Question 12.19

I figured I could use scanf more safely if I checked its return value to make sure that the user typed the numeric values I expect, but sometimes it seems to go into an infinite loop.

When scanf is attempting to convert numbers, any non-numeric characters it encounters terminate the conversion and are left on the input stream. Therefore, unless some other steps are taken, unexpected non-numeric input ``jams'' scanf again and again: scanf never gets past the bad character(s) to encounter later, valid data. If the user types a character like `x' in response to a numeric scanf format such as %d or %f, code that simply re-prompts and retries the same scanf call will immediately reencounter the same `x'.