as shown previously by human design error during requirements, design, code, test, or maintenance of the software.
