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App Dev Worksheet: Debugging

App development lesson 21: Debugging: find the bug line · Set 79 · 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 SHOULD it show, if every line did what its comment says?
    line 1: let score = 44; // start at 41
    line 2: score = score + 3; // add 3
    line 3: score = score + 4; // add 4
    line 4: show(score); // show it
  2. 2.🐞 After fixing a bug you should ___. (a) never test (b) delete the test (c) test it again (d) release at once
  3. 3.🐞 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 + 2; // add 2
    line 3: points = points + 2; // double it
    line 4: points = points + 2; // add 2
    line 5: show(points); // show it
  4. 4.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 32; // start at 30
    line 2: stars = stars + 2; // add 2
    line 3: stars = stars + 6; // add 6
    line 4: stars = stars - 3; // take away 3
    line 5: show(stars); // show it
  5. 5.🐞 What is a good first step when an app gives a wrong result? (a) delete the app (b) buy a new phone (c) add more colours (d) find where it goes wrong
  6. 6.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 40; // start at 37
    line 2: score = score - 2; // take away 2
    line 3: score = score - 4; // take away 4
    line 4: show(score); // show it     (a) line 1 (b) line 2 (c) line 3
  7. 7.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let score = 35; // start at 34
    line 2: score = score - 2; // take away 2
    line 3: score = score * 2; // double it
    line 4: score = score + 6; // add 6
    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 coins = 39; // start at 39
    line 2: coins = coins + 6; // add 6
    line 3: coins = coins * 2; // double it
    line 4: coins = coins - 2; // add 2
    line 5: show(coins); // show it
  9. 9.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 35; // start at 35
    line 2: points = points * 2; // double it
    line 3: points = points - 5; // take away 2
    line 4: show(points); // 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 stars = 51; // start at 48
    line 2: stars = stars + 5; // add 5
    line 3: stars = stars * 2; // double it
    line 4: show(stars); // show it
  11. 11.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 48; // start at 48
    line 2: stars = stars + 2; // double it
    line 3: stars = stars - 1; // take away 1
    line 4: show(stars); // show it
  12. 12.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 39; // start at 38
    line 2: points = points + 2; // add 2
    line 3: points = points * 2; // double it
    line 4: points = points + 6; // add 6
    line 5: show(points); // show it     (a) line 2 (b) line 1 (c) line 3 (d) line 4
  13. 13.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 34; // start at 33
    line 2: score = score + 2; // add 2
    line 3: score = score - 2; // take away 2
    line 4: score = score + 5; // add 5
    line 5: show(score); // show it
  14. 14.🐞 Finding and fixing bugs is called ___. (a) decorating (b) downloading (c) designing (d) debugging
  15. 15.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 32; // start at 32
    line 2: stars = stars * 2; // double it
    line 3: stars = stars - 3; // add 3
    line 4: show(stars); // 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 coins = 30; // start at 30
    line 2: coins = coins + 2; // add 2
    line 3: coins = coins - 3; // add 3
    line 4: coins = coins - 3; // take away 3
    line 5: show(coins); // show it
  17. 17.🐞 What is a bug? (a) a new feature (b) a nice icon (c) a mistake in the code (d) a fast phone
  18. 18.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 51; // start at 49
    line 2: lives = lives + 6; // add 6
    line 3: lives = lives + 5; // add 5
    line 4: lives = lives + 3; // add 3
    line 5: show(lives); // show it
  19. 19.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 35; // start at 35
    line 2: points = points - 6; // add 6
    line 3: points = points - 1; // take away 1
    line 4: show(points); // show it
  20. 20.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 35; // start at 35
    line 2: stars = stars - 6; // add 6
    line 3: stars = stars + 6; // add 6
    line 4: show(stars); // show it
  21. 21.🐞 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 - 8; // take away 5
    line 3: coins = coins * 2; // double it
    line 4: coins = coins + 3; // add 3
    line 5: show(coins); // show it     (a) line 1 (b) line 3 (c) line 4 (d) line 2
  22. 22.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 49; // start at 49
    line 2: score = score * 2; // double it
    line 3: score = score * 2; // double it
    line 4: score = score + 4; // add 2
