Provide an example, using a small function. It's recommended that the precondition be checked at the start of a function. Suppose that you accidently call a correctly implemented function, but the precondition is false. A. Easily modifiable code generally has a quicker run time. B. Most real world programs require change at some time.
Most text editors make it easy to modify code.
Several people may be writing the same function at the same time. An error message will be printed. The program will loop indefinitely. The system will crash. D. Any of the above results could happen.