Last week, one student told me: “Software is so complex and it is impossible to remove all defects. The more I tested software, the more defects I found and the more I fixed those defects, the more defects appeared”. I understand his frustration because it is not possible to remove defects based on testing alone.

I work in an aerospace company and I can tell you that an aircraft is a complex hardware and software systems. Although no one can prove that the aircraft has zero defects but our company does take full responsibility for any defects. However, we do not rely on product testing to remove defects because we know that testing is very expensive and ineffective way to eliminate defects. We focus on following a well defined development and manufacturing processes, we use measured procedures and statistical methods to build everything corrected from the beginning. Of course we do test our products but testing is the last resort to ensure the products are of very high quality.

My question is why software industry can not apply what the manufacturing industry has been doing for years? That brings me to another fundamental question why software people are not taught about software process? Why most universities are still teaching students about programming languages and testing but not the process of develop software?

Process is a sequence of steps performed for a given reason. Process integrates people, procedures and tools to create a final product. The product can be an aircraft, a car, a mobile phone or computer software. Process is what people do, using procedures, methods, tools, and equipments to transform raw materials such as wood, metal into a product such as a house, a car. A software process is a set of steps (including procedures, methods and tools) that people follow to develop software product. The key concept here is that the quality of the product is determined by the quality of the process used to develop it. So when the product has defect, you must go back to the process and identify what is the cause, where does it happen in the process and fix it so it will not happen again. By apply statistical method to measure every process steps, engineer can effective create a range of expected results that can be achieved by following a software process. By continuously improve the development process and remove the cause of defects, a software engineer can produce software product with much fewer defects. I am carefully not to say “Zero defects” here because it is difficult to prove it but software with much fewer defects is better than software full of defects.

The concept of process is the key element in a new software curriculum called Software Engineering. In this field, students will learn the application of a disciplined and quantifiable approach to the development of software. This discipline consists of knowledge, tools, and methods for defining requirements, architect a software system, design and implement software products, conduct testing and verify that the product meet requirements. The philosophy of this discipline is software quality is the responsible of software people who create the software product. However, if software people do not improve their skills, do not distinguish between the “engineering of software” and the “programming of software” then the software industry cannot go very far. As long as software people insist that quality is not their responsibility, quality cannot be improved.


  • Blogs of Prof. John Vu, Carnegie Mellon University