The End of Error

10 Multiplication and division

In the first Gulf War, the U.S. prepared Patriot missiles for immediate launch if needed, and kept them ready for several days before they were used. Their ability to hit targets depends on accurate calculations using elapsed time in tenths of a second. After about 100 hours had passed (3.6 million ticks), a Patriot was launched to defend against an attacking Scud missile. The guidance system multiplied the ticks since boot by a float value of 0.1, or about 360 000 seconds. That big number to the left of the decimal point only left room for one decimal to the right of the decimal point; the important bits were ...