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App Dev Worksheet: Debugging

App development lesson 21: Debugging: find the bug line · Set 906 · 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.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 36; // start at 36
    line 2: coins = coins - 1; // take away 1
    line 3: coins = coins + 1; // take away 1
    line 4: show(coins); // show it     (a) line 1 (b) line 2 (c) line 3
  2. 2.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 34; // start at 34
    line 2: coins = coins + 5; // add 5
    line 3: coins = coins - 4; // add 4
    line 4: coins = coins + 2; // add 2
    line 5: show(coins); // show it
  3. 3.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let stars = 45; // start at 45
    line 2: stars = stars * 2; // double it
    line 3: stars = stars - 5; // add 5
    line 4: show(stars); // show it     (a) line 1 (b) line 3 (c) line 2
  4. 4.🐞 What is a bug? (a) a new feature (b) a mistake in the code (c) a fast phone (d) a nice icon
  5. 5.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 46; // start at 46
    line 2: score = score + 3; // add 3
    line 3: score = score + 1; // take away 1
    line 4: show(score); // 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 coins = 44; // start at 44
    line 2: coins = coins * 2; // double it
    line 3: coins = coins - 1; // take away 1
    line 4: coins = coins - 5; // add 5
    line 5: show(coins); // show it
  7. 7.🐞 Finding and fixing bugs is called ___. (a) downloading (b) debugging (c) decorating (d) designing
  8. 8.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 34; // start at 34
    line 2: points = points - 5; // take away 2
    line 3: points = points + 2; // add 2
    line 4: show(points); // show it
  9. 9.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 44; // start at 44
    line 2: score = score + 3; // add 3
    line 3: score = score + 3; // add 3
    line 4: score = score + 2; // double it
    line 5: show(score); // show it
  10. 10.🐞 What is a good first step when an app gives a wrong result? (a) find where it goes wrong (b) buy a new phone (c) add more colours (d) delete the app
  11. 11.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 35; // start at 32
    line 2: coins = coins + 5; // add 5
    line 3: coins = coins + 6; // add 6
    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 stars = 48; // start at 48
    line 2: stars = stars * 2; // double it
    line 3: stars = stars + 2; // double it
    line 4: show(stars); // show it
  13. 13.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 37; // start at 35
    line 2: lives = lives * 2; // double it
    line 3: lives = lives * 2; // double it
    line 4: show(lives); // show it
  14. 14.🐞 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 34
    line 2: coins = coins - 1; // take away 1
    line 3: coins = coins + 6; // add 6
    line 4: show(coins); // show it
  15. 15.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 34; // start at 34
    line 2: coins = coins * 2; // double it
    line 3: coins = coins + 4; // add 4
    line 4: coins = coins - 6; // take away 5
    line 5: show(coins); // 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 = 45; // start at 45
    line 2: points = points * 3; // double it
    line 3: points = points + 5; // add 5
    line 4: points = points * 2; // double it
    line 5: show(points); // show it
  17. 17.🐞 A comment in code (after //) is for ___. (a) the phone screen (b) the app store (c) the battery (d) people reading the code
  18. 18.🐞 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 3
    line 3: lives = lives - 2; // take away 2
    line 4: show(lives); // show it     (a) line 1 (b) line 3 (c) line 2
  19. 19.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 36; // start at 35
    line 2: coins = coins + 6; // add 6
    line 3: coins = coins * 2; // double it
    line 4: show(coins); // show it
  20. 20.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 46; // start at 46
    line 2: lives = lives * 3; // double it
    line 3: lives = lives * 2; // double it
    line 4: lives = lives * 2; // double it
    line 5: show(lives); // show it     (a) line 1 (b) line 4 (c) line 2 (d) line 3
  21. 21.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 46; // start at 46
    line 2: points = points - 1; // take away 1
    line 3: points = points - 5; // take away 5
    line 4: points = points + 3; // add 2
    line 5: show(points); // show it
  22. 22.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 30; // start at 30
    line 2: score = score - 7; // take away 4
    line 3: score = score - 2; // take away 2
    line 4: score = score + 6; // add 6
    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 score = 35; // start at 35
    line 2: score = score * 2; // double it
