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App Dev Worksheet: Debugging

App development lesson 21: Debugging: find the bug line · Set 512 · 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 stars = 31; // start at 31
    line 2: stars = stars - 2; // take away 1
    line 3: stars = stars - 1; // take away 1
    line 4: stars = stars * 2; // double it
    line 5: show(stars); // show it
  2. 2.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 48; // start at 46
    line 2: coins = coins + 5; // add 5
    line 3: coins = coins * 2; // double it
    line 4: coins = coins * 2; // double it
    line 5: show(coins); // show it     (a) line 1 (b) line 4 (c) line 3 (d) line 2
  3. 3.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 44; // start at 44
    line 2: points = points * 2; // double it
    line 3: points = points + 2; // double it
    line 4: show(points); // show it
  4. 4.🐞 Finding and fixing bugs is called ___. (a) downloading (b) decorating (c) designing (d) debugging
  5. 5.🐞 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 + 5; // add 5
    line 3: coins = coins + 3; // add 3
    line 4: coins = coins * 2; // double it
    line 5: show(coins); // 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 lives = 31; // start at 31
    line 2: lives = lives + 2; // take away 2
    line 3: lives = lives * 2; // double it
    line 4: show(lives); // show it
  7. 7.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 44; // start at 44
    line 2: lives = lives * 2; // double it
    line 3: lives = lives + 2; // double it
    line 4: lives = lives + 5; // add 5
    line 5: show(lives); // show it     (a) line 4 (b) line 2 (c) line 1 (d) line 3
  8. 8.🐞 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 46
    line 2: score = score - 2; // take away 2
    line 3: score = score + 2; // take away 2
    line 4: show(score); // show it
  9. 9.🐞 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 - 5; // take away 5
    line 3: stars = stars - 3; // add 3
    line 4: stars = stars * 2; // double it
    line 5: show(stars); // show it     (a) line 1 (b) line 4 (c) line 2 (d) line 3
  10. 10.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let score = 33; // start at 33
    line 2: score = score * 2; // double it
    line 3: score = score - 4; // add 4
    line 4: show(score); // show it
  11. 11.🐞 What is a bug? (a) a nice icon (b) a mistake in the code (c) a fast phone (d) a new feature
  12. 12.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 47; // start at 47
    line 2: points = points + 2; // double it
    line 3: points = points + 2; // add 2
    line 4: show(points); // show it
  13. 13.🐞 A comment in code (after //) is for ___. (a) the phone screen (b) the battery (c) the app store (d) people reading the code
  14. 14.🐞 What is a good first step when an app gives a wrong result? (a) add more colours (b) find where it goes wrong (c) delete the app (d) buy a new phone
  15. 15.🐞 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 36
    line 2: coins = coins - 4; // take away 4
    line 3: coins = coins + 6; // add 3
    line 4: coins = coins * 2; // double it
    line 5: show(coins); // show it
  16. 16.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 45; // start at 45
    line 2: score = score + 2; // take away 2
    line 3: score = score * 2; // double it
    line 4: show(score); // show it
  17. 17.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 33; // start at 31
    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
  18. 18.🐞 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 35
    line 2: coins = coins + 5; // add 5
    line 3: coins = coins - 2; // take away 2
    line 4: show(coins); // show it
  19. 19.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 50; // start at 48
    line 2: points = points + 2; // add 2
    line 3: points = points * 2; // double it
    line 4: points = points - 4; // take away 4
    line 5: show(points); // show it
  20. 20.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 48; // start at 48
    line 2: score = score + 2; // add 2
    line 3: score = score + 5; // add 4
    line 4: score = score * 2; // double it
    line 5: show(score); // show it
  21. 21.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 53; // start at 50
    line 2: stars = stars + 6; // add 6
    line 3: stars = stars * 2; // double it
    line 4: show(stars); // show it
  22. 22.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 42; // start at 39
    line 2: lives = lives + 4; // add 4
    line 3: lives = lives * 2; // double it
    line 4: show(lives); // show it