    line 5: show(score); // show it     (a) line 3 (b) line 4 (c) line 1 (d) line 2
  23. 23.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 35; // start at 33
    line 2: stars = stars * 2; // double it
    line 3: stars = stars - 1; // take away 1
    line 4: show(stars); // show it
  24. 24.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 35; // start at 32
    line 2: score = score * 2; // double it
    line 3: score = score + 3; // add 3
    line 4: show(score); // show it     (a) line 3 (b) line 2 (c) line 1
  25. 25.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 41; // start at 38
    line 2: stars = stars + 5; // add 5
    line 3: stars = stars * 2; // double it
    line 4: 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 = 41; // start at 40
    line 2: coins = coins - 3; // take away 3
    line 3: coins = coins + 4; // add 4
    line 4: 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 points = 46; // start at 46
    line 2: points = points - 8; // take away 5
    line 3: points = points * 2; // double it
    line 4: show(points); // show it
  28. 28.🐞 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 + 1; // take away 1
    line 3: score = score * 2; // double it
    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
  29. 29.🐞 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 + 3; // add 3
    line 3: coins = coins + 2; // add 2
    line 4: show(coins); // show it     (a) line 3 (b) line 2 (c) line 1
  30. 30.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 44; // start at 41
    line 2: lives = lives + 3; // add 3
    line 3: lives = lives + 3; // add 3
    line 4: lives = lives - 3; // take away 3
    line 5: show(lives); // show it     (a) line 4 (b) line 3 (c) line 1 (d) line 2
  31. 31.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 42; // start at 42
    line 2: coins = coins * 3; // double it
    line 3: coins = coins - 5; // take away 5
    line 4: coins = coins + 2; // add 2
    line 5: show(coins); // show it     (a) line 4 (b) line 1 (c) line 2 (d) line 3
  32. 32.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 34; // start at 34
    line 2: lives = lives + 5; // add 5
    line 3: lives = lives * 3; // double it
    line 4: lives = lives - 5; // take away 5
    line 5: show(lives); // show it
  33. 33.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let stars = 41; // start at 40
    line 2: stars = stars * 2; // double it
    line 3: stars = stars * 2; // double it
    line 4: show(stars); // show it     (a) line 2 (b) line 1 (c) line 3
  34. 34.🐞 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 * 2; // double it
    line 3: points = points + 7; // add 4
    line 4: points = points + 6; // add 6
    line 5: show(points); // show it
  35. 35.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 37; // start at 37
    line 2: stars = stars - 6; // add 6
    line 3: stars = stars * 2; // double it
    line 4: stars = stars - 4; // take away 4
    line 5: show(stars); // show it
  36. 36.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 50; // start at 50
    line 2: stars = stars * 2; // double it
    line 3: stars = stars * 3; // double it
    line 4: show(stars); // 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 stars = 38; // start at 37
    line 2: stars = stars - 5; // take away 5
    line 3: stars = stars + 6; // add 6
    line 4: show(stars); // show it
  38. 38.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 51; // start at 49
    line 2: coins = coins * 2; // double it
    line 3: coins = coins + 6; // add 6
    line 4: coins = coins + 3; // add 3
    line 5: show(coins); // show it     (a) line 4 (b) line 3 (c) line 1 (d) line 2
  39. 39.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 44; // start at 44
    line 2: points = points - 1; // take away 1
    line 3: points = points + 8; // add 6
    line 4: show(points); // show it     (a) line 2 (b) line 1 (c) line 3
  40. 40.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 41; // start at 38
    line 2: coins = coins - 4; // take away 4
    line 3: coins = coins - 3; // take away 3
    line 4: coins = coins - 3; // take away 3
    line 5: show(coins); // show it

Answer key

  1. 48
  2. test it again
  3. 80
  4. 37
  5. find where it goes wrong
  6. line 1
  7. 70
  8. 92
  9. 65
  10. 106
  11. 49
  12. line 1
  13. 39
  14. debugging
  15. 67
  16. 32
  17. a mistake in the code
  18. 65
  19. 28
  20. 35
  21. line 2
  22. line 4
  23. 69
  24. line 1
  25. 92
  26. 41
  27. 82
  28. line 2
  29. line 1
  30. line 1
  31. line 2
  32. 112
  33. line 1
  34. 74
  35. 58
  36. 300
  37. 38
  38. line 1
  39. line 3
  40. 28

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