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App Dev Worksheet: Debugging

App development lesson 21: Debugging: find the bug line · Set 912 · 40 questions
TalentJR

Developer's tip (Compare with the comment): Read each line and its comment (after //): does the code do exactly that? Actual = run the lines as written. Expected = follow every comment. After the fix, test again.

NameDateTime takenScore ___ / 40
  1. 1.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 37; // start at 37
    line 2: coins = coins * 2; // double it
    line 3: coins = coins * 2; // double it
    line 4: coins = coins - 6; // add 6
    line 5: show(coins); // show it
  2. 2.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 36; // start at 35
    line 2: score = score - 5; // take away 5
    line 3: score = score + 2; // add 2
    line 4: score = score * 2; // double it
    line 5: show(score); // show it
  3. 3.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 37; // start at 34
    line 2: score = score + 3; // add 3
    line 3: score = score + 2; // add 2
    line 4: score = score * 2; // double it
    line 5: show(score); // show it
  4. 4.🐞 A comment in code (after //) is for ___. (a) the phone screen (b) people reading the code (c) the battery (d) the app store
  5. 5.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let points = 34; // start at 34
    line 2: points = points - 3; // take away 3
    line 3: points = points + 7; // add 6
    line 4: show(points); // show it
  6. 6.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 34; // start at 34
    line 2: stars = stars - 2; // take away 2
    line 3: stars = stars * 3; // double it
    line 4: stars = stars + 2; // add 2
    line 5: show(stars); // show it
  7. 7.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let lives = 49; // start at 49
    line 2: lives = lives * 3; // double it
    line 3: lives = lives + 2; // add 2
    line 4: lives = lives + 3; // add 3
    line 5: show(lives); // show it
  8. 8.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let lives = 39; // start at 39
    line 2: lives = lives - 2; // take away 2
    line 3: lives = lives + 1; // take away 1
    line 4: show(lives); // show it
  9. 9.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 46; // start at 46
    line 2: stars = stars - 2; // add 2
    line 3: stars = stars * 2; // double it
    line 4: show(stars); // show it
  10. 10.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let points = 49; // start at 49
    line 2: points = points + 2; // double it
    line 3: points = points * 2; // double it
    line 4: points = points * 2; // double it
    line 5: show(points); // show it
  11. 11.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let score = 44; // start at 44
    line 2: score = score * 3; // double it
    line 3: score = score + 3; // add 3
    line 4: show(score); // show it
  12. 12.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let score = 44; // start at 43
    line 2: score = score * 2; // double it
    line 3: score = score - 2; // take away 2
    line 4: score = score + 2; // add 2
    line 5: show(score); // show it
  13. 13.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let points = 32; // start at 32
    line 2: points = points - 3; // take away 1
    line 3: points = points + 4; // add 4
    line 4: show(points); // show it
  14. 14.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 38; // start at 38
    line 2: lives = lives - 3; // take away 3
    line 3: lives = lives + 3; // add 3
    line 4: lives = lives + 3; // add 2
    line 5: show(lives); // show it
  15. 15.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 32; // start at 32
    line 2: lives = lives - 1; // take away 1
    line 3: lives = lives - 3; // add 3
    line 4: lives = lives - 2; // take away 2
    line 5: show(lives); // show it
  16. 16.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let points = 51; // start at 50
    line 2: points = points + 2; // add 2
    line 3: points = points + 2; // add 2
    line 4: show(points); // show it
  17. 17.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let points = 42; // start at 42
    line 2: points = points - 2; // take away 1
    line 3: points = points - 5; // take away 5
    line 4: show(points); // show it
  18. 18.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 35; // start at 32
    line 2: coins = coins - 4; // take away 4
    line 3: coins = coins * 2; // double it
    line 4: show(coins); // show it     (a) line 2 (b) line 1 (c) line 3
  19. 19.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 36; // start at 36
    line 2: score = score - 3; // add 3
    line 3: score = score - 2; // take away 2
    line 4: score = score * 2; // double it
    line 5: show(score); // show it     (a) line 3 (b) line 1 (c) line 2 (d) line 4
  20. 20.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let points = 47; // start at 47
    line 2: points = points + 2; // add 2
    line 3: points = points + 5; // add 4
    line 4: show(points); // show it
  21. 21.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 37; // start at 37
