As we were writing the final chapters of this book in the summer of 2022, we realized Hat software engineering was fifty years old. In 1969 the term ' software engincering has been introduced at a NATO conference to discuss software development problems: large software systems were late, did not deliver the functionality needled by their users, cost more than expected, and were unreliable. Progress in software engineering has been remarkable over our professional life. Our societies could not function without large professional software systems. For developing any type of system, there is an alphabet soup of technologies - 12ER, NET, SaaS, SAP, BPELAWS, SOAP, CBSE, etc. - that support the development and deployment of large enterprise applications. National utilities and infrastructure - energy, communications, and transport - all rely on complex and most reliable computer-based systems. The software has allowed us to explore space and to create the World Wide Web - the most momentous information system in the history of mankind.