Software Reliability : Introduction

• Software Reliability can be defined as the ability of a software product to perform consistently and be trustworthy to its users i.e. The software product must perform as required and should not deviate from its goal. 
• Reliability means trustworthy or consistent.
• Reliability of a software product is an important aspect as it shows the actual ability of the software product.

Software Reliability : Software Metrics

• Software metrics are the standards of measurement for a software product for certain properties and functionalities. Software metrics can be broadly classified into three categories. These are listed below :

Software Metrics : Software Reliability

1. Process Metrics
   • The Process Metric are used for the improvement of the development and maintenance of a software product. It mainly measures the efficiency of the software product.
2. Product Metrics
   • The Product Metric are used for demonstrating the software product characteristics and features such as the performance and its quality.
3. Project Metrics
   • The Project Metrics are used for demonstrating the characteristics of whole software project which includes the total time, total cost, productivity and teams.

Software Reliability : Defect Rate

• Defect Rate can be defined as the number of defect detected per unit the number of test cycles.

Defect Rate = (No of Defects Detected* 100) / (No of Test Cycles)

Software Reliability : Defect Density

• Defect density is defined as the number of defects arrived during a specific period of time per unit the size of software/module.

Defect Density = (Defect Count) / (Size of module or software)

• The defect density is counted per thousand lines of code and is called as KLOC.
• The standard for defect density is not fixed. But, one defect per thousand lines of code is considered as good quality of the project.

Software Reliability : Defect Prevention

• Defect Prevention is a plan made out to reduce the number of defects in a software product by identifying the cause of defect and preventing them to cause other problems in the software.
• The strategy of defect prevention is to analyse the phases of the software product where the defects were arrived previously and preventing the occurrence of those defects in future.
• Defect Prevention causes an increase in productivity and effort reduction.

Software Reliability : Defect Containment

• It is a strategy, an attempt to increase the software quality and reducing the cost of the software product simultaneously.
• Defect containment is reported usually as a percentage of defects captured in the phase in which they are originated.
• Also, it is a process of displaying the information about the issues and problems occurred and reported for a software system.

Software Reliability : Inspection in Software Quality

• Inspection in software project often leads to verification of quality of that software product.
• With a goal of identifying the defects, Inspection refers to peers review of a software product done by individuals in order to look for defects using certain well defined processes.
• The stages of inspection of software quality includes:
  1. Planning.
  2. Overview Meetings.
  3. Preparation.
  4. Inspection Meeting.
  5. Follow Up.
  6. Rework.