Final answer:
Programmed edit checks are the control primarily directed at ensuring input validity by validating data before it's processed.
Step-by-step explanation:
A control that is primarily directed at ensuring input validity is programmed edit checks. These checks are designed to verify that the data entered into a system is valid before it is processed. These might include checking that numerical information falls within a certain range, verifying that dates are in the correct format, and ensuring consistency across related fields. Other options such as written approvals, confirming input acceptance, and online prompting are forms of control but do not serve the specific purpose of validating input data to the extent that programmed edit checks do.