Mission-Critical and Safety-Critical Systems Handbook

CHAPTER 2

Failsafe Software Design:Embedded Programming in a Fail-Certain World

Jeffrey M. Sieracki

1. Software Matters

Ask yourself why you trust your microwave oven. Think about that as your daughter stares in the window and watches her milk warm. There in your kitchen is a ubiquitous lifestyle tool with components that could, in seconds, do severe harm to you or your family. Yet careful design of the physical cavity, the door, and various electronic and software interlocks render it as benign as a cereal spoon in most circumstances and far safer than the ordinary kitchen range next to it.

Meanwhile, tired and grumpy in the morning, you push a few buttons trusting utterly that your tea water or frozen sausage will heat up to your liking. A ...