What input validation check ensures that data has been entered?

The presence check is a type of input validation that specifically ensures that data has been entered into a field. This validation step is crucial in many applications, especially where certain data fields are mandatory for the process or operation to function properly. When a presence check is implemented, the system verifies that a user has not left a required input field blank. If the field is empty, the system can notify the user to provide the necessary information before proceeding.

In contrast, the other options focus on different aspects of data validation:

• A range check is employed to verify that the entered data falls within a predetermined range of acceptable values.
• A format check ensures that the data aligns with a specific format, such as a date or email address structure, validating the pattern of the entered data but not confirming if something is entered at all.
• A check digit is used to validate the integrity of data, often applied to numerical entries like barcodes or account numbers, and checks that a number is accurate based on an algorithm rather than ensuring something is entered.

Thus, the presence check stands out as the method that guarantees that input has indeed been provided.