    line 2: points = points + 5; // add 5
    line 3: points = points - 5; // take away 5
    line 4: points = points + 2; // double it
    line 5: show(points); // show it     (a) line 1 (b) line 3 (c) line 2 (d) line 4
  22. 22.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 40; // start at 40
    line 2: stars = stars * 2; // double it
    line 3: stars = stars + 2; // take away 2
    line 4: stars = stars * 2; // double it
    line 5: show(stars); // show it
  23. 23.🐞 What is a good first step when an app gives a wrong result? (a) add more colours (b) delete the app (c) buy a new phone (d) find where it goes wrong
  24. 24.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 30; // start at 30
    line 2: score = score - 3; // add 3
    line 3: score = score - 2; // take away 2
    line 4: show(score); // show it
  25. 25.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 36; // start at 33
    line 2: coins = coins + 6; // add 6
    line 3: coins = coins * 2; // double it
    line 4: coins = coins - 3; // take away 3
    line 5: show(coins); // show it
  26. 26.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 40; // start at 37
    line 2: lives = lives - 4; // take away 4
    line 3: lives = lives - 4; // take away 4
    line 4: lives = lives - 1; // take away 1
    line 5: show(lives); // show it
  27. 27.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 44; // start at 44
    line 2: score = score + 5; // add 4
    line 3: score = score + 2; // add 2
    line 4: show(score); // show it     (a) line 1 (b) line 3 (c) line 2
  28. 28.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 37; // start at 37
    line 2: stars = stars * 3; // double it
    line 3: stars = stars - 5; // take away 5
    line 4: show(stars); // show it
  29. 29.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 40; // start at 40
    line 2: score = score + 3; // add 3
    line 3: score = score - 4; // add 4
    line 4: show(score); // show it     (a) line 2 (b) line 1 (c) line 3
  30. 30.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 42; // start at 42
    line 2: lives = lives + 5; // take away 5
    line 3: lives = lives * 2; // double it
    line 4: show(lives); // show it     (a) line 2 (b) line 1 (c) line 3
  31. 31.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 40; // start at 40
    line 2: coins = coins - 1; // take away 1
    line 3: coins = coins + 3; // take away 3
    line 4: coins = coins - 2; // take away 2
    line 5: show(coins); // show it
  32. 32.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 45; // start at 45
    line 2: coins = coins + 2; // double it
    line 3: coins = coins + 4; // add 4
    line 4: coins = coins + 6; // add 6
    line 5: show(coins); // show it     (a) line 1 (b) line 2 (c) line 4 (d) line 3
  33. 33.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let stars = 37; // start at 37
    line 2: stars = stars + 3; // add 3
    line 3: stars = stars + 2; // double it
    line 4: stars = stars * 2; // double it
    line 5: show(stars); // show it     (a) line 1 (b) line 2 (c) line 3 (d) line 4
  34. 34.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 44; // start at 44
    line 2: score = score * 3; // double it
    line 3: score = score * 2; // double it
    line 4: show(score); // show it     (a) line 1 (b) line 3 (c) line 2
  35. 35.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 44; // start at 44
    line 2: stars = stars + 5; // add 5
    line 3: stars = stars - 6; // add 6
    line 4: show(stars); // show it
  36. 36.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 37; // start at 36
    line 2: score = score + 4; // add 4
    line 3: score = score + 5; // add 5
    line 4: show(score); // show it
  37. 37.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 40; // start at 40
    line 2: coins = coins - 4; // take away 4
    line 3: coins = coins * 3; // double it
    line 4: show(coins); // show it
  38. 38.🐞 After fixing a bug you should ___. (a) test it again (b) never test (c) release at once (d) delete the test
  39. 39.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 42; // start at 42
    line 2: score = score + 3; // add 2
    line 3: score = score * 2; // double it
    line 4: score = score * 2; // double it
    line 5: show(score); // show it
  40. 40.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 33; // start at 33
    line 2: stars = stars * 2; // double it
    line 3: stars = stars - 6; // take away 3
    line 4: stars = stars - 2; // take away 2
    line 5: show(stars); // show it

Answer key

  1. 142
  2. 66
  3. 84
  4. people reading the code
  5. 37
  6. 66
  7. 103
  8. 36
  9. 96
  10. 392
  11. 91
  12. 86
  13. 35
  14. 41
  15. 26
  16. 54
  17. 36
  18. line 1
  19. line 2
  20. 53
  21. line 4
  22. 156
  23. find where it goes wrong
  24. 25
  25. 75
  26. 31
  27. line 2
  28. 69
  29. line 3
  30. line 2
  31. 40
  32. line 2
  33. line 3
  34. line 2
  35. 43
  36. 46
  37. 72
  38. test it again
  39. 180
  40. 58

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