Validation is an automatic computer check to ensure that the data entered is sensible and reasonable. It does not check the accuracy of data.
Check digit: the last one or two digits in a code are used to check the other digits are correct
Example: bar code readers in supermarkets use check digits
Format check: checks the data is in the right format
Example: a National Insurance number is in the form LL 99 99 99 L where L is any letter and 9 is any number
Length check: checks the data isn't too short or too long
Example: a password which needs to be six letters long
Lookup table: looks up acceptable values in a table
Example: there are only seven possible days of the week
Presence check: checks that data has been entered into a field
Example:in most databases a key field cannot be left blank
Verification is performed to ensure that the data entered exactly matches the original source.
There are two main methods of verification:
Double entry - entering the data twice and comparing the two copies. This effectively doubles the workload, and as most people are paid by the hour, it costs more too.
Proofreading data - this method involves someone checking the data entered against the original document. This is also time consuming and costly.