Editing Defensive design (section)

===Computer software ===

Implementation decisions and [[software design]] approaches can make software safer and catch user errors.
[[Source code|Code]] that implements this is termed a [[sanity check]].

* Data entry screens can "sanitize" inputs, e.g. numeric fields contain only digits, signs and a single decimal point if appropriate.

* Inputs can be checked for legitimate values, e.g. for counts of workplace injuries (or number of people injured) the number can be 0 but can't be negative and must be a whole number; for number of hours worked in one week the amount for any specified employee can be 0, can be fractional, but can't be negative and can't be greater than 168, nor more than 24 times the number of days they were in attendance.

* A word processor requested to load a saved document should scan it to ensure it is in good form and not [[Data corruption|corrupted]]. If it is corrupted, the program should say so, then either accept the partial document that was valid, or refuse the entire document. In either case it should remain running and not quit.