Software Dependability
Copyright Notice
- © ACT Europe under the GNU Free Documentation License
- Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation; provided its original author is mentioned and the link to http://libre.act-europe.fr/ is kept. A copy of the license is included in available at: 
- http://www.fsf.org/licenses/fdl.html

Useful Books
- Programming in Ada 95
 * by John Barnes (Addison Wesley)
- High Integrity Ada: The SPARK Approach
 * by John Barnes (Addison Wesley)
- Object-Oriented Software Construction
 * by Bertrand Meyer (Prentice Hall)
- Objects Unencapsulated: Java, Eiffel, and C++
 * by Ian Joyner (Prentice Hall)
- C Traps and Pitfalls
 * by Andrew Koenig (Addison Wesley)
- Effective C++
 * by Scott Myers (Addison Wesley)
Relevant Links
- http://www.fsf.org
 * The site of the GNU project and the Free Software Foundation
- http://libre.act-europe.fr
 * Interesting Free Software projects written in Ada 95
- http://www.adahome.com/Tutorials/Lovelace/lovelace.htm
 * Lovelace, on-line Ada 95 tutorial
- http://www.adaic.com/whyada/ada-vs-c/cada_art.html
 * Comparing Development Costs of C and Ada

Software Dependability

The Blue Screen of Death

More BSOD Embarrassments

Software Dependability
- Dependability /= usability
 * A word processor, for example, must be usable, not necessarily dependable!

Warning about Defect Rates  

Software Failures: Availability
- Denial-of-service attacks
 * Example: attack against GRC.com
­	Attacked by 195 Windows 2000 servers running insecure versions of Microsoft's IIS web server. IIS was the apparent point of hacker entry into the system

Software Failures: Reliability
- January 15, 1990: 9 hour nation-wide telecom shutdown
 * 1 month earlier ATT updated its software in 114 switching stations
 * Cause: 1 misplaced “break” statement in a C program
- January 2001: 230,000 units new Internet-enabled mobile phone recalled
 * Users reported that their phones were freezing after accessing certain Web sites, and when they were powered back on, all stored information (addresses, e-mails, bookmarks, memos) had been lost
- Matracom 6500 PABX (telephone switch)
 * Random phone messages are garbled
 * Long phone calls are cut
- Windows 95/98/ME/2000
 * September 1997: propulsion system of the USS Yorktown ship failed
­	Cause: Windows NT 4.0 crashed
 * Personal experience: Installed an HP scanner on a SONY VAIO with Windows 2000. Now I cannot enter suspend mode and when I try the screen disappears until powered-off (with loss of work :()

Software Failures: Safety
- 1986: Therac 25 radiation machine kills patients
 * Cause: poor testing of the software
- June 4, 1996: maiden flight of Ariane 5 failed: rocket destroyed
 * Cause: Code from Ariane 4 guidance system reused in Ariane 5 but not tested
- 2000: Deadly accident in French highway
 * Cause: Software malfunction in car braking system. Car manufacturer acknowledges responsibility

Software Failures: Security
- November 2, 1988 Internet Worm
 * A self-replicating program was released upon the Internet
 * This program (a worm) invaded VAX and Sun computers running versions of Berkeley UNIX, and used their resources to attack still more computers.
 * Within hours this program had spread across the U.S., infecting thousands of computers and making many of them unusable due to the burden of its activity. 
 * Cause: undetected buffer overflow in C routine gets()
- Many more interesting virus stories (especially on Windows …)

1 in 3 Software Projects Doesn’t Even Get There!
- US Internal Revenue Service Modernization
 * $4 Billion, dropped in early 1997
- FBI Fingerprint system
 * $500 million, dropped
- Bell Atlantic 411
 * November 1996, outage, backed out of upgrade