Software Reliability

There is no doubt on the reliability of a computer program which is an important element of its overall quality. If a program is frequently and repeatedly fails to perform it will matters little whether other software quality issues are acceptable.

The Software reliability unlike various other quality factors can be directed, measured, and estimated by using developmental and historical data. Software reliability is described in statistical terms as the possibility of failure free operation of a computer program in a specified environment for a specified time [MUS87]. To describe, program P is estimated to have a reliability of 0.96 over 8 elapsed processing hours. Another way, if program P were to be executed 100 times and need 8 hours of elapsed processing time execution time it is likely to operate correctly without failure 96 times out of 100.

Whenever software reliability is discussed a pivotal question is arises which is like what is meant through the term failure? By the context of any discussion of software reliability and quality, one failure is non conformance to software needs. Since, even within this definition there are gradations. Failures can be only catastrophic or annoying   . 1 failure can be corrected within seconds while other needs weeks or even months to correct. The complicating matter  even  further the  correction of  1  failure may  in fact  result in  the introduction of other errors which ultimately result in other failures.