UNIT 7
Software Reliability
Solution: Software reliability is also defined as the probability that a software system fulfils its assigned task in a given environment for a predefined number of input cases, assuming that the hardware and the inputs are free of error.
“It is the probability of a failure free operation of a program for a specified time in a specified environment”
Reliability metrics are used to quantitatively express the reliability of the software product. The option of which metric is to be used depends upon the type of system to which it applies & the requirements of the application domain. Some reliability metrics which can be used to quantify the reliability of the software product are as follows:
Requirements are a means of establishing a written agreement between user and software developer that a system will be designed with such required features. Requirement Reliability metrics calculates quality factors of the required document.
The reliability metric of code and design will evaluate the program on complexity, size, and modularity. Complex modules are not welcomed as there is a high probability of occurring bugs. The reliability will reduce if modules have a combination of high complexity and large size or high complexity and small size.
These metrics use two methods to calculate reliability. First, it provides that the system is equipped with the tasks that are specified in the requirements. Because of this, the bugs due to the lack of functionality reduces.
The second method is calculating the code, finding the bugs & fixing them. To ensure that the system includes the functionality specified, test plans are written that include multiple test cases.
2. Give an Overview of S/W Quality management System ISO 9000
ISO (International Standards Organization) is a large group or consortium of 63 countries established to plan and fosters standardization. ISO declared its 9000 series of standards in 1987. It serves as a reference for the contract which determines the guidelines for maintaining a quality system. The ISO standard mainly addresses operational methods and organizational methods such as responsibilities, reporting, etc. ISO 9000 defines a set of guidelines.