LIGN 17 Final Review Sheet

# LIGN 17 Final Review Sheet - LIGN 17 Final Review Sheet...

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1 LIGN 17 Final Review Sheet March 11, 2011 Error Detecting Codes: For each of the systems we’ve discussed in class, you should be able to describe and implement the algorithm it uses; you should also be able to describe what kinds of errors it can catch/correct, and what kinds of errors (if any) it misses. 1. Compute the check digit for the following 3 Credit Cards, using the Luhn Algorithm: 4217 8989 5432 724 ? 5239 2349 8723 657 ? 3339 2348 9992 66 ? 2. If the underlined digit in each of the following cases is incorrect, what number belongs in its place? Once again, use the Luhn algorithm to determine the correct answer. (Note: these numbers were generated haphazardly. It is possible that the underlined number is actually correct.) 8237 4443 89 04 6213 6123 787 8 4326 4127 7521 8882 6634 1111 3. Complete the following table, and answer the questions below: Credit Card Digit Contribution to Luhn Sum Even Position Odd Position 0 1 2 3 4 5 6 7 8 9 Which two digits, if they are adjacent and transposed, will the Luhn algorithm not catch? Why is this clear from the table above?

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2 3. Determine the check digit for the UPC’s below: 423467883 ? 234876544 ? 567234535 ? 4. If the underlined digit in each of the UPC’s below is incorrect, determine what its correct value should be: 9 342398377 44444 44447 624894 7537 5. What kinds of transposition errors will UPCs not be able to catch? 6. Will either of the above systems be able to catch non-transposition errors that effect
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LIGN 17 Final Review Sheet - LIGN 17 Final Review Sheet...

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