1. Coding Seven’s and Nine’s Sol: DM.11 Classwork: Students will take turns reading the “Coding Introduction” Worksheet aloud Homework (day 46): Worksheet (1-12) Coding Project due Test Day!

2. Zip Codes Because of the volume of mail, the US Postal Service uses machines to read and sort much of this country’s mail. In order to do this it is necessary for ZIP Codes to be represented by a code that can be read by machines. In the next slide, there are several five-digit ZIP Codes and the machine-readable characters that represent them. Can you “Crack the code?” What symbols, for example represent 5? Or 7? Try to determine the symbols that represent each of the ten digits of our number system.

4. Secret Codes For reasons of secrecy, codes are often used to disguise information that is sent from one party to another. The next slide illustrates a message that is coded. The coding has been done by exchanging one letter of the alphabet for another. Can you decode the message?

6. CODED INFORMATION Error Detecting Code is a code that detects certain types of errors. Check Digit using 9 A. United States Postal Service 1. Find the sum of the first ten digits. 2. Divide the sum by 9. 3. The check digit id is the remainder. (once divided if the remainder does not match the last number of the postal code it was entered incorrectly)

7. Ex: Determine the check digit which should be appended to the US postal service money order identification number 63024383845. 1. Sum = 41 2. Divided by 9 = 4.555555… 3. Check Digit ID = 5

8. B. American Express/ VISA Traveler’s Checks 1. Find the sum of all the digits. 2. The sum must be divisible by 9.

9. Ex: Determine the check digit which should be appended to the American express/ VISA travelers Cheque ID number 387505055. Sum = 38 Adding what would make it divisible by 9? 7 Check digit is 7 (because that is what makes it divisible by 9)

10. Check Digit using 7 A. Airline Tickets, Federal Express Mail, UPS Packages, Avis & National Car Rentals. 1. Take the actual number (without the check digit) & divide by 7. 2. The check digit is the remainder.