→Incidents: Clarify what happened with the Patriot missile battery, which was, despite popular wisdom, not caused by using floating-point, but rather by using two different unit conversions that disagreed, with a discrepancy that increased with uptime.
* On 25 February 1991, aan [[loss of significance]]error in a [[MIM-104 Patriot]] missile battery [[MIM-104 Patriot#Failure at Dhahran|prevented it from intercepting]] an incoming [[Al Hussein (missile)|Scud]] missile in [[Dhahran]], [[Saudi Arabia]], contributing to the death of 28 soldiers from the U.S. Army's [[14th Quartermaster Detachment]].<ref name="GAO report IMTEC 92-26"/> The errorweapons wascontrol actuallycomputer introducedcounted time in an integer number of tenths of a second since boot. For conversion to a floating-point number of seconds in velocity and position calculations, the software originally multiplied this number by a 24-bit [[Fixed-point arithmetic|fixed-point]] computationbinary approximation to 0.1, specifically <math display="block">0.00011001100110011001100_2 = 0.1 \times (1 - 2^{-20}).</math> Some parts of the software were later adapted to use a more accurate conversion to floating-point, but some parts were not updated and still used the 24-bit approximation.<ref name="Skeel"/> but These parts of the underlyingsoftware issuedrifted wouldfrom haveone another by about 3.43 milliseconds per hour. After 20 hours, the discrepancy of about 68.7 ms was enough for the radar tracking system to lose track of Scuds; the control system in the Dhahran missile battery had been running for about 100 hours when it failed to track and intercept an incoming Scud.<ref name="GAO report IMTEC 92-26"/> The error arose not from the sameuse withof floating-point, arithmeticbut from the use of two different unit conversions when representing time in different parts of a calculation.
* {{Clarify|date=November 2024|reason=It is not clear how this is an incident (the section title may have to be modified to cover more than incidents) and how this is due to floating-point arithmetic (rather than number approximations in general). The term "invisible" may also be misleading without following explanations. |text=[[Salami slicing tactics#Financial schemes|Salami slicing]] is the practice of removing the 'invisible' part of a transaction into a separate account.}}
