Validation and Verification : Introduction

A common problem with computer systems is that it is very easy to put incorrect data into them. For example :

• You could mistype a name or an address in a database resulting in letters being sent to the wrong people.
• An EFTPOS till could misread a barcode and charge the wrong price for a product.
• A MICR reader could misread the account number on a cheque and take money out of the wrong bank account.

If you put incorrect data into a computer system then you will get incorrect results out of it. Processing incorrect inputs will produce incorrect outputs. This leads to the acronym :

GIGO : Garbage In Garbage Out

Sometimes incorrect data can actually cause a computer system to stop working temporarily. This is a particular problem in batch processing systems when data may be processed overnight. If incorrect data stops a batch processing system from working then a whole night's processing time may be lost.

People who develop computer systems go to a lot of trouble to make it difficult for incorrect data to be entered. The two main techniques used for this purpose are :

Validation	A validation check is an automatic check made by a computer to ensure that any data entered into the computer is sensible.
Verification	A verification check ensures that data is correctly transferred into a computer from the medium that it was originally stored on.

GCSE ICT Companion 04 - (C) P Meakin 2004