In principle, coding involves translating a design into a running program. Correctness of the result typically assumes:

• Design is complete and unambiguous
• All design assumptions will be understood and followed
• Programmer(s) will make no errors

In practice, these assumptions are unfounded for complex applications.

Two classical examples:

1. F-16 Control: In early version, programmer omitted term that the programmer considered unnecessary in formula. As a result, the system did not distinguish between northern and southern hemispheres, and the plane would flip upside down whenever it crossed the equator.

   Source: Reported in a letter by Earl Boebert in Software Engineering Notes, April 1980,Volume 5, Number 2, page 5.

2. Mariner 1 Space Probe to Venus (July 22, 1962):
   

   Correct Statement:	Do 3 I = 1, 3
   Actual statement:	Do 3 I = 1. 3

   
   Result: $18.5 million Vehicle veered off course and was destroyed

   Source: Annals of the History of Computing, 1984, Volume 6, Number 1, page 6.

created 3 January 2006 last revised 7 January 2006

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