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Identification numbers

Identification numbers. Wong Wai Ling, Lam Pui Ki 2011-3-22. Introduction. Identification number clearly identify a person or a thing Check digit an extra digit for the purpose of error detection. U.S. Postal Service Money Order. 11-digit sum of the first 10 digits is divided by 9

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Identification numbers

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  1. Identification numbers Wong Wai Ling, Lam Pui Ki 2011-3-22

  2. Introduction Identification number clearly identify a person or a thing Check digit an extra digit for the purpose of error detection

  3. U.S. Postal Service Money Order 11-digit sum of the first 10 digits is divided by 9 remainder = check digit Disadvantages can’t detect mistake 1) replace 0 by 92) numbers interchange

  4. Euro bank-notes

  5. Euro bank-notes First letter identify the country that issues the note add up the numbers, add each single digit in the sum until a single digit remains sum = 4+7+9+5 = 25, 2+5 = 7

  6. Euro bank-notes Checksum single digit obtained previously refer to the particular country

  7. UPC (Universal Product Code) 12-digit 1st: category 2nd-6th: manufacturer 7th-11th: identify the product 12th: check digit sum = 3(1st)+1(2nd)+3(3rd)+ … +3(11th)+1(12th) sum should end with a 0. (e.g. 10,20,30,…) can detect all single position error and about 89% of other kinds of errors

  8. The U.S. banking system use a variation of the UPC scheme append check digits to the numbers assigned to banks Each bank has a 8-digit routing number sum = 7(1st)+3(2nd)+9(3rd)+ … +7(7th)+3(8th) an extra 9th digit (check digit) = last digit of the sum   i.e. sum = 53 → check digit = 3 numbers 7,3,9 are called weights can detect most transposition errors

  9. EAN (Europe Article Number) 13-digit become worldwide standard existing UPC numbers are converted to EAN by adding an extra “0” at the beginning sum = 1(1st)+3(2nd)+1(3rd)+ … +1(11th)+3(12th)+1(13th) does not affect the check digit compared with UPC

  10. Codabar Credit cards, libraries, blood banks, etc Computation 1) add the digits in odd positions 2) double the result 3) add the numbers in odd positions that exceed 4 4) add the remaining digits (even positions) check digit = the number needed to bring the total result to end with 0

  11. Example – Credit Card detect 100% single position error and 98% common error

  12. ISBN (International Standard Book Number) published country publisher identification number check digit 10-digit e.g. a1 - a2a3a4a5 - a6a7a8a9 - a10 ↑ ↑ ↑ ↑ sum = 10a1+9a2+8a3+7a4+6a5+5a6+4a7+3a8+2a9+1a10 is divisible by 11 however, the 10th digit (check digit) could be 10 solution: use “X” instead of “10” detect 100% single position error and transposition error another type: 13-digit, same as EAN

  13. Activity The ISBN 0-669-03925-4 is the result of a transposition of two adjacent digits not involving the first or last digit. Determine the correct ISBN.

  14. Bar Code A series of dark and light spaces that represents characters Binary code A system for representing data with two symbols Bar coding Method for automated data collection

  15. Decode Information A beam of light passes through the bars and spaces by scanning device The differences in reflection intensities Dark bars reflect less; light spaces reflect more

  16. UPC Bar Code most often encountered, first used on grocery items in 1973 translate 12-digit number into bars 12-digit number two five-digit numbers in between two single-digit

  17. UPC Bar Code (Example) 12-digit: 0-12345-67890-5 1st number (0) : kinds of product next 5 digits (12345): manufacturer number next 5 digits (67890): product number last digit (5) : check digit

  18. UPC Code digits are represented by a space divided into 7 modules of equal width 2 long bars with one-module thickness in each end separated by a light space of one-module thickness the modules are named as guard bar patterns

  19. UPC Code-Center bar pattern separate the manufacturer’s number and the product number not a part of identification number 5 modules: a light space, a long dark bar, a light space, a long dark bar, a light space

  20. UPC Code one-module-thickness light space 0 one-module-thickness dark bar 1 code in the product number can be obtained from the code in the manufacturer’s number, vice versa

  21. UPC Code replace 1 by 0, 0 by 1 Example 0111011 for manufacture’s number = 1000100 for the product number manufacture’s number : odd number of 1’s product number : even number of 1’s Determine whether the barcode is scanned from LHS or RHS scanning can be done correctly

  22. Homework 1. Prove that the ISBN detects 100% of the single position errors. 2. The following is an actual identification number and bar code from a roll of wallpaper. What appears to be wrong with them? Speculate on the reason for the apparent violation of the UPC format. (write at least two)

  23. Homework(Extra) Extra : Compare the advantages and the disadvantages of thealgorithm methods stated in class. Give examples on the purpose of each method.

  24. Thank you!

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