They also provide double key verify capability. Character Level Validations Character sieves disallow certain characters, e.g., no letters are permitted in numeric fields. Good systems will provide a variety of character sieves. These must be instantaneous so they do not slow down the user. Field Level Validations Extensive field edits help you catch errors that can be detected as soon as the field is completed.
Some examples are range checks, date validations, database lookups and multi-field calculations.
Professional quality systems allow you to do most, if not all, of your field edits with out having to write program code. Some errors cannot be detected until all of the data for a transaction has been entered. These validations must be essentially instantaneous or else the user cannot reach his or her potential productive speed. Professional data entry systems have quick and easy methods for the Verify Operator to make corrections. There is no need to double key verify fields that can be validated by other methods, so this feature must be optional by field.