Complex systems, services and enterprises are very dependent on computer-communication technology and in particular to their supporting and controlling software systems. This paper describes aspects of software system quality from different points of view. It provides a historical overview of the evolution of software quality and the means and methods used to achieve and enhance it. The traditional software quality models trace their origins to the well-established manufacturing industries. Since quality of a product consists of many attributes, we identify the commonly accepted established entities that conform to our vision of good quality. Notions and meanings of quality vary across disciplines and application domains. The quality of product is a concern of several stakeholders or participants which include users, designers, maintainers, marketing and sales people, the enterprise owners, etc. Their views of quality would differ from perspectives and their intentions. Quality is a dynamic attribute which keeps on changing over the life time of the product, product line and product family.