2. Commercial Data Processing Lesson 3: Data Validation

3. Commercial Data Processing By the end of this lesson you will be aware of:  GIGO  Validation  Verification  Check Digit  Range Check

4. Commercial Data Processing data collection & preparation data input data processing & storage output of data Data must be collected before it can be input. It can be collected in from a source document, such as an order form. 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 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. Processed data is either displayed on a monitor, printed onto paper (often as a turnaround document) or output to a file. The Data Processing Cycle

5. Commercial Data Processing 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). The Data Processing Cycle

6. Commercial Data Processing Verification  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. Verification is the process of checking the data for complete accuracy.

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

8. Commercial Data Processing Validation Using Check Digit  The last number of a bar code is a Check Digit. Check digit It is a computer check digit which help to makes sure the bar code read by the reader is correct and accurate. 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. Calculating the Check Digit

9. Commercial Data Processing Validation Using Check Digit  1.Scan the bar code. 2.Perform the calculation on the numbers scanned in. 3.Compare the check digit scanned and the check digit calculated IF check digit: scanned = calculated THEN  Bar Code is correct, ie it has been validated OTHERWISE  Bar Code is wrong, and error sounded usually BEEP! Validating The Bar Code

10. Commercial Data Processing Validation Using Other Methods Type of CheckHow They Work Range Check Checks a number entered is within a specific range. Examples Enter a number between 0 and 100. Enter a month, must be between 1 and 12. Field Length Checks the number of characters entered to see if there are enough. Examples Passwords that must be between 6 and 8 characters.

11. Commercial Data Processing Answer the following questions in your jotter. 1.Explain that it is important that data must be correct. 2.Explain what is meant by GIGO. 3.Explain the difference between validation and verification. 4.Give an example of when verification is needed and suggest how it can be done. 5.Explain how a check digit can be used in validating data. 6.Explain how a range check can be used in validating data.

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