1. Safety Critical Systems

2. What is meant by Safety Critical Systems
Safety critical systems are systems where safety is the top priority. Should the system fail it could result in loss of life; injury, damage to property/equipment or environmental damage.
Example of a safety-critical system failing.

3. Examples of Safety Critical Systems
Some examples:
Seatbelts
Nuclear Reactor Control systems
Railway signal control systems
Amusement rides
Emergency Service dispatch systems
Fire alarm
Telecommunications
Robotic surgery machines
Fuses
Pace makers
Air Traffic Control Systems
Radiation therapy
Traffic Lights
Airbag systems

4. Nuclear Reactor
Nuclear systems are very complex having many different safety precautions built in.
For example if the temperature gets too hot or the reaction goes out of control, control rods can be injected into the reaction in order to prevent meltdown.
Power plants can be built next to large bodies of water so that the water can help to dissipate heat generated by the power plant.

5. Air Traffic control
Air traffic control is important as without it planes and other aircraft can fly too close to each other or have trouble navigating.
The system includes many different users using computer systems that track planes and allow them to communicate directly to pilots. Having many different people reduces the chance of errors as if one person is unfit then someone else can take there place.

6. High Level of Dependability
Due to the severe consequences should the system fail many design methods are implemented to reduce the chance of a system failure.
Often, three different ways are created for the system to run which should all create the same output from the inputs. These are all used and if one of the three routines differ then the software may have a bug and this routine is not run with the other 2 as backup and a error message produced.
A life-critical system is designed to lose less than one life per billion hours running.

7. Questions Give an example of a safety critical system.
What are the consequences of a fire alarm system failing?
What is a method used to prevent system failure?
Why do we need safety critical systems?
Would it be suitable for a small team of programmers to develop a safety critical system?