Validation is an automatic computer check to ensure that the data entered is sensible and reasonable. It does not check the accuracy of data.
For example, a format check for the telephone number is in the format of 5 digits then a space follwed by 6 digits. A validation text can be displayed in case the data entered doesn’t satisfy the validation.
Types of validation:
Range checks - these are used with numerical fields to limit the range of numbers a user can enter.
Format checks - these only allow valid text or numbers. Many use input 'masks' such as 000LLL. Such a mask would only allow 3 numbers followed by 3 letters.
Member lists - this method of validation is used to limit entries to those that are members of a list of allowed entries. The choices may appear in a drop-down list to reduce transcription errors or be in the form of a list of acceptable entries that the input is checked against.
Check digits - this type of check is used with numbers. An extra 'check digit' is calculated from the numbers to be entered and added to the end. The numbers can then be checked at any stage by re-calculating the check digit from the other numbers and seeing if it matches the one entered. One example where a check digit is used is in the 10 digit ISBN number which uniquely identifies books. The last number of the ISBN is actually the check digit for the other numbers, for example - the ISBN 0192761501.
Presence checks - these simply check that an entry has been made in a particular field. It it has not then the system will not allow the record to be saved or any entries to be made in later fields.