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App Dev Worksheet: Debugging

App development lesson 21: Debugging: find the bug line · Set 691 · 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.🐞 A comment in code (after //) is for ___. (a) the phone screen (b) the battery (c) the app store (d) people reading the code
  2. 2.🐞 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; // double it
    line 3: stars = stars - 2; // take away 2
    line 4: stars = stars + 4; // take away 4
    line 5: show(stars); // show it
  3. 3.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let score = 49; // start at 46
    line 2: score = score - 1; // take away 1
    line 3: score = score * 2; // double it
    line 4: score = score + 3; // add 3
    line 5: show(score); // show it
  4. 4.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 53; // start at 50
    line 2: lives = lives + 3; // add 3
    line 3: lives = lives * 2; // double it
    line 4: show(lives); // show it     (a) line 3 (b) line 2 (c) line 1
  5. 5.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let lives = 44; // start at 41
    line 2: lives = lives * 2; // double it
    line 3: lives = lives + 6; // add 6
    line 4: lives = lives + 5; // add 5
    line 5: show(lives); // show it
  6. 6.🐞 What is a bug? (a) a mistake in the code (b) a new feature (c) a nice icon (d) a fast phone
  7. 7.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let score = 46; // start at 43
    line 2: score = score + 6; // add 6
    line 3: score = score + 4; // add 4
    line 4: score = score * 2; // double it
    line 5: show(score); // 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 points = 37; // start at 37
    line 2: points = points - 3; // take away 3
    line 3: points = points - 3; // add 3
    line 4: show(points); // show it
  9. 9.🐞 Finding and fixing bugs is called ___. (a) decorating (b) debugging (c) downloading (d) designing
  10. 10.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 49; // start at 49
    line 2: points = points + 3; // add 3
    line 3: points = points + 6; // add 6
    line 4: points = points - 3; // add 3
    line 5: show(points); // show it
  11. 11.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 40; // start at 40
    line 2: coins = coins - 4; // take away 2
    line 3: coins = coins - 2; // take away 2
    line 4: show(coins); // 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 coins = 45; // start at 45
    line 2: coins = coins + 4; // add 3
    line 3: coins = coins + 2; // add 2
    line 4: coins = coins * 2; // double it
    line 5: show(coins); // show it
  13. 13.🐞 What is a good first step when an app gives a wrong result? (a) buy a new phone (b) delete the app (c) add more colours (d) find where it goes wrong
  14. 14.🐞 After fixing a bug you should ___. (a) never test (b) delete the test (c) release at once (d) test it again
  15. 15.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 45; // start at 43
    line 2: stars = stars - 4; // take away 4
    line 3: stars = stars * 2; // double it
    line 4: stars = stars + 6; // add 6
    line 5: show(stars); // show it
  16. 16.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 45; // start at 45
    line 2: lives = lives + 2; // double it
    line 3: lives = lives * 2; // double it
    line 4: lives = lives * 2; // double it
    line 5: show(lives); // 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 score = 41; // start at 41
    line 2: score = score * 2; // double it
    line 3: score = score + 7; // add 5
    line 4: show(score); // show it
  18. 18.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 49; // start at 47
    line 2: score = score + 3; // add 3
    line 3: score = score * 2; // double it
    line 4: score = score * 2; // double it
    line 5: show(score); // show it
  19. 19.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 32; // start at 32
    line 2: score = score - 3; // add 3
    line 3: score = score * 2; // double it
    line 4: show(score); // show it
  20. 20.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let stars = 44; // start at 44
    line 2: stars = stars + 3; // take away 3
    line 3: stars = stars - 3; // take away 3
    line 4: show(stars); // show it     (a) line 3 (b) line 1 (c) line 2
  21. 21.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 34; // start at 34
    line 2: lives = lives * 3; // double it
    line 3: lives = lives + 6; // add 6
    line 4: lives = lives + 4; // add 4
    line 5: show(lives); // show it
  22. 22.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 33; // start at 33
    line 2: score = score + 2; // add 2
    line 3: score = score + 6; // add 6
    line 4: score = score + 2; // double it
    line 5: show(score); // show it
  23. 23.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let points = 37; // start at 37
