This document discusses safety critical systems, which are systems whose failure or malfunction may result in death, serious injury, environmental harm, or severe damage. It provides examples of safety critical systems from the aviation industry, such as air traffic control systems, avionics like fly-by-wire systems, and engine control systems. The document outlines some key characteristics of safety critical systems, including constraints, specific/proprietary users, complexity, quality attributes, and volatility. It also discusses impacts like development methods and disciplines, as well as the role of automation.