Define software reliability. What is the difference between hardware & software reliability?

Ans: Software reliability is the possibility that software will provide failure-free operation in a fixed environment for a fixed interval of time. Probability of failure is the possibility that the software will fail on the next input selected. Software reliability is usually measured per some unit of time whereas probability of failure is usually time independent. These two measures are able to be easily related if you know the frequency with which inputs are executed per unit of time. Mean-time-to-failure is an average interval of time between failures this is as well sometimes referred to as Mean-time-before-failure.

Software reliability is liable to change repeatedly during test periods. While hardware reliability may perhaps change during certain periods such as initial burn in or the end of useful life however it has a much greater tendency then software value.

Hardware faults aren't physical faults whereas software faults are design faults that are harder to classify, visualise, detect and correct. In reality the division among hardware and software reliability is somewhat artificial. Both perhaps defined in the same way therefore one may combine hardware and software reliability to get system reliability. The basis of failure in hardware has generally being physically deterioration.