  23. 23.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 39; // start at 38
    line 2: lives = lives * 2; // double it
    line 3: lives = lives - 1; // take away 1
    line 4: show(lives); // show it     (a) line 1 (b) line 3 (c) line 2
  24. 24.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 39; // start at 36
    line 2: stars = stars - 2; // take away 2
    line 3: stars = stars - 1; // take away 1
    line 4: show(stars); // show it
  25. 25.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 32; // start at 32
    line 2: points = points * 3; // double it
    line 3: points = points + 3; // add 3
    line 4: show(points); // show it
  26. 26.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 36; // start at 36
    line 2: points = points + 4; // add 3
    line 3: points = points * 2; // double it
    line 4: show(points); // show it     (a) line 3 (b) line 2 (c) line 1
  27. 27.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 38; // start at 38
    line 2: coins = coins + 3; // add 3
    line 3: coins = coins * 3; // double it
    line 4: show(coins); // show it     (a) line 1 (b) line 3 (c) line 2
  28. 28.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 43; // start at 42
    line 2: points = points * 2; // double it
    line 3: points = points - 2; // take away 2
    line 4: show(points); // show it     (a) line 1 (b) line 2 (c) line 3
  29. 29.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 49; // start at 49
    line 2: points = points + 4; // take away 4
    line 3: points = points + 5; // add 5
    line 4: points = points + 5; // add 5
    line 5: show(points); // show it     (a) line 2 (b) line 1 (c) line 3 (d) line 4
  30. 30.🐞 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 + 2; // add 2
    line 3: coins = coins + 2; // double it
    line 4: show(coins); // show it
  31. 31.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 35; // start at 32
    line 2: coins = coins + 4; // add 4
    line 3: coins = coins * 2; // double it
    line 4: coins = coins + 2; // add 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 = 49; // start at 47
    line 2: coins = coins + 4; // add 4
    line 3: coins = coins * 2; // double it
    line 4: show(coins); // show it     (a) line 3 (b) line 1 (c) line 2
  33. 33.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 47; // start at 47
    line 2: stars = stars + 2; // take away 2
    line 3: stars = stars + 2; // add 2
    line 4: show(stars); // show it
  34. 34.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let stars = 39; // start at 37
    line 2: stars = stars * 2; // double it
    line 3: stars = stars - 2; // take away 2
    line 4: show(stars); // show it     (a) line 3 (b) line 2 (c) line 1
  35. 35.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 35; // start at 35
    line 2: stars = stars + 5; // add 5
    line 3: stars = stars * 2; // double it
    line 4: stars = stars - 3; // add 3
    line 5: show(stars); // show it
  36. 36.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 38; // start at 38
    line 2: score = score - 2; // take away 2
    line 3: score = score * 2; // double it
    line 4: score = score - 3; // add 3
    line 5: show(score); // show it
  37. 37.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 32; // start at 32
    line 2: stars = stars - 4; // take away 4
    line 3: stars = stars * 3; // double it
    line 4: stars = stars * 2; // double it
    line 5: show(stars); // show it
  38. 38.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 43; // start at 42
    line 2: score = score - 2; // take away 2
    line 3: score = score * 2; // double it
    line 4: show(score); // show it     (a) line 2 (b) line 3 (c) line 1
  39. 39.🐞 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 45
    line 2: stars = stars + 2; // add 2
    line 3: stars = stars * 2; // double it
    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 points = 47; // start at 47
    line 2: points = points - 2; // add 2
    line 3: points = points * 2; // double it
    line 4: show(points); // show it     (a) line 2 (b) line 1 (c) line 3

Answer key

  1. 58
  2. line 1
  3. 90
  4. debugging
  5. 96
  6. 58
  7. line 3
  8. 42
  9. line 3
  10. 70
  11. a mistake in the code
  12. 51
  13. people reading the code
  14. find where it goes wrong
  15. 70
  16. 94
  17. 77
  18. 38
  19. 100
  20. 110
  21. 112
  22. 92
  23. line 1
  24. 33
  25. 99
  26. line 2
  27. line 3
  28. line 1
  29. line 2
  30. 72
  31. 80
  32. line 1
  33. 47
  34. line 1
  35. 77
  36. 69
  37. 168
  38. line 1
  39. 188
  40. line 2

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