Commercial Data Processing

1. Commercial Data Processing Lesson 3: Data Validation

2. By the end of this lesson you will be aware of: • GIGO • Validation • Verification • Check Digit • Range Check

3. The Data Processing Cycle The Data Processing Cycle Data must be collected before it can be input. It can be collected in from a source document, such as an order form. data collection & preparation Data has to be entered into the computer for processing. Inputting data directly ie automatically, reduces the mistakes made by people and makes this stage quicker. data input Data is processed, ie fed into the program and manipulated. There are 2 types of processing: interactive and batch. Data is then stored on some form of backing store. data processing & storage Processed data is either displayed on a monitor, printed onto paper (often as a turnaround document) or output to a file. output of data

4. The Data Processing Cycle Error Checking • Data entered into a CDP processing system must be correct. • Data however entered, manually or automatically, cannot be assumed to be correct. • Data has to be checked for errors. • There is a well known adage: Garbage In Garbage Out (GIGO).

5. Verification Verification is the process of checking the datafor complete accuracy. • Verification is needed for passwords and pin numbers. • Data to be verified is entered twice. • The data is then compared if it is exactly the same both times then it is correct, any difference it is wrong.

6. Validation Validation is the process of checking that the data should be correct and accurate. • Validated data cannot be guaranteed to be correct. • There are several methods of validating data from check digit, range checks, length checks and more.

7. Calculating the Check Digit A check digit is calculated using the other numbers in the bar code. Eg 3+2+0+0+0+0+0+0+0+3+7+7=22 divide by 5 = 4.4 so check digit 4 So 4 is added to the end of the bar code 3200000003774. Validation Using Check Digit  Check digit The last number of a bar code is a Check Digit. It is a computer check digit which help to makes sure the bar code read by the reader is correct and accurate.

8. Validation Using Check Digit  Validating The Bar Code • Scanthe bar code. • Perform the calculation on the numbers scanned in. • Compare the check digit scanned and the check digit calculated IF check digit: scanned = calculatedTHEN • Bar Code is correct, ie it has been validated OTHERWISE • Bar Code is wrong, and error sounded usually BEEP!

9. Validation Using Other Methods

10. Answer the following questions in your jotter. Explain that it is important that data must be correct. Explain what is meant by GIGO. Explain the difference between validation and verification. Give an example of when verification is needed and suggest how it can be done. Explain how a check digit can be used in validating data. Explain how a range check can be used in validating data.

11. Extension Tasks Past Paper Question Read the through information contain in http://www.teach-ict.com/as_a2/topics/validation_verification/verification_validation/validation1.htm