A validation check ascertains that the value (or data) input into a computer is valid. Validation checks are performed automatically by a computer to ensure that entered data is correct and reasonable. However, validation checks do not check whether or not the data entered is accurate. For instance, if a table accepts values ranging from 9 to 15, values greater or lower than this range are not accepted or validated by the computer, and an error is generated. There are numerous types of validation checks used to authenticate the correctness of entered data. They are used to authenticate online forms, email addresses and programming language syntax, and they are used by programs such as Microsoft Excel and Access.
Required Field Validation
A required field validation check is commonly used in filling out online forms. It determines whether or not a user has filled out the important fields in a form. A required field validation check will not allow a form to be processed until all the mandatory fields are filled out. If one or more mandatory fields are left blank, a pop-up box appears, alerting the user to the missing fields.
A range validation check determines whether or not an entered value falls within a predetermined range. For instance, if a text box allows values that fall within a set range -- say, from 5 to 10 -- all user-entered values that fall outside this range are not accepted. The range validation check alerts the user that the control value entered is inaccurate, so the user can make the necessary amendments. Range validation checks are also used to check the consistency of dates entered in forms.
Pattern Matching Validation
Pattern matching validation is used to check whether or not data entered by a user follows a preset pattern. Email addresses are validated with pattern matching checks. Email validators check the syntax of an entered email address to determine whether or not it follows the SMTP protocol for email address standards. Email addresses are composed of two parts -- the local part and the domain name. For instance, firstname.lastname@example.org has "abcd" as its local part and "example.com" as the domain name. Email pattern matching validation checks read and authenticate entered email addresses to check for syntax or other inconsistencies. Abcd.example.com, abc..email@example.com, a@b@firstname.lastname@example.org are all invalid email addresses.
Numeric validation checks determine whether or not data entered in a field or a text box has a numeric value (1, 2, 3, etc.), an alphabetic value (a, b, c, etc.) or an alphanumeric value (which includes symbols: &, %, #, etc.). Numeric validation checks allow users to only enter numeric values, and a pop-up alerts the user if he enters values other than numbers.