241 Computer Science Certification Practice Exam

A precondition is a condition that must hold before a method starts so it can operate correctly. It’s like a contract between the caller and the method: the method relies on certain inputs, the object being in a valid state, or resources being available. If the precondition isn’t met, the method may fail, throw an error, or return incorrect results, because it was not designed to handle those out-of-range or invalid scenarios. For example, a method that returns the element at a given index assumes the index is within the bounds of the collection and that the collection is not null. That assumption before the method runs ensures safe access and correct behavior. Readability concerns how easy the code is to understand, not what must be true for execution. An exception is an event that happens during execution when something goes wrong, not the requirement that must be satisfied beforehand. Input Protection isn’t the standard term for this concept.