    line 2: points = points - 7; // take away 5
    line 3: points = points - 2; // take away 2
    line 4: points = points - 4; // take away 4
    line 5: show(points); // show it
  24. 24.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let stars = 39; // start at 39
    line 2: stars = stars + 5; // add 3
    line 3: stars = stars * 2; // double it
    line 4: stars = stars + 2; // add 2
    line 5: show(stars); // show it     (a) line 2 (b) line 4 (c) line 1 (d) line 3
  25. 25.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 35; // start at 35
    line 2: stars = stars + 5; // add 5
    line 3: stars = stars * 3; // double it
    line 4: stars = stars - 2; // take away 2
    line 5: show(stars); // show it
  26. 26.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 45; // start at 45
    line 2: coins = coins * 2; // double it
    line 3: coins = coins - 1; // take away 1
    line 4: coins = coins + 5; // add 3
    line 5: show(coins); // show it
  27. 27.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 31; // start at 31
    line 2: stars = stars + 4; // add 4
    line 3: stars = stars - 2; // take away 2
    line 4: stars = stars + 1; // take away 1
    line 5: show(stars); // show it
  28. 28.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let stars = 36; // start at 36
    line 2: stars = stars + 4; // add 2
    line 3: stars = stars - 4; // take away 4
    line 4: show(stars); // show it     (a) line 2 (b) line 1 (c) line 3
  29. 29.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 38; // start at 38
    line 2: points = points + 2; // double it
    line 3: points = points + 6; // add 6
    line 4: points = points + 3; // add 3
    line 5: show(points); // show it
  30. 30.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 35; // start at 35
    line 2: stars = stars - 1; // take away 1
    line 3: stars = stars + 5; // take away 5
    line 4: stars = stars + 3; // add 3
    line 5: show(stars); // show it
  31. 31.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 49; // start at 47
    line 2: points = points + 6; // add 6
    line 3: points = points * 2; // double it
    line 4: show(points); // show it     (a) line 2 (b) line 1 (c) line 3
  32. 32.🐞 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 + 3; // add 3
    line 3: lives = lives - 1; // take away 1
    line 4: lives = lives + 5; // add 4
    line 5: show(lives); // show it     (a) line 3 (b) line 1 (c) line 4 (d) line 2
  33. 33.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 39; // start at 39
    line 2: coins = coins + 1; // take away 1
    line 3: coins = coins + 2; // add 2
    line 4: show(coins); // show it     (a) line 1 (b) line 3 (c) line 2
  34. 34.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 47; // start at 47
    line 2: coins = coins + 6; // add 6
    line 3: coins = coins - 5; // add 5
    line 4: coins = coins + 3; // add 3
    line 5: show(coins); // show it     (a) line 3 (b) line 1 (c) line 4 (d) line 2
  35. 35.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 43; // start at 43
    line 2: points = points + 3; // add 3
    line 3: points = points + 2; // double it
    line 4: points = points * 2; // double it
    line 5: show(points); // show it
  36. 36.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let lives = 36; // start at 36
    line 2: lives = lives - 5; // take away 5
    line 3: lives = lives + 2; // take away 2
    line 4: show(lives); // show it
  37. 37.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 34; // start at 34
    line 2: points = points + 2; // double it
    line 3: points = points + 5; // add 5
    line 4: points = points * 2; // double it
    line 5: show(points); // show it
  38. 38.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 41; // start at 41
    line 2: stars = stars * 2; // double it
    line 3: stars = stars + 6; // add 3
    line 4: show(stars); // show it
  39. 39.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 46; // start at 45
    line 2: lives = lives - 4; // take away 4
    line 3: lives = lives * 2; // double it
    line 4: show(lives); // show it
  40. 40.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 46; // start at 45
    line 2: points = points + 3; // add 3
    line 3: points = points * 2; // double it
    line 4: points = points - 3; // take away 3
    line 5: show(points); // show it

Answer key

  1. people reading the code
  2. 62
  3. 93
  4. line 1
  5. 93
  6. a mistake in the code
  7. 106
  8. 37
  9. debugging
  10. 55
  11. 34
  12. 100
  13. find where it goes wrong
  14. test it again
  15. 88
  16. 188
  17. 87
  18. 208
  19. 58
  20. line 2
  21. 112
  22. 43
  23. 26
  24. line 2
  25. 78
  26. 92
  27. 32
  28. line 2
  29. 49
  30. 42
  31. line 1
  32. line 4
  33. line 2
  34. line 3
  35. 96
  36. 29
  37. 82
  38. 88
  39. 84
  40. 95

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