Software is the collection of computer programs, related data, and associated documentation developed for a particular customer or for a general market. It is an essential part of the modern world, and it has become pervasive in telecommunications, utilities, commerce, culture, entertainment, and so on. The question What is software quality? can generate different answers, depending on the involved practitioner's role in a software system. There are two main groups of people involved in a software product or service:

• Consumers: are people who use software. In this group, we can differentiate between customers (that is, people responsible for the acquisition of software products or services) and users (that is, people who use the software products or services for various purposes). Nevertheless, the dual roles of customers and users are quite common.
• Producers: are people involved with the development, management, maintenance, marketing, and service of software products.

The quality expectations of consumers are that a software system performs useful functions as specified. For software producers, the fundamental quality question is fulfilling their contractual obligations by producing software products that conform to the Service Level Agreement (SLA). The definition of software quality by the well-known software engineer Roger Pressman comprises both points of view: