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

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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