Validation and verification 1.2 GCSE WJEC ICT Validation and verification 1.2

Objectives/Amcanion Understand what validation and verification mean Know the different types of validation and verification checks with examples Answer exam style questions

Task - RESEARCH VALIDATION VERIFICATION Definition Type of checks – explanation & example Batch & hash total Transcription errors and transposition errors

Validation Validation is a way of trying to reduce the number of errors in the data being entered into a computer system. So validation aims to make sure that data is Sensible, reasonable, complete and within acceptable boundaries. There are different validation checks that can be used to help reduce errors, they are:

Validation Checks Validation type How it works Example usage Check digit The last one or two digits in a code are used to check the other digits are correct Bar code readers in supermarkets use check digits Format check Checks the data is in the right format 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 A password which needs to be six letters long

Validation Checks Lookup table Looks up acceptable values in a table There are only seven possible days of the week Presence check Checks that data has been entered into a field In most databases a key field cannot be left blank Range check Checks that a value falls within the specified range Number of hours worked must be less than 50 and more than 0 Spell check Looks up words in a dictionary When word processing

Type Explanation Example Batch total Hash total Checks that something is not missing by adding together a number field in different records and checking the total. If an invoice has three items costing 1p, 2p and 3p, the computer will look for a batch total of 6p. Hash total Exactly the same as a batch total, but the field checked is meaningless. If a company signs up three new customers with phone numbers ending with 2, 4 and 3, the computer will look for a hash total of 9.

Verification Transcription errors sometimes occur when copying data to a computer (when reading bad handwriting, for example).  Transposition errors can sometimes happen when characters are accidentally swapped around (accidentally pressing Q instead of W, for example). Verification checks can be used as techniques to overcome these possible sources of error. Verification just means stopping errors when data is copied from one medium to another. Below are some types of verification checks: Double keying Visual check Parity check

Verification Type Explanation Example Double keying Data is entered twice to check that both sets of data matches up. Creating passwords when registering for social networking websites. Visual check Also known as proofreading (double-checking something). Looking over a CV before sending it to somewhere you want to work. Parity check Checks that data is correct when it is transmitted (sent) somewhere. Uploading files to a website will involve some kind of parity check.

BINGO Validation Parity Check Batch Total Hash Total Transcription Transposition Verification Double Keying Visual Check Presence Check Length Check Range Check