What is the most important difference between the two classes of safety critical system?

What is the most important difference between the two classes of safety critical system?
Ans: Safety-critical software falls into two classes:
1. Primary safety-critical software: This is software that is embedded as a controller in a system. Malfunctioning of such software can cause a hardware malfunction, which results in human injury or environmental damage. The insulin pump software, introduced in Chapter 1, is an example of a primary safety-critical system. System failure may lead to user injury.
2. Secondary safety-critical software: This is software that can indirectly result in an injury. An example of such software is a computer-aided engineering design system whose malfunctioning might result in a design fault in the object being designed. This fault may cause injury to people if the designed system malfunctions. Another example of a secondary safety-critical system is the mental health care management system, MHC-PMS. Failure of this system, whereby an unstable patient may not be treated properly, could lead to that patient injuring themselves or others.