It is common to use programmable computers in applications where their failure could be life threatening and could result in extensive damage. When computers are used to replace electromechanical devices that can achieves higher reliability levels, then safety may even be impaired. Even when computers can improves safety, it is not clear that the end result is actually an increase in system safety. Despite potential problems, however, computers are being introduced to control some hazardous systems. The majority of people using these computers believe that these programmable computers never fail and whatever comes out of them has to be taken for granted. It is likely that typical programmers leave around 50 errors per thousand lines of code that they write; Software errors do not have serious sequences because people can repair the damage at some cost in time and aggravation, but some products do not provide much opportunity for people to correct errors. When a computer controls a linear accelerator or an airplane, the results of an error cannot be discarded or ignored. If the patient dies or the airplane crashes, the computation cannot be "done over". Applying typical programming practices to critical systems like these can result in tragedy.

This paper sheds some light on the danger, risks, and gives examples of computer software failure. It is shown that even if people are extremely cautious and lucky on using computer systems, they must still anticipate the occurrences of failure and hence serious catastrophes may rise in critical applications. Factors that may reduce this danger are discussed.

Keywords:

Software Engineering, Real Time Systems, Human Computer Interaction, Software Testing, Fault tolerance, Fatal Medical and Aviation accident, and reliability of software system

Computer Science Department, Science Collage, King Abdulaziz University

Email: halawani@kau.edu.sa