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Data validation and verification


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Validation and verification are two ways to check that the data entered into a computer is correct. Data [data: information without context, eg a list of students with numbers beside their names is data, when it's made clear that those numbers represent their placing in a 100 metre race, the data becomes information ] entered incorrectly is of little use.


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 secondary school student is likely to be aged between 11 and 16. The computer can be programmed only to accept numbers between 11 and 16. This is a range check.

However, this does not guarantee that the number typed in is correct. For example, a student's age might be 14, but if 11 is entered it will be valid but incorrect.

Types of validation

There are a number of validation types that can be used to check the data that is being entered.


Validation typeHow it worksExample usage
Check digitthe last one or two digits in a code are used to check the other digits are correctbar code readers in supermarkets use check digits
Format checkchecks the data is in the right formata National Insurance number is in the form LL 99 99 99 L where L is any letter and 9 is any number
Length checkchecks the data isn't too short or too longa password which needs to be six letters long
Lookup tablelooks up acceptable values in a tablethere are only seven possible days of the week
Presence checkchecks that data has been entered into a field [field: a smaller piece of data in larger collection, eg name in an electronic address book, where name is a field ]in most databases [database: a structured collection of records or data stored in a computer system ] a key field [key field: a unique identifier for a database record or table entry ] cannot be left blank
Range checkchecks that a value falls within the specified rangenumber of hours worked must be less than 50 and more than 0
Spell checklooks up words in a dictionarywhen word processing


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