Software Crisis

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  • Topic: Radiation therapy, Therac-25, NASA
  • Pages : 57 (22150 words )
  • Download(s) : 154
  • Published : October 7, 2010
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Software Crisis
Software crisis was a term used in the early days of computing science. The term was used to describe the impact of rapid increases in computer power and the complexity of the problems which could be tackled. In essence, it refers to the difficulty of writing correct, understandable, and verifiable computer programs. The roots of the software crisis are complexity, expectations, and change.

The major cause of the software crisis is that the machines have become several orders of magnitude more powerful! To put it quite bluntly: as long as there were no machines, programming was no problem at all; when we had a few weak computers, programming became a mild problem, and now we have gigantic computers, programming has become an equally gigantic problem. – Edsger Dijkstra, The Humble Programmer (EWD340), Communications of the ACM The causes of the software crisis were linked to the overall complexity of hardware and the software development process. The crisis manifested itself in several ways: Projects running over-budget.

Projects running over-time.
Software was very inefficient.
Software was of low quality.
Software often did not meet requirements.
Projects were unmanageable and code difficult to maintain. Software was never delivered.
Poor/inadequate planning
Loose control and review
Technical incompetence
Non-engineering approach

An Investigation of the Therac-25 AccidentsNancy Leveson, University of WashingtonClark S. Turner, University of California, IrvineReprinted with permission, IEEE Computer, Vol. 26, No. 7, July 1993, pp. 18-41.

Computers are increasingly being introduced into safety-critical systems and, as a consequence, have been involved in accidents. Some of the most widely cited software-related accidents in safety-critical systems involved a computerized radiation therapy machine called the Therac-25. Between June 1985 and January 1987, six known accidents involved massive overdoses by the Therac-25 -- with resultant deaths and serious injuries. They have been described as the worst series of radiation accidents in the 35-year history of medical accelerators.[1] With information for this article taken from publicly available documents, we present a detailed accident investigation of the factors involved in the overdoses and the attempts by the users, manufacturers, and the US and Canadian governments to deal with them. Our goal is to help others learn from this experience, not to criticize the equipment's manufacturer or anyone else. The mistakes that were made are not unique to this manufacturer but are, unfortunately, fairly common in other safety-critical systems. As Frank Houston of the US Food and Drug Administration (FDA) said, "A significant amount of software for life-critical systems comes from small firms, especially in the medical device industry; firms that fit the profile of those resistant to or uninformed of the principles of either system safety or software engineering."[2] Furthermore, these problems are not limited to the medical industry. It is still a common belief that any good engineer can build software, regardless of whether he or she is trained in state-of-the-art software-engineering procedures. Many companies building safety-critical software are not using proper procedures from a software-engineering and safety-engineering perspective. Most accidents are system accidents; that is, they stem from complex interactions between various components and activities. To attribute a single cause to an accident is usually a serious mistake. In this article, we hope to demonstrate the complex nature of accidents and the need to investigate all aspects of system development and operation to understand what has happened and to prevent future accidents. Despite what can be learned from such investigations, fears of potential liability or loss of business make it difficult to find out the details behind...
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