What are Critical Systems ?
Critical systems are systems in which defects could have a dramatic impact on human life, the environment or significant assets. Such systems are expected to satisfy a variety of specific qualities including reliability, availability, security and safety. With the steady infiltration of computers and software in all aspects of our modern world, critical systems increasingly depend on software functionality. These systems are commonplace in many different products, ranging from aircraft systems to home use medical devices.
One example is a software-based system for controlling signal lights at a traffic intersection. Another example is a modern Anti-lock Brake System (ABS) in an automobile that relies on software to determine when and how to regulate braking force. Yet another example is software processing of medical images used for diagnoses and treatment planning.
What is safety critical software ?
Software that implements a critical decision-making process,
Software that controls or monitors safety critical functions,
Software that intervenes when an unsafe condition is present or imminent
Software that executes on the same target system as safety critical software,
Software that impacts systems that run safety critical software
Software that handles safety critical data including display of safety critical information
Software used to verify and validate safety critical software
Critical software may or may not be embedded. Critical software can also be one element in a system of systems.