Software Engineering Background

1
Software Engineering Background

• Dr. David A. Gaitros

2
Classic Software Engineering problems

• IBM OS/260
• Decade long project with many cost overruns.
• Fred Brooks claims to have made a multi-million
  dollar mistake by not developing a coherent
  architecture first.
• Ariane 5 Flight 501
• First unsuccessful flight of the Equropean Ariane
  5 expendable launch system. Reused software from
  the Ariane 4 and a data conversion problem not
  previousley discovered.

3
Classic Software Engineering problems

• MIM-104 Patriot surface-to-air missile system.
• Not designed to stay in operation for an extended
  period of time. The longer the system was on the
  higher the error on a continuous calculation
  which through of the accuracy of the system.
• Mariner 1
• A hardware failure caused the system to lose
  contact with the ground and the computer took
  over. A mistranslation of an equation sent the
  rocket off course.

4
Classic Software Engineering problems

• Therac-25 Radiation Therapy Machine
• Allowed patients to receive lethal doses of
  radiation.
• Denver Airport Baggage Handling
• Significant mechanical and software problems
  plagued the automated baggage handling system. In
  tests of the system, bags were misloaded, were
  misrouted, or fell out of telecarts, causing the
  system to jam.

5
Classic Software Engineering problems

• Mars Climate Orbiter
• The Mars Climate Orbiter crashed because a
  contractor delivered a navigational instrument
  that output Imperial units instead of metric.
• 180 Degree Bug
• Torpedoes use to be programmed so that if they
  deviated more than 90 degrees they exploded to
  avoid self destruction of the ship. One time a
  ship fired a torpedo that go stuck in the tube
  and he ordered the ship to return to the harbor!
  BOOM!

6
Classic Software Engineering problems

• USS Yorktown Stops, 1998
• A crewmember of the computer controlled
  guided-missile cruiser USS Yorktown mistakenly
  entered a zero on their console. A divide by zero
  operation caused the engines to shut down.
• Pentium Chip
• 1994 pentium chip used pre-calculated set of
  numbers to speed up division. Initially there
  were five missing numbers. Cost - 4 billion.

7
However Before Software Engineering

• Scientists accurately calculated the mathematics
  needed to detonate a nuclear explosion.
• Man traveled to the moon on a computer less
  powerful than todays hand held calculators.
• The Unix operating system was developed using the
  C-programming language which has been touted by
  the world of Software Engineers to be the worst
  language to use.
• The Voyager spacecraft is still working.
• The SR-71 Aircraft was developed in the 1950s
  and is still today the fastest production
  aircraft ever built.

8
Why were some projects successful and other not?

• Answer
• Poor software developers produce poor software.
• Mediocre software developers produce mediocre
  software.
• Outstanding software developers produce superior
  quality software.
• Software Engineering was conceived to take the
  human element out of the equation.

9
Class Discussion

• What were some of the initiatives designed to aid
  in improving the quality of software?
• What would you compare the development of
  software to?
• What are the attributes of a good software
  developer?
• What are the attributes of an excellent software
  developer?
• Have these attributes changed over the years?