1. Credit Cards
UPC Codes

2. What is it?
A UPC is a 12 digit code generally used to identify a product.
Can also be used as coupons
Why use a UPC instead of just a price tag?
Can change price in computer easily
Universal PRODUCT Code not Universal PRICE code
If you decided to change the price of an item you would have to but new bar codes on everything!

3. Parts of the code

4. How is a code valid?
The purpose of a check digit is to guard against input errors or fraud. Follow these steps:
Underline the odd positions, add them up.
Multiply by 3
Add the even positions up
Add the two together
The sum must end in a 0 to be valid

5. 1.) Show that 0 -1 2 3 4 5 -6 7 8 9 0 -5 is a valid UPC number.
Add the odd positions
= 20
Multiply by 3
20 x 3 = 60
Add the even positions (don’t add the check digit)
= 25
Add the two together
= 85
Add a 5 so the sum ends in zero
= 90
Since the number added is the same as the check digit, then the code is VALID!

6. 1.) Determine if 6 – 7 1 8 6 0 – 0 1 3 6 6 – 4 is a valid UPC number.
If not, change the check digit to make it valid!
Add the odd positions
= 22
Multiply by 3
22 x 3 = 66
Add the even positions (don’t add the check digit)
= 22
Add the two together
= 88
Add a 2 so the sum ends in zero
= 90
The check digit needs to be changed to 2 in order to make it valid.

7. 1.) Determine the check digit (d) for the UPC number 23567128942d.
Add the odd positions
= 27
Multiply by 3
27 x 3 = 81
Add the even positions (don’t add the check digit)
= 22
Add the two together
= 103
Add a 7 so the sum ends in zero
= 110
d = 7

8. Credit Cards

9. How is a credit card valid?
Follow these steps:
Add the odd position digits
Multiply by 2
Add the number of odd position digits greater than 4
Add the even position digits
The sum must end in a 0 to be valid

10. 1.) Show that 4024 0706 1620 3102 is a valid credit card number.
Add the odd positions
= 12
Multiply by 2
12 x 2 = 24
Add the number of odd position digits greater than 4
(None) = 24
Add the even positions (don’t add the check digit)
= 24; = 48
Add a 2 so the sum ends in zero
= 50
Since the number added is the same as the check digit, then the code is VALID!

11. 1.) Determine if 5529 4203 5061 5465 is a valid credit card
number. If not, change the check digit to make it valid.
Add the odd positions
= 33
Multiply by 2
33 x 2 = 66
Add the number of odd position digits greater than 4
(5,5,6,5,6) = 71
Add the even positions (don’t add the check digit)
= 24; = 95
Add a 6 so the sum ends in zero
= 100
Since the number added is the check digit, it is VALID!

12. 1.) Determine the check digit (d) for the credit card number
Add the odd positions
= 33
Multiply by 2
33 x 2 = 66
Add the number of odd position digits greater than 4
(6,5,5,7) = 70
Add the even positions (don’t add the check digit)
= 27; = 97
Add a 6 so the sum ends in zero
= 100; d = 3

13. ARE YOU READY??
1.) Is the following UPC numbers valid codes  
2.) Find the check digit (d) for the UPC numbers d
3.) Is the following Credit Card number valid?  
4.) Find the check digit (d) for the Credit Card number d