About Quality Pre paired By: Muhammad Azhar

Scope What is Quality Quality Attributes Conclusion on software Quality Quality Concepts Quality Costs

Definition of software Quality 1. "Quality is Conformance to requirements" – CROSBY. 2. "Software Quality means fitness for purpose" – OULD 3. Quality is all the features that allow a product to satisfy stated or implied needs at an affordable cost - ISO-8402

Software Quality Attributes ISO-9126  Functionality Suitability Accuracy Interoperability Compliance Security  Reliability Maturity Fault Tolerance Recoverability  Usability Understandability Learnability Operability  Efficiency Time Behavior Resource Behavior  Maintainability Analyzability Changeability Stability Testability  Portability Adaptability Installability Conformance Replaceability

Quality Attributes IEEE 1059  Accuracy  Completeness  Consistency  Efficiency  Expandability  Flexibility  Interpretability  Maintainability  Manageability  Portability  Readability  Reusability  Reliability  Safety  Security  Survivability  Testability  Usability

Conclusions on software Quality 1. It is generally accepted that quality of the process plays a crucial role in determining the quality of the product. 2. Quality must be built into software from the outset - it cannot be added on later. 3. It is people that determine whether or not a quality product is produced.

Quality Concepts Quality is what distinguishes a good company from a great one. Quality is what distinguishes a good company from a great one. Quality is meeting or exceeding our customer's needs and requirements. Quality is meeting or exceeding our customer's needs and requirements. Software Quality is measurable. Software Quality is measurable. Quality is continuous improvement. Quality is continuous improvement. The quality of a software product comes from the quality of the process used to create it. The quality of a software product comes from the quality of the process used to create it.

Quality Costs Philip Crosby wrote in his book ‘Quality is Free’ Book name “Quality is Free. New York: ISBN ”ISBN  Prevention Costs  Appraisal Costs  Internal failure Costs  External failure costs

Prevention Cost 1. These are costs of activities specifically designed to prevent poor quality (coding errors, design errors, bad documentation, un maintainable coding). 2. E.g., Staff Training, Requirement Analysis, Fault-tolerant design, defensive programming, usability analysis, clear specification, accurate internal documentation, evaluation of the reliability of development tools

Appraisal Costs 1. These are Costs of activities designed to find quality problems, such as code inspections and any type of testing 2. E.g., Design Review, Code Inspection, White box testing, Black box testing, training testers, Beta testing, test automation, usability testing

Internal Failure Cost 1. Bug fixes, Regression testing 2. Wasted in-house user time 3. Wasted tester time, Wasted writer time 4. Wasted marketer time 5. Wasted advertisements 6. Direct cost of late shipment 7. Opportunity cost of late shipment

External Failure Cost  Technical support calls, Investigation of customer complaints, refunds and recalls, coding/testing of interim bug fix releases, shipping of updated product, added expense of supporting multiple versions of the product, lost sales, lost customer goodwill, warranty costs, liability costs, penalties  Crosby demonstrates that the costs of conformance plus the costs of nonconformance due to internal failures is less than the costs of nonconformance due to external failures.

What Is Total Cost Of Quality? 1. Total Cost of Quality = Sum of all costs. 2. Total Cost of Quality = Prevention + Appraisal + Internal failure + External failure

Relative cost of a bug fix