    line 3: score = score - 6; // add 6
    line 4: show(score); // show it
  24. 24.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 32; // start at 30
    line 2: lives = lives * 2; // double it
    line 3: lives = lives - 1; // take away 1
    line 4: lives = lives - 3; // take away 3
    line 5: show(lives); // show it     (a) line 2 (b) line 3 (c) line 4 (d) line 1
  25. 25.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 47; // start at 47
    line 2: points = points * 2; // double it
    line 3: points = points - 6; // add 6
    line 4: show(points); // show it     (a) line 3 (b) line 2 (c) line 1
  26. 26.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 38; // start at 38
    line 2: coins = coins * 3; // double it
    line 3: coins = coins - 5; // take away 5
    line 4: show(coins); // show it
  27. 27.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 35; // start at 34
    line 2: score = score - 4; // take away 4
    line 3: score = score * 2; // double it
    line 4: show(score); // show it     (a) line 2 (b) line 3 (c) line 1
  28. 28.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 35; // start at 35
    line 2: points = points - 1; // take away 1
    line 3: points = points - 2; // add 2
    line 4: points = points + 3; // add 3
    line 5: show(points); // show it
  29. 29.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 30; // start at 30
    line 2: points = points - 5; // take away 3
    line 3: points = points * 2; // double it
    line 4: show(points); // show it     (a) line 2 (b) line 1 (c) line 3
  30. 30.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let lives = 37; // start at 37
    line 2: lives = lives * 2; // double it
    line 3: lives = lives + 2; // double it
    line 4: lives = lives - 2; // take away 2
    line 5: show(lives); // show it
  31. 31.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 41; // start at 41
    line 2: coins = coins * 3; // double it
    line 3: coins = coins * 2; // double it
    line 4: coins = coins - 4; // take away 4
    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 = 36; // start at 34
    line 2: coins = coins - 4; // take away 4
    line 3: coins = coins + 6; // add 6
    line 4: show(coins); // show it     (a) line 3 (b) line 2 (c) line 1
  33. 33.🐞 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 + 1; // take away 1
    line 3: coins = coins - 1; // take away 1
    line 4: show(coins); // show it     (a) line 3 (b) line 2 (c) line 1
  34. 34.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let stars = 41; // start at 39
    line 2: stars = stars + 3; // add 3
    line 3: stars = stars + 3; // add 3
    line 4: stars = stars * 2; // double it
    line 5: show(stars); // show it     (a) line 2 (b) line 4 (c) line 3 (d) line 1
  35. 35.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 43; // start at 43
    line 2: lives = lives * 2; // double it
    line 3: lives = lives - 4; // take away 1
    line 4: lives = lives - 1; // take away 1
    line 5: show(lives); // show it
  36. 36.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 50; // start at 49
    line 2: score = score + 2; // add 2
    line 3: score = score * 2; // double it
    line 4: show(score); // show it     (a) line 3 (b) line 1 (c) line 2
  37. 37.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let points = 41; // start at 39
    line 2: points = points + 3; // add 3
    line 3: points = points + 6; // add 6
    line 4: points = points - 3; // take away 3
    line 5: show(points); // show it
  38. 38.🐞 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 + 5; // add 5
    line 3: stars = stars - 1; // take away 1
    line 4: show(stars); // show it     (a) line 2 (b) line 3 (c) line 1
  39. 39.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 36; // start at 33
    line 2: stars = stars + 2; // add 2
    line 3: stars = stars + 2; // add 2
    line 4: stars = stars * 2; // double it
    line 5: show(stars); // show it
  40. 40.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 43; // start at 43
    line 2: coins = coins - 3; // take away 3
    line 3: coins = coins * 2; // double it
    line 4: coins = coins - 6; // add 6
    line 5: show(coins); // show it     (a) line 4 (b) line 2 (c) line 1 (d) line 3

Answer key

  1. line 3
  2. 45
  3. line 3
  4. a mistake in the code
  5. 50
  6. 92
  7. debugging
  8. 31
  9. 52
  10. find where it goes wrong
  11. 43
  12. 192
  13. 148
  14. 39
  15. 66
  16. 190
  17. people reading the code
  18. line 2
  19. 84
  20. line 2
  21. 43
  22. 27
  23. 76
  24. line 1
  25. line 3
  26. 71
  27. line 1
  28. 35
  29. line 2
  30. 146
  31. 242
  32. line 1
  33. line 2
  34. line 1
  35. 81
  36. line 1
  37. 45
  38. line 1
  39. 80
  40. line